<!-- review: finished -->

<a id="http-scgi"></a>

# SCGI

Allows passing requests to an SCGI server.

<a id="configuration-example-38"></a>

## Configuration Example

```nginx
location / {
    include   scgi_params;
    scgi_pass localhost:9000;
}
```

<a id="directives-40"></a>

## Directives

<a id="index-0"></a>

<a id="scgi-bind"></a>

### scgi_bind

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_bind` address [`transparent`] | `off`;   |
|------------------------------------------------------------------------------------------|------------------------------------------------|
| Default                                                                                  | —                                              |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                         |

Makes outgoing connections to an SCGI server originate from the specified local IP address with an optional port. Parameter value can contain variables. The special value `off` cancels the effect of the scgi_bind directive inherited from the previous configuration level, which allows the system to auto-assign the local IP address and port.

The `transparent` parameter allows outgoing connections to an SCGI server originate from a non-local IP address, for example, from a real IP address of a client:

```nginx
scgi_bind $remote_addr transparent;
```

In order for this parameter to work, it is usually necessary to run Angie worker processes with the [superuser](https://en.angie.software//angie/docs/configuration/modules/core.md#user) privileges. On Linux it is not required as if the `transparent` parameter is specified, worker processes inherit the CAP_NET_RAW capability from the master process.

#### NOTE
It is necessary to configure kernel routing table to intercept network traffic from the SCGI server.

<a id="index-1"></a>

<a id="scgi-buffer-size"></a>

### scgi_buffer_size

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_buffer_size` size;   |
|------------------------------------------------------------------------------------------|----------------------------|
| Default                                                                                  | `scgi_buffer_size 4k|8k;`  |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location     |

Sets the size of the buffer used for reading the first part of the response received from the SCGI server. This part usually contains a small response header. By default, the buffer size is equal to one memory page. This is either 4K or 8K, depending on a platform. It can be made smaller, however.

<a id="index-2"></a>

<a id="scgi-buffering"></a>

### scgi_buffering

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_buffering` `on` | `off`;   |
|------------------------------------------------------------------------------------------|----------------------------------|
| Default                                                                                  | `scgi_buffering on;`             |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location           |

Enables or disables buffering of responses from the SCGI server.

| `on`   | Angie receives a response from the SCGI server as soon as possible, saving it into the buffers set by the [scgi_buffer_size](#scgi-buffer-size) and [scgi_buffers](#scgi-buffers) directives. Sending to the client is performed in parallel: filled buffers are passed for sending, but their total size is limited by [scgi_busy_buffers_size](#scgi-busy-buffers-size). If a buffer is not completely filled, it is not passed for sending unless it contains the last part of the response. Therefore, buffered reading is not suitable when you need immediate delivery of every few bytes. If the whole response does not fit into memory, a part of it can be saved to a [temporary file](#scgi-temp-path) on the disk. Writing to temporary files is controlled by the [scgi_max_temp_file_size](#scgi-max-temp-file-size) and [scgi_temp_file_write_size](#scgi-temp-file-write-size) directives.   |
|--------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `off`  | The response is passed to a client immediately as it is received. Angie works in a "read — send" loop and does not wait for the buffer to fill completely: for example, 10 bytes read from a 4K buffer are sent right away. At the same time, if the entire response fits into the buffer, Angie can read it in full. The maximum size of the data that Angie can receive from the server at a time is set by the [scgi_buffer_size](#scgi-buffer-size) directive. With `off`, [scgi_limit_rate](#scgi-limit-rate) does not work.                                                                                                                                                                                                                                                                                                                                                                            |

Buffering can also be enabled or disabled by passing "yes" or "no" in the `X-Accel-Buffering` response header field. This capability can be disabled using the [scgi_ignore_headers](#scgi-ignore-headers) directive.

<a id="index-3"></a>

<a id="scgi-buffers"></a>

### scgi_buffers

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_buffers` number size;   |
|------------------------------------------------------------------------------------------|-------------------------------|
| Default                                                                                  | `scgi_buffers 8 4k | 8k;`     |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location        |

Sets the number and size of the buffers used for reading a response from the SCGI server, for a single connection.

By default, the buffer size is equal to one memory page. This is either 4K or 8K, depending on a platform.

<a id="index-4"></a>

<a id="scgi-busy-buffers-size"></a>

### scgi_busy_buffers_size

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_busy_buffers_size` size;     |
|------------------------------------------------------------------------------------------|------------------------------------|
| Default                                                                                  | `scgi_busy_buffers_size 8k | 16k;` |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location             |

When [buffering](#scgi-buffering) of responses from the SCGI server is enabled, limits the total size of buffers that can be busy sending a response to the client while the response is not yet fully read. In the meantime, the rest of the buffers can be used for reading the response and, if needed, buffering part of the response to a temporary file.

By default, size is limited by the size of two buffers set by the [scgi_buffer_size](#scgi-buffer-size) and [scgi_buffers](#scgi-buffers) directives.

<a id="index-5"></a>

<a id="scgi-cache"></a>

### scgi_cache

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_cache` zone | `off`;   |
|------------------------------------------------------------------------------------------|------------------------------|
| Default                                                                                  | `scgi_cache off;`            |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location       |

Defines a shared memory zone used for caching. The same zone can be used in several places. Parameter value can contain variables.

| `off`   | disables caching inherited from the previous configuration level.   |
|---------|---------------------------------------------------------------------|

<a id="index-6"></a>

<a id="scgi-cache-background-update"></a>

### scgi_cache_background_update

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_cache_background_update` `on` | `off`;   |
|------------------------------------------------------------------------------------------|------------------------------------------------|
| Default                                                                                  | `scgi_cache_background_update off;`            |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                         |

Allows starting a background subrequest to update an expired cache item, while a stale cached response is returned to the client.

#### WARNING
Note that it is necessary to [allow](#scgi-cache-use-stale-updating) the usage of a stale cached response when it is being updated.

<a id="index-7"></a>

<a id="scgi-cache-bypass"></a>

### scgi_cache_bypass

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_cache_bypass` string ...;   |
|------------------------------------------------------------------------------------------|-----------------------------------|
| Default                                                                                  | —                                 |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location            |

Defines conditions under which the response will not be taken from a cache. If at least one value of the string parameters is not empty and is not equal to "0" then the response will not be taken from the cache:

```nginx
scgi_cache_bypass $cookie_nocache $arg_nocache$arg_comment;
scgi_cache_bypass $http_pragma    $http_authorization;
```

Can be used along with the [scgi_no_cache](#scgi-no-cache) directive.

<a id="index-8"></a>

<a id="scgi-cache-key"></a>

### scgi_cache_key

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_cache_key` string;   |
|------------------------------------------------------------------------------------------|----------------------------|
| Default                                                                                  | —                          |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location     |

Defines a key for caching, for example

```nginx
scgi_cache_key localhost:9000$request_uri;
```

<a id="index-9"></a>

<a id="scgi-cache-lock"></a>

### scgi_cache_lock

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_cache_lock` `on` | `off`;   |
|------------------------------------------------------------------------------------------|-----------------------------------|
| Default                                                                                  | `scgi_cache_lock off;`            |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location            |

When enabled, only one request at a time will be allowed to populate a new cache element identified according to the [scgi_cache_key](#scgi-cache-key) directive by passing a request to an SCGI server. Other requests of the same cache element will either wait for a response to appear in the cache or the cache lock for this element to be released, up to the time set by the [scgi_cache_lock_timeout](#scgi-cache-lock-timeout) directive.

<a id="index-10"></a>

<a id="scgi-cache-lock-age"></a>

### scgi_cache_lock_age

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_cache_lock_age` time;   |
|------------------------------------------------------------------------------------------|-------------------------------|
| Default                                                                                  | `scgi_cache_lock_age 5s;`     |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location        |

If the last request passed to the SCGI server for populating a new cache element has not completed for the specified time, one more request may be passed to the SCGI server.

<a id="index-11"></a>

<a id="scgi-cache-lock-timeout"></a>

### scgi_cache_lock_timeout

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_cache_lock_timeout` time;   |
|------------------------------------------------------------------------------------------|-----------------------------------|
| Default                                                                                  | `scgi_cache_lock_timeout 5s;`     |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location            |

Sets a timeout for [scgi_cache_lock](#scgi-cache-lock). When the time expires, the request will be passed to the SCGI server, however, the response will not be cached.

<a id="index-12"></a>

<a id="scgi-cache-max-range-offset"></a>

### scgi_cache_max_range_offset

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_cache_max_range_offset` number;   |
|------------------------------------------------------------------------------------------|-----------------------------------------|
| Default                                                                                  | —                                       |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                  |

Sets an offset in bytes for byte-range requests. If the range is beyond the offset, the range request will be passed to the SCGI server and the response will not be cached.

<a id="index-13"></a>

<a id="scgi-cache-methods"></a>

### scgi_cache_methods

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_cache_methods` `GET` | `HEAD` | `POST` ...;   |
|------------------------------------------------------------------------------------------|-----------------------------------------------------|
| Default                                                                                  | `scgi_cache_methods GET HEAD;`                      |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                              |

If the client request method is listed in this directive then the response will be cached. "GET" and "HEAD" methods are always added to the list, though it is recommended to specify them explicitly. See also the [scgi_no_cache](#scgi-no-cache) directive.

<a id="index-14"></a>

<a id="scgi-cache-min-uses"></a>

### scgi_cache_min_uses

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_cache_min_uses` number;   |
|------------------------------------------------------------------------------------------|---------------------------------|
| Default                                                                                  | `scgi_cache_min_uses 1;`        |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location          |

Sets the number of requests after which the response will be cached.

#### WARNING
Cache metadata is stored in shared memory. Manually deleting cache files does
not reset the counters and may lead to unpredictable behavior. To
completely reset the cache, stop the server, delete the cache directory, and restart.

#### NOTE
Third-party cache purge modules (e.g., [Cache Purge](https://en.angie.software//angie/docs/installation/external-modules/cache-purge.md#external-cache-purge)) only delete
files but do not reset the scgi_cache_min_uses counter. The directive
is intended to protect the cache from pollution by infrequent requests, and resetting
the counter during purge may negatively affect performance.

<a id="index-15"></a>

<a id="scgi-cache-path"></a>

### scgi_cache_path

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_cache_path` path [`levels=`levels] [`use_temp_path=``on` | `off`] `keys_zone=`name:size [`inactive=`time] [`max_size=`size] [`min_free=`size] [`manager_files=`number] [`manager_sleep=`time] [`manager_threshold=`time] [`loader_files=`number] [`loader_sleep=`time] [`loader_threshold=`time];   |
|------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Default                                                                                  | —                                                                                                                                                                                                                                                                                                         |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http                                                                                                                                                                                                                                                                                                      |

Sets the path and other parameters of a cache. Cache data are stored in files. The file name in a cache is a result of applying the MD5 function to the [cache key](#scgi-cache-key).

The `levels` parameter defines hierarchy levels of a cache: from 1 to 3, each level accepts values 1 or 2. For example, in the following configuration:

```nginx
scgi_cache_path /data/angie/cache levels=1:2 keys_zone=one:10m;
```

file names in a cache will look like this:

```nginx
/data/angie/cache/c/29/b7f54b2df7773722d382f4809d65029c
```

A cached response is first written to a temporary file, and then the file is renamed. Temporary files and the cache can be put on different file systems. However, be aware that in this case a file is copied across two file systems instead of the cheap renaming operation. It is thus recommended that for any given location both cache and a directory holding temporary files are put on the same file system.

The directory for temporary files is set based on the `use_temp_path` parameter.

| `on`   | If this parameter is omitted or set to the value on, the directory set by the [scgi_temp_path](#scgi-temp-path) directive for the given location will be used.   |
|--------|------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `off`  | Temporary files will be put directly in the cache directory.                                                                                                     |

In addition, all active keys and information about data are stored in a shared memory zone, whose name and size are configured by the `keys_zone` parameter. One megabyte zone can store about 8 thousand keys. Cache metadata is stored in shared memory.

Cached data that are not accessed during the time specified by the `inactive` parameter get removed from the cache regardless of their freshness.

By default, `inactive` is set to 10 minutes.

A special **cache manager** process monitors the maximum cache size and the minimum amount of free space on the file system with cache and when the size is exceeded or there is not enough free space, it removes the least recently used data. The data is removed in iterations.

| `max_size`          | maximum cache size                                                                       |
|---------------------|------------------------------------------------------------------------------------------|
| `min_free`          | minimum amount of free space on the file system with cache                               |
| `manager_files`     | limits the number of items to be deleted during one iteration<br/><br/>By default, `100` |
| `manager_threshold` | limits the duration of one iteration<br/><br/>By default, `200` milliseconds             |
| `manager_sleep`     | configures a pause between iterations<br/><br/>By default, `50` milliseconds             |

A minute after Angie starts, the special **cache loader** process is activated. It loads information about previously cached data stored on file system into a cache zone. The loading is also done in iterations.

| `loader_files`     | limits the number of items to load during one iteration<br/><br/>By default, `100`   |
|--------------------|--------------------------------------------------------------------------------------|
| `loader_threshold` | limits the duration of one iteration<br/><br/>By default, `200` milliseconds         |
| `loader_sleep`     | configures a pause between iterations<br/><br/>By default, `50` milliseconds         |

<a id="index-16"></a>

<a id="scgi-cache-revalidate"></a>

### scgi_cache_revalidate

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_cache_revalidate` `on` | `off`;   |
|------------------------------------------------------------------------------------------|-----------------------------------------|
| Default                                                                                  | `scgi_cache_revalidate off;`            |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                  |

Enables revalidation of expired cache items using conditional requests with the `If-Modified-Since`  and `If-None-Match`  header fields.

<a id="index-17"></a>

<a id="scgi-cache-use-stale"></a>

### scgi_cache_use_stale

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_cache_use_stale` `error` | `timeout` | `invalid_header` | `updating` | `http_500` | `http_503` | `http_403` | `http_404` | `http_429` | `off` ...;   |
|------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Default                                                                                  | `scgi_cache_use_stale off;`                                                                                                                                |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                                                                                                                                     |

Determines in which cases a stale cached response can be used. The directive's parameters match the parameters of the [scgi_next_upstream](#scgi-next-upstream) directive.

| `error`    | permits using a stale cached response if a SCGI server to process a request cannot be selected.                                                                                        |
|------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `updating` | additional parameter, permits using a stale cached response if it is currently being updated. This allows minimizing the number of accesses to SCGI servers when updating cached data. |

Using a stale cached response can also be enabled directly in the response header for a specified number of seconds after the response became stale:

* The [stale-while-revalidate](https://datatracker.ietf.org/doc/html/rfc5861#section-3) extension of the `Cache-Control` header field permits using a stale cached response if it is currently being updated.
* The [stale-if-error](https://datatracker.ietf.org/doc/html/rfc5861#section-4) extension of the `Cache-Control` header field permits using a stale cached response in case of an error.

#### NOTE
This method has lower priority than setting parameters using the directive.

To minimize the number of accesses to SCGI servers when populating a new cache element, the [scgi_cache_lock](#scgi-cache-lock) directive can be used.

<a id="index-18"></a>

<a id="scgi-cache-valid"></a>

### scgi_cache_valid

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_cache_valid` [code ...] time;   |
|------------------------------------------------------------------------------------------|---------------------------------------|
| Default                                                                                  | —                                     |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                |

Sets caching time for different response codes. For example, the following directives

```nginx
scgi_cache_valid 200 302 10m;
scgi_cache_valid 404      1m;
```

set 10 minutes of caching for responses with codes 200 and 302 and 1 minute for responses with code 404.

If only caching time is specified,

```nginx
scgi_cache_valid 5m;
```

then only 200, 301, and 302 responses are cached.

In addition, it can be specified to cache any responses using the `any` parameter:

```nginx
scgi_cache_valid 200 302 10m;
scgi_cache_valid 301      1h;
scgi_cache_valid any      1m;
```

#### NOTE
Parameters of caching can also be set directly in the response header. This has higher priority than setting caching time using the directive.

* The `X-Accel-Expires` header field sets caching time of a response in seconds. The zero value disables caching for a response. If the value starts with the @ prefix, it sets an absolute time in seconds since Epoch, up to which the response may be cached.
* If the header does not include the `X-Accel-Expires` field, parameters of caching may be set in the header fields `Expires` or `Cache-Control`.
* If the header includes the `Set-Cookie` field, such a response will not be cached.
* If the header includes the `Vary` field with the special value "\*", such a response will not be cached. If the header includes the `Vary` field with another value, such a response will be cached taking into account the corresponding request header fields.

Processing of one or more of these response header fields can be disabled using the [scgi_ignore_headers](#scgi-ignore-headers) directive.

<a id="index-19"></a>

<a id="scgi-connect-timeout"></a>

### scgi_connect_timeout

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_connect_timeout` time;   |
|------------------------------------------------------------------------------------------|--------------------------------|
| Default                                                                                  | `scgi_connect_timeout 60s;`    |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location         |

Defines a timeout for establishing a connection with an SCGI server. It should be noted that this timeout cannot usually exceed 75 seconds.

<a id="index-20"></a>

<a id="scgi-connection-drop"></a>

### scgi_connection_drop

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_connection_drop` time | `on` | `off`;   |
|------------------------------------------------------------------------------------------|-----------------------------------------------|
| Default                                                                                  | `scgi_connection_drop off;`                   |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                        |

Enables termination of all connections to the proxied server after it has been
removed from the group or marked as permanently unavailable by a [reresolve](https://en.angie.software//angie/docs/configuration/modules/http/http_upstream.md#reresolve) process or the [API command](https://en.angie.software//angie/docs/configuration/modules/http/http_api.md#api-config-methods)
`DELETE`.

A connection is terminated when the next read or write event is processed for
either the client or the proxied server.

Setting time enables a connection termination [timeout](https://en.angie.software//angie/docs/configuration/configfile.md#syntax);
with `on` set, connections are dropped immediately.

<a id="index-21"></a>

<a id="scgi-force-ranges"></a>

### scgi_force_ranges

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_force_ranges` `on` | `off`;   |
|------------------------------------------------------------------------------------------|-------------------------------------|
| Default                                                                                  | `scgi_force_ranges off;`            |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location              |

Enables byte-range support for both cached and uncached responses from the SCGI server regardless of the `Accept-Ranges` field in these responses.

<a id="index-22"></a>

<a id="scgi-hide-header"></a>

### scgi_hide_header

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_hide_header` field;   |
|------------------------------------------------------------------------------------------|-----------------------------|
| Default                                                                                  | —                           |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location      |

By default, Angie does not pass the header fields `Status` and `X-Accel-...` from the response of an SCGI server to a client. The `scgi_hide_header` directive sets additional fields that will not be passed. If, conversely, the passing of fields needs to be permitted, the [scgi_pass_header](#scgi-pass-header) directive can be used.

<a id="index-23"></a>

<a id="scgi-ignore-client-abort"></a>

### scgi_ignore_client_abort

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_ignore_client_abort` `on` | `off`;   |
|------------------------------------------------------------------------------------------|--------------------------------------------|
| Default                                                                                  | `scgi_ignore_client_abort off;`            |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                     |

Determines whether the connection with an SCGI server should be closed when a client closes the connection without waiting for a response.

<a id="index-24"></a>

<a id="scgi-ignore-headers"></a>

### scgi_ignore_headers

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_ignore_headers` field ...;   |
|------------------------------------------------------------------------------------------|------------------------------------|
| Default                                                                                  | —                                  |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location             |

Disables processing of certain response header fields from the SCGI server. The following fields can be ignored: `X-Accel-Redirect`, `X-Accel-Expires`, `X-Accel-Limit-Rate`, `X-Accel-Buffering`, `X-Accel-Charset`, `Expires`, `Cache-Control`, `Set-Cookie`, and `Vary`.

If not disabled, processing of these header fields has the following effect:

* `X-Accel-Expires`, `Expires`, `Cache-Control`, `Set-Cookie`, and `Vary` set the parameters of response [caching](#scgi-cache-valid);
* `X-Accel-Redirect` performs an [internal redirect](https://en.angie.software//angie/docs/configuration/modules/http/index.md#internal) to the specified URI;
* `X-Accel-Limit-Rate` sets the [rate limit](https://en.angie.software//angie/docs/configuration/modules/http/index.md#limit-rate) for transmission of a response to a client;
* `X-Accel-Buffering` enables or disables [buffering](#scgi-buffering) of a response;
* `X-Accel-Charset` sets the desired [charset](https://en.angie.software//angie/docs/configuration/modules/http/http_charset.md#id1) of a response.

<a id="index-25"></a>

<a id="scgi-intercept-errors"></a>

### scgi_intercept_errors

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_intercept_errors` `on` | `off`;   |
|------------------------------------------------------------------------------------------|-----------------------------------------|
| Default                                                                                  | `scgi_intercept_errors off;`            |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                  |

Determines whether SCGI server responses with codes greater than or equal to 300 should be passed to a client or be intercepted and redirected to Angie for processing with the [error_page](https://en.angie.software//angie/docs/configuration/modules/http/index.md#error-page) directive.

<a id="index-26"></a>

<a id="scgi-limit-rate"></a>

### scgi_limit_rate

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_limit_rate` rate;   |
|------------------------------------------------------------------------------------------|---------------------------|
| Default                                                                                  | `scgi_limit_rate 0;`      |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location    |

Limits the speed of reading the response from the SCGI server.
The rate is specified in bytes per second; variables can be used.

| `0`   | disables rate limiting   |
|-------|--------------------------|

#### NOTE
The limit is set per a request, and so if Angie simultaneously opens two connections to the SCGI server, the overall rate will be twice as much as the specified limit. The limitation works only if [buffering](#scgi-buffering) of responses from the SCGI server is enabled.

<a id="index-27"></a>

<a id="scgi-max-temp-file-size"></a>

### scgi_max_temp_file_size

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_max_temp_file_size` size;   |
|------------------------------------------------------------------------------------------|-----------------------------------|
| Default                                                                                  | `scgi_max_temp_file_size 1024m;`  |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location            |

When [buffering](#scgi-buffering) of responses from the SCGI server is enabled, and the whole response does not fit into the buffers set by the [scgi_buffer_size](#scgi-buffer-size) and [scgi_buffers](#scgi-buffers) directives, a part of the response can be saved to a temporary file. This directive sets the maximum size of the temporary file. The size of data written to the temporary file at a time is set by the [scgi_temp_file_write_size](#scgi-temp-file-write-size) directive.

| `0`   | disables buffering of responses to temporary files   |
|-------|------------------------------------------------------|

#### NOTE
This restriction does not apply to responses that will be [cached](#scgi-cache) or [stored](#scgi-store) on disk.

<a id="index-28"></a>

<a id="scgi-next-upstream"></a>

### scgi_next_upstream

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_next_upstream` `error` | `timeout` | `invalid_header` | `http_500` | `http_503` | `http_403` | `http_404` | `http_429` | `non_idempotent` | `off` ...;   |
|------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Default                                                                                  | `scgi_next_upstream error timeout;`                                                                                                                            |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                                                                                                                                         |

Specifies in which cases a request should be passed to the next server:

| `error`          | an error occurred while establishing a connection with the server, passing a request to it, or reading the response header;                                                                                                                                                                             |
|------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `timeout`        | a timeout has occurred while establishing a connection with the server, passing a request to it, or reading the response header;                                                                                                                                                                        |
| `invalid_header` | a server returned an empty or invalid response;                                                                                                                                                                                                                                                         |
| `http_500`       | a server returned a response with the code 500;                                                                                                                                                                                                                                                         |
| `http_503`       | a server returned a response with the code 503;                                                                                                                                                                                                                                                         |
| `http_403`       | a server returned a response with the code 403;                                                                                                                                                                                                                                                         |
| `http_404`       | a server returned a response with the code 404;                                                                                                                                                                                                                                                         |
| `http_429`       | a server returned a response with the code 429;                                                                                                                                                                                                                                                         |
| `non_idempotent` | normally, requests with a [non-idempotent](https://datatracker.ietf.org/doc/html/rfc7231#section-4.2.2) method<br/>(`POST`, `LOCK`, `PATCH`) are not passed to the next<br/>server if a request has been sent to an upstream server; enabling this<br/>option explicitly allows retrying such requests; |
| `off`            | disables passing a request to the next server.                                                                                                                                                                                                                                                          |

#### NOTE
One should bear in mind that passing a request to the next server is only possible if nothing has been sent to a client yet. That is, if an error or timeout occurs in the middle of the transferring of a response, fixing this is impossible.

The directive also defines what is considered an [unsuccessful attempt](https://en.angie.software//angie/docs/configuration/modules/http/http_upstream.md#max-fails) of communication with a server.

| `error`<br/><br/>`timeout`<br/><br/>`invalid_header`   | are always considered unsuccessful attempts, even if they are not specified in the directive   |
|--------------------------------------------------------|------------------------------------------------------------------------------------------------|
| `http_500`<br/><br/>`http_503`<br/><br/>`http_429`     | are considered unsuccessful attempts only if they are specified in the directive               |
| `http_403`<br/><br/>`http_404`                         | are never considered unsuccessful attempts                                                     |

Passing a request to the next server can be limited by the [number of tries](#scgi-next-upstream-tries) and by [time](#scgi-next-upstream-timeout).

<a id="index-29"></a>

<a id="scgi-next-upstream-timeout"></a>

### scgi_next_upstream_timeout

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_next_upstream_timeout` time;   |
|------------------------------------------------------------------------------------------|--------------------------------------|
| Default                                                                                  | `scgi_next_upstream_timeout 0;`      |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location               |

Limits the time during which a request can be passed to the [next](#scgi-next-upstream) server.

| `0`   | turns off this limitation   |
|-------|-----------------------------|

<a id="index-30"></a>

<a id="scgi-next-upstream-tries"></a>

### scgi_next_upstream_tries

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_next_upstream_tries` number;   |
|------------------------------------------------------------------------------------------|--------------------------------------|
| Default                                                                                  | `scgi_next_upstream_tries 0;`        |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location               |

Limits the number of possible tries for passing a request to the [next](#scgi-next-upstream) server.

| `0`   | turns off this limitation   |
|-------|-----------------------------|

<a id="index-31"></a>

<a id="scgi-no-cache"></a>

### scgi_no_cache

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_no_cache` string ...;   |
|------------------------------------------------------------------------------------------|-------------------------------|
| Default                                                                                  | —                             |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location        |

Defines conditions under which the response will not be saved to a cache. If at least one value of the string parameters is not empty and is not equal to "0" then the response will not be saved:

```nginx
scgi_no_cache $cookie_nocache $arg_nocache$arg_comment;
scgi_no_cache $http_pragma    $http_authorization;
```

Can be used along with the [scgi_cache_bypass](#scgi-cache-bypass) directive.

<a id="index-32"></a>

<a id="scgi-param"></a>

### scgi_param

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_param` parameter value [`if_not_empty`];   |
|------------------------------------------------------------------------------------------|--------------------------------------------------|
| Default                                                                                  | —                                                |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                           |

Sets a parameter that should be passed to the SCGI server. The value can contain text, variables, and their combination. These directives are inherited from the previous configuration level if and only if there are no scgi_param directives defined on the current level.

Standard [CGI environment variables](https://datatracker.ietf.org/doc/html/rfc3875#section-4.1) should be provided as SCGI headers, see the scgi_params file provided in the distribution:

```nginx
location / {
    include scgi_params;
#    ...
}
```

In the standard `scgi_params` file, `REQUEST_METHOD` is set to
`$upstream_request_method`.

If the directive is specified with `if_not_empty` then such a parameter will be passed to the server only if its value is not empty:

```nginx
scgi_param HTTPS $https if_not_empty;
```

<a id="index-33"></a>

<a id="scgi-pass"></a>

### scgi_pass

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_pass` uri;         |
|------------------------------------------------------------------------------------------|--------------------------|
| Default                                                                                  | —                        |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | location, if in location |

Sets the address of an SCGI server. The address can be specified as a domain name or IP address, and an optional port:

```nginx
scgi_pass localhost:9000;
```

or as a UNIX domain socket path:

```nginx
scgi_pass unix:/tmp/scgi.socket;
```

If a domain name resolves to several addresses, all of them will be used in a round-robin fashion. In addition, an address can be specified as a [server group](https://en.angie.software//angie/docs/configuration/modules/http/http_upstream.md#http-upstream).

Parameter value can contain variables. In this case, if an address is specified as a domain name, the name is searched among the described server groups, and, if not found, is determined using a [resolver](https://en.angie.software//angie/docs/configuration/modules/http/index.md#resolver).

#### NOTE
If `scgi_pass` is specified in a `location` with a trailing slash in the prefix
(for example, `location /name/`),
and the [auto_redirect](https://en.angie.software//angie/docs/configuration/modules/http/index.md#auto-redirect) directive is set to `default`,
requests without a trailing slash will be redirected (`/name -> /name/`).

<a id="index-34"></a>

<a id="scgi-pass-header"></a>

### scgi_pass_header

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_pass_header` field ...;   |
|------------------------------------------------------------------------------------------|---------------------------------|
| Default                                                                                  | —                               |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location          |

Permits passing [otherwise disabled](#scgi-hide-header) header fields from a SCGI server to a client.

<a id="index-35"></a>

<a id="scgi-pass-request-body"></a>

### scgi_pass_request_body

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_pass_request_body` `on` | `off`;   |
|------------------------------------------------------------------------------------------|------------------------------------------|
| Default                                                                                  | `scgi_pass_request_body on;`             |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                   |

Indicates whether the original request body is passed to the SCGI server. See also the [scgi_pass_request_headers](#scgi-pass-request-headers) directive.

<a id="index-36"></a>

<a id="scgi-pass-request-headers"></a>

### scgi_pass_request_headers

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_pass_request_headers` `on` | `off`;   |
|------------------------------------------------------------------------------------------|---------------------------------------------|
| Default                                                                                  | `scgi_pass_request_headers on;`             |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                      |

Indicates whether the header fields of the original request are passed to the SCGI server. See also the [scgi_pass_request_body](#scgi-pass-request-body) directive.

<a id="index-37"></a>

<a id="scgi-read-timeout"></a>

### scgi_read_timeout

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_read_timeout` time;   |
|------------------------------------------------------------------------------------------|-----------------------------|
| Default                                                                                  | `scgi_read_timeout 60s;`    |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location      |

Defines a timeout for reading a response from the SCGI server. The timeout is set only between two successive read operations, not for the transmission of the whole response. If the SCGI server does not transmit anything within this time, the connection is closed.

<a id="index-38"></a>

<a id="scgi-request-buffering"></a>

### scgi_request_buffering

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_request_buffering` `on` | `off`;   |
|------------------------------------------------------------------------------------------|------------------------------------------|
| Default                                                                                  | `scgi_request_buffering on;`             |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                   |

Enables or disables buffering of a client request body.

| `on`   | the request body is fully [read](https://en.angie.software//angie/docs/configuration/modules/http/index.md#client-body-buffer-size) from the client before sending the request to an SCGI server.                      |
|--------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `off`  | the request body is sent to the SCGI server immediately as it is received. In this case, the request cannot be passed to the [next server](#scgi-next-upstream) if Angie has already started sending the request body. |

When HTTP/1.1 chunked transfer encoding is used to send the original request body, the request body will be buffered regardless of the directive value.

<a id="index-39"></a>

<a id="scgi-send-timeout"></a>

### scgi_send_timeout

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_send_timeout` time;   |
|------------------------------------------------------------------------------------------|-----------------------------|
| Default                                                                                  | `scgi_send_timeout 60s;`    |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location      |

Sets a timeout for transmitting a request to the SCGI server. The timeout is set only between two successive write operations, not for the transmission of the whole request. If the SCGI server does not receive anything within this time, the connection is closed.

<a id="index-40"></a>

<a id="scgi-socket-keepalive"></a>

### scgi_socket_keepalive

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_socket_keepalive` `on` | `off`;   |
|------------------------------------------------------------------------------------------|-----------------------------------------|
| Default                                                                                  | `scgi_socket_keepalive off;`            |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                  |

Configures the "TCP keepalive" behavior for outgoing connections to a SCGI server.

| `off`   | By default, the operating system's settings are in effect for the socket.   |
|---------|-----------------------------------------------------------------------------|
| `on`    | The SO_KEEPALIVE socket option is turned on for the socket.                 |

<a id="index-41"></a>

<a id="scgi-store"></a>

### scgi_store

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_store` `on` | `off` | string;   |
|------------------------------------------------------------------------------------------|---------------------------------------|
| Default                                                                                  | `scgi_store off;`                     |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                |

Enables saving of files to a disk.

| `on`   | saves files with paths corresponding to the directives [alias](https://en.angie.software//angie/docs/configuration/modules/http/index.md#alias) or [root](https://en.angie.software//angie/docs/configuration/modules/http/index.md#root)   |
|--------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `off`  | disables saving of files                                                                                                                                                                                                                    |

The file name can be set explicitly using the string with variables:

```nginx
scgi_store /data/www$original_uri;
```

The modification time of files is set according to the received `Last-Modified` response header field. The response is first written to a temporary file, and then the file is renamed. Temporary files and the persistent store can be put on different file systems. However, be aware that in this case a file is copied across two file systems instead of the cheap renaming operation. It is thus recommended that for any given location both saved files and a directory holding temporary files, set by the [scgi_temp_path](#scgi-temp-path) directive, are put on the same file system.

This directive can be used to create local copies of static unchangeable files, e.g.:

```nginx
location /images/ {
    root              /data/www;
    error_page        404 = /fetch$uri;
}

location /fetch/ {
    internal;

    scgi_pass         backend:9000;
    ...

    scgi_store        on;
    scgi_store_access user:rw group:rw all:r;
    scgi_temp_path    /data/temp;

    alias             /data/www/;
}
```

<a id="index-42"></a>

<a id="scgi-store-access"></a>

### scgi_store_access

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_store_access` users:permissions ...;   |
|------------------------------------------------------------------------------------------|----------------------------------------------|
| Default                                                                                  | `scgi_store_access user:rw;`                 |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                       |

Sets access permissions for newly created files and directories, e.g.:

```nginx
scgi_store_access user:rw group:rw all:r;
```

If any `group` or `all` access permissions are specified then user
permissions may be omitted:

```nginx
scgi_store_access group:rw all:r;
```

<a id="index-43"></a>

<a id="scgi-temp-file-write-size"></a>

### scgi_temp_file_write_size

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_temp_file_write_size` size;   |
|------------------------------------------------------------------------------------------|-------------------------------------|
| Default                                                                                  | `scgi_temp_file_write_size 8k|16k;` |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location              |

Limits the size of data written to a temporary file at a time, when buffering of responses from the SCGI server to temporary files is enabled. By default, size is limited by two buffers set by the [scgi_buffer_size](#scgi-buffer-size) and [scgi_buffers](#scgi-buffers) directives. The maximum size of a temporary file is set by the [scgi_max_temp_file_size](#scgi-max-temp-file-size) directive.

<a id="index-44"></a>

<a id="scgi-temp-path"></a>

### scgi_temp_path

| [Syntax](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)   | `scgi_temp_path` path [level1 [level2 [level3]]]\`;                                                                                                                       |
|------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Default                                                                                  | `scgi_temp_path scgi_temp;`<br/>(the path depends on the `--http-scgi-temp-path` [build option](https://en.angie.software//angie/docs/installation/sourcebuild.md#paths)) |
| [Context](https://en.angie.software//angie/docs/configuration/configfile.md#configfile)  | http, server, location                                                                                                                                                    |

Defines a directory for storing temporary files with data received from SCGI servers. Up to three-level subdirectory hierarchy can be used underneath the specified directory. For example, in the following configuration

```nginx
scgi_temp_path /spool/angie/scgi_temp 1 2;
```

a temporary file might look like this:

```nginx
/spool/angie/scgi_temp/7/45/00000123457
```

See also the `use_temp_path` parameter of the [scgi_cache_path](#scgi-cache-path) directive.