Module ngx_stream_log_module

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Module ngx_stream_log_module

Example Configuration
Directives
access_log
log_format
open_log_file_cache

The ngx_stream_log_module module (1.11.4) writes session logs
in the specified format.

Example Configuration

log_format basic '$remote_addr [$time_local] '
'$protocol $status $bytes_sent $bytes_received '
'$session_time';

access_log /spool/logs/nginx-access.log basic buffer=32k;

Directives

Syntax:

access_log
path
format
[buffer=size]
[gzip[=level]]
[flush=time]
[if=condition];
access_log off;

Default:

access_log off;

Context:

stream, server

Sets the path, format,
and configuration for a buffered log write.
Several logs can be specified on the same configuration level.
Logging to syslog
can be configured by specifying
the “syslog:” prefix in the first parameter.
The special value off cancels all
access_log directives on the current level.

If either the buffer or gzip
parameter is used, writes to log will be buffered.

The buffer size must not exceed the size of an atomic write to a disk file.
For FreeBSD this size is unlimited.

When buffering is enabled, the data will be written to the file:

if the next log line does not fit into the buffer;

if the buffered data is older than specified by the flush
parameter;

when a worker process is re-opening log
files or is shutting down.

If the gzip parameter is used, then the buffered data will
be compressed before writing to the file.
The compression level can be set between 1 (fastest, less compression)
and 9 (slowest, best compression).
By default, the buffer size is equal to 64K bytes, and the compression level
is set to 1.
Since the data is compressed in atomic blocks, the log file can be decompressed
or read by “zcat” at any time.

Example:

access_log /path/to/log.gz basic gzip flush=5m;

For gzip compression to work, nginx must be built with the zlib library.

The file path can contain variables,
but such logs have some constraints:

the user
whose credentials are used by worker processes should
have permissions to create files in a directory with
such logs;

buffered writes do not work;

the file is opened and closed for each log write.
However, since the descriptors of frequently used files can be stored
in a cache, writing to the old file
can continue during the time specified by the open_log_file_cache
directive’s valid parameter

The if parameter enables conditional logging.
A session will not be logged if the condition evaluates to “0”
or an empty string.

Syntax:

log_format
name
[escape=default|json|none]
string ...;

Default:

—

Context:

stream

Specifies the log format, for example:

log_format proxy '$remote_addr [$time_local] '
'$protocol $status $bytes_sent $bytes_received '
'$session_time "$upstream_addr" '
'"$upstream_bytes_sent" "$upstream_bytes_received" "$upstream_connect_time"';

The escape parameter (1.11.8) allows setting
json or default characters escaping
in variables, by default, default escaping is used.
The none parameter (1.13.10) disables escaping.

For default escaping,
characters “"”, “\”,
and other characters with values less than 32 or above 126
are escaped as “\xXX”.
If the variable value is not found,
a hyphen (“-”) will be logged.

For json escaping,
all characters not allowed
in JSON strings
will be escaped:
characters “"” and
“\” are escaped as
“\"” and “\\”,
characters with values less than 32 are escaped as
“\n”,
“\r”,
“\t”,
“\b”,
“\f”, or
“\u00XX”.

Syntax:

open_log_file_cache
max=N
[inactive=time]
[min_uses=N]
[valid=time];
open_log_file_cache off;

Default:

open_log_file_cache off;

Context:

stream, server

Defines a cache that stores the file descriptors of frequently used logs
whose names contain variables.
The directive has the following parameters:

max

sets the maximum number of descriptors in a cache;
if the cache becomes full the least recently used (LRU)
descriptors are closed

inactive

sets the time after which the cached descriptor is closed
if there were no access during this time;
by default, 10 seconds

min_uses

sets the minimum number of file uses during the time
defined by the inactive parameter
to let the descriptor stay open in a cache;
by default, 1

valid

sets the time after which it should be checked that the file
still exists with the same name; by default, 60 seconds

off

disables caching

Usage example:

open_log_file_cache max=1000 inactive=20s valid=1m min_uses=2;