nginx / current / reference / http-ngx_http_session_log_module.html

Module ngx_http_session_log_module

The ngx_http_session_log_module module enables logging sessions (that is, aggregates of multiple HTTP requests) instead of individual HTTP requests.

This module is available as part of our commercial subscription .

Example Configuration

The following configuration sets up a session log and maps requests to sessions according to the request client address and “User-Agent” request header field:

    session_log_zone /path/to/log format=combined
                     zone=one:1m timeout=30s

    location /media/ {
        session_log one;


Syntax: session_log name | off;
session_log off;
Context: http, server, location

Enables the use of the specified session log. The special value off cancels all session_log directives inherited from the previous configuration level.

Syntax: session_log_format name string ...;
session_log_format combined "...";
Context: http

Specifies the output format of a log. The value of the $body_bytes_sent variable is aggregated across all requests in a session. The values of all other variables available for logging correspond to the first request in a session.

Syntax: session_log_zone path zone=name:size [format=format] [timeout=time] [id=id] [md5=md5] ;
Context: http

Sets the path to a log file and configures the shared memory zone that is used to store currently active sessions.

A session is considered active for as long as the time elapsed since the last request in the session does not exceed the specified timeout (by default, 30 seconds). Once a session is no longer active, it is written to the log.

The id parameter identifies the session to which a request is mapped. The id parameter is set to the hexadecimal representation of an MD5 hash (for example, obtained from a cookie using variables). If this parameter is not specified or does not represent the valid MD5 hash, nginx computes the MD5 hash from the value of the md5 parameter and creates a new session using this hash. Both the id and md5 parameters can contain variables.

The format parameter sets the custom session log format configured by the session_log_format directive. If format is not specified, the predefined “combined” format is used.

Embedded Variables

The ngx_http_session_log_module module supports two embedded variables:

current session ID;
current session ID in binary form (16 bytes).