log-var-set: Set variables before access log writing

Debian/Ubuntu installation

These docs apply to the APT package nginx-module-log-var-set provided by the GetPageSpeed Extras repository.

1. Configure the APT repository as described in APT repository setup.
2. Install the module:

sudo apt-get update
sudo apt-get install nginx-module-log-var-set

Show suites and architectures

| Distro   | Suite             | Component   | Architectures   |
|----------|-------------------|-------------|-----------------|
| debian   | bookworm          | main        | amd64, arm64    |
| debian   | bookworm-mainline | main        | amd64, arm64    |
| debian   | trixie            | main        | amd64, arm64    |
| debian   | trixie-mainline   | main        | amd64, arm64    |
| ubuntu   | focal             | main        | amd64, arm64    |
| ubuntu   | focal-mainline    | main        | amd64, arm64    |
| ubuntu   | jammy             | main        | amd64, arm64    |
| ubuntu   | jammy-mainline    | main        | amd64, arm64    |
| ubuntu   | noble             | main        | amd64, arm64    |
| ubuntu   | noble-mainline    | main        | amd64, arm64    |

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ngx_http_log_var_set_module allows setting the variable to the given value before access log writing.

Table of Content

• Name
• Table of Content
• Status
• Synopsis
• Installation
• Directives
• log_var_set
• Author
• License

Status

This Nginx module is currently considered experimental. Issues and PRs are welcome if you encounter any problems.

Synopsis

log_format main '$remote_addr - $remote_user [$time_local] '
                    '"$request" $status $body_bytes_sent '
                    '"$http_referer" "$http_user_agent" '
                    '"$log_field1" "$log_field2"';
access_log /spool/logs/nginx-access.log;

server {
    listen 127.0.0.1:80;
    server_name localhost;

    location / {
        log_var_set $log_field1 $upstream_http_custom_header1;
        log_var_set $log_field2 $upstream_http_custom_header2;
        proxy_pass http://example.upstream.com;
    }
}

Directives

log_var_set

Syntax: log_var_set $variable value [if=condition];

Default: -

Context: http, server, location

Sets the request variable to the given value before access log writing. The value may contain variables from request or response, such as $upstream_http_*. These directives are inherited from the previous configuration level only when there is no directive for the same variable defined at the current level.