Access and Error Logs

Trickster can write per-backend HTTP access logs and error logs, with customizable formats, rotation and retention. Both logs are off by default; each is enabled by configuring its filename.

Basic Configuration

backends:
  example1:
    provider: rp
    origin_url: http://example.com/
    access_log:
      filename: /var/log/trickster/example1.access.log
      error_filename: /var/log/trickster/example1.error.log

• The access log receives one line per request handled by the backend and is written only when filename is set.
• The error log receives one line per request whose response status is at or above error_threshold (default 400) and is written only when error_filename is set. An error-logged request also appears in the access log when both are configured.
• Two backends may share a filename; they will safely share the underlying file and its rotation.
• When instance_id is set in the main config, it is inserted into log filenames just as with the application log (e.g., example1.access.1.log).

Log Format

The format option accepts either a named preset or a custom format string using Apache-style % tokens, so the well-known conventions from Apache HTTP Server, Apache Traffic Server, Lighttpd, and similar servers apply directly.

Presets

Custom Formats

    access_log:
      filename: /var/log/trickster/example1.access.log
      format: '%h %u %t "%r" %>s %b %{ms}T %{cache-status}x'

Supported tokens:

Trickster-specific values use the %{key}x extension namespace:

Missing values render as -. Values derived from the request (like headers and usernames) are backslash-escaped so they cannot corrupt the log line structure. Unknown tokens fail validation at startup.

The json preset emits these fields per line: time, client_ip, user, method, path, query, proto, status, bytes, duration_ms, host, referer, user_agent, backend, provider, path_config, cache_status, engine.

Rotation and Retention

Access and error logs are rotated and pruned automatically, using nginx/logrotate-style numbered archives (example1.access.log.1.gz is the most recent archive, .2.gz the next, and so on).

    access_log:
      filename: /var/log/trickster/example1.access.log
      rotation:
        size: 256MB   # rotate when the live file would exceed this size (default 256MB)
        interval: 1d  # also rotate when the live file is older than this (default off)
      retention:
        count: 3      # keep at most 3 archives (default 80)
        age: 7d       # also prune archives older than this (default 7d)
      compress: true  # gzip archives (default true)

• size and interval may be combined; the log rotates when either threshold is reached. Setting both to 0 disables rotation.
• Sizes accept KB, MB, GB and TB suffixes (binary multiples), or a plain byte count.
• retention.count: 0 disables count-based pruning and keeps all archives.
• Writes are buffered for up to one second or 64 KiB. A process or machine crash can lose the buffered tail; an orderly shutdown flushes it.
• Interval rotation keeps its epoch in a <filename>.rotation sidecar so a restart does not reset the interval clock.

Archives created by older Trickster releases use timestamped lumberjack names and are not included in numbered-archive retention. They form a bounded legacy set and may be removed manually after upgrading.

When upgrading from the original logging implementation, note these filename and retention changes:

• retention.count: 0 now keeps all archives; configure a positive count to bound archive retention.
• With main.instance_id enabled, filenames without a .log suffix now also include the instance ID (trickster.out becomes trickster.2.out). Update log shippers that still follow the unsuffixed filename.

The same rotation, retention and compress options are also available in the main logging: config section to control rotation of the Trickster application log, with the same defaults.

Error Log Settings

Each error_* option inherits its value from the corresponding access log option when unset:

    access_log:
      filename: /var/log/trickster/example1.access.log
      format: combined
      error_filename: /var/log/trickster/example1.error.log
      error_format: ''      # default: inherits format
      error_threshold: 400  # log responses with status >= this (default 400)
      error_rotation:       # default: inherits rotation
        size: 64MB
      error_retention:      # default: inherits retention
        count: 7
      error_compress: true  # default: inherits compress