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Access Logs

Who Calls Whom?

By default, logs are written to stdout, in text format.

Configuration

To enable the access logs:

[accessLog]
accessLog: {}
--accesslog=true

filePath

By default access logs are written to the standard output. To write the logs into a log file, use the filePath option.

format

By default, logs are written using the Common Log Format (CLF). To write logs in JSON, use json in the format option. If the given format is unsupported, the default (CLF) is used instead.

Common Log Format

<remote_IP_address> - <client_user_name_if_available> [<timestamp>] "<request_method> <request_path> <request_protocol>" <origin_server_HTTP_status> <origin_server_content_size> "<request_referrer>" "<request_user_agent>" <number_of_requests_received_since_Traefik_started> "<Traefik_frontend_name>" "<Traefik_backend_URL>" <request_duration_in_ms>ms 

bufferingSize

To write the logs in an asynchronous fashion, specify a bufferingSize option. This option represents the number of log lines Traefik will keep in memory before writing them to the selected output. In some cases, this option can greatly help performances.

# Configuring a buffer of 100 lines
[accessLog]
  filePath = "/path/to/access.log"
  bufferingSize = 100
# Configuring a buffer of 100 lines
accessLog:
  filePath: "/path/to/access.log"
  bufferingSize: 100
# Configuring a buffer of 100 lines
--accesslog=true
--accesslog.filepath="/path/to/access.log"
--accesslog.bufferingsize=100

Filtering

To filter logs, you can specify a set of filters which are logically "OR-connected". Thus, specifying multiple filters will keep more access logs than specifying only one.

The available filters are:

  • statusCodes, to limit the access logs to requests with a status codes in the specified range
  • retryAttempts, to keep the access logs when at least one retry has happened
  • minDuration, to keep access logs when requests take longer than the specified duration
# Configuring Multiple Filters
[accessLog]
  filePath = "/path/to/access.log"
  format = "json"

  [accessLog.filters]    
    statusCodes = ["200", "300-302"]
    retryAttempts = true
    minDuration = "10ms"
# Configuring Multiple Filters
accessLog:
  filePath: "/path/to/access.log"
  format: json
  filters:    
    statusCodes:
      - "200"
      - "300-302"
    retryAttempts: true
    minDuration: "10ms"
# Configuring Multiple Filters
--accesslog=true
--accesslog.filepath="/path/to/access.log"
--accesslog.format="json"
--accesslog.filters.statuscodes="200, 300-302"
--accesslog.filters.retryattempts
--accesslog.filters.minduration="10ms"

Limiting the Fields

You can decide to limit the logged fields/headers to a given list with the fields.names and fields.header options

Each field can be set to:

  • keep to keep the value
  • drop to drop the value
  • redact to replace the value with "redacted"

The defaultMode for fields.header is drop.

# Limiting the Logs to Specific Fields
[accessLog]
  filePath = "/path/to/access.log"
  format = "json"

  [accessLog.fields]
    defaultMode = "keep"

    [accessLog.fields.names]
      "ClientUsername" = "drop"

    [accessLog.fields.headers]
      defaultMode = "keep"

      [accessLog.fields.headers.names]
        "User-Agent" = "redact"
        "Authorization" = "drop"
        "Content-Type" = "keep"
# Limiting the Logs to Specific Fields
accessLog:
  filePath: "/path/to/access.log"
  format: json
  fields:
    defaultMode: keep
    names:
      ClientUsername: drop
    headers:
      defaultMode: keep
      names:
          User-Agent: redact
          Authorization: drop
          Content-Type: keep
# Limiting the Logs to Specific Fields
--accesslog=true
--accesslog.filepath="/path/to/access.log"
--accesslog.format="json"
--accesslog.fields.defaultmode="keep"
--accesslog.fields.names.ClientUsername="drop"
--accesslog.fields.headers.defaultmode="keep"
--accesslog.fields.headers.names.User-Agent="redact"
--accesslog.fields.headers.names.Authorization="drop"
--accesslog.fields.headers.names.Content-Type="keep"
Available Fields
Field Description
StartUTC The time at which request processing started.
StartLocal The local time at which request processing started.
Duration The total time taken (in nanoseconds) by processing the response, including the origin server's time but not the log writing time.
FrontendName The name of the Traefik frontend.
BackendName The name of the Traefik backend.
BackendURL The URL of the Traefik backend.
BackendAddr The IP:port of the Traefik backend (extracted from BackendURL)
ClientAddr The remote address in its original form (usually IP:port).
ClientHost The remote IP address from which the client request was received.
ClientPort The remote TCP port from which the client request was received.
ClientUsername The username provided in the URL, if present.
RequestAddr The HTTP Host header (usually IP:port). This is treated as not a header by the Go API.
RequestHost The HTTP Host server name (not including port).
RequestPort The TCP port from the HTTP Host.
RequestMethod The HTTP method.
RequestPath The HTTP request URI, not including the scheme, host or port.
RequestProtocol The version of HTTP requested.
RequestLine RequestMethod + RequestPath + RequestProtocol
RequestContentSize The number of bytes in the request entity (a.k.a. body) sent by the client.
OriginDuration The time taken by the origin server ('upstream') to return its response.
OriginContentSize The content length specified by the origin server, or 0 if unspecified.
OriginStatus The HTTP status code returned by the origin server. If the request was handled by this Traefik instance (e.g. with a redirect), then this value will be absent.
OriginStatusLine OriginStatus + Status code explanation
DownstreamStatus The HTTP status code returned to the client.
DownstreamStatusLine DownstreamStatus + Status code explanation
DownstreamContentSize The number of bytes in the response entity returned to the client. This is in addition to the "Content-Length" header, which may be present in the origin response.
RequestCount The number of requests received since the Traefik instance started.
GzipRatio The response body compression ratio achieved.
Overhead The processing time overhead caused by Traefik.
RetryAttempts The amount of attempts the request was retried.

Log Rotation

Traefik will close and reopen its log files, assuming they're configured, on receipt of a USR1 signal. This allows the logs to be rotated and processed by an external program, such as logrotate.

Warning

This does not work on Windows due to the lack of USR signals.