traefik/docs/content/observability/access-logs.md

Access Logs

Who Calls Whom? {.subtitle}

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

Configuration Examples

??? example "Enabling Access Logs"

```toml
[accessLog]
```

Configuration Options

filePath

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

in the Common Log Format (CLF), extended with additional fields.

format

By default, logs are written using the Common Log Format (CLF). To write logs in JSON, use json in the format option.

!!! note "Common Log Format"

CLF - Common Log Format

```html
<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.

??? example "Configuring a buffer of 100 lines"

```toml
[accessLog]
filePath = "/path/to/access.log"
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

??? example "Configuring Multiple Filters"

```toml
[accessLog]
filePath = "/path/to/access.log"
format = "json"

  [accessLog.filters]    
    statusCodes = ["200", "300-302"]
    retryAttempts = true
    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"

??? example "Limiting the Logs to Specific Fields"

```toml
[accessLog]
    filePath = "/path/to/access.log"
    format = "json"
    
    [accessLog.filters]
        statusCodes = ["200", "300-302"]

    [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"
```

??? list "Available Fields"

```ini
StartUTC
StartLocal
Duration
FrontendName
BackendName
BackendURL
BackendAddr
ClientAddr
ClientHost
ClientPort
ClientUsername
RequestAddr
RequestHost
RequestPort
RequestMethod
RequestPath
RequestProtocol
RequestLine
RequestContentSize
OriginDuration
OriginContentSize
OriginStatus
OriginStatusLine
DownstreamStatus
DownstreamStatusLine
DownstreamContentSize
RequestCount
GzipRatio
Overhead
RetryAttempts
```

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.

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