HTTP Access Logging

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Linkerd proxies can be configured to generate an HTTP access log that records all HTTP requests that transit the proxy.

The config.linkerd.io/access-log annotation is used to enable proxy HTTP access logging. Adding this annotation to a namespace or workload configures the proxy injector to set an environment variable in the proxy container that configures access logging.

HTTP access logging is disabled by default because it has a performance impact, compared to proxies without access logging enabled. Enabling access logging may increase tail latency and CPU consumption under load. The severity of this performance cost may vary depending on the traffic being proxied, and may be acceptable in some environments.

Note

The proxy’s HTTP access log is distinct from proxy debug logging, which is configured separately. See the documentation on modifying the proxy log level for details on configuring the proxy’s debug logging.

Access Log Formats

The value of the config.linkerd.io/access-log annotation determines the format of HTTP access log entries, and can be either “apache” or “json”.

Setting the config.linkerd.io/access-log: "apache" annotation configures the proxy to emit HTTP access logs in the Apache Common Log Format. For example:

10.42.0.63:51160 traffic.booksapp.serviceaccount.identity.linkerd.cluster.local - [2022-08-23T20:28:20.071809491Z] "GET http://webapp:7000/ HTTP/2.0" 200
10.42.0.63:51160 traffic.booksapp.serviceaccount.identity.linkerd.cluster.local - [2022-08-23T20:28:20.187706137Z] "POST http://webapp:7000/authors HTTP/2.0" 303
10.42.0.63:51160 traffic.booksapp.serviceaccount.identity.linkerd.cluster.local - [2022-08-23T20:28:20.301798187Z] "GET http://webapp:7000/authors/104 HTTP/2.0" 200
10.42.0.63:51160 traffic.booksapp.serviceaccount.identity.linkerd.cluster.local - [2022-08-23T20:28:20.409177224Z] "POST http://webapp:7000/books HTTP/2.0" 303
10.42.0.1:43682 - - [2022-08-23T20:28:23.049685223Z] "GET /ping HTTP/1.1" 200

Setting the config.linkerd.io/access-log: json annotation configures the proxy to emit access logs in a JSON format. For example:

{"client.addr":"10.42.0.70:32996","client.id":"traffic.booksapp.serviceaccount.identity.linkerd.cluster.local","host":"webapp:7000","method":"GET","processing_ns":"39826","request_bytes":"","response_bytes":"19627","status":200,"timestamp":"2022-08-23T20:33:42.321746212Z","total_ns":"14441135","trace_id":"","uri":"http://webapp:7000/","user_agent":"Go-http-client/1.1","version":"HTTP/2.0"}
{"client.addr":"10.42.0.70:32996","client.id":"traffic.booksapp.serviceaccount.identity.linkerd.cluster.local","host":"webapp:7000","method":"POST","processing_ns":"30036","request_bytes":"33","response_bytes":"0","status":303,"timestamp":"2022-08-23T20:33:42.436964052Z","total_ns":"14122403","trace_id":"","uri":"http://webapp:7000/authors","user_agent":"Go-http-client/1.1","version":"HTTP/2.0"}
{"client.addr":"10.42.0.70:32996","client.id":"traffic.booksapp.serviceaccount.identity.linkerd.cluster.local","host":"webapp:7000","method":"GET","processing_ns":"38664","request_bytes":"","response_bytes":"2350","status":200,"timestamp":"2022-08-23T20:33:42.551768300Z","total_ns":"6998222","trace_id":"","uri":"http://webapp:7000/authors/105","user_agent":"Go-http-client/1.1","version":"HTTP/2.0"}
{"client.addr":"10.42.0.70:32996","client.id":"traffic.booksapp.serviceaccount.identity.linkerd.cluster.local","host":"webapp:7000","method":"POST","processing_ns":"42492","request_bytes":"46","response_bytes":"0","status":303,"timestamp":"2022-08-23T20:33:42.659401621Z","total_ns":"9274163","trace_id":"","uri":"http://webapp:7000/books","user_agent":"Go-http-client/1.1","version":"HTTP/2.0"}
{"client.addr":"10.42.0.1:56300","client.id":"-","host":"10.42.0.69:7000","method":"GET","processing_ns":"35848","request_bytes":"","response_bytes":"4","status":200,"timestamp":"2022-08-23T20:33:49.254262428Z","total_ns":"1416066","trace_id":"","uri":"/ping","user_agent":"kube-probe/1.24","version":"HTTP/1.1"}

Consuming Access Logs

The HTTP access log is written to the proxy container’s stderr stream, while the proxy’s standard debug logging is written to the proxy container’s stdout stream. Currently, the kubectl logs command will always output both the container’s stdout and stderr streams. However, KEP 3289 will add support for separating a container’s stdout or stderr in the kubectl logs command.