# Traffic Log

With TrafficLog policy you can easily set up access logs on every data-plane in a Mesh.

Configuring access logs in Kuma is a 3-step process:

# Add a logging backend

A logging backend is essentially a sink for access logs.

In the current release of Kuma, a logging backend can be either a file or a TCP log collector, such as Logstash.

    # Add a TrafficLog resource

    You need to create a TrafficLog policy to select a subset of traffic and forward its access logs into one of the logging backends configured for that Mesh.

      When backend field of a TrafficLog policy is omitted, the logs will be forwarded into the defaultBackend of that Mesh.

      # Log aggregation and visualisation

      Kuma is presenting a simple solution to aggregate the logs of your containers and the access logs of your data-planes.

        Nice to have

        Having your Logs and Traces in the same visualisation tool can come really handy. By adding the traceId in your app logs you can visualize your logs and the related Jaeger traces. To learn more about it go read this article (opens new window).

        To set up tracing see the traffic-trace policy.

        You can also forward the access logs to a collector (such as logstash) that can further transmit them into systems like Splunk, ELK and Datadog.

        # Access Log Format

        Kuma gives you full control over the format of access logs.

        The shape of a single log record is defined by a template string that uses command operators (opens new window) to extract and format data about a TCP connection or an HTTP request.



        where %START_TIME% and %KUMA_SOURCE_SERVICE% are examples of available command operators.

        A complete set of supported command operators consists of:

        1. All command operators supported by Envoy (opens new window)
        2. Command operators unique to Kuma

        The latter include:

        Command Operator Description
        %KUMA_MESH% name of the mesh in which traffic is flowing
        %KUMA_SOURCE_SERVICE% name of a service that is the source of traffic
        %KUMA_DESTINATION_SERVICE% name of a service that is the destination of traffic
        %KUMA_SOURCE_ADDRESS_WITHOUT_PORT% address of a Dataplane that is the source of traffic

        # Access Logs for TCP and HTTP traffic

        All access log command operators are valid to use with both TCP and HTTP traffic.

        If a command operator is specific to HTTP traffic, such as %REQ(X?Y):Z% or %RESP(X?Y):Z%, it will be replaced by a symbol "-" in case of TCP traffic.

        Internally, Kuma determines traffic protocol based on the value of kuma.io/protocol tag on the inbound interface of a destination Dataplane.

        The default format string for TCP traffic is:


        The default format string for HTTP traffic is:


        To provide different format for TCP and HTTP logging you can define two separate logging backends with the same address and different format. Then define two TrafficLog entity, one for TCP and one for HTTP with kuma.io/protocol: http selector.

        # Access Logs in JSON format

        If you need an access log with entries in JSON format, you have to provide a template string that is a valid JSON object, e.g.

          "start_time":          "%START_TIME%",
          "source":              "%KUMA_SOURCE_SERVICE%",
          "destination":         "%KUMA_DESTINATION_SERVICE%",
          "source_address":      "%KUMA_SOURCE_ADDRESS_WITHOUT_PORT%",
          "destination_address": "%UPSTREAM_HOST%",
          "duration_millis":     "%DURATION%",
          "bytes_received":      "%BYTES_RECEIVED%",
          "bytes_sent":          "%BYTES_SENT%"

        To use it with Logstash, use json_lines codec and make sure your JSON is formatted into one line.

        # Logging external services

        When running Kuma on Kubernetes you can also log the traffic to external services. To do it, the matched TrafficPermission destination section has to have wildcard * value. In such case %KUMA_DESTINATION_SERVICE% will have value external and %UPSTREAM_HOST% will have an IP of the service.

        # Matching

        TrafficLog is an Outbound Connection Policy. The only supported value for destinations.match is kuma.io/service.

        Last Updated: 6/2/2022, 9:41:22 AM