View log messages for callouts

This page describes logging for Application Load Balancer callouts.

For a product overview, see Service Extensions overview.

Enable logging on a backend service

You can enable logging for Application Load Balancer callouts while creating the service by enabling logging on the backend service that's the target of a request (and not on the backend service associated with the extension).

Note: Logging settings, if any, on the callout backend service, which is the backend service pointing to the callout, are ignored.

To enable logging for the target backend service for a regional internal Application Load Balancer, use the gcloud compute backend-services update command.

gcloud compute backend-services update BACKEND_SERVICE \
    --enable-logging \
    --logging-sample-rate=RATE \
    --region=REGION \
    --logging-optional=LOGGING_OPTIONAL_MODE \
    --logging-optional-fields=OPTIONAL_FIELDS

Replace the following:

• BACKEND_SERVICE: the name of the backend service
• RATE: a value from 0.0 through 1.0, where 0.0 means no requests are logged and 1.0 means 100% of requests are logged. The default value is 1.0. This setting is effective only when used with the enable-logging parameter. When you omit enable-logging, logging is disabled.
• REGION: the region of the backend

• LOGGING_OPTIONAL_MODE: enables logging for optional fields in one of these modes:

  • INCLUDE_ALL_OPTIONAL includes all optional fields.
  • EXCLUDE_ALL_OPTIONAL (default) excludes all optional fields.
  • CUSTOM includes a custom list of optional fields.
• OPTIONAL_FIELDS: a comma-separated list of optional fields when you select the CUSTOM mode

For more information, see the "Monitor and troubleshoot" pages of the Application Load Balancer documentation, such as Internal Application Load Balancer logging and monitoring.

After you enable logging on the backend service, HTTP or HTTPS requests are logged by using Cloud Logging logs requests.

To view logs, in the Google Cloud console, go to the the Logs Explorer page.

Log messages for a backend service

In general, Application Load Balancer log entries contain information that is useful for monitoring and debugging your HTTP or HTTPS traffic. Log entries contain the following types of information:

• Information shown in most Google Cloud logs, such as severity, project ID, project number, and timestamp as described in the LogEntry log.
• HttpRequest log fields.

Request logs for HTTP and HTTPS load balancers contain a service_extension_info object in the load balancer log entry JSON payload with the following information:

Field	Type	Description
backend_target_name	string	Name of the backend target of the extension
backend_target_type	string	Type of the backend target
chain	string	Name of the extension chain within the service extension resource that matches the request
extension	string	Name of the extension within the extension chain
per_processing_request_info	array	Information about each ProcessingRequest message that's sent to the ext_proc server
per_processing_request_info[].event_type	enum	The event type of ProcessingRequest. Can be one of these: REQUEST_HEADERS, REQUEST_BODY, RESPONSE_HEADERS, or RESPONSE_BODY.
per_processing_request_info[].grpc_status	enum	The most recent status on the gRPC stream. For more information, see gRPC status codes.
per_processing_request_info[].latency	duration	The duration from when the first byte of the ProcessingRequest message is sent to the extension to when the last byte of the ProcessingResponse message is received.
resource	string	Name of the extension resource

What's next

• Monitor callout backend services