Varnish HTTP Cache

The Varnish integration collects cache and session metrics. It monitors the number of objects entering and exiting the cache, as well as the number of sessions and backend connections. The integration also collects Varnish logs and parses them into a standardized JSON payload.

For more information about Varnish, see the Varnish HTTP Cache documentation.

Prerequisites

To collect Varnish telemetry, you must install the Ops Agent:

  • For metrics, install version 2.15.0 or higher.
  • For logs, install version 2.16.0 or higher.

This integration supports Varnish versions 6.x and 7.0.x.

Configure your Varnish instance

The Varnish logging processor processes logs using varnishncsa. Varnish can enable varnishncsa logging by following this guide, depending on the operating system.

By default, logs are written to /var/log/varnish/varnishncsa.log. If you choose another destination, you must update the receiver configuration. Logs are expected to be in the default format, and a log rotation should be set up.

Configure the Ops Agent for Varnish

Following the guide to configure the Ops Agent, add the required elements to collect telemetry from Varnish instances, and restart the agent.

Example configuration

The following command creates the configuration to collect and ingest telemetry for Varnish and restarts the Ops Agent on Linux.

# Configures Ops Agent to collect telemetry from the app and restart Ops Agent.

set -e

sudo tee /etc/google-cloud-ops-agent/config.yaml > /dev/null << EOF
metrics:
  receivers:
    varnish:
      type: varnish
  service:
    pipelines:
      varnish:
        receivers:
          - varnish
logging:
  receivers:
    varnish:
      type: varnish
  service:
    pipelines:
      varnish:
        receivers:
          - varnish

EOF

sudo service google-cloud-ops-agent restart
sleep 30

Configure logs collection

To ingest logs from Varnish, you must create receivers for the logs that Varnish produces and then create a pipeline for the new receivers.

To configure a receiver for your varnish logs, specify the following fields:

Field Default Description
exclude_paths A list of filesystem path patterns to exclude from the set matched by include_paths.
include_paths [/var/log/varnish/varnishncsa.log] A varnishncsa default log path to read by tailing each file.
type This value must be varnish.
record_log_file_path false If set to true, then the path to the specific file from which the log record was obtained appears in the output log entry as the value of the agent.googleapis.com/log_file_path label. When using a wildcard, only the path of the file from which the record was obtained is recorded.
wildcard_refresh_interval 60s The interval at which wildcard file paths in include_paths are refreshed. Given as a time duration, for example, 30s or 2m. This property might be useful under high logging throughputs where log files are rotated faster than the default interval.

What is logged

The logName is derived from the receiver IDs specified in the configuration. Detailed fields inside the LogEntry are as follows.

varnish logs contain the following fields in the LogEntry:

Field Type Description
httpRequest.protocol string Protocol used for the request
httpRequest.referer string Contents of the Referer header
httpRequest.remoteIp string The IP address (IPv4 or IPv6) of the client that issued the HTTP request
httpRequest.requestMethod string HTTP method
httpRequest.requestUrl string Request URL (typically just the path part of the URL
httpRequest.responseSize string Response size
httpRequest.status string HTTP status code
httpRequest.userAgent string Contents of the User-Agent header
jsonPayload.host string Contents of the Host header
jsonPayload.user string Authenticated username for the request

Configure metrics collection

To ingest metrics from Varnish, you must create receivers for the metrics that Varnish produces and then create a pipeline for the new receivers.

To configure a receiver for your varnish metrics, specify the following fields:

Field Default Description
cache_dir This specifies the cache dir instance name to use when collecting metrics. If not specified, defaults to the host.
collection_interval 60s A time.Duration value, such as 30s or 5m.
exec_dir The directory where the varnishadm and varnishstat executables are located. If not provided, the user's PATH setting is used.
type This value must be varnish.

What is monitored

The following table provides the list of metrics that the Ops Agent collects from the Varnish instance.

Metric type 
Kind, Type
Monitored resources
Labels
workload.googleapis.com/varnish.backend.connection.count
CUMULATIVEINT64
gce_instance
kind
workload.googleapis.com/varnish.backend.request.count
CUMULATIVEINT64
gce_instance
 
workload.googleapis.com/varnish.cache.operation.count
CUMULATIVEINT64
gce_instance
operation
workload.googleapis.com/varnish.client.request.count
CUMULATIVEINT64
gce_instance
state
workload.googleapis.com/varnish.client.request.error.count
CUMULATIVEINT64
gce_instance
status_code
workload.googleapis.com/varnish.object.count
GAUGEINT64
gce_instance
 
workload.googleapis.com/varnish.object.expired
CUMULATIVEINT64
gce_instance
 
workload.googleapis.com/varnish.object.moved
CUMULATIVEINT64
gce_instance
 
workload.googleapis.com/varnish.object.nuked
CUMULATIVEINT64
gce_instance
 
workload.googleapis.com/varnish.session.count
CUMULATIVEINT64
gce_instance
kind
workload.googleapis.com/varnish.thread.operation.count
CUMULATIVEINT64
gce_instance
operation

Sample dashboard

To view your Varnish metrics, you must have a chart or dashboard configured. Cloud Monitoring provides a library of sample dashboards for integrations, which contain preconfigured charts. For information about installing these dashboards, see Installing sample dashboards.

Verify the configuration

This section describes how to verify that you correctly configured the Varnish receiver. It might take one or two minutes for the Ops Agent to begin collecting telemetry.

To verify that the logs are ingested, go to the Logs Explorer and run the following query to view the Varnish logs:

resource.type="gce_instance"
logName=("projects/PROJECT_ID/logs/varnish")

To verify that the metrics are ingested, go to Metrics Explorer and run the following query in the MQL tab.

fetch gce_instance
| metric 'workload.googleapis.com/varnish.backend.connection.count'
| every 1m

What's next

For a walkthrough on how to use Ansible to install the Ops Agent, configure a third-party application, and install a sample dashboard, see the Install the Ops Agent to troubleshoot third-party applications video.