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

# Create a back up of the existing file so existing configurations are not lost.
sudo cp /etc/google-cloud-ops-agent/config.yaml /etc/google-cloud-ops-agent/config.yaml.bak

# Configure the Ops Agent.
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`
`CUMULATIVE`, `INT64` gce_instance	`kind`
`workload.googleapis.com/varnish.backend.request.count`
`CUMULATIVE`, `INT64` gce_instance
`workload.googleapis.com/varnish.cache.operation.count`
`CUMULATIVE`, `INT64` gce_instance	`operation`
`workload.googleapis.com/varnish.client.request.count`
`CUMULATIVE`, `INT64` gce_instance	`state`
`workload.googleapis.com/varnish.client.request.error.count`
`CUMULATIVE`, `INT64` gce_instance	`status_code`
`workload.googleapis.com/varnish.object.count`
`GAUGE`, `INT64` gce_instance
`workload.googleapis.com/varnish.object.expired`
`CUMULATIVE`, `INT64` gce_instance
`workload.googleapis.com/varnish.object.moved`
`CUMULATIVE`, `INT64` gce_instance
`workload.googleapis.com/varnish.object.nuked`
`CUMULATIVE`, `INT64` gce_instance
`workload.googleapis.com/varnish.session.count`
`CUMULATIVE`, `INT64` gce_instance	`kind`
`workload.googleapis.com/varnish.thread.operation.count`
`CUMULATIVE`, `INT64` 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.