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 commands create the configuration to collect and ingest telemetry for Varnish and restart the Ops Agent.

# 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 a receiver for the logs that Varnish produces and then create a pipeline for the new receiver.

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.
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.
type This value must be varnish.
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.

The varnish logs contain the following fields in the LogEntry:

Field Type Description
httpRequest object See HttpRequest
jsonPayload.host string Contents of the Host header
jsonPayload.user string Authenticated username for the request
severity string (LogSeverity) Log entry level (translated).

Configure metrics collection

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

This receiver does not support the use of multiple instances in the configuration, for example, to monitor multiple endpoints. All such instances write to the same time series, and Cloud Monitoring has no way to distinguish among them.

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, relies on the executables being in the user's PATH.
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

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 Varnish logs are being sent to Cloud Logging, do the following:

  1. In the Google Cloud console, go to the Logs Explorer page:

    Go to Logs Explorer

    If you use the search bar to find this page, then select the result whose subheading is Logging.

  2. Enter the following query in the editor, and then click Run query: 
    resource.type="gce_instance"
log_id("varnish")

To verify that Varnish metrics are being sent to Cloud Monitoring, do the following:

  1. In the Google Cloud console, go to the  Metrics explorer page:

    Go to Metrics explorer

    If you use the search bar to find this page, then select the result whose subheading is Monitoring.

  2. In the toolbar of the query-builder pane, select the button whose name is either  MQL or  PromQL.
  3. Verify that MQL is selected in the Language toggle. The language toggle is in the same toolbar that lets you format your query.
  4. Enter the following query in the editor, and then click Run query: 
    fetch gce_instance
| metric 'workload.googleapis.com/varnish.backend.connection.count'
| every 1m

View dashboard

To view your Varnish metrics, you must have a chart or dashboard configured. The Varnish integration includes one or more dashboards for you. Any dashboards are automatically installed after you configure the integration and the Ops Agent has begun collecting metric data.

You can also view static previews of dashboards without installing the integration.

To view an installed dashboard, do the following:

  1. In the Google Cloud console, go to the  Dashboards page:

    Go to Dashboards

    If you use the search bar to find this page, then select the result whose subheading is Monitoring.

  2. Select the Dashboard List tab, and then choose the Integrations category.
  3. Click the name of the dashboard you want to view.

If you have configured an integration but the dashboard has not been installed, then check that the Ops Agent is running. When there is no metric data for a chart in the dashboard, installation of the dashboard fails. After the Ops Agent begins collecting metrics, the dashboard is installed for you.

To view a static preview of the dashboard, do the following:

  1. In the Google Cloud console, go to the  Integrations page:

    Go to Integrations

    If you use the search bar to find this page, then select the result whose subheading is Monitoring.

  2. Click the Compute Engine deployment-platform filter.
  3. Locate the entry for Varnish and click View Details.
  4. Select the Dashboards tab to see a static preview. If the dashboard is installed, then you can navigate to it by clicking View dashboard.

For more information about dashboards in Cloud Monitoring, see Dashboards and charts.

For more information about using the Integrations page, see Manage integrations.

Install alerting policies

Alerting policies instruct Cloud Monitoring to notify you when specified conditions occur. The Varnish integration includes one or more alerting policies for you to use. You can view and install these alerting policies from the Integrations page in Monitoring.

To view the descriptions of available alerting policies and install them, do the following:

  1. In the Google Cloud console, go to the  Integrations page:

    Go to Integrations

    If you use the search bar to find this page, then select the result whose subheading is Monitoring.

  2. Locate the entry for Varnish and click View Details.
  3. Select the Alerts tab. This tab provides descriptions of available alerting policies and provides an interface for installing them.
  4. Install alerting policies. Alerting policies need to know where to send notifications that the alert has been triggered, so they require information from you for installation. To install alerting policies, do the following:
    1. From the list of available alerting policies, select those that you want to install.

    2. In the Configure notifications section, select one or more notification channels. You have the option to disable the use of notification channels, but if you do, then your alerting policies fire silently. You can check their status in Monitoring, but you receive no notifications.

      For more information about notification channels, see Manage notification channels.

    3. Click Create Policies.

For more information about alerting policies in Cloud Monitoring, see Introduction to alerting.

For more information about using the Integrations page, see Manage integrations.

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.