src/go/plugin/go.d/modules/varnish/integrations/varnish.md
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# Varnish
<img src="https://netdata.cloud/img/varnish.svg" width="150"/>
Plugin: go.d.plugin
Module: varnish
<img src="https://img.shields.io/badge/maintained%20by-Netdata-%2300ab44" />
## Overview
This collector monitors Varnish instances, supporting both the open-source Varnish-Cache and the commercial Varnish-Plus.
It tracks key performance metrics, along with detailed statistics for Backends (VBE) and Storages (SMF, SMA, MSE).
It relies on the [`varnishstat`](https://varnish-cache.org/docs/trunk/reference/varnishstat.html) CLI tool but avoids directly executing the binary.
Instead, it utilizes `ndsudo`, a Netdata helper specifically designed to run privileged commands securely within the Netdata environment.
This approach eliminates the need to use `sudo`, improving security and potentially simplifying permission management.
This collector is supported on all platforms.
This collector supports collecting metrics from multiple instances of this integration, including remote instances.
### Default Behavior
#### Auto-Detection
Automatically detects and monitors Varnish instances running on the host or inside Docker containers.
#### Limits
The default configuration for this integration does not impose any limits on data collection.
#### Performance Impact
The default configuration for this integration is not expected to impose a significant performance impact on the system.
## Metrics
Metrics grouped by *scope*.
The scope defines the instance that the metric belongs to. An instance is uniquely identified by a set of labels.
### Per Varnish instance
These metrics refer to the entire monitored application.
This scope has no labels.
Metrics:
| Metric | Dimensions | Unit |
|:------|:----------|:----|
| varnish.client_session_connections | accepted, dropped | connections/s |
| varnish.client_requests | received | requests/s |
| varnish.cache_hit_ratio_total | hit, miss, hitpass, hitmiss | percent |
| varnish.cache_hit_ratio_delta | hit, miss, hitpass, hitmiss | percent |
| varnish.cache_expired_objects | expired | objects/s |
| varnish.cache_lru_activity | nuked, moved | objects/s |
| varnish.threads | threads | threads |
| varnish.thread_management_activity | created, failed, destroyed, limited | threads/s |
| varnish.thread_queue_len | queue_length | threads |
| varnish.backends_requests | sent | requests/s |
| varnish.esi_parsing_issues | errors, warnings | issues/s |
| varnish.mgmt_process_uptime | uptime | seconds |
| varnish.child_process_uptime | uptime | seconds |
### Per Backend
These metrics refer to the Backend (VBE).
This scope has no labels.
Metrics:
| Metric | Dimensions | Unit |
|:------|:----------|:----|
| varnish.backend_data_transfer | req_header, req_body, resp_header, resp_body | bytes/s |
### Per Storage
These metrics refer to the Storage (SMA, SMF, MSE).
This scope has no labels.
Metrics:
| Metric | Dimensions | Unit |
|:------|:----------|:----|
| varnish.storage_space_usage | free, used | bytes |
| varnish.storage_allocated_objects | allocated | objects |
## Alerts
There are no alerts configured by default for this integration.
## Setup
### Prerequisites
No action required.
### Configuration
#### File
The configuration file name for this integration is `go.d/varnish.conf`.
You can edit the configuration file using the `edit-config` script from the
Netdata [config directory](/docs/netdata-agent/configuration/README.md#the-netdata-config-directory).
```bash
cd /etc/netdata 2>/dev/null || cd /opt/netdata/etc/netdata
sudo ./edit-config go.d/varnish.conf
```
#### Options
The following options can be defined globally: update_every.
<details open><summary>Config options</summary>
| Name | Description | Default | Required |
|:----|:-----------|:-------|:--------:|
| update_every | Data collection frequency. | 10 | no |
| timeout | Timeout for executing the binary, specified in seconds. | 2 | no |
| instance_name | Specifies the name of the Varnish instance to collect metrics from. This corresponds to the `-n` argument used with the [varnishstat](https://varnish-cache.org/docs/trunk/reference/varnishstat.html) command. | | no |
| docker_container | Specifies the name of the Docker container where the Varnish instance is running. If set, the `varnishstat` command will be executed within this container. | | no |
</details>
#### Examples
##### Custom update_every
Allows you to override the default data collection interval.
```yaml
jobs:
- name: varnish
update_every: 5
```
## Troubleshooting
### Debug Mode
**Important**: Debug mode is not supported for data collection jobs created via the UI using the Dyncfg feature.
To troubleshoot issues with the `varnish` collector, run the `go.d.plugin` with the debug option enabled. The output
should give you clues as to why the collector isn't working.
- Navigate to the `plugins.d` directory, usually at `/usr/libexec/netdata/plugins.d/`. If that's not the case on
your system, open `netdata.conf` and look for the `plugins` setting under `[directories]`.
```bash
cd /usr/libexec/netdata/plugins.d/
```
- Switch to the `netdata` user.
```bash
sudo -u netdata -s
```
- Run the `go.d.plugin` to debug the collector:
```bash
./go.d.plugin -d -m varnish
```
### Getting Logs
If you're encountering problems with the `varnish` collector, follow these steps to retrieve logs and identify potential issues:
- **Run the command** specific to your system (systemd, non-systemd, or Docker container).
- **Examine the output** for any warnings or error messages that might indicate issues. These messages should provide clues about the root cause of the problem.
#### System with systemd
Use the following command to view logs generated since the last Netdata service restart:
```bash
journalctl _SYSTEMD_INVOCATION_ID="$(systemctl show --value --property=InvocationID netdata)" --namespace=netdata --grep varnish
```
#### System without systemd
Locate the collector log file, typically at `/var/log/netdata/collector.log`, and use `grep` to filter for collector's name:
```bash
grep varnish /var/log/netdata/collector.log
```
**Note**: This method shows logs from all restarts. Focus on the **latest entries** for troubleshooting current issues.
#### Docker Container
If your Netdata runs in a Docker container named "netdata" (replace if different), use this command:
```bash
docker logs netdata 2>&1 | grep varnish
```