Varnish Cache¶

The varnish probe monitors Varnish Cache via varnishstat -j -1, reporting cache hit/miss rates, client request throughput, backend connections, thread lifecycle, session counts, object counts and memory allocation.

Quick start¶

probes:
  - name: varnish
    type: varnish

No parameters are required for a single-instance Varnish installation. The probe runs varnishstat as the agent user — ensure it has access to the Varnish shared memory file.

Parameters¶

Parameter	Default	Description
`instance_name`	—	Varnish instance name (`-n` flag for `varnishstat`). Required when multiple Varnish instances run on the same host
`varnishstat_path`	`varnishstat`	Path to the `varnishstat` binary if not in PATH

Metrics¶

Metric	Unit	Description
`senhub.varnish.up`	1	1 when `varnishstat` completed successfully
`varnish.cache.operations`	{operation}	Cache lookups by result (hit/miss/hitpass), tagged with `result`
`varnish.client.requests.received`	{request}	Client requests received
`varnish.backend.connections.failed`	{connection}	Failed backend connection attempts
`varnish.threads.created`	{thread}	Threads created since start
`varnish.threads.failed`	{thread}	Failed thread creation attempts
`varnish.threads.destroyed`	{thread}	Threads destroyed
`varnish.sessions.accepted`	{session}	Client sessions accepted
`varnish.sessions.dropped`	{session}	Sessions dropped due to overflow
`varnish.objects.stored`	{object}	Objects currently stored in cache
`varnish.memory.allocated`	By	Memory allocated for cache storage

Operational notes¶

The varnishstat command reads from the Varnish shared memory log; the user running the agent must be in the varnish group or run as root.
instance_name maps to varnishstat -n <name> and is needed when you run multiple Varnish instances (different working directories via varnishd -n).
Metric names align with the OpenTelemetry Collector contrib varnishreceiver where equivalents exist.