Varnish is a web application accelerator, acting as a caching reverse proxy to speed up delivery of your HTTP content and dynamic websites by an order of magnitude.

The Librato Agent gathers internal stats helping you track the health, performance, and effectiveness of your Varnish accelerators. We use collectd’s native Varnish plugin to gather metrics from your running HAProxy instances.


The Varnish integration depends on the Librato Agent. If you haven’t already, you will first need to install the Librato Agent. Once this is complete, select the Varnish icon in the integrations catalogue.


Toggle the Enabled switch to activate the Varnish integration on your Librato account and create the preconfigured Varnish Space.


At this point your integration is complete and any Varnish metrics associated with this integration will be allowed through your Librato Agent service-side filters.

Plugin Configuration

This integration gathers metrics from a running Varnish installation using the varnishstats utility. The most useful metric classes have been enabled out of the box. Additional metric classes can be enabled in the varnish.conf configuration file. Here is our default configuration for the Varnish plugin.

LoadPlugin varnish
<Plugin "varnish">
     CollectBackend     true
     CollectCache       true
     CollectConnections true
     CollectFetch       true
     CollectObjects     true
     CollectSession     true
     CollectSHM         true
     CollectTotals      true
     CollectWorkers     true

Varnish Workspace

Visit your preconfigured Space to observe your new metrics as they stream in. You can use this Space to monitor the performance and overall health of your Varnish servers.


Varnish Metrics and tags

The varnish integration supports the following metrics and tags.

Note: All metrics are prefixed with librato.varnish..

Tag Name Description
host Host name or IP address of monitored Varnish configuration

Backend Metrics

Name Description Tags
backend.connections.failures Failed connections host
backend.connections.not-attempted Non-attempted connections host
backend.connections.recycled Recycle connectionms host
backend.connections.retries Retried connections host
backend.connections.reuses Reused connections host
backend.connections.success Successful connections host
backend.connections.too-many Too-many connection responses host
backend.connections.was-closed Was-closed responses host
backend.http_requests.requests Request counts host

Cache Metrics

Name Description Tags
cache.cache_result.hit Cache hits host
cache.cache_result.hitpass Cache hit-passes host
cache.cache_result.miss Cache misses host

Connection, Session and Fetch Metrics

Name Description Tags
connections.connections.accepted Accepted Connections host
connections.connections.dropped Dropped Connections host
connections.connections.received Received Connections host
fetch.http_requests.bad_headers Requests with bad headers host
fetch.http_requests.chunked Chunked requests host
fetch.http_requests.close Closed requests host
fetch.http_requests.eof End of file requests host
fetch.http_requests.failed Failed requests host
fetch.http_requests.head HEAD requests host
fetch.http_requests.length Length of requests host
fetch.http_requests.no_body_1xx 1xx responses without a body host
fetch.http_requests.no_body_204 204 responses without a body host
fetch.http_requests.no_body_304 304 responses without a body host
fetch.http_requests.oldhttp Old requests host Requests with 0 length host
objects.total_objects.expired Number of expired objects host
objects.total_objects.header_overflow Number of objects with header overflow host
objects.total_objects.lru_moved Number of moved objects host
objects.total_objects.lru_nuked Number of nuked objects host
objects.total_objects.sent_sendfile Number of sendfile objects sent host
objects.total_objects.sent_write Number of write objects sent host
objects.total_objects.workspace_overflow Number of workspace overflow objects host
session.total_operations.closed Closed session operations host
session.total_operations.herd Herd session operations host
session.total_operations.linger Lingering session operations host
session.total_operations.pipeline Session operations in the pipeline host
session.total_operations.readahead Read aheadsession operations host
totals.total_bytes.body-bytes Total bytes in body host
totals.total_bytes.header-bytes Total bytes in headers host
totals.total_operations.fetches Total operation fetches host
totals.total_operations.gunzip Total gunzip operations host
totals.total_operations.gzip Total gzip operations host
totals.total_operations.pass Total pass operations host
totals.total_operations.pipe Total pipe operations host
totals.total_requests.requests Total requests host
totals.total_sessions.sessions Total sessions host

Shared Memory Metrics

Name Description Tags
shm.total_operations.contention Shared memory operations in contention host
shm.total_operations.cycles Shared memory operation cycles host
shm.total_operations.flushes Shared memory operation flushes host
shm.total_operations.records Shared memory operation records host
shm.total_operations.writes Shared memory operation writes host

Worker Metrics

Name Description Tags
workers.total_requests.queued Total worker requests queued host
workers.total_requests.queue_length Queue length for worker requests host
workers.total_threads.created Total number of worker threads created host
workers.total_threads.dropped Total number of worker threads dropped host
workers.total_threads.failed Total number of work threads failed host Total number of worker threads limited host


For specific answers to Librato Agent questions check out our Librato Agent FAQ.

Please let us know what you think about this integration. We would love to incorporate your feedback and any ideas you have on dashboard design into the ongoing development of our integrations.