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Plugin Varnish

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Florian Forster edited this page Nov 26, 2023 · 1 revision
Name: Varnish plugin
Type: read
Callbacks: config, init, read
Status: supported
FirstVersion: 5.0
Copyright: 2010 Jérôme Renard, 2010 Marc Fournier, 2010 Florian Forster
License: GPLv2
Manpage: collectd.conf(5)
See also: List of Plugins

Description

The Varnish plugin collects information about Varnish, an HTTP accelerator.

Synopsis

 <Plugin "varnish">
   <Instance>
     CollectCache       true
     CollectConnections true
     CollectBackend     true
     CollectSHM         true
     CollectESI         false
     CollectFetch       false
     CollectHCB         false
     CollectSMA         false
     CollectSMS         false
     CollectSM          false
     CollectTotals      false
     CollectWorkers     false
   </Instance>
 </Plugin>

Example graphs

Varnish-example.png

Available statistics

Setting Description Default
CollectBackend Back-end connection statistics, such as successful, reused, and closed connections. enabled
CollectCache Cache hits and misses. enabled
CollectConnections Number of client connections received, accepted and dropped. enabled
CollectESI Edge Side Includes (ESI) parse statistics. disabled
CollectFetch Statistics about fetches (HTTP requests sent to the backend). disabled
CollectHCB Inserts and look-ups in the crit bit tree based hash. Look-ups are divided into locked and unlocked look-ups. disabled
CollectSHM Statistics about the shared memory log, a memory region to store log messages which is flushed to disk when full. enabled
CollectSM file (memory mapped file) storage statistics. disabled
CollectSMA malloc or umem (umem_alloc(3MALLOC) based) storage statistics. The umem storage component is Solaris specific. disabled
CollectSMS synth (synthetic content) storage statistics. This storage component is used internally only. disabled
CollectTotals Collects overview counters, such as the number of sessions created, the number of requests and bytes transferred. disabled
CollectWorkers Collect statistics about worker threads. disabled

Information for Varnish power users

Below is the list of available statistics and whether or not they can be collected with the Varnish plugin:

Field name Description Collected (Yes/No) Collectd option
uptime Child uptime No n/a
client_conn Client connections accepted Yes CollectConnections
client_drop Connection dropped, no sess Yes
client_req Client requests received Yes
cache_hit Cache hits Yes CollectCache
cache_hitpass Cache hits for pass Yes
cache_miss Cache misses Yes
backend_conn Backend conn. success Yes CollectBackend
backend_unhealthy Backend conn. not attempted Yes
backend_busy Backend conn. too many Yes
backend_fail Backend conn. failures Yes
backend_reuse Backend conn. reuses Yes
backend_toolate Backend conn. was closed Yes
backend_recycle Backend conn. recycles Yes
backend_unused Backend conn. unused Yes
fetch_head Fetch head Yes CollectFetch
fetch_length Fetch with Length Yes
fetch_chunked Fetch chunked Yes
fetch_eof Fetch EOF Yes
fetch_bad Fetch had bad headers Yes
fetch_close Fetch wanted close Yes
fetch_oldhttp Fetch pre HTTP/1.1 closed Yes
fetch_zero Fetch zero len Yes
fetch_failed Fetch failed Yes
n_sess_mem N struct sess_mem No n/a
n_sess N struct sess No
n_object N struct object No
n_vampireobject N unresurrected objects No
n_objectcore N struct objectcore No
n_objecthead N struct objecthead No
n_smf N struct smf No
n_smf_frag N small free smf No
n_smf_large N large free smf No
n_vbe_conn N struct vbe_conn No
n_wrk N worker threads Yes CollectWorkers
n_wrk_create N worker threads created Yes
n_wrk_failed N worker threads not created Yes
n_wrk_max N worker threads limited Yes
n_wrk_queue N queued work requests Yes
n_wrk_overflow N overflowed work requests Yes
n_wrk_drop N dropped work requests Yes
n_backend N backends No n/a
n_expired N expired objects No
n_lru_nuked N LRU nuked objects No
n_lru_saved N LRU saved objects No
n_lru_moved N LRU moved objects No
n_deathrow N objects on deathrow No
losthdr HTTP header overflows No
n_objsendfile Objects sent with sendfile No
n_objwrite Objects sent with write No
n_objoverflow Objects overflowing workspace No
s_sess Total Sessions Yes CollectTotals
s_req Total Requests Yes
s_pipe Total pipe Yes
s_pass Total pass Yes
s_fetch Total fetch Yes
s_hdrbytes Total header bytes Yes
s_bodybytes Total body bytes Yes
sess_closed Session Closed No n/a
sess_pipeline Session Pipeline No
sess_readahead Session Read Ahead No
sess_linger Session Linger No
sess_herd Session herd No
shm_records SHM records Yes CollectSHM
shm_writes SHM writes Yes
shm_flushes SHM flushes due to overflow Yes
shm_cont SHM MTX contention Yes
shm_cycles SHM cycles through buffer Yes
sm_nreq allocator requests Yes CollectSM
sm_nobj outstanding allocations Yes
sm_balloc bytes allocated Yes
sm_bfree bytes free Yes
sma_nreq SMA allocator requests Yes CollectSMA
sma_nobj SMA outstanding allocations Yes
sma_nbytes SMA outstanding bytes Yes
sma_balloc SMA bytes allocated Yes
sma_bfree SMA bytes free Yes
sms_nreq SMS allocator requests Yes CollectSMS
sms_nobj SMS outstanding allocations Yes
sms_nbytes SMS outstanding bytes Yes
sms_balloc SMS bytes allocated Yes
sms_bfree SMS bytes freed Yes
backend_req Backend requests made No n/a
n_vcl N vcl total No
n_vcl_avail N vcl available No
n_vcl_discard N vcl discarded No
n_purge N total active purges No
n_purge_add N new purges added No
n_purge_retire N old purges deleted No
n_purge_obj_test N objects tested No
n_purge_re_test N regexps tested against No
n_purge_dups N duplicate purges removed No
hcb_nolock HCB Lookups without lock Yes CollectHCB
hcb_lock HCB Lookups with lock Yes
hcb_insert HCB Inserts Yes
esi_parse Objects ESI parsed (unlock) Yes CollectESI
esi_errors ESI parse errors (unlock) Yes

Caveats

Unresolved symbols in libvarnishapi

(This is fixed as of release 2.1.4 in official varnish-cache.org repository, tested on Debian)

Version 2.1.2 of Varnish and likely other versions had unresolved symbols in the varnishapi library used by collectd. This led to the configure script being unable to link a test program and thus considering the library as unavailable.

There's a thread on the mailing-list discussing these problems starting at: http://mailman.verplant.org/pipermail/collectd/2010-June/003876.html

Without going in the details, check that the commands below return the same result on you system:

  $ pkg-config --libs varnishapi
  -lvarnishapi -lvarnish -lvarnishcompat

  $ ldconfig -p | egrep "libvarnish.*.so$"
  libvarnishcompat.so (libc6,x86-64) => /usr/lib/libvarnishcompat.so
  libvarnishapi.so (libc6,x86-64) => /usr/lib/libvarnishapi.so
  libvarnish.so (libc6,x86-64) => /usr/lib/libvarnish.so

If not, the details of how to work around the problem are found here.

Compatibility with Varnish 3.0

The actual plugin is compatible with Varnish 3.0 starting with collectd version-5.1.

Previous versions were not compatible, because the function used to fetch statistics (VSL_OpenStats()) is no longer available in the Varnish 3.0 API (BC break).

Compatibility with Varnish 4.0

The actual plugin is compatible with Varnish 4.0 starting with collectd version-5.5.

Dependencies

  • libvarnishapi

See also

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