Problem with "Backend conn. not attempted"

Simon Effenberg se at plista.com
Fri Jan 14 13:11:29 CET 2011


Hi,

since i upgraded from 2.1.2 to 2.1.4 about a week ago no problems
occurred but yesterday the "Backend conn. not attempted" arrised and i
have no idea what is going on. (see Figure 2.)

It seems to be the backends (and yes last night i switched from haproxy
1.3 to 1.4 whereas varnish only connects to the locally haproxy daemon
but the problem occures half a day before that) but the log says nothing
about an unhealty backend (see Figure 1. and remember it is
'localhost').

Any idea what could be the problem? Is there any information you would
need?

/simon

ps: no fd problem i think because "Connection: close" is in use and an
'lsof' on the varnish pid show round about 70 open fd's..


Figure 1:

$ varnishlog -r /tmp/debugging.binlog  | grep Backend_health | grep -v "Still healthy"
# no output
$ varnishlog -r /tmp/debugging.binlog  | grep Backend_health | head -n 5
    0 Backend_health - default Still healthy 4--X-RH 10 4 10 0.040812 0.011764 HTTP/1.1 200 OK
    0 Backend_health - default Still healthy 4--X-RH 10 4 10 0.000876 0.009042 HTTP/1.1 200 OK
    0 Backend_health - default Still healthy 4--X-RH 10 4 10 0.001131 0.007064 HTTP/1.1 200 OK
    0 Backend_health - default Still healthy 4--X-RH 10 4 10 0.000887 0.005520 HTTP/1.1 200 OK
    0 Backend_health - default Still healthy 4--X-RH 10 4 10 0.000855 0.004354 HTTP/1.1 200 OK
$ varnishlog -r /tmp/debugging.binlog  | grep Backend_health | tail -n 5
    0 Backend_health - default Still healthy 4--X-RH 10 4 10 0.003904 0.001866 HTTP/1.1 200 OK
    0 Backend_health - default Still healthy 4--X-RH 10 4 10 0.000964 0.001640 HTTP/1.1 200 OK
    0 Backend_health - default Still healthy 4--X-RH 10 4 10 0.000781 0.001426 HTTP/1.1 200 OK
    0 Backend_health - default Still healthy 4--X-RH 10 4 10 0.001127 0.001351 HTTP/1.1 200 OK
    0 Backend_health - default Still healthy 4--X-RH 10 4 10 0.001301 0.001338 HTTP/1.1 200 OK

Figure 2:

$ varnishstat -1:
---------------------------------
client_conn          53645273        87.99 Client connections accepted
client_drop                 0         0.00 Connection dropped, no sess/wrk
client_req           53201813        87.27 Client requests received
cache_hit            51129547        83.87 Cache hits
cache_hitpass               0         0.00 Cache hits for pass
cache_miss            2092386         3.43 Cache misses
backend_conn          1819100         2.98 Backend conn. success
backend_unhealthy       278118         0.46 Backend conn. not attempted
backend_busy                0         0.00 Backend conn. too many
backend_fail                0         0.00 Backend conn. failures
backend_reuse               0         0.00 Backend conn. reuses
backend_toolate             0         0.00 Backend conn. was closed
backend_recycle             0         0.00 Backend conn. recycles
backend_unused              0         0.00 Backend conn. unused
fetch_head                  0         0.00 Fetch head
fetch_length          1790403         2.94 Fetch with Length
fetch_chunked           21484         0.04 Fetch chunked
fetch_eof                   0         0.00 Fetch EOF
fetch_bad                   0         0.00 Fetch had bad headers
fetch_close                24         0.00 Fetch wanted close
fetch_oldhttp               0         0.00 Fetch pre HTTP/1.1 closed
fetch_zero                  0         0.00 Fetch zero len
fetch_failed               14         0.00 Fetch failed
n_sess_mem              13000          .   N struct sess_mem
n_sess                  12907          .   N struct sess
n_object                92065          .   N struct object
n_vampireobject             0          .   N unresurrected objects
n_objectcore            92438          .   N struct objectcore
n_objecthead            76044          .   N struct objecthead
n_smf                       0          .   N struct smf
n_smf_frag                  0          .   N small free smf
n_smf_large                 0          .   N large free smf
n_vbe_conn                  0          .   N struct vbe_conn
n_wrk                     600          .   N worker threads
n_wrk_create              600         0.00 N worker threads created
n_wrk_failed                0         0.00 N worker threads not created
n_wrk_max                   0         0.00 N worker threads limited
n_wrk_queue                 0         0.00 N queued work requests
n_wrk_overflow            746         0.00 N overflowed work requests
n_wrk_drop                  0         0.00 N dropped work requests
n_backend                   1          .   N backends
n_expired             1678862          .   N expired objects
n_lru_nuked                 0          .   N LRU nuked objects
n_lru_saved                 0          .   N LRU saved objects
n_lru_moved          16107120          .   N LRU moved objects
n_deathrow                  0          .   N objects on deathrow
losthdr                     0         0.00 HTTP header overflows
n_objsendfile               0         0.00 Objects sent with sendfile
n_objwrite           52363470        85.89 Objects sent with write
n_objoverflow               0         0.00 Objects overflowing workspace
s_sess               53645264        87.99 Total Sessions
s_req                53201813        87.27 Total Requests
s_pipe                   4203         0.01 Total pipe
s_pass                    633         0.00 Total pass
s_fetch               1771016         2.90 Total fetch
s_hdrbytes        17059440767     27982.21 Total header bytes
s_bodybytes      367428478958    602684.61 Total body bytes
sess_closed          36642075        60.10 Session Closed
sess_pipeline               5         0.00 Session Pipeline
sess_readahead              5         0.00 Session Read Ahead
sess_linger          50364562        82.61 Session Linger
sess_herd            19035641        31.22 Session herd
shm_records        2311880141      3792.12 SHM records
shm_writes          238329715       390.93 SHM writes
shm_flushes                21         0.00 SHM flushes due to overflow
shm_cont              2464869         4.04 SHM MTX contention
shm_cycles                924         0.00 SHM cycles through buffer
sm_nreq                     0         0.00 allocator requests
sm_nobj                     0          .   outstanding allocations
sm_balloc                   0          .   bytes allocated
sm_bfree                    0          .   bytes free
sma_nreq              3582284         5.88 SMA allocator requests
sma_nobj               184130          .   SMA outstanding allocations
sma_nbytes          895131255          .   SMA outstanding bytes
sma_balloc        19762542699          .   SMA bytes allocated
sma_bfree         18867411444          .   SMA bytes free
sms_nreq               297047         0.49 SMS allocator requests
sms_nobj                    0          .   SMS outstanding allocations
sms_nbytes                  0          .   SMS outstanding bytes
sms_balloc          123833356          .   SMS bytes allocated
sms_bfree           123833356          .   SMS bytes freed
backend_req           1814892         2.98 Backend requests made
n_vcl                       1         0.00 N vcl total
n_vcl_avail                 1         0.00 N vcl available
n_vcl_discard               0         0.00 N vcl discarded
n_purge                     2          .   N total active purges
n_purge_add                 2         0.00 N new purges added
n_purge_retire              0         0.00 N old purges deleted
n_purge_obj_test        55396         0.09 N objects tested
n_purge_re_test         55396         0.09 N regexps tested against
n_purge_dups                0         0.00 N duplicate purges removed
hcb_nolock           53181129        87.23 HCB Lookups without lock
hcb_lock              1458761         2.39 HCB Lookups with lock
hcb_insert            1458761         2.39 HCB Inserts
esi_parse                   0         0.00 Objects ESI parsed (unlock)
esi_errors                  0         0.00 ESI parse errors (unlock)
accept_fail                 3         0.00 Accept failures
client_drop_late            0         0.00 Connection dropped late
uptime                 609653         1.00 Client uptime
backend_retry               0         0.00 Backend conn. retry
dir_dns_lookups             0         0.00 DNS director lookups
dir_dns_failed              0         0.00 DNS director failed lookups
dir_dns_hit                 0         0.00 DNS director cached lookups hit
dir_dns_cache_full            0         0.00 DNS director full dnscache
---------------------------------





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