On 11/28/2017 02:27 PM, Ivan Larionov wrote: > Another interesting fact is that I can't reproduce this issue if squid > has no other traffic except my testing requests. But it's easy to > reproduce when server has other traffic.
I did not check your logs carefully, but I believe that (when things do not work the way you expect) your Squid is retrying a failed persistent connection (rather than re-forwarding the request after receiving a bad response). See the "pconn race happened" line below: > 1_retry.log:2017/11/28 12:55:12.731| 17,3| FwdState.cc(416) fail: > ERR_ZERO_SIZE_OBJECT "Bad Gateway" > 1_retry.log:2017/11/28 12:55:12.731| 17,5| FwdState.cc(430) fail: pconn race > happened > 1_retry.log:2017/11/28 12:55:12.731| 93,5| AsyncJob.cc(84) mustStop: > HttpStateData will stop, reason: HttpStateData::continueAfterParsingHeader > 1_retry.log:2017/11/28 12:55:12.731| 17,3| FwdState.cc(618) retryOrBail: > re-forwarding (1 tries, 40 secs) > 1_retry.log:2017/11/28 12:55:12.731| 17,4| FwdState.cc(621) retryOrBail: > retrying the same destination Assuming you tested with forward_max_tries set to 1, the retryOrBail lines above confirm the off-by-one problem I was describing in my previous response. AFAICT, compensating by setting forward_max_tries to zero will _not_ work (for reasons unrelated to the problem at hand). FWIW, your current options include those outlined at http://wiki.squid-cache.org/SquidFaq/AboutSquid#How_to_add_a_new_Squid_feature.2C_enhance.2C_of_fix_something.3F Alex. > On Tue, Nov 28, 2017 at 7:32 AM, Alex Rousskov wrote: > > On 11/27/2017 05:19 PM, Ivan Larionov wrote: > > > I see retries only when squid config has 2 parents. If I comment out > > everything related to "newproxy" I can't reproduce this behavior > anymore. > > The posted logs are not detailed enough to confirm or deny that IMO, but > I suspect that you are dealing with at least one bug. > > > > > https://wiki.squid-cache.org/SquidFaq/InnerWorkings#When_does_Squid_re-forward_a_client_request.3F > > <https://wiki.squid-cache.org/SquidFaq/InnerWorkings#When_does_Squid_re-forward_a_client_request.3F> > > > >> Squid does not try to re-forward a request if at least one of the > following conditions is true: > >> > >> The number of forwarding attempts exceeded forward_max_tries. For > >> example, if you set forward_max_tries to 1 (one), then no requests > >> will be re-forwarded. > > > AFAICT, there is an off-by-one bug in Squid that violates the above: > > > if (n_tries > Config.forward_max_tries) > > return false; > > The n_tries counter is incremented before Squid makes a request > forwarding attempt. With n_tries and Config.forward_max_tries both set > to 1, the quoted FwdState::checkRetry() code will not prevent > re-forwarding. There is a similar problem in FwdState::reforward(). This > reasoning needs confirmation/testing. > > Please note that simply changing the ">" operator to ">=" may break > other things in a difficult-to-detect-by-simple-tests ways. The correct > fix may be more complex than it looks and may involve making policy > decisions regarding forward_max_tries meaning. The best fix would remove > checkRetry() and reforward() duplication. This code is difficult to work > with; many related code names are misleading. > > > >> Squid has no alternative destinations to try. Please note that > >> alternative destinations may include multiple next hop IP addresses > >> and multiple peers. > > The fact that Squid sends two requests to the same peer with only one > peer address selected suggests that Squid is retrying a failed > persistent connection rather than re-forwarding after receiving a bad > response. Again, the logs are not detailed enough to distinguish the two > cases. I can only see that a single peer/destination address was > selected (not two), which is correct/expected behavior. I cannot see > what happened next with sufficient detail. > > Going forward, you have several options, including: > > A. Post a link to compressed ALL,7+ logs to confirm bug(s). > B. Fix the broken condition(s) in FwdState. See above. > > HTH, > > Alex. > > > > 2017/11/27 15:53:40.542| 5,2| TcpAcceptor.cc(220) doAccept: New > connection on FD 15 > > 2017/11/27 15:53:40.542| 5,2| TcpAcceptor.cc(295) acceptNext: connection > > on local=0.0.0.0:3128 <http://0.0.0.0:3128> <http://0.0.0.0:3128> > remote=[::] FD 15 flags=9 > > 2017/11/27 15:53:40.543| 11,2| client_side.cc(2372) parseHttpRequest: > > HTTP Client local=127.0.0.1:3128 <http://127.0.0.1:3128> > <http://127.0.0.1:3128> > > remote=127.0.0.1:53798 <http://127.0.0.1:53798> > <http://127.0.0.1:53798> FD 45 flags=1 > > 2017/11/27 15:53:40.543| 11,2| client_side.cc(2373) parseHttpRequest: > > HTTP Client REQUEST: > > --------- > > GET http://HOST:12345/ HTTP/1.1 > > Host: HOST:12345 > > User-Agent: curl/7.51.0 > > Accept: */* > > Proxy-Connection: Keep-Alive > > > > > > ---------- > > 2017/11/27 15:53:40.543| 85,2| client_side_request.cc(745) > > clientAccessCheckDone: The request GET http://HOST:12345/ is ALLOWED; > > last ACL checked: localhost > > 2017/11/27 15:53:40.543| 85,2| client_side_request.cc(721) > > clientAccessCheck2: No adapted_http_access configuration. default: ALLOW > > 2017/11/27 15:53:40.543| 85,2| client_side_request.cc(745) > > clientAccessCheckDone: The request GET http://HOST:12345/ is ALLOWED; > > last ACL checked: localhost > > 2017/11/27 15:53:40.543| 17,2| FwdState.cc(133) FwdState: Forwarding > > client request local=127.0.0.1:3128 <http://127.0.0.1:3128> > <http://127.0.0.1:3128> > > remote=127.0.0.1:53798 <http://127.0.0.1:53798> > <http://127.0.0.1:53798> FD 45 flags=1, > > url=http://HOST:12345/ > > 2017/11/27 15:53:40.543| 44,2| peer_select.cc(258) peerSelectDnsPaths: > > Find IP destination for: http://HOST:12345/' via 127.0.0.1 > > 2017/11/27 15:53:40.543| 44,2| peer_select.cc(280) peerSelectDnsPaths: > > Found sources for 'http://HOST:12345/' > > 2017/11/27 15:53:40.543| 44,2| peer_select.cc(281) peerSelectDnsPaths: > > always_direct = DENIED > > 2017/11/27 15:53:40.543| 44,2| peer_select.cc(282) peerSelectDnsPaths: > > never_direct = ALLOWED > > 2017/11/27 15:53:40.543| 44,2| peer_select.cc(292) peerSelectDnsPaths: > > cache_peer = local=127.0.0.3 remote=127.0.0.1:18070 > <http://127.0.0.1:18070> > > <http://127.0.0.1:18070> flags=1 > > 2017/11/27 15:53:40.543| 44,2| peer_select.cc(295) peerSelectDnsPaths: > > timedout = 0 > > 2017/11/27 15:53:40.543| 11,2| http.cc(2229) sendRequest: HTTP Server > > local=127.0.0.3:57091 <http://127.0.0.3:57091> > <http://127.0.0.3:57091> remote=127.0.0.1:18070 <http://127.0.0.1:18070> > > <http://127.0.0.1:18070> FD 40 flags=1 > > 2017/11/27 15:53:40.543| 11,2| http.cc(2230) sendRequest: HTTP Server > > REQUEST: > > --------- > > GET http://HOST:12345/ HTTP/1.1 > > User-Agent: curl/7.51.0 > > Accept: */* > > Host: HOST:12345 > > Cache-Control: max-age=259200 > > Connection: keep-alive > > > > > > ---------- > > > > [SKIPPED 40 seconds until parent closes TCP connection with FIN,ACK] > > > > 2017/11/27 15:54:20.627| 11,2| http.cc(1299) continueAfterParsingHeader: > > WARNING: HTTP: Invalid Response: No object data received for > > http://HOST:12345/ AKA HOST/ > > 2017/11/27 15:54:20.627| 17,2| FwdState.cc(655) > > handleUnregisteredServerEnd: self=0x3e31838*2 err=0x409b338 > > http://HOST:12345/ > > 2017/11/27 15:54:20.627| 11,2| http.cc(2229) sendRequest: HTTP Server > > local=127.0.0.3:41355 <http://127.0.0.3:41355> > <http://127.0.0.3:41355> remote=127.0.0.1:18070 <http://127.0.0.1:18070> > > <http://127.0.0.1:18070> FD 40 flags=1 > > 2017/11/27 15:54:20.627| 11,2| http.cc(2230) sendRequest: HTTP Server > > REQUEST: > > --------- > > GET http://HOST:12345/ HTTP/1.1 > > User-Agent: curl/7.51.0 > > Accept: */* > > Host: HOST:12345 > > Cache-Control: max-age=259200 > > Connection: keep-alive > > > > > > ---------- > > > > [SKIPPED 40 seconds again until parent closes TCP connection with > FIN,ACK] > > > > 2017/11/27 15:55:00.728| ctx: enter level 0: 'http://HOST:12345/' > > 2017/11/27 15:55:00.728| 11,2| http.cc(719) processReplyHeader: HTTP > > Server local=127.0.0.3:41355 <http://127.0.0.3:41355> > <http://127.0.0.3:41355> > > remote=127.0.0.1:18070 <http://127.0.0.1:18070> > <http://127.0.0.1:18070> FD 40 flags=1 > > 2017/11/27 15:55:00.728| 11,2| http.cc(720) processReplyHeader: HTTP > > Server REPLY: > > --------- > > HTTP/1.0 502 Bad Gateway > > Cache-Control: no-cache > > Connection: close > > Content-Type: text/html > > > > <html><body><h1>502 Bad Gateway</h1> > > The server returned an invalid or incomplete response. > > </body></html> > > > > ---------- > > 2017/11/27 15:55:00.728| ctx: exit level 0 > > 2017/11/27 15:55:00.728| 20,2| store.cc(996) checkCachable: > > StoreEntry::checkCachable: NO: not cachable > > 2017/11/27 15:55:00.728| 20,2| store.cc(996) checkCachable: > > StoreEntry::checkCachable: NO: not cachable > > 2017/11/27 15:55:00.728| 88,2| client_side_reply.cc(2073) > > processReplyAccessResult: The reply for GET http://HOST:12345/ is > > ALLOWED, because it matched (access_log stdio:/var/log/squid/access.log > > line) > > 2017/11/27 15:55:00.728| 11,2| client_side.cc(1409) sendStartOfMessage: > > HTTP Client local=127.0.0.1:3128 <http://127.0.0.1:3128> > <http://127.0.0.1:3128> > > remote=127.0.0.1:53798 <http://127.0.0.1:53798> > <http://127.0.0.1:53798> FD 45 flags=1 > > 2017/11/27 15:55:00.728| 11,2| client_side.cc(1410) > sendStartOfMessage: > > HTTP Client REPLY: > > --------- > > HTTP/1.1 502 Bad Gateway > > Date: Mon, 27 Nov 2017 23:54:20 GMT > > Cache-Control: no-cache > > Content-Type: text/html > > X-Cache: MISS from ip-172-23-18-130 > > X-Cache-Lookup: MISS from ip-172-23-18-130:3128 > > Transfer-Encoding: chunked > > Connection: keep-alive > > > > > > ---------- > > > > > -- > With best regards, Ivan Larionov. _______________________________________________ squid-users mailing list squid-users@lists.squid-cache.org http://lists.squid-cache.org/listinfo/squid-users
