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https://issues.apache.org/jira/browse/TS-2193?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13763219#comment-13763219
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John Plevyak commented on TS-2193:
----------------------------------
I am concerned about the proxy.config.dns.dedicated_thread option. It is
testing a configuration where event threads are not ET_NET. While originally
the design accounted for that possibility, it was the case that all event
threads were ET_NET soon thereafter and I an worried that there are implicit
assumptions that it is the case (as seems to be with the session manager).
Is this really necessary? DNS processing should be cheap.
Several fixes come to mind:
1) make the SessionManager not depend on being called on an ET_NET (this should
probably be done in any case). It could simply shift to any ET_NET thread if
it was called from another.
2) make the DNS processor call back on an ET_NET thread (this is stupid since
there is no good reason for it to assume the caller has such a restriction and
indeed what about the other ET_XXXX type?).
3) make the DNS processor run across threads by hashing hosts to all ET_NET
threads. This will fix both the issue we are seeing as well as spread the load.
We should probably do both 1 and 3. There will be a temptation to do 2)
because it will be the "easy" fix but I think it is the wrong way out.
> Trafficserver 4.1 Crash with proxy.config.dns.dedicated_thread = 1
> ------------------------------------------------------------------
>
> Key: TS-2193
> URL: https://issues.apache.org/jira/browse/TS-2193
> Project: Traffic Server
> Issue Type: Bug
> Components: DNS
> Affects Versions: 4.1.0
> Reporter: Tommy Lee
> Fix For: 4.1.0
>
> Attachments: bt-01.txt
>
>
> Hi all,
> I've tried to enable DNS Thread without luck.
> When i set proxy.config.dns.dedicated_thread to 1, it crashes with the
> information below.
> The ATS is working in Forward Proxy mode.
> Thanks in advance.
> --------------------------------------
> traffic.out
> NOTE: Traffic Server received Sig 11: Segmentation fault
> /usr/local/cache-4.1/bin/traffic_server - STACK TRACE:
> /lib/x86_64-linux-gnu/libpthread.so.0(+0xfcb0)[0x2af714875cb0]
> /usr/local/cache-4.1/bin/traffic_server(_Z16_acquire_sessionP13SessionBucketPK8sockaddrR7INK_MD5P6HttpSM+0x52)[0x51dac2]
> /usr/local/cache-4.1/bin/traffic_server(_ZN18HttpSessionManager15acquire_sessionEP12ContinuationPK8sockaddrPKcP17HttpClientSessionP6HttpSM+0x3d1)[0x51e0f1]
> /usr/local/cache-4.1/bin/traffic_server(_ZN6HttpSM19do_http_server_openEb+0x30c)[0x53644c]
> /usr/local/cache-4.1/bin/traffic_server(_ZN6HttpSM14set_next_stateEv+0x6a0)[0x537560]
> /usr/local/cache-4.1/bin/traffic_server(_ZN6HttpSM14set_next_stateEv+0x57e)[0x53743e]
> /usr/local/cache-4.1/bin/traffic_server(_ZN6HttpSM14set_next_stateEv+0x57e)[0x53743e]
> /usr/local/cache-4.1/bin/traffic_server(_ZN6HttpSM27state_hostdb_reverse_lookupEiPv+0xb9)[0x526b99]
> /usr/local/cache-4.1/bin/traffic_server(_ZN6HttpSM12main_handlerEiPv+0xd8)[0x531be8]
> /usr/local/cache-4.1/bin/traffic_server[0x5d7c8a]
> /usr/local/cache-4.1/bin/traffic_server(_ZN18HostDBContinuation8dnsEventEiP7HostEnt+0x821)[0x5decd1]
> /usr/local/cache-4.1/bin/traffic_server(_ZN8DNSEntry9postEventEiP5Event+0x44)[0x5f7a94]
> /usr/local/cache-4.1/bin/traffic_server[0x5fd382]
> /usr/local/cache-4.1/bin/traffic_server(_ZN10DNSHandler8recv_dnsEiP5Event+0x852)[0x5fee72]
> /usr/local/cache-4.1/bin/traffic_server(_ZN10DNSHandler9mainEventEiP5Event+0x14)[0x5ffd94]
> /usr/local/cache-4.1/bin/traffic_server(_ZN7EThread13process_eventEP5Eventi+0x91)[0x6b2a41]
> /usr/local/cache-4.1/bin/traffic_server(_ZN7EThread7executeEv+0x514)[0x6b3534]
> /usr/local/cache-4.1/bin/traffic_server[0x6b17ea]
> /lib/x86_64-linux-gnu/libpthread.so.0(+0x7e9a)[0x2af71486de9a]
> /lib/x86_64-linux-gnu/libc.so.6(clone+0x6d)[0x2af71558dccd]
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