Details
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Bug
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Status: Closed (View Workflow)
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Major
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Resolution: Fixed
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2.4.10
Description
Galera monitor crashes with the following backtrace:
2020-07-01 23:10:11 alert : Fatal: MaxScale 2.4.10 received fatal signal 11. Commit ID: 7781f7042ab077811e2431794c2280162c0a6a3d System name: Linux Release string: Ubuntu 18.04.4 LTS
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nm: /lib/x86_64-linux-gnu/libc.so.6: no symbols
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2020-07-01 23:10:15 alert :
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/usr/lib/x86_64-linux-gnu/maxscale/libgaleramon.so(_ZNK13GaleraMonitor16diagnostics_jsonEv+0x154): /usr/include/c++/7/bits/hashtable_policy.h:1291
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/usr/lib/x86_64-linux-gnu/maxscale/libmaxscale-common.so.1.0.0(_ZNK8maxscale7Monitor7to_jsonEPKc+0x255): server/core/monitor.cc:673
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/usr/lib/x86_64-linux-gnu/maxscale/libmaxscale-common.so.1.0.0(_ZN14MonitorManager15monitor_to_jsonEPKN8maxscale7MonitorEPKc+0x5e): server/core/monitormanager.cc:469
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/usr/lib/x86_64-linux-gnu/maxscale/libmaxscale-common.so.1.0.0(+0xe11e3): server/core/resource.cc:626
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/usr/lib/x86_64-linux-gnu/maxscale/libmaxscale-common.so.1.0.0(_ZNK8Resource4callERK11HttpRequest+0xb4): server/core/resource.cc:119
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/usr/lib/x86_64-linux-gnu/maxscale/libmaxscale-common.so.1.0.0(+0xe6f8c): server/core/resource.cc:1347 (discriminator 1)
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/usr/lib/x86_64-linux-gnu/maxscale/libmaxscale-common.so.1.0.0(+0xe8b3c): server/core/resource.cc:1387
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/usr/lib/x86_64-linux-gnu/maxscale/libmaxscale-common.so.1.0.0(_ZN7maxbase6Worker14handle_messageERNS_12MessageQueueERKNS_19MessageQueueMessageE+0x6d): maxutils/maxbase/src/worker.cc:475
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/usr/lib/x86_64-linux-gnu/maxscale/libmaxscale-common.so.1.0.0(_ZN7maxbase12MessageQueue18handle_poll_eventsEPNS_6WorkerEj+0x158): maxutils/maxbase/src/messagequeue.cc:306
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/usr/lib/x86_64-linux-gnu/maxscale/libmaxscale-common.so.1.0.0(_ZN7maxbase6Worker15poll_waiteventsEv+0x1b6): maxutils/maxbase/src/worker.cc:858
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/usr/lib/x86_64-linux-gnu/maxscale/libmaxscale-common.so.1.0.0(_ZN7maxbase6Worker3runEPNS_9SemaphoreE+0x53): maxutils/maxbase/src/worker.cc:559
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/usr/lib/x86_64-linux-gnu/libstdc++.so.6(+0xbd6df): ??:?
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/lib/x86_64-linux-gnu/libpthread.so.0(+0x76db): ??:?
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/lib/x86_64-linux-gnu/libc.so.6(clone+0x3f): ??:0
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The crash seems to happen here:
galeramon.cc
107for (auto ptr : servers())108{109auto it = m_info.find(ptr);110111if (it != m_info.end())112{113json_t* obj = json_object();The strange thing is that it seems to be inside the std::unordered_map bucket selection code:
hashtable_policy.h
1286std::size_t1287_M_bucket_index(const __node_type* __p, std::size_t __n) const1288noexcept( noexcept(declval<const _H1&>()(declval<const _Key&>()))1289&& noexcept(declval<const _H2&>()((__hash_code)0,1290(std::size_t)0)) )1291{ return _M_h2()(_M_h1()(_M_extract()(__p->_M_v())), __n); }Could it be related to the hashing function being used?The simplest answer turned out to be the real one: the m_info array was being concurrently used.