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Matt Clark
Asked: 2016-04-28 07:06:15 +0800 CST

How to preform a core dump on MongoDB

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I am in the process of investigating a potential memory leak within MongoDB, last night I experienced an issue where the resident memory in use, had an unexpect climb to +10GB.

I am trying to preform a core dump to examine the contents of the memory, but am having an issue doing so.

I tried using the procedure found here, using kill -SIGQUIT 9999, however this does not seem to produce an actual core dump from mongod, instead, the only thing I can find is what appears to be a few useless lines at the end of my log file.

2016-04-27T14:28:01.413+0000 F -        [initandlisten] Got signal: 3 (Quit).

 0x1310252 0x130f189 0x130f992 0x349f40f500 0x349f0e0d03 0x12b4fc4 0x977f26 0x97a9bd 0x349f01ecdd 0x974881
----- BEGIN BACKTRACE -----
{"backtrace":[{"b":"400000","o":"F10252","s":"_ZN5mongo15printStackTraceERSo"},{"b":"400000","o":"F0F189"},{"b":"400000","o":"F0F992"},{"b":"349F400000","o":"F500"},{"b":"349F000000","o":"E0D03","s":"__select"},{"b":"400000","o":"EB4FC4","s":"_ZN5mongo8Listener13initAndListenEv"},{"b":"400000","o":"577F26","s":"_ZN5mongo13initAndListenEi"},{"b":"400000","o":"57A9BD","s":"main"},{"b":"349F000000","o":"1ECDD","s":"__libc_start_main"},{"b":"400000","o":"574881"}],"processInfo":{ "mongodbVersion" : "3.2.4", "gitVersion" : "e2ee9ffcf9f5a94fad76802e28cc978718bb7a30", "compiledModules" : [], "uname" : { "sysname" : "Linux", "release" : "2.6.39-300.17.2.el6uek.x86_64", "version" : "#1 SMP Wed Nov 7 17:48:36 PST 2012", "machine" : "x86_64" }, "somap" : [ { "elfType" : 2, "b" : "400000", "buildId" : "5FD49352786BCEAEC14C2C99263D7EDCC9F681FD" }, { "b" : "7FFF433DF000", "elfType" : 3, "buildId" : "1E333CA5361BDB0097E9F47A6280B1AB5EEF4F0A" }, { "path" : "/usr/lib64/libssl.so.10", "elfType" : 3, "buildId" : "145F7FE3952D398F1580F65D309F7B84C170C46B" }, { "path" : "/usr/lib64/libcrypto.so.10", "elfType" : 3, "buildId" : "04B2B7E614BF9844F5191F8A81E15B0F60A1EF3A" }, { "path" : "/lib64/librt.so.1", "elfType" : 3, "buildId" : "A34F8F7191C98A2AAEC9150CD504EE6E3E1BA7CD" }, { "path" : "/lib64/libdl.so.2", "elfType" : 3, "buildId" : "15B0822C819020F18BBF0E0C0286373155E03BE2" }, { "path" : "/usr/lib64/libstdc++.so.6", "elfType" : 3, "buildId" : "1A4BC78E7DA0FA025262D516D00E04AFD1B0F429" }, { "path" : "/lib64/libm.so.6", "elfType" : 3, "buildId" : "4506D67E9AC196C2A4C51CF9804C469B5465AA89" }, { "path" : "/lib64/libgcc_s.so.1", "elfType" : 3, "buildId" : "CE152B8676517F23E7F54AD6408330979BE41443" }, { "path" : "/lib64/libpthread.so.0", "elfType" : 3, "buildId" : "7A688BCD17DD94352FD083FB9A64DCAF6296428E" }, { "path" : "/lib64/libc.so.6", "elfType" : 3, "buildId" : "9482B5DFEC6960CE8D5D90CECF6C77DC18A11272" }, { "path" : "/lib64/ld-linux-x86-64.so.2", "elfType" : 3, "buildId" : "CBC6E7266FCF291CEE239F38D1DD7B59D82AADBD" }, { "path" : "/lib64/libgssapi_krb5.so.2", "elfType" : 3, "buildId" : "5A849E6F82D34BFDF59D7B3ACD00BE9A7E24B6F1" }, { "path" : "/lib64/libkrb5.so.3", "elfType" : 3, "buildId" : "C2F73DA1AF5D07B0B72F82ED3690456C4EDF3E0E" }, { "path" : "/lib64/libcom_err.so.2", "elfType" : 3, "buildId" : "6A8EE2F10B2BB3A361B366DB93A0884E70A4D03B" }, { "path" : "/lib64/libk5crypto.so.3", "elfType" : 3, "buildId" : "2C7D5C2761C37E2B0B9F2719A8AF6ADA48D4895C" }, { "path" : "/lib64/libz.so.1", "elfType" : 3, "buildId" : "209A7EBEAB54483FED76E2A984B4AEAE29C66D69" }, { "path" : "/lib64/libkrb5support.so.0", "elfType" : 3, "buildId" : "DE4E1481ECA0ADF2F15A4D830CF2C43A29350087" }, { "path" : "/lib64/libkeyutils.so.1", "elfType" : 3, "buildId" : "8A8734DC37305D8CC2EF8F8C3E5EA03171DB07EC" }, { "path" : "/lib64/libresolv.so.2", "elfType" : 3, "buildId" : "E48B7A85C3EE7A22CBCAC817C407458CC0A9D47F" }, { "path" : "/lib64/libselinux.so.1", "elfType" : 3, "buildId" : "A287DC6B86A9823038F057105CE64671E0B392EC" } ] }}
 mongod(_ZN5mongo15printStackTraceERSo+0x32) [0x1310252]
 mongod(+0xF0F189) [0x130f189]
 mongod(+0xF0F992) [0x130f992]
 libpthread.so.0(+0xF500) [0x349f40f500]
 libc.so.6(__select+0x33) [0x349f0e0d03]
 mongod(_ZN5mongo8Listener13initAndListenEv+0x4B4) [0x12b4fc4]
 mongod(_ZN5mongo13initAndListenEi+0x1316) [0x977f26]
 mongod(main+0x15D) [0x97a9bd]
 libc.so.6(__libc_start_main+0xFD) [0x349f01ecdd]
 mongod(+0x574881) [0x974881]
-----  END BACKTRACE  -----

Any idea how I can go about getting a core dump here?

linux dump mongodb

1 Answers

  1. This link contains a good checklist why core dumps are not generated

    Make sure your current directory (at the time of crash -- server may change directories) is writable. If the server calls setuid, the directory has to be writable by that user.

    Also check /proc/sys/kernel/core_pattern. That may redirect core dumps to another directory, and that directory must be writable. More info here.

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