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64 lines
1.9 KiB
Markdown
64 lines
1.9 KiB
Markdown
# Parsing Stack Traces
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## `addr2line`
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[`addr2line`][1] is a utility to translate addresses into filenames and line numbers.
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```
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addr2line -e mongod -ifC <offset>
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```
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## `c++filt`
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Use [`c++filt`][2] to demangle function names by pasting the whole stack trace to stdin.
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## Finding the Right Binary
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To find the correct binary for a specific log you need to:
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1. Get the commit from the header of the logs.
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2. Use git to locate that commit and check for the surrounding "version bump" commit.
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3. Download and open the binary:
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```
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curl -O http://s3.amazonaws.com/downloads.mongodb.org/linux/mongodb-linux-x86_64-debugsymbols-1.x.x.tgz
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```
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You can also get the debugsymbols archive for official builds through [the Downloads page][3]. In the
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Archived Releases section, click on the appropriate platform link to view the available archives.
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Select the appropriate debug symbols archive.
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### Example: Reading the Log
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Note that the log has lines like this:
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```
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/home/abc/mongod(_ZN5mongo15printStackTraceERSo+0x27) [0x689280]
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```
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You want to use the address in between the brackets `0x689280`. Note that you will get more than one
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stack frame for the address if the code is inlined.
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### Example: Using `addr2line`
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Actual example from a v1.8.1 64-bit Linux build:
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```
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$ curl http://downloads.mongodb.org/linux/mongodb-linux-x86_64-debugsymbols-1.8.1.tgz > out.tgz
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$ tar -xzf out.tgz
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$ cd mongodb-linux-x86_64-debugsymbols-1.8.1/
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$ cd bin
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$ addr2line --help
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$ addr2line -i -e mongod 0x6d6a74
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/mnt/home/buildbot/slave/Linux_64bit_V1.8/mongo/db/repl/health.cpp:394
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$ addr2line -i -e mongod 0x6d0694
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/mnt/home/buildbot/slave/Linux_64bit_V1.8/mongo/db/repl/rs.h:385
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/mnt/home/buildbot/slave/Linux_64bit_V1.8/mongo/db/repl/replset_commands.cpp:111
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```
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[1]: https://sourceware.org/binutils/docs/binutils/addr2line.html
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[2]: https://sourceware.org/binutils/docs-2.17/binutils/c_002b_002bfilt.html
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[3]: https://www.mongodb.com/download-center
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