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scylladb/docs/kb/decode-stack-trace.rst

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=====================
Decoding Stack Traces
=====================
**Topic: Decoding stack traces in ScyllaDB logs**
**Environment: Any ScyllaDB setup on any supported OS**
**Audience: All**
Synopsis
--------
This article describes how to decode the stack traces found in ScyllaDB logs.
What are Stack Traces?
----------------------
Stack traces can appear in the logs due to various errors or in the course of regular database operation. It is useful to be able to decode the trace in order to understand what exactly happened. Decoding the stack trace requires the Debug binaries for the specific ScyllaDB build and OS in use are installed.
Note that sharing the stack trace as part of your support ticket or Github issue, helps the ScyllaDB support team to understand the issue better.
Install Debug Binary files
--------------------------
Install the Debug binaries according to your OS distribution
.. tabs::
.. group-tab:: RPM based distributions
.. code-block:: none
yum install scylla-debuginfo
.. group-tab:: DEB based distributions
.. code-block:: none
apt-get install scylla-server-dbg
Validate the debug binary file name
-----------------------------------
To later determine the actual debug binary, look in the ``/usr/lib/debug/`` directory
for a file named scylla.debug.
For example:
.. code-block:: none
# find /usr/lib/debug/ | grep scylla.debug
/usr/lib/debug/usr/bin/scylla.debug
Locate and Analyze the Logs
----------------------------
**Procedure**
#. Copy the stack from the :doc:`system log </getting-started/logging>` and place it in a file (trace.txt, for example).
.. code-block:: none
Jul 14 16:56:50 hostname01 scylla: Aborting on shard 8.
Jul 14 16:56:50 hostname01 scylla: Backtrace:
Jul 14 16:56:50 hostname01 scylla: 0x0000000000688602
Jul 14 16:56:50 hostname01 scylla: 0x00000000005a36fc
Jul 14 16:56:50 hostname01 scylla: 0x00000000005a39a5
Jul 14 16:56:50 hostname01 scylla: 0x00000000005a3a53
Jul 14 16:56:50 hostname01 scylla: /lib64/libpthread.so.0+0x000000000000f6cf
Jul 14 16:56:50 hostname01 scylla: /lib64/libc.so.6+0x0000000000036276
Jul 14 16:56:50 hostname01 scylla: /lib64/libc.so.6+0x0000000000037967
Jul 14 16:56:50 hostname01 scylla: 0x00000000024ce37b
Jul 14 16:56:50 hostname01 scylla: 0x00000000024d2a47
Jul 14 16:56:50 hostname01 scylla: 0x00000000024df1d5
Jul 14 16:56:50 hostname01 scylla: 0x00000000023dccec
Jul 14 16:56:50 hostname01 scylla: 0x00000000023feac1
Jul 14 16:56:50 hostname01 scylla: 0x00000000024324b9
Jul 14 16:56:50 hostname01 scylla: 0x00000000024357e4
Jul 14 16:56:50 hostname01 scylla: 0x0000000001eace90
Jul 14 16:56:50 hostname01 scylla: 0x0000000001eaf944
Jul 14 16:56:50 hostname01 scylla: 0x0000000000584ab6
Jul 14 16:56:50 hostname01 scylla: 0x0000000000584c71
Jul 14 16:56:50 hostname01 scylla: 0x00000000006522ff
Jul 14 16:56:50 hostname01 scylla: 0x00000000006554e5
Jul 14 16:56:50 hostname01 scylla: 0x000000000073d3cd
Jul 14 16:56:50 hostname01 scylla: /lib64/libpthread.so.0+0x0000000000007e24
Jul 14 16:56:50 hostname01 scylla: /lib64/libc.so.6+0x00000000000febac
#. Locate the files for backtrace.
.. code-block:: shell
find . -name "scylla*.debug"
With ScyllaDB 4.1 for example, returns:
.. code-block:: shell
/usr/lib/debug/opt/scylladb/libexec/scylla-4.1.1-0.20200703.1d9bbbc9577.x86_64.debug
#. Run the decoder:
.. code-block:: none
./seastar-addr2line -e /usr/lib/debug/usr/bin/scylla.debug -f trace.txt > trace_decoded.txt
``trace_decoded.txt`` now contains the decoded version of the stack trace:
For example:
.. code-block:: none
void seastar::backtrace<seastar::backtrace_buffer::append_backtrace()::{lambda(seastar::frame)#1}>(seastar::backtrace_buffer::append_backtrace()::{lambda(seastar::frame)#1}&&) at /usr/src/debug/scylla-4.1.1/seastar/util/backtrace.hh:56
seastar::backtrace_buffer::append_backtrace() at /usr/src/debug/scylla-4.1.1/seastar/core/reactor.cc:390
(inlined by) print_with_backtrace at /usr/src/debug/scylla-4.1.1/seastar/core/reactor.cc:411
seastar::print_with_backtrace(char const*) at /usr/src/debug/scylla-4.1.1/seastar/core/reactor.cc:418
sigabrt_action at /usr/src/debug/scylla-4.1.1/seastar/core/reactor.cc:3939
(inlined by) operator() at /usr/src/debug/scylla-4.1.1/seastar/core/reactor.cc:3921
(inlined by) _FUN at /usr/src/debug/scylla-4.1.1/seastar/core/reactor.cc:3917
...
seastar::reactor::run_tasks(seastar::reactor::task_queue&) at /usr/src/debug/scylla-4.1.1/seastar/core/reactor.cc:2621
seastar::reactor::run_some_tasks() at /usr/src/debug/scylla-4.1.1/seastar/core/reactor.cc:3033
seastar::reactor::run_some_tasks() at /opt/scylladb/include/c++/7/chrono:377
(inlined by) seastar::reactor::run() at /usr/src/debug/scylla-4.1.1/seastar/core/reactor.cc:3180