devstack/doc/source/debugging.rst
Ian Wienand 2bbc9bbbb8 Add service to tcpdump during run
This adds a service to run a tcpdump during the run.  This can be
useful to capture various network traffic for post analysis.

There didn't seem to quite be an appropriate place to document it, so
a new debugging file is started, with some terse explaination of our
various system-wide debugging services.

Change-Id: I09aaa57611c5047d09a9bce7932d34e9d50b30e6
2019-03-29 11:20:19 -07:00

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=====================
System-wide debugging
=====================
A lot can go wrong during a devstack run, and there are a few inbuilt
tools to help you.
dstat
-----
Enable the ``dstat`` service to produce performance logs during the
devstack run. These will be logged to the journal and also as a CSV
file.
memory_tracker
--------------
The ``memory_tracker`` service periodically monitors RAM usage and
provides consumption output when available memory is seen to be
falling (i.e. processes are consuming memory). It also provides
output showing locked (unswappable) memory.
tcpdump
-------
Enable the ``tcpdump`` service to run a background tcpdump. You must
set the ``TCPDUMP_ARGS`` variable to something suitable (there is no
default). For example, to trace iSCSI communication during a job in
the OpenStack gate and copy the result into the log output, you might
use:
.. code-block:: yaml
job:
name: devstack-job
parent: devstack
vars:
devstack_services:
tcpdump: true
devstack_localrc:
TCPDUMP_ARGS: "-i any tcp port 3260"
zuul_copy_output:
'{{ devstack_log_dir }}/tcpdump.pcap': logs