System-wide debugging

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:

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
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