Tracing Ceph with LTTng-UST issue

[Lina SADI]

Hello,

We are writing to you regarding an issue we encountered while attempting to
trace Ceph with LTTng-UST. Below are the steps we have followed so far:

   1.

   *Compiling Ceph with LTTng Support*:
   - We modified the debian/rules file to enable LTTng support using the
      following flags: -DWITH_LTTNG=ON and
      -DWITH_OSD_INSTRUMENT_FUNCTIONS=ON.
      - The compilation process took approximately 7 hours on a virtual
      machine running Debian 12 with a kernel version 6.1.0-27-amd64, 8 GB of
      RAM, and 2 CPU cores.
      - The build steps can be found in our GitHub
      <https://github.com/KedadsaChakib/ceph-configuration/blob/main/build/README.md>
       repository.
   2.

   *Deploying a Ceph Cluster*:
   - We deployed the cluster manually (1MON,1MGR,2OSDs). Please find the
      script here
      <https://github.com/KedadsaChakib/ceph-configuration/blob/main/cluster/cluster-dep-script.sh>
      .
   3.

   *Attempting to Trace with LTTng-UST*:
   - We tried listing the tracepoints using the following command :

      # lttng list -u

      - This command did not return any Ceph-related tracepoints:

      UST events:
      -------------
      NONE

      4.

   *Preloading liblttng-ust-fork.so*:
   - We attempted to preload liblttng-ust-fork.so before starting the Ceph
      daemons (MON, OSD, MGR) as follows:

      # systemctl edit ceph-mon at debian

      - We added the following configuration:

      [Service]
      Environment="LD_PRELOAD=/usr/lib/x86_64-linux-gnu/liblttng-ust-fork.so



   - After restarting the daemons, we executed lttng list -u, which
      displayed tracepoints related to the libraries (lttng_ust_lib:*),
      trace logs (lttng_ust_tracelog:*), and state dump events (
      lttng_ust_statedump:*), instead of the expected Ceph-related
      tracepoints.

*Expected Result*:

   UST events:
   -------------
   PID: 100859 - Name: /path/to/ceph-osd
       pg:queue_op (loglevel: TRACE_DEBUG_LINE (13)) (type: tracepoint)
       osd:do_osd_op_post (loglevel: TRACE_DEBUG_LINE (13)) (type: tracepoint)
       osd:do_osd_op_pre_unknown (loglevel: TRACE_DEBUG_LINE (13))
(type: tracepoint)
       osd:do_osd_op_pre_copy_from (loglevel: TRACE_DEBUG_LINE (13))
(type: tracepoint)
       osd:do_osd_op_pre_copy_get (loglevel: TRACE_DEBUG_LINE (13))
(type: tracepoint)
       ...


*Actual Result*:

   UST events:
   -------------
   lttng_ust_lib:*
   lttng_ust_tracelog:*
   lttng_ust_statedump:*


We would greatly appreciate any help  you could provide to resolve this problem.
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