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| author |  Jeff Hostetler <jeffhost@microsoft.com> | 2021-09-20 15:36:12 +0000 |
|---|---|---|
| committer |  Junio C Hamano <gitster@pobox.com> | 2021-09-20 08:57:58 -0700 |
| commit | 64bc75244b5bdc26112cf7b8533a832b692a5fda (patch) | |
| tree | a437715e40883730a1d6eede3123eb39e7d99d73 /Documentation/technical | |
| parent | The sixth batch (diff) | |
| download | tgif-64bc75244b5bdc26112cf7b8533a832b692a5fda.tar.xz | |
trace2: add trace2_child_ready() to report on background children
Create "child_ready" event to capture the state of a child process
created in the background.
When a child command is started a "child_start" event is generated in
the Trace2 log. For normal synchronous children, a "child_exit" event
is later generated when the child exits or is terminated. The two events
include information, such as the "child_id" and "pid", to allow post
analysis to match-up the command line and exit status.
When a child is started in the background (and may outlive the parent
process), it is not possible for the parent to emit a "child_exit"
event. Create a new "child_ready" event to indicate whether the
child was successfully started. Also include the "child_id" and "pid"
to allow similar post processing.
This will be used in a later commit with the new "start_bg_command()".
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'Documentation/technical')
| -rw-r--r-- | Documentation/technical/api-trace2.txt | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/Documentation/technical/api-trace2.txt b/Documentation/technical/api-trace2.txt index b9f3198fbe..ef7fe02a8f 100644 --- a/Documentation/technical/api-trace2.txt +++ b/Documentation/technical/api-trace2.txt @@ -613,6 +613,46 @@ stopping after the waitpid() and includes OS process creation overhead). So this time will be slightly larger than the atexit time reported by the child process itself. +`"child_ready"`:: + This event is generated after the current process has started + a background process and released all handles to it. ++ +------------ +{ + "event":"child_ready", + ... + "child_id":2, + "pid":14708, # child PID + "ready":"ready", # child ready state + "t_rel":0.110605 # observed run-time of child process +} +------------ ++ +Note that the session-id of the child process is not available to +the current/spawning process, so the child's PID is reported here as +a hint for post-processing. (But it is only a hint because the child +process may be a shell script which doesn't have a session-id.) ++ +This event is generated after the child is started in the background +and given a little time to boot up and start working. If the child +startups normally and while the parent is still waiting, the "ready" +field will have the value "ready". +If the child is too slow to start and the parent times out, the field +will have the value "timeout". +If the child starts but the parent is unable to probe it, the field +will have the value "error". ++ +After the parent process emits this event, it will release all of its +handles to the child process and treat the child as a background +daemon. So even if the child does eventually finish booting up, +the parent will not emit an updated event. ++ +Note that the `t_rel` field contains the observed run time in seconds +when the parent released the child process into the background. +The child is assumed to be a long-running daemon process and may +outlive the parent process. So the parent's child event times should +not be compared to the child's atexit times. + `"exec"`:: This event is generated before git attempts to `exec()` another command rather than starting a child process. |