Commit Graph

26 Commits

Author SHA1 Message Date
Jeff Hostetler 64bc75244b 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 <>
Signed-off-by: Junio C Hamano <>
2021-09-20 08:57:58 -07:00
Junio C Hamano 6f64eeab60 Merge branch 'es/trace2-log-parent-process-name'
trace2 logs learned to show parent process name to see in what
context Git was invoked.

* es/trace2-log-parent-process-name:
  tr2: log parent process name
  tr2: make process info collection platform-generic
2021-08-24 15:32:40 -07:00
Emily Shaffer 2f732bf15e tr2: log parent process name
It can be useful to tell who invoked Git - was it invoked manually by a
user via CLI or script? By an IDE?  In some cases - like 'repo' tool -
we can influence the source code and set the GIT_TRACE2_PARENT_SID
environment variable from the caller process. In 'repo''s case, that
parent SID is manipulated to include the string "repo", which means we
can positively identify when Git was invoked by 'repo' tool. However,
identifying parents that way requires both that we know which tools
invoke Git and that we have the ability to modify the source code of
those tools. It cannot scale to keep up with the various IDEs and
wrappers which use Git, most of which we don't know about. Learning
which tools and wrappers invoke Git, and how, would give us insight to
decide where to improve Git's usability and performance.

Unfortunately, there's no cross-platform reliable way to gather the name
of the parent process. If procfs is present, we can use that; otherwise
we will need to discover the name another way. However, the process ID
should be sufficient to look up the process name on most platforms, so
that code may be shareable.

Git for Windows gathers similar information and logs it as a "data_json"
event. However, since "data_json" has a variable format, it is difficult
to parse effectively in some languages; instead, let's pursue a
dedicated "cmd_ancestry" event to record information about the ancestry
of the current process and a consistent, parseable way.

Git for Windows also gathers information about more than one generation
of parent. In Linux further ancestry info can be gathered with procfs,
but it's unwieldy to do so. In the interest of later moving Git for
Windows ancestry logging to the 'cmd_ancestry' event, and in the
interest of later adding more ancestry to the Linux implementation - or
of adding this functionality to other platforms which have an easier
time walking the process tree - let's make 'cmd_ancestry' accept an
array of parentage.

Signed-off-by: Emily Shaffer <>
Signed-off-by: Junio C Hamano <>
2021-07-22 13:35:20 -07:00
Junio C Hamano 9c7a1fc9b6 Merge branch 'js/trace2-discard-event-docfix'

* js/trace2-discard-event-docfix:
  docs: fix api-trace2 doc for "too_many_files" event
2021-07-08 13:14:57 -07:00
Josh Steadmon 7ba68e0cf1 docs: fix api-trace2 doc for "too_many_files" event
In 87db61a (trace2: write discard message to sentinel files,
2019-10-04), we added a new "too_many_files" event for when trace2
logging would create too many files in an output directory.
Unfortunately, the api-trace2 doc described a "discard" event instead.
Fix the doc to use the correct event name.

Signed-off-by: Josh Steadmon <>
Signed-off-by: Junio C Hamano <>
2021-06-04 12:11:16 +09:00
Ævar Arnfjörð Bjarmason f6d25d7878 api docs: document that BUG() emits a trace2 error event
Correct documentation added in e544221d97 (trace2:
Documentation/technical/api-trace2.txt, 2019-02-22) to state that
calling BUG() also emits an "error" event. See ee4512ed48 (trace2:
create new combined trace facility, 2019-02-22) for the initial

The BUG() function did not emit an event then however, that was only
changed later in 0a9dde4a04 (usage: trace2 BUG() invocations,
2021-02-05), that commit changed the code, but didn't update any of
the docs.

Let's also add a cross-reference from api-error-handling.txt.

Signed-off-by: Ævar Arnfjörð Bjarmason <>
Signed-off-by: Junio C Hamano <>
2021-04-13 14:57:13 -07:00
Jonathan Tan 0ee10fd129 usage: add trace2 entry upon warning()
Emit a trace2 error event whenever warning() is called, just like when
die(), error(), or usage() is called.

This helps debugging issues that would trigger warnings but not errors.
In particular, this might have helped debugging an issue I encountered
with commit graphs at $DAYJOB [1].

There is a tradeoff between including potentially relevant messages and
cluttering up the trace output produced. I think that warning() messages
should be included in traces, because by its nature, Git is used over
multiple invocations of the Git tool, and a failure (currently traced)
in a Git invocation might be caused by an unexpected interaction in a
previous Git invocation that only has a warning (currently untraced) as
a symptom - as is the case in [1].


Signed-off-by: Jonathan Tan <>
Signed-off-by: Junio C Hamano <>
2020-11-24 17:39:38 -08:00
Josh Steadmon 3d3adaad91 trace2: teach Git to log environment variables
Via trace2, Git can already log interesting config parameters (see the
trace2_cmd_list_config() function). However, this can grant an
incomplete picture because many config parameters also allow overrides
via environment variables.

To allow for more complete logs, we add a new trace2_cmd_list_env_vars()
function and supporting implementation, modeled after the pre-existing
config param logging implementation.

Signed-off-by: Josh Steadmon <>
Acked-by: Jeff Hostetler <>
Signed-off-by: Junio C Hamano <>
2020-03-23 13:14:53 -07:00
Junio C Hamano 26c816a67d Merge branch 'hw/doc-in-header'
* hw/doc-in-header:
  trace2: move doc to trace2.h
  submodule-config: move doc to submodule-config.h
  tree-walk: move doc to tree-walk.h
  trace: move doc to trace.h
  run-command: move doc to run-command.h
  parse-options: add link to doc file in parse-options.h
  credential: move doc to credential.h
  argv-array: move doc to argv-array.h
  cache: move doc to cache.h
  sigchain: move doc to sigchain.h
  pathspec: move doc to pathspec.h
  revision: move doc to revision.h
  attr: move doc to attr.h
  refs: move doc to refs.h
  remote: move doc to remote.h and refspec.h
  sha1-array: move doc to sha1-array.h
  merge: move doc to ll-merge.h
  graph: move doc to graph.h and graph.c
  dir: move doc to dir.h
  diff: move doc to diff.h and diffcore.h
2019-12-16 13:08:39 -08:00
Heba Waly 6c51cb525d trace2: move doc to trace2.h
Move the functions documentation from
Documentation/technical/api-trace2.txt to trace2.h as it's easier for the
developers to find the usage information beside the code instead of looking
for it in another doc file.

Only the functions documentation section is removed from
Documentation/technical/api-trace2.txt as the file is full of
details that seemed more appropriate to be in a separate doc file
as it is, with a link to the doc file added in the trace2.h.
Also the functions doc is removed to avoid having redundandt info which
will be hard to keep syncronized with the documentation in the header file.

Signed-off-by: Heba Waly <>
Signed-off-by: Junio C Hamano <>
2019-11-18 15:21:29 +09:00
Elijah Newren 031fd4b93b Documentation: fix a bunch of typos, both old and new
Reported-by: Jens Schleusener <>
Signed-off-by: Elijah Newren <>
Signed-off-by: Junio C Hamano <>
2019-11-07 13:42:00 +09:00
Josh Steadmon 87db61a436 trace2: write discard message to sentinel files
Add a new "discard" event type for trace2 event destinations. When the
trace2 file count check creates a sentinel file, it will include the
normal trace2 output in the sentinel, along with this new discard

Writing this message into the sentinel file is useful for tracking how
often the file count check triggers in practice.

Bump up the event format version since we've added a new event type.

Signed-off-by: Josh Steadmon <>
Signed-off-by: Junio C Hamano <>
2019-10-05 17:53:51 +09:00
Josh Steadmon 22541013d0 docs: clarify trace2 version invariants
Make it explicit that we always want trace2 "version" events to be the
first event of any trace session. Also list the changes that would or
would not cause the EVENT format version field to be incremented.

Signed-off-by: Josh Steadmon <>
Signed-off-by: Junio C Hamano <>
2019-10-04 09:26:42 +09:00
Josh Steadmon 3d4548e7e2 docs: mention trace2 target-dir mode in git-config
Move the description of trace2's target-directory behavior into the
shared trace2-target-values file so that it is included in both the
git-config and api-trace2 docs. Leave the SID discussion only in
api-trace2 since it's a technical detail.

Signed-off-by: Josh Steadmon <>
Signed-off-by: Junio C Hamano <>
2019-10-04 09:26:42 +09:00
Junio C Hamano fff813c6ae Merge branch 'js/trace2-signo-typofix'
Documentation fix.

* js/trace2-signo-typofix:
  trace2: correct trace2 field name documentation
2019-07-19 11:30:23 -07:00
Josh Steadmon 24df0d49c4 trace2: correct trace2 field name documentation
Correct the api-trace2 documentation, which lists "signal" as an
expected field for the signal event type, but which actually outputs
"signo" as the field name.

Signed-off-by: Josh Steadmon <>
Signed-off-by: Junio C Hamano <>
2019-07-09 16:28:40 -07:00
Carlo Marcelo Arenas Belón 6114a405bd trace2: correct typo in technical documentation
an apparent typo for the environment variable was included with 81567caf87
("trace2: update docs to describe system/global config settings",
2019-04-15), and was missed when renamed variables by e4b75d6a1d
("trace2: rename environment variables to GIT_TRACE2*", 2019-05-19)

Signed-off-by: Carlo Marcelo Arenas Belón <>
Signed-off-by: Junio C Hamano <>
2019-06-27 10:56:54 -07:00
SZEDER Gábor e4b75d6a1d trace2: rename environment variables to GIT_TRACE2*
For an environment variable that is supposed to be set by users, the
GIT_TR2* env vars are just too unclear, inconsistent, and ugly.

Most of the established GIT_* environment variables don't use
abbreviations, and in case of the few that do (GIT_DIR,
GIT_COMMON_DIR, GIT_DIFF_OPTS) it's quite obvious what the
abbreviations (DIR and OPTS) stand for.  But what does TR stand for?
Track, traditional, trailer, transaction, transfer, transformation,
transition, translation, transplant, transport, traversal, tree,
trigger, truncate, trust, or ...?!

The trace2 facility, as the '2' suffix in its name suggests, is
supposed to eventually supercede Git's original trace facility.  It's
reasonable to expect that the corresponding environment variables
follow suit, and after the original GIT_TRACE variables they are
called GIT_TRACE2; there is no such thing is 'GIT_TR'.

All trace2-specific config variables are, very sensibly, in the
'trace2' section, not in 'tr2'.

OTOH, we don't gain anything at all by omitting the last three
characters of "trace" from the names of these environment variables.

So let's rename all GIT_TR2* environment variables to GIT_TRACE2*,
before they make their way into a stable release.

Signed-off-by: SZEDER Gábor <>
Signed-off-by: Junio C Hamano <>
2019-05-28 10:20:34 -07:00
Junio C Hamano 5b2d1c0c6e Merge branch 'jh/trace2-sid-fix'
Polishing of the new trace2 facility continues.  The system-level
configuration can specify site-wide trace2 settings, which can be
overridden with per-user configuration and environment variables.

* jh/trace2-sid-fix:
  trace2: fixup access problem on /etc/gitconfig in read_very_early_config
  trace2: update docs to describe system/global config settings
  trace2: make SIDs more unique
  trace2: clarify UTC datetime formatting
  trace2: report peak memory usage of the process
  trace2: use system/global config for default trace2 settings
  config: add read_very_early_config()
  trace2: find exec-dir before trace2 initialization
  trace2: add absolute elapsed time to start event
  trace2: refactor setting process starting time
  config: initialize opts structure in repo_read_config()
2019-05-13 23:50:31 +09:00
Jeff Hostetler 81567caf87 trace2: update docs to describe system/global config settings
Signed-off-by: Jeff Hostetler <>
Signed-off-by: Junio C Hamano <>
2019-04-16 13:37:07 +09:00
Jeff Hostetler 08881b9a4c trace2: make SIDs more unique
Update SID component construction to use the current UTC datetime
and a portion of the SHA1 of the hostname.

Use an simplified date/time format to make it easier to use the
SID component as a logfile filename.

Signed-off-by: Jeff Hostetler <>
Signed-off-by: Junio C Hamano <>
2019-04-16 13:37:07 +09:00
Jeff Hostetler bad229aef2 trace2: clarify UTC datetime formatting
Update tr2_tbuf_utc_datetime to generate extended UTC format.
Update tr2_tgt_event target to use extended format in 'time' columns.

Signed-off-by: Jeff Hostetler <>
Signed-off-by: Junio C Hamano <>
2019-04-16 13:37:07 +09:00
Jeff Hostetler 39f4317744 trace2: add absolute elapsed time to start event
Add elapsed process time to "start" event to measure
the performance of early process startup.

Signed-off-by: Jeff Hostetler <>
Signed-off-by: Junio C Hamano <>
2019-04-16 13:37:06 +09:00
Jeff Hostetler a089724958 trace2: refactor setting process starting time
Create trace2_initialize_clock() and call from main() to capture
process start time in isolation and before other sub-systems are

Signed-off-by: Jeff Hostetler <>
Signed-off-by: Junio C Hamano <>
2019-04-16 13:37:06 +09:00
Josh Steadmon a4d3a283db trace2: write to directory targets
When the value of a trace2 environment variable is an absolute path
referring to an existing directory, write output to files (one per
process) underneath the given directory. Files will be named according
to the final component of the trace2 SID, followed by a counter to avoid
potential collisions.

This makes it more convenient to collect traces for every git invocation
by unconditionally setting the relevant trace2 envvar to a constant
directory name.

Signed-off-by: Josh Steadmon <>
Reviewed-by: Jeff Hostetler <>
Signed-off-by: Junio C Hamano <>
2019-03-22 14:27:02 +09:00
Jeff Hostetler e544221d97 trace2: Documentation/technical/api-trace2.txt
Created design document for Trace2 feature.

Signed-off-by: Jeff Hostetler <>
Signed-off-by: Junio C Hamano <>
2019-02-22 15:27:59 -08:00