git/Documentation/technical/api-trace2.txt, branch v2.35.2

trace2: increment event format version

2021-11-11T23:01:04Z

In 64bc752 (trace2: add trace2_child_ready() to report on background children, 2021-09-20), we added a new "child_ready" event. In Documentation/technical/api-trace2.txt, we promise that adding a new event type will result in incrementing the trace2 event format version number, but this was not done. Correct this in code & docs. Signed-off-by: Josh Steadmon Signed-off-by: Junio C Hamano

trace2: add trace2_child_ready() to report on background children

2021-09-20T15:57:58Z

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

Merge branch 'es/trace2-log-parent-process-name'

2021-08-24T22:32:40Z

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

tr2: log parent process name

2021-07-22T20:35:20Z

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

Merge branch 'js/trace2-discard-event-docfix'

2021-07-08T20:14:57Z

Docfix. * js/trace2-discard-event-docfix: docs: fix api-trace2 doc for "too_many_files" event

docs: fix api-trace2 doc for "too_many_files" event

2021-06-04T03:11:16Z

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

api docs: document that BUG() emits a trace2 error event

2021-04-13T21:57:13Z

Correct documentation added in e544221d97a (trace2: Documentation/technical/api-trace2.txt, 2019-02-22) to state that calling BUG() also emits an "error" event. See ee4512ed481 (trace2: create new combined trace facility, 2019-02-22) for the initial implementation. The BUG() function did not emit an event then however, that was only changed later in 0a9dde4a04c (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

usage: add trace2 entry upon warning()

2020-11-25T01:39:38Z

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]. [1] https://lore.kernel.org/git/20200629220744.1054093-1-jonathantanmy@google.com/ Signed-off-by: Jonathan Tan Signed-off-by: Junio C Hamano

trace2: teach Git to log environment variables

2020-03-23T20:14:53Z

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

Merge branch 'hw/doc-in-header'

2019-12-16T21:08:39Z

* 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