formats in the future. This might be used to define a binary format,
for example.
+Trace2 is controlled using `trace2.*` config values in the system and
+global config files and `GIT_TR2*` environment variables. Trace2 does
+not read from repo local or worktree config files or respect `-c`
+command line config settings.
+
== Trace2 Targets
Trace2 defines the following set of Trace2 Targets.
Format details are given in a later section.
-`GIT_TR2` (NORMAL)::
+=== The Normal Format Target
+
+The normal format target is a tradition printf format and similar
+to GIT_TRACE format. This format is enabled with the `GIT_TR`
+environment variable or the `trace2.normalTarget` system or global
+config setting.
+
+For example
- a simple printf format like GIT_TRACE.
-+
------------
$ export GIT_TR2=~/log.normal
$ git version
git version 2.20.1.155.g426c96fcdb
------------
-+
+
+or
+
+------------
+$ git config --global trace2.normalTarget ~/log.normal
+$ git version
+git version 2.20.1.155.g426c96fcdb
+------------
+
+yields
+
------------
$ cat ~/log.normal
12:28:42.620009 common-main.c:38 version 2.20.1.155.g426c96fcdb
12:28:42.621250 trace2/tr2_tgt_normal.c:124 atexit elapsed:0.001265 code:0
------------
-`GIT_TR2_PERF` (PERF)::
+=== The Performance Format Target
+
+The performance format target (PERF) is a column-based format to
+replace GIT_TRACE_PERFORMANCE and is suitable for development and
+testing, possibly to complement tools like gprof. This format is
+enabled with the `GIT_TR2_PERF` environment variable or the
+`trace2.perfTarget` system or global config setting.
+
+For example
- a column-based format to replace GIT_TRACE_PERFORMANCE suitable for
- development and testing, possibly to complement tools like gprof.
-+
------------
$ export GIT_TR2_PERF=~/log.perf
$ git version
git version 2.20.1.155.g426c96fcdb
------------
-+
+
+or
+
+------------
+$ git config --global trace2.perfTarget ~/log.perf
+$ git version
+git version 2.20.1.155.g426c96fcdb
+------------
+
+yields
+
------------
$ cat ~/log.perf
12:28:42.620675 common-main.c:38 | d0 | main | version | | | | | 2.20.1.155.g426c96fcdb
-12:28:42.621001 common-main.c:39 | d0 | main | start | | | | | git version
+12:28:42.621001 common-main.c:39 | d0 | main | start | | 0.001173 | | | git version
12:28:42.621111 git.c:432 | d0 | main | cmd_name | | | | | version (version)
12:28:42.621225 git.c:662 | d0 | main | exit | | 0.001227 | | | code:0
12:28:42.621259 trace2/tr2_tgt_perf.c:211 | d0 | main | atexit | | 0.001265 | | | code:0
------------
-`GIT_TR2_EVENT` (EVENT)::
+=== The Event Format Target
+
+The event format target is a JSON-based format of event data suitable
+for telemetry analysis. This format is enabled with the `GIT_TR2_EVENT`
+environment variable or the `trace2.eventTarget` system or global config
+setting.
+
+For example
- a JSON-based format of event data suitable for telemetry analysis.
-+
------------
$ export GIT_TR2_EVENT=~/log.event
$ git version
git version 2.20.1.155.g426c96fcdb
------------
-+
-------------
-$ cat ~/log.event
-{"event":"version","sid":"1547659722619736-11614","thread":"main","time":"2019-01-16 17:28:42.620713","file":"common-main.c","line":38,"evt":"1","exe":"2.20.1.155.g426c96fcdb"}
-{"event":"start","sid":"1547659722619736-11614","thread":"main","time":"2019-01-16 17:28:42.621027","file":"common-main.c","line":39,"argv":["git","version"]}
-{"event":"cmd_name","sid":"1547659722619736-11614","thread":"main","time":"2019-01-16 17:28:42.621122","file":"git.c","line":432,"name":"version","hierarchy":"version"}
-{"event":"exit","sid":"1547659722619736-11614","thread":"main","time":"2019-01-16 17:28:42.621236","file":"git.c","line":662,"t_abs":0.001227,"code":0}
-{"event":"atexit","sid":"1547659722619736-11614","thread":"main","time":"2019-01-16 17:28:42.621268","file":"trace2/tr2_tgt_event.c","line":163,"t_abs":0.001265,"code":0}
-------------
-
-== Enabling a Target
-A Trace2 Target is enabled when the corresponding environment variable
-(`GIT_TR2`, `GIT_TR2_PERF`, or `GIT_TR2_EVENT`) is set. The following
-values are recognized.
+or
-`0`::
-`false`::
-
- Disables the target.
-
-`1`::
-`true`::
-
- Enables the target and writes stream to `STDERR`.
-
-`[2-9]`::
+------------
+$ git config --global trace2.eventTarget ~/log.event
+$ git version
+git version 2.20.1.155.g426c96fcdb
+------------
- Enables the target and writes to the already opened file descriptor.
+yields
-`<absolute-pathname>`::
+------------
+$ cat ~/log.event
+{"event":"version","sid":"sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.620713Z","file":"common-main.c","line":38,"evt":"1","exe":"2.20.1.155.g426c96fcdb"}
+{"event":"start","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621027Z","file":"common-main.c","line":39,"t_abs":0.001173,"argv":["git","version"]}
+{"event":"cmd_name","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621122Z","file":"git.c","line":432,"name":"version","hierarchy":"version"}
+{"event":"exit","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621236Z","file":"git.c","line":662,"t_abs":0.001227,"code":0}
+{"event":"atexit","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621268Z","file":"trace2/tr2_tgt_event.c","line":163,"t_abs":0.001265,"code":0}
+------------
- Enables the target, opens and writes to the file in append mode.
+=== Enabling a Target
- If the target already exists and is a directory, the traces will be
- written to files (one per process) underneath the given directory. They
- will be named according to the last component of the SID (optionally
- followed by a counter to avoid filename collisions).
+To enable a target, set the corresponding environment variable or
+system or global config value to one of the following:
-`af_unix:[<socket_type>:]<absolute-pathname>`::
+include::../trace2-target-values.txt[]
- Enables the target, opens and writes to a Unix Domain Socket
- (on platforms that support them).
-+
-Socket type can be either `stream` or `dgram`. If the socket type is
-omitted, Git will try both.
+If the target already exists and is a directory, the traces will be
+written to files (one per process) underneath the given directory. They
+will be named according to the last component of the SID (optionally
+followed by a counter to avoid filename collisions).
== Trace2 API
These are concerned with the lifetime of the overall git process.
+`void trace2_initialize_clock()`::
+
+ Initialize the Trace2 start clock and nothing else. This should
+ be called at the very top of main() to capture the process start
+ time and reduce startup order dependencies.
+
`void trace2_initialize()`::
Determines if any Trace2 Targets should be enabled and
- initializes the Trace2 facility. This includes starting the
- elapsed time clocks and thread local storage (TLS).
+ initializes the Trace2 facility. This includes setting up the
+ Trace2 thread local storage (TLS).
+
This function emits a "version" message containing the version of git
and the Trace2 protocol.
+
This function should be called from `main()` as early as possible in
-the life of the process.
+the life of the process after essential process initialization.
`int trace2_is_enabled()`::
Emits a "def_param" messages for "important" configuration
settings.
+
-The environment variable `GIT_TR2_CONFIG_PARAMS` can be set to a
+The environment variable `GIT_TR2_CONFIG_PARAMS` or the `trace2.configParams`
+config value can be set to a
list of patterns of important configuration settings, for example:
`core.*,remote.*.url`. This function will iterate over all config
settings and emit a "def_param" message for each match.
`void trace2_cmd_set_config(const char *key, const char *value)`::
- Emits a "def_param" message for a specific configuration
- setting IFF it matches the `GIT_TR2_CONFIG_PARAMS` pattern.
+ Emits a "def_param" message for a new or updated key/value
+ pair IF `key` is considered important.
+
This is used to hook into `git_config_set()` and catch any
configuration changes and update a value previously reported by
=== NORMAL Format
-NORMAL format is enabled when the `GIT_TR2` environment variable is
-set.
-
Events are written as lines of the form:
------------
Note that this may contain embedded LF or CRLF characters that are
not escaped, so the event may spill across multiple lines.
-If `GIT_TR2_BRIEF` is true, the `time`, `filename`, and `line` fields
-are omitted.
+If `GIT_TR2_BRIEF` or `trace2.normalBrief` is true, the `time`, `filename`,
+and `line` fields are omitted.
This target is intended to be more of a summary (like GIT_TRACE) and
less detailed than the other targets. It ignores thread, region, and
=== PERF Format
-PERF format is enabled when the `GIT_TR2_PERF` environment variable
-is set.
-
Events are written as lines of the form:
------------
15:33:33.532712 wt-status.c:2331 | d0 | main | region_leave | r1 | 0.127568 | 0.001504 | status | label:print
------------
-If `GIT_TR2_PERF_BRIEF` is true, the `time`, `file`, and `line`
-fields are omitted.
+If `GIT_TR2_PERF_BRIEF` or `trace2.perfBrief` is true, the `time`, `file`,
+and `line` fields are omitted.
------------
d0 | main | region_leave | r1 | 0.011717 | 0.009122 | index | label:preload
=== EVENT Format
-EVENT format is enabled when the `GIT_TR2_EVENT` environment
-variable is set.
-
Each event is a JSON-object containing multiple key/value pairs
written as a single line and followed by a LF.
------------
{
"event":"version",
- "sid":"1547659722619736-11614",
+ "sid":"20190408T191827.272759Z-H9b68c35f-P00003510",
"thread":"main",
- "time":"2019-01-16 17:28:42.620713",
+ "time":"2019-04-08T19:18:27.282761Z",
"file":"common-main.c",
- "line":38,
+ "line":42,
...
}
------------
`"repo":<repo-id>`::
when present, is the integer repo-id as described previously.
-If `GIT_TR2_EVENT_BRIEF` is true, the `file` and `line` fields are omitted
-from all events and the `time` field is only present on the "start" and
-"atexit" events.
+If `GIT_TR2_EVENT_BRIEF` or `trace2.eventBrief` is true, the `file`
+and `line` fields are omitted from all events and the `time` field is
+only present on the "start" and "atexit" events.
==== Event-Specific Key/Value Pairs
{
"event":"start",
...
+ "t_abs":0.001227, # elapsed time in seconds
"argv":["git","version"]
}
------------
The `category` field may be used in a future enhancement to
do category-based filtering.
+
-The `GIT_TR2_EVENT_NESTING` environment variable can be used to
+`GIT_TR2_EVENT_NESTING` or `trace2.eventNesting` can be used to
filter deeply nested regions and data events. It defaults to "2".
`"region_leave"`::
$ cat ~/log.perf
d0 | main | version | | | | | 2.20.1.160.g5676107ecd.dirty
-d0 | main | start | | | | | git status
+d0 | main | start | | 0.001173 | | | git status
d0 | main | def_repo | r1 | | | | worktree:/Users/jeffhost/work/gfw
d0 | main | cmd_name | | | | | status (status)
...
...
$ cat ~/log.perf
d0 | main | version | | | | | 2.20.1.162.gb4ccea44db.dirty
-d0 | main | start | | | | | git status
+d0 | main | start | | 0.001173 | | | git status
d0 | main | def_repo | r1 | | | | worktree:/Users/jeffhost/work/gfw
d0 | main | cmd_name | | | | | status (status)
...
...
$ cat ~/log.perf
d0 | main | version | | | | | 2.20.1.156.gf9916ae094.dirty
-d0 | main | start | | | | | git status
+d0 | main | start | | 0.001173 | | | git status
d0 | main | def_repo | r1 | | | | worktree:/Users/jeffhost/work/gfw
d0 | main | cmd_name | | | | | status (status)
d0 | main | region_enter | r1 | 0.001791 | | index | label:do_read_index .git/index