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 <steadmon@google.com>
Acked-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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
event.
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 <steadmon@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
trace2 can write files into a target directory. With heavy usage, this
directory can fill up with files, causing difficulty for
trace-processing systems.
This patch adds a config option (trace2.maxFiles) to set a maximum
number of files that trace2 will write to a target directory. The
following behavior is enabled when the maxFiles is set to a positive
integer:
When trace2 would write a file to a target directory, first check
whether or not the traces should be discarded. Traces should be
discarded if:
* there is a sentinel file declaring that there are too many files
* OR, the number of files exceeds trace2.maxFiles.
In the latter case, we create a sentinel file named git-trace2-discard
to speed up future checks.
The assumption is that a separate trace-processing system is dealing
with the generated traces; once it processes and removes the sentinel
file, it should be safe to generate new trace files again.
The default value for trace2.maxFiles is zero, which disables the file
count check.
The config can also be overridden with a new environment variable:
GIT_TRACE2_MAX_FILES.
Signed-off-by: Josh Steadmon <steadmon@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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 <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Teach git to read the system and global config files for
default Trace2 settings. This allows system-wide Trace2 settings to
be installed and inherited to make it easier to manage a collection of
systems.
The original GIT_TR2* environment variables are loaded afterwards and
can be used to override the system settings.
Only the system and global config files are used. Repo and worktree
local config files are ignored. Likewise, the "-c" command line
arguments are also ignored. These limits are for performance reasons.
(1) For users not using Trace2, there should be minimal overhead to
detect that Trace2 is not enabled. In particular, Trace2 should not
allocate lots of otherwise unused data strucutres.
(2) For accurate performance measurements, Trace2 should be initialized
as early in the git process as possible, and before most of the normal
git process initialization (which involves discovering the .git directory
and reading a hierarchy of config files).
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
