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2020-03-23trace2: teach Git to log environment variablesLibravatar Josh Steadmon1-0/+2
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>
2019-10-05trace2: discard new traces if target directory has too many filesLibravatar Josh Steadmon1-0/+3
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>
2019-05-28trace2: rename environment variables to GIT_TRACE2*Libravatar SZEDER Gábor1-10/+10
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>
2019-04-16trace2: use system/global config for default trace2 settingsLibravatar Jeff Hostetler1-0/+127
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>