From: Jeff Hostetler <email@example.com> To: Josh Steadmon <firstname.lastname@example.org>, email@example.com Cc: firstname.lastname@example.org Subject: Re: [RFC PATCH v2 2/2] trace2: don't overload target directories Date: Mon, 5 Aug 2019 11:34:11 -0400 [thread overview] Message-ID: <email@example.com> (raw) In-Reply-To: <firstname.lastname@example.org> On 8/2/2019 6:02 PM, Josh Steadmon wrote: > 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 directory is overloaded. A directory is overloaded > if there is a sentinel file declaring an overload, or if the number of > files exceeds trace2.maxFiles. If the latter, create a sentinel file > to speed up later overload 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 > overload check. > > The config can also be overridden with a new environment variable: > GIT_TRACE2_MAX_FILES. > > Potential future work: > * Write a message into the sentinel file (should match the requested > trace2 output format). > * Add a performance test to make sure that contention between multiple > processes all writing to the same target directory does not become an > issue. This looks much nicer than the V1 version. Having it be a real feature rather than a test feature helps. I don't see anything wrong with this. I do worry about the overhead a bit. If you really have that many files in the target directory, having every command count them at startup might be an issue. As an alternative, you might consider doing something like this:  have an option to make the target directory path expand to something like "<path>/yyyymmdd/" and create the per-process files as "<path>/yyyymmdd/<sid>". If there are 0, 1 or 2 directories, logging is enabled. We assume that the post-processor is keeping up and all is well. We need to allow 2 so that we continue to log around midnight. If there are 3 or more directories, logging is disabled. The post-processor is more than 24 hours behind for whatever reason. We assume here that the post-processor will process and delete the oldest-named directory, so it is a valid measure of the backlog. I suggest "yyyymmdd" here for simplicity in this discussion as daily log rotation is common. If that's still overloading, you could make it a longer prefix of the <sid>. And include the hour, for example. I suggest 3 as the cutoff lower bound, because we need to allow 2 for midnight rotation. But you may want to increase it to allow for someone to be offline for a long weekend, for example. Anyway, this is just a suggestion. It would give you the throttling, but without the need for every command to count the contents of the target directory. And it would still allow your post-processor to operate in near real-time on the contents of the current day's target directory or to hang back if that causes too much contention. Feel free to ignore this :-) Jeff
next prev parent reply other threads:[~2019-08-05 15:34 UTC|newest] Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-07-29 22:20 [RFC PATCH] " Josh Steadmon 2019-07-30 13:29 ` Derrick Stolee 2019-07-30 21:52 ` Josh Steadmon 2019-07-30 16:46 ` Jeff Hostetler 2019-07-30 22:01 ` Josh Steadmon 2019-07-30 22:02 ` Josh Steadmon 2019-07-30 18:00 ` Jeff Hostetler 2019-07-30 22:08 ` Josh Steadmon 2019-08-02 22:02 ` [RFC PATCH v2 0/2] " Josh Steadmon 2019-08-02 22:02 ` [RFC PATCH v2 1/2] docs: mention trace2 target-dir mode in git-config Josh Steadmon 2019-08-02 22:02 ` [RFC PATCH v2 2/2] trace2: don't overload target directories Josh Steadmon 2019-08-05 15:34 ` Jeff Hostetler [this message] 2019-08-05 18:17 ` Josh Steadmon 2019-08-05 18:01 ` SZEDER Gábor 2019-08-05 18:09 ` Josh Steadmon 2019-09-14 0:25 ` [RFC PATCH v3 0/3] " Josh Steadmon 2019-09-14 0:25 ` [RFC PATCH v3 1/3] docs: mention trace2 target-dir mode in git-config Josh Steadmon 2019-09-14 0:25 ` [RFC PATCH v3 2/3] trace2: don't overload target directories Josh Steadmon 2019-09-14 0:26 ` [RFC PATCH v3 3/3] trace2: write overload message to sentinel files Josh Steadmon 2019-09-16 12:07 ` Derrick Stolee 2019-09-16 14:11 ` Jeff Hostetler 2019-09-16 18:20 ` Josh Steadmon 2019-09-19 18:23 ` Jeff Hostetler 2019-09-19 22:47 ` Josh Steadmon 2019-09-20 15:59 ` Jeff Hostetler 2019-09-16 18:07 ` Josh Steadmon 2019-10-03 23:32 ` [PATCH v4 0/4] trace2: don't overload target directories Josh Steadmon 2019-10-03 23:32 ` [PATCH v4 1/4] docs: mention trace2 target-dir mode in git-config Josh Steadmon 2019-10-03 23:32 ` [PATCH v4 2/4] docs: clarify trace2 version invariants Josh Steadmon 2019-10-03 23:32 ` [PATCH v4 3/4] trace2: don't overload target directories Josh Steadmon 2019-10-04 0:25 ` Junio C Hamano 2019-10-04 21:57 ` Josh Steadmon 2019-10-04 9:12 ` Johannes Schindelin 2019-10-04 22:05 ` Josh Steadmon 2019-10-03 23:32 ` [PATCH v4 4/4] trace2: write overload message to sentinel files Josh Steadmon 2019-10-04 22:08 ` [PATCH v5 0/4] trace2: discard new traces if the target directory contains too many files Josh Steadmon 2019-10-04 22:08 ` [PATCH v5 1/4] docs: mention trace2 target-dir mode in git-config Josh Steadmon 2019-10-04 22:08 ` [PATCH v5 2/4] docs: clarify trace2 version invariants Josh Steadmon 2019-10-04 22:08 ` [PATCH v5 3/4] trace2: discard new traces if target directory has too many files Josh Steadmon 2019-10-04 22:08 ` [PATCH v5 4/4] trace2: write discard message to sentinel files Josh Steadmon
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