From c6e7a1b8e9da7813661096b096c65b137b72e35f Mon Sep 17 00:00:00 2001 From: Willy Tarreau Date: Sun, 28 Jun 2020 01:24:12 +0200 Subject: [PATCH] MINOR: cli: make "show sess" stop at the last known session "show sess" and particularly "show sess all" can be very slow when dumping lots of information, and while dumping, new sessions might appear, making the output really endless. When threads are used, this causes a double problem: - all threads are paused during the dump, so an overly long dump degrades the quality of service ; - since all threads are paused, more events get postponed, possibly resulting in more streams to be dumped on next invocation of the dump function. This patch addresses this long-lasting issue by doing something simple: the CLI's stream is moved at the end of the steams list, serving as an identifiable marker to end the dump, because all entries past it were added after the command was entered. As a result, the CLI's stream always appears as the last one. It may make sense to backport this to stable branches where dumping live streams is difficult as well. --- doc/management.txt | 6 +++++- src/stream.c | 13 +++++++++++-- 2 files changed, 16 insertions(+), 3 deletions(-) diff --git a/doc/management.txt b/doc/management.txt index 00ce3909e..0877992b6 100644 --- a/doc/management.txt +++ b/doc/management.txt @@ -2390,7 +2390,11 @@ show servers state [] show sess Dump all known sessions. Avoid doing this on slow connections as this can be huge. This command is restricted and can only be issued on sockets - configured for levels "operator" or "admin". + configured for levels "operator" or "admin". Note that on machines with + quickly recycled connections, it is possible that this output reports less + entries than really exist because it will dump all existing sessions up to + the last one that was created before the command was entered; those which + die in the mean time will not appear. show sess Display a lot of internal information about the specified session identifier. diff --git a/src/stream.c b/src/stream.c index f0618de4d..287f40647 100644 --- a/src/stream.c +++ b/src/stream.c @@ -3137,6 +3137,15 @@ static int cli_parse_show_sess(char **args, char *payload, struct appctx *appctx appctx->ctx.sess.section = 0; /* start with stream status */ appctx->ctx.sess.pos = 0; + /* we need to put an end marker into the streams list. We're just moving + * ourselves there, so that once we found ourselves we know we've reached + * the end. Without this we can run forever if new streams arrive faster + * than we can dump them. + */ + HA_SPIN_LOCK(STRMS_LOCK, &streams_lock); + LIST_DEL(&si_strm(appctx->owner)->list); + LIST_ADDQ(&streams, &si_strm(appctx->owner)->list); + HA_SPIN_UNLOCK(STRMS_LOCK, &streams_lock); return 0; } @@ -3188,8 +3197,8 @@ static int cli_io_handler_dump_sess(struct appctx *appctx) LIST_INIT(&appctx->ctx.sess.bref.users); } - /* and start from where we stopped */ - while (appctx->ctx.sess.bref.ref != &streams) { + /* and start from where we stopped, never going further than ourselves */ + while (appctx->ctx.sess.bref.ref != si_strm(appctx->owner)->list.n) { char pn[INET6_ADDRSTRLEN]; struct stream *curr_strm;