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From 98169577b83b45a40105cf58e6cffe0272074817 Mon Sep 17 00:00:00 2001
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From: Peter Portante <peter.a.portante@gmail.com>
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Date: Sun, 28 Jan 2018 16:48:04 -0500
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Subject: [PATCH] journalctl: Periodically call sd_journal_process in
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 journalctl
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If `journalctl` take a long time to process messages, and during that
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time journal file rotation occurs, a `journalctl` client will keep
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those rotated files open until it calls `sd_journal_process()`, which
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typically happens as a result of calling `sd_journal_wait()` below in
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the "following" case.  By periodically calling `sd_journal_process()`
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during the processing loop we shrink the window of time a client
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instance has open file descriptors for rotated (deleted) journal
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files.
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(Lennart: slightly reworked version, that dropped some of the commenting
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which was solved otherwise)
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(cherry picked from commit ec316d199a13d8db3f6550d60e369893de2fb417)
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Related: #1540538
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---
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 src/journal/journalctl.c | 16 ++++++++++++++++
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 1 file changed, 16 insertions(+)
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diff --git a/src/journal/journalctl.c b/src/journal/journalctl.c
Pablo Greco 48fc63
index 0be70764ef..1e6d0761c7 100644
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--- a/src/journal/journalctl.c
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+++ b/src/journal/journalctl.c
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@@ -67,6 +67,8 @@
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 #define DEFAULT_FSS_INTERVAL_USEC (15*USEC_PER_MINUTE)
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+#define PROCESS_INOTIFY_INTERVAL 1024   /* Every 1,024 messages processed */
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+
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 enum {
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         /* Special values for arg_lines */
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         ARG_LINES_DEFAULT = -2,
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@@ -2294,6 +2296,20 @@ int main(int argc, char *argv[]) {
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                                 goto finish;
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                         n_shown++;
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+
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+                        /* If journalctl take a long time to process messages, and during that time journal file
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+                         * rotation occurs, a journalctl client will keep those rotated files open until it calls
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+                         * sd_journal_process(), which typically happens as a result of calling sd_journal_wait() below
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+                         * in the "following" case.  By periodically calling sd_journal_process() during the processing
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+                         * loop we shrink the window of time a client instance has open file descriptors for rotated
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+                         * (deleted) journal files. */
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+                        if ((n_shown % PROCESS_INOTIFY_INTERVAL) == 0) {
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+                                r = sd_journal_process(j);
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+                                if (r < 0) {
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+                                        log_error_errno(r, "Failed to process inotify events: %m");
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+                                        goto finish;
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+                                }
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+                        }
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                 }
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                 if (!arg_follow) {