journalctl: Periodically call sd_journal_process in journalctl

If `journalctl` take a long time to process messages, and during that
time journal file rotation occurs, a `journalctl` client will keep
those rotated files open until it calls `sd_journal_process()`, which
typically happens as a result of calling `sd_journal_wait()` below in
the "following" case.  By periodically calling `sd_journal_process()`
during the processing loop we shrink the window of time a client
instance has open file descriptors for rotated (deleted) journal
files.

(Lennart: slightly reworked version, that dropped some of the commenting
which was solved otherwise)

diff --git a/src/journal/journalctl.c b/src/journal/journalctl.c
index bb9cfb6dc4dfb7354ab1c05393b405484755771b..0aa4c1f7724d6757d9e75a95329a9d6495ba2b61 100644 (file)
--- a/src/journal/journalctl.c
+++ b/src/journal/journalctl.c
@@ -81,6 +81,8 @@
 
 #define DEFAULT_FSS_INTERVAL_USEC (15*USEC_PER_MINUTE)
 
+#define PROCESS_INOTIFY_INTERVAL 1024   /* Every 1,024 messages processed */
+
 #if HAVE_PCRE2
 DEFINE_TRIVIAL_CLEANUP_FUNC(pcre2_match_data*, pcre2_match_data_free);
 DEFINE_TRIVIAL_CLEANUP_FUNC(pcre2_code*, pcre2_code_free);
@@ -2639,6 +2641,20 @@ int main(int argc, char *argv[]) {
                                 goto finish;
 
                         n_shown++;
+
+                        /* If journalctl take a long time to process messages, and during that time journal file
+                         * rotation occurs, a journalctl client will keep those rotated files open until it calls
+                         * sd_journal_process(), which typically happens as a result of calling sd_journal_wait() below
+                         * in the "following" case.  By periodically calling sd_journal_process() during the processing
+                         * loop we shrink the window of time a client instance has open file descriptors for rotated
+                         * (deleted) journal files. */
+                        if ((n_shown % PROCESS_INOTIFY_INTERVAL) == 0) {
+                                r = sd_journal_process(j);
+                                if (r < 0) {
+                                        log_error_errno(r, "Failed to process inotify events: %m");
+                                        goto finish;
+                                }
+                        }
                 }
 
                 if (!arg_follow) {