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journalctl: add new --sync switch for syncing the journal to disk 

With this new "--sync" switch we add a synchronous way to sync
everything queued to disk, and return only after that's complete. This
command gives the guarantee that anything queued before has hit the disk
before the command returns.

While we are at it, also improve the man pages and help text for
journalctl a bit.
This commit is contained in:
Lennart Poettering 2015-11-11 12:59:09 +01:00
parent 404f08d341
commit 94b6551662
5 changed files with 171 additions and 18 deletions
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24
man/journalctl.xml
View File

@ -772,14 +772,32 @@
the <option>--verify</option> operation.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--sync</option></term>
<listitem><para>Ask the journal daemon to write all yet
unwritten journal data to the backing file system and
synchronize all journals. This call does not return until the
operation is complete. This command guarantees that any log
messages written before its invocation are safely stored on
disk at the time it returns.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--flush</option></term>
<listitem><para>Asks the journal daemon to flush any log data
stored in <filename>/run/log/journal</filename> into
<filename>/var/log/journal</filename>, if persistent storage is
enabled. This call does not return until the operation is
complete.</para></listitem>
<filename>/var/log/journal</filename>, if persistent storage
is enabled. This call does not return until the operation is
complete. Note that this call is idempotent: the data is only
flushed from <filename>/run/log/journal</filename> into
<filename>/var/log/journal</filename> once during system
runtime, and this command exits cleanly without executing any
operation if this has already has happened. This command
effectively guarantees that all data is flushed to
<filename>/var/log/journal</filename> at the time it
returns.</para></listitem>
</varlistentry>
<varlistentry>

23
man/systemd-journald.service.xml
View File

@ -131,15 +131,30 @@ systemd-tmpfiles --create --prefix /var/log/journal</programlisting>
this is enabled). This must be used after
<filename>/var/</filename> is mounted, as otherwise log data
from <filename>/run</filename> is never flushed to
<filename>/var</filename> regardless of the
configuration.</para></listitem>
<filename>/var</filename> regardless of the configuration. The
<command>journalctl --flush</command> command uses this signal
to request flushing of the journal files, and then waits for
the operation to complete. See
<citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
for details.</para></listitem>
</varlistentry>
<varlistentry>
<term>SIGUSR2</term>
<listitem><para>Request immediate rotation of the journal
files.</para></listitem>
files. The <command>journalctl --rotate</command> command uses
this signal to request journal file
rotation.</para></listitem>
</varlistentry>
<varlistentry>
<term>SIGRTMIN+1</term>
<listitem><para>Request that all unwritten log data is written
to disk. The <command>journalctl --sync</command> command uses
this signal to trigger journal synchronization, and then waits
for the operation to complete.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
@ -261,7 +276,7 @@ systemd-tmpfiles --create --prefix /var/log/journal</programlisting>
<citerefentry><refentrytitle>systemd-coredump</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry project='die-net'><refentrytitle>setfacl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>4</manvolnum></citerefentry>,
<command>pydoc systemd.journal</command>.
<command>pydoc systemd.journal</command>
</para>
</refsect1>

106
src/journal/journalctl.c
View File

@ -135,6 +135,7 @@ static enum {
ACTION_FLUSH,
ACTION_ROTATE,
ACTION_VACUUM,
ACTION_SYNC,
} arg_action = ACTION_SHOW;
typedef struct BootId {
@ -201,7 +202,7 @@ static void help(void) {
printf("%s [OPTIONS...] [MATCHES...]\n\n"
"Query the journal.\n\n"
"Flags:\n"
"Options:\n"
" --system Show the system journal\n"
" --user Show the user journal for the current user\n"
" -M --machine=CONTAINER Operate on local container\n"
@ -234,7 +235,7 @@ static void help(void) {
" -m --merge Show entries from all available journals\n"
" -D --directory=PATH Show journal files from directory\n"
" --file=PATH Show journal file\n"
" --root=ROOT Operate on catalog files underneath the root ROOT\n"
" --root=ROOT Operate on catalog files below a root directory\n"
#ifdef HAVE_GCRYPT
" --interval=TIME Time interval for changing the FSS sealing key\n"
" --verify-key=KEY Specify FSS verification key\n"
@ -244,20 +245,21 @@ static void help(void) {
" -h --help Show this help text\n"
" --version Show package version\n"
" -F --field=FIELD List all values that a specified field takes\n"
" --new-id128 Generate a new 128-bit ID\n"
" --disk-usage Show total disk usage of all journal files\n"
" --vacuum-size=BYTES Reduce disk usage below specified size\n"
" --vacuum-files=INT Leave only the specified number of journal files\n"
" --vacuum-time=TIME Remove journal files older than specified time\n"
" --verify Verify journal file consistency\n"
" --sync Synchronize unwritten journal messages to disk\n"
" --flush Flush all journal data from /run into /var\n"
" --rotate Request immediate rotation of the journal files\n"
" --header Show journal header information\n"
" --list-catalog Show all message IDs in the catalog\n"
" --dump-catalog Show entries in the message catalog\n"
" --update-catalog Update the message catalog database\n"
" --new-id128 Generate a new 128-bit ID\n"
#ifdef HAVE_GCRYPT
" --setup-keys Generate a new FSS key pair\n"
" --verify Verify journal file consistency\n"
#endif
, program_invocation_short_name);
}
@ -289,6 +291,7 @@ static int parse_argv(int argc, char *argv[]) {
ARG_UPDATE_CATALOG,
ARG_FORCE,
ARG_UTC,
ARG_SYNC,
ARG_FLUSH,
ARG_ROTATE,
ARG_VACUUM_SIZE,
@ -345,6 +348,7 @@ static int parse_argv(int argc, char *argv[]) {
{ "machine", required_argument, NULL, 'M' },
{ "utc", no_argument, NULL, ARG_UTC },
{ "flush", no_argument, NULL, ARG_FLUSH },
{ "sync", no_argument, NULL, ARG_SYNC },
{ "rotate", no_argument, NULL, ARG_ROTATE },
{ "vacuum-size", required_argument, NULL, ARG_VACUUM_SIZE },
{ "vacuum-files", required_argument, NULL, ARG_VACUUM_FILES },
@ -729,6 +733,10 @@ static int parse_argv(int argc, char *argv[]) {
arg_action = ACTION_ROTATE;
break;
case ARG_SYNC:
arg_action = ACTION_SYNC;
break;
case '?':
return -EINVAL;
@ -1782,10 +1790,8 @@ static int flush_to_var(void) {
&error,
NULL,
"ssi", "systemd-journald.service", "main", SIGUSR1);
if (r < 0) {
log_error("Failed to kill journal service: %s", bus_error_message(&error, r));
return r;
}
if (r < 0)
return log_error_errno(r, "Failed to kill journal service: %s", bus_error_message(&error, r));
mkdir_p("/run/systemd/journal", 0755);
@ -1840,6 +1846,85 @@ static int rotate(void) {
return 0;
}
static int sync_journal(void) {
_cleanup_bus_flush_close_unref_ sd_bus *bus = NULL;
_cleanup_close_ int watch_fd = -1;
usec_t start;
int r;
start = now(CLOCK_REALTIME);
/* Let's watch /run/systemd/sync until it's mtime is above
* the time we started the sync. Let's enqueue SIGRTMIN+1 to
* start the sync. */
for (;;) {
struct stat st;
/* See if a sync happened by now. */
if (stat("/run/systemd/journal/synced", &st) < 0) {
if (errno != ENOENT)
return log_error_errno(errno, "Failed to stat /run/systemd/journal/synced: %m");
} else {
if (timespec_load(&st.st_mtim) >= start)
return 0;
}
/* Let's ask for a sync, but only once. */
if (!bus) {
_cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
r = bus_connect_system_systemd(&bus);
if (r < 0)
return log_error_errno(r, "Failed to get D-Bus connection: %m");
r = sd_bus_call_method(
bus,
"org.freedesktop.systemd1",
"/org/freedesktop/systemd1",
"org.freedesktop.systemd1.Manager",
"KillUnit",
&error,
NULL,
"ssi", "systemd-journald.service", "main", SIGRTMIN+1);
if (r < 0)
return log_error_errno(r, "Failed to kill journal service: %s", bus_error_message(&error, r));
continue;
}
/* Let's install the inotify watch, if we didn't do that yet. */
if (watch_fd < 0) {
mkdir_p("/run/systemd/journal", 0755);
watch_fd = inotify_init1(IN_NONBLOCK|IN_CLOEXEC);
if (watch_fd < 0)
return log_error_errno(errno, "Failed to create inotify watch: %m");
r = inotify_add_watch(watch_fd, "/run/systemd/journal", IN_CREATE|IN_ATTRIB|IN_DONT_FOLLOW|IN_ONLYDIR);
if (r < 0)
return log_error_errno(errno, "Failed to watch journal directory: %m");
/* Recheck the flag file immediately, so that we don't miss any event since the last check. */
continue;
}
/* OK, all preparatory steps done, let's wait until
* inotify reports an event. */
r = fd_wait_for_event(watch_fd, POLLIN, USEC_INFINITY);
if (r < 0)
return log_error_errno(r, "Failed to wait for event: %m");
r = flush_fd(watch_fd);
if (r < 0)
return log_error_errno(r, "Failed to flush inotify events: %m");
}
return 0;
}
int main(int argc, char *argv[]) {
int r;
_cleanup_journal_close_ sd_journal *j = NULL;
@ -1875,6 +1960,11 @@ int main(int argc, char *argv[]) {
goto finish;
}
if (arg_action == ACTION_SYNC) {
r = sync_journal();
goto finish;
}
if (arg_action == ACTION_ROTATE) {
r = rotate();
goto finish;

35
src/journal/journald-server.c
View File

@ -1243,7 +1243,7 @@ static int dispatch_sigusr1(sd_event_source *es, const struct signalfd_siginfo *
assert(s);
log_info("Received request to flush runtime journal from PID %"PRIu32, si->ssi_pid);
log_info("Received request to flush runtime journal from PID " PID_FMT, si->ssi_pid);
server_flush_to_var(s);
server_sync(s);
@ -1259,7 +1259,7 @@ static int dispatch_sigusr2(sd_event_source *es, const struct signalfd_siginfo *
assert(s);
log_info("Received request to rotate journal from PID %"PRIu32, si->ssi_pid);
log_info("Received request to rotate journal from PID " PID_FMT, si->ssi_pid);
server_rotate(s);
server_vacuum(s, true, true);
@ -1277,12 +1277,27 @@ static int dispatch_sigterm(sd_event_source *es, const struct signalfd_siginfo *
return 0;
}
static int dispatch_sigrtmin1(sd_event_source *es, const struct signalfd_siginfo *si, void *userdata) {
Server *s = userdata;
assert(s);
log_debug("Received request to sync from PID " PID_FMT, si->ssi_pid);
server_sync(s);
/* Let clients know when the most recent sync happened. */
(void) touch("/run/systemd/journal/synced");
return 0;
}
static int setup_signals(Server *s) {
int r;
assert(s);
assert(sigprocmask_many(SIG_SETMASK, NULL, SIGINT, SIGTERM, SIGUSR1, SIGUSR2, -1) >= 0);
assert(sigprocmask_many(SIG_SETMASK, NULL, SIGINT, SIGTERM, SIGUSR1, SIGUSR2, SIGRTMIN+1, -1) >= 0);
r = sd_event_add_signal(s->event, &s->sigusr1_event_source, SIGUSR1, dispatch_sigusr1, s);
if (r < 0)
@ -1312,6 +1327,19 @@ static int setup_signals(Server *s) {
if (r < 0)
return r;
/* SIGRTMIN+1 causes an immediate sync. We process this very
* late, so that everything else queued at this point is
* really written to disk. Clients can watch
* /run/systemd/journal/synced with inotify until its mtime
* changes to see when a sync happened. */
r = sd_event_add_signal(s->event, &s->sigrtmin1_event_source, SIGRTMIN+1, dispatch_sigrtmin1, s);
if (r < 0)
return r;
r = sd_event_source_set_priority(s->sigrtmin1_event_source, SD_EVENT_PRIORITY_NORMAL+15);
if (r < 0)
return r;
return 0;
}
@ -1869,6 +1897,7 @@ void server_done(Server *s) {
sd_event_source_unref(s->sigusr2_event_source);
sd_event_source_unref(s->sigterm_event_source);
sd_event_source_unref(s->sigint_event_source);
sd_event_source_unref(s->sigrtmin1_event_source);
sd_event_source_unref(s->hostname_event_source);
sd_event_source_unref(s->notify_event_source);
sd_event_source_unref(s->watchdog_event_source);

1
src/journal/journald-server.h
View File

@ -72,6 +72,7 @@ struct Server {
sd_event_source *sigusr2_event_source;
sd_event_source *sigterm_event_source;
sd_event_source *sigint_event_source;
sd_event_source *sigrtmin1_event_source;
sd_event_source *hostname_event_source;
sd_event_source *notify_event_source;
sd_event_source *watchdog_event_source;