diff options
| -rw-r--r-- | Makefile.am | 2 | ||||
| -rw-r--r-- | man/sd_journal_get_fd.xml | 133 | ||||
| -rw-r--r-- | src/journal/journal-internal.h | 2 | ||||
| -rw-r--r-- | src/journal/libsystemd-journal.sym | 5 | ||||
| -rw-r--r-- | src/journal/sd-journal.c | 45 | ||||
| -rw-r--r-- | src/shared/missing.h | 4 | ||||
| -rw-r--r-- | src/systemd/sd-journal.h | 1 |
7 files changed, 180 insertions, 12 deletions
diff --git a/Makefile.am b/Makefile.am index 0bcde9c584..634c67d13f 100644 --- a/Makefile.am +++ b/Makefile.am @@ -576,6 +576,7 @@ MANPAGES_ALIAS = \ man/SD_JOURNAL_FOREACH_DATA.3 \ man/sd_journal_get_monotonic_usec.3 \ man/sd_journal_get_cutoff_monotonic_usec.3 \ + man/sd_journal_reliable_fd.3 \ man/sd_journal_process.3 \ man/sd_journal_wait.3 \ man/SD_JOURNAL_NOP.3 \ @@ -649,6 +650,7 @@ man/sd_journal_restart_data.3: man/sd_journal_get_data.3 man/SD_JOURNAL_FOREACH_DATA.3: man/sd_journal_get_data.3 man/sd_journal_get_monotonic_usec.3: man/sd_journal_get_realtime_usec.3 man/sd_journal_get_cutoff_monotonic_usec.3: man/sd_journal_get_cutoff_realtime_usec.3 +man/sd_journal_reliable_fd.3: man/sd_journal_get_fd.3 man/sd_journal_process.3: man/sd_journal_get_fd.3 man/sd_journal_wait.3: man/sd_journal_get_fd.3 man/SD_JOURNAL_NOP.3: man/sd_journal_get_fd.3 diff --git a/man/sd_journal_get_fd.xml b/man/sd_journal_get_fd.xml index e3b5eaa13d..189d21352b 100644 --- a/man/sd_journal_get_fd.xml +++ b/man/sd_journal_get_fd.xml @@ -44,6 +44,7 @@ <refnamediv> <refname>sd_journal_get_fd</refname> + <refname>sd_journal_reliable_fd</refname> <refname>sd_journal_process</refname> <refname>sd_journal_wait</refname> <refname>SD_JOURNAL_NOP</refname> @@ -63,6 +64,11 @@ </funcprototype> <funcprototype> + <funcdef>int <function>sd_journal_reliable_fd</function></funcdef> + <paramdef>sd_journal* <parameter>j</parameter></paramdef> + </funcprototype> + + <funcprototype> <funcdef>int <function>sd_journal_process</function></funcdef> <paramdef>sd_journal* <parameter>j</parameter></paramdef> </funcprototype> @@ -82,12 +88,36 @@ <para><function>sd_journal_get_fd()</function> returns a file descriptor that may be asynchronously polled in an external event loop and is signaled readable as - soon as the journal changes, for example because new - entries were added. The file descriptor is suitable - for usage in + soon as the journal changes, because new entries or + files were added, rotation took place, or files have + been deleted, and similar. The file descriptor is + suitable for usage in <citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry> - where it will yield POLLIN on all changes. The call - takes one argument: the journal context object.</para> + where it will yield POLLIN on changes. The call takes + one argument: the journal context object. Note that + not all file systems are capable of generating the + necessary events for wakeups from this file descriptor + to be enirely reliable. In particular network files + systems do not generate suitable file change events in + all cases. In such a case an application should not + rely alone on wake-ups from this file descriptor but + wake up and recheck the journal in regular time + intervals, for example every 2s. To detect + cases where this is necessary, use + <function>sd_journal_reliable_fd()</function>, + below.</para> + + <para><function>sd_journal_reliable_fd()</function> + may be used to check whether the wakeup events from + the file descriptor returned by + <function>sd_journal_get_fd</function> are sufficient + to track changes to the journal. If this call returns + 0, it is necessary to regularly recheck for journal + changes (suggestion: every 2s). If this call returns a + positive integer this is not necessary, and wakeups + from the file descriptor returned by + <function>sd_journal_get_fd()</function> are + sufficient as only source for wake-ups.</para> <para>After each POLLIN wake-up <function>sd_journal_process()</function> needs to be @@ -97,14 +127,19 @@ that spurious wake-ups are possible).</para> <para>A synchronous alternative for using - <function>sd_journal_get_fd()</function> and + <function>sd_journal_get_fd()</function>, + <function>sd_journal_reliable_fd()</function> and <function>sd_journal_process()</function> is <function>sd_journal_wait()</function>. It will - synchronously wait until the journal gets changed up - to a certain time-out as specified in its second - argument. Pass <literal>(uint64_t) -1</literal> to - wait indefinitely. Internally this call simply - combines <function>sd_journal_get_fd()</function>, + synchronously wait until the journal gets changed, + possibly using a 2s time-out if this is necessary (see + above). In either way the maximum time this call + sleeps may be controlled with the + <parameter>timeout_usec</parameter> parameter. Pass + <literal>(uint64_t) -1</literal> to wait + indefinitely. Internally this call simply combines + <function>sd_journal_get_fd()</function>, + <function>sd_journal_reliable_fd()</function>, <function>poll()</function> and <function>sd_journal_process()</function> into one.</para> @@ -117,6 +152,15 @@ <para><function>sd_journal_get_fd()</function> returns a valid file descriptor on success or a negative errno-style error code.</para> + <para><function>sd_journal_reliable_fd()</function> + returns a positive integer if the file descriptor + returned by <function>sd_journal_get_fd()</function> + is sufficient as sole wake-up source for journal + change events. Returns 0 if it is not sufficient and + the journal needs to be checked manually in regular + time intervals for changes. Returns a negative + errno-style error code on failure.</para> + <para><function>sd_journal_process()</function> and <function>sd_journal_wait()</function> return one of <literal>SD_JOURNAL_NOP</literal>, @@ -140,6 +184,7 @@ <title>Notes</title> <para>The <function>sd_journal_get_fd()</function>, + <function>sd_journal_reliable_fd()</function>, <function>sd_journal_process()</function> and <function>sd_journal_wait()</function> interfaces are available as shared library, which can be compiled and @@ -150,13 +195,77 @@ </refsect1> <refsect1> + <title>Examples</title> + + <para>Iterating through the journal, in a live view tracking all changes:</para> + + <programlisting>#include <stdio.h> +#include <string.h> +#include <systemd/sd-journal.h> + +int main(int argc, char *argv[]) { + int r; + sd_journal *j; + r = sd_journal_open(&j, SD_JOURNAL_LOCAL_ONLY); + if (r < 0) { + fprintf(stderr, "Failed to open journal: %s\n", strerror(-r)); + return 1; + } + for (;;) { + const char *d; + size_t l; + r = sd_journal_next(j); + if (r < 0) { + fprintf(stderr, "Failed to iterate to next entry: %s\n", strerror(-r)); + break; + } + if (r == 0) { + /* Reached the end, let's wait for changes, and try again */ + r = sd_journal_wait(j, (uint64_t) -1); + if (r < 0) { + fprintf(stderr, "Failed to wait for changes: %s\n", strerror(-r)); + break; + } + continue; + } + r = sd_journal_get_data(j, "MESSAGE", &d, &l); + if (r < 0) { + fprintf(stderr, "Failed to read message field: %s\n", strerror(-r)); + continue; + } + printf("%.*s\n", (int) l, d); + } + sd_journal_close(j); + return 0; +}</programlisting> + + <para>Waiting with <function>poll()</function> (this + example lacks all error checking for the sake of + simplicity):</para> + + <programlisting>#include <sys/poll.h> +#include <systemd/sd-journal.h> + +int wait_for_changes(sd_journal *j) { + struct pollfd pollfd; + pollfd.fd = sd_journal_get_fd(); + pollfd.events = POLLIN; + poll(&pollfd, 1, sd_journal_reliable_fd() > 0 ? -1 : 2000); + return sd_journal_process(j); +} + </programlisting> + </refsect1> + + + <refsect1> <title>See Also</title> <para> <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>, - <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> + <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry> </para> </refsect1> diff --git a/src/journal/journal-internal.h b/src/journal/journal-internal.h index f68ca996a8..75a4129e5b 100644 --- a/src/journal/journal-internal.h +++ b/src/journal/journal-internal.h @@ -119,6 +119,8 @@ struct sd_journal { char *unique_field; JournalFile *unique_file; uint64_t unique_offset; + + bool on_network; }; char *journal_make_match_string(sd_journal *j); diff --git a/src/journal/libsystemd-journal.sym b/src/journal/libsystemd-journal.sym index 96293b8a29..ad78fcc74d 100644 --- a/src/journal/libsystemd-journal.sym +++ b/src/journal/libsystemd-journal.sym @@ -80,3 +80,8 @@ global: sd_journal_enumerate_unique; sd_journal_restart_unique; } LIBSYSTEMD_JOURNAL_190; + +LIBSYSTEMD_JOURNAL_196 { +global: + sd_journal_fd_reliable; +} LIBSYSTEMD_JOURNAL_195; diff --git a/src/journal/sd-journal.c b/src/journal/sd-journal.c index d5d2d78f1c..a346691e21 100644 --- a/src/journal/sd-journal.c +++ b/src/journal/sd-journal.c @@ -25,6 +25,8 @@ #include <unistd.h> #include <sys/inotify.h> #include <sys/poll.h> +#include <sys/vfs.h> +#include <linux/magic.h> #include "sd-journal.h" #include "journal-def.h" @@ -35,9 +37,12 @@ #include "lookup3.h" #include "compress.h" #include "journal-internal.h" +#include "missing.h" #define JOURNAL_FILES_MAX 1024 +#define JOURNAL_FILES_RECHECK_USEC (2 * USEC_PER_SEC) + static void detach_location(sd_journal *j) { Iterator i; JournalFile *f; @@ -1184,6 +1189,25 @@ _public_ int sd_journal_seek_tail(sd_journal *j) { return 0; } +static void check_network(sd_journal *j, int fd) { + struct statfs sfs; + + assert(j); + + if (j->on_network) + return; + + if (fstatfs(fd, &sfs) < 0) + return; + + j->on_network = + sfs.f_type == CIFS_MAGIC_NUMBER || + sfs.f_type == CODA_SUPER_MAGIC || + sfs.f_type == NCP_SUPER_MAGIC || + sfs.f_type == NFS_SUPER_MAGIC || + sfs.f_type == SMB_SUPER_MAGIC; +} + static int add_file(sd_journal *j, const char *prefix, const char *filename) { char *path; int r; @@ -1233,6 +1257,8 @@ static int add_file(sd_journal *j, const char *prefix, const char *filename) { return r; } + check_network(j, f->fd); + j->current_invalidate_counter ++; log_debug("File %s got added.", f->path); @@ -1366,6 +1392,8 @@ static int add_directory(sd_journal *j, const char *prefix, const char *dirname) } } + check_network(j, dirfd(d)); + closedir(d); return 0; @@ -1453,6 +1481,8 @@ static int add_root_directory(sd_journal *j, const char *p) { } } + check_network(j, dirfd(d)); + closedir(d); return 0; @@ -2079,6 +2109,14 @@ _public_ int sd_journal_wait(sd_journal *j, uint64_t timeout_usec) { return determine_change(j); } + if (j->on_network) { + /* If we are on the network we need to regularly check + * for changes manually */ + + if (timeout_usec == (uint64_t) -1 || timeout_usec > JOURNAL_FILES_RECHECK_USEC) + timeout_usec = JOURNAL_FILES_RECHECK_USEC; + } + do { r = fd_wait_for_event(j->inotify_fd, POLLIN, timeout_usec); } while (r == -EINTR); @@ -2344,3 +2382,10 @@ _public_ void sd_journal_restart_unique(sd_journal *j) { j->unique_file = NULL; j->unique_offset = 0; } + +_public_ int sd_journal_reliable_fd(sd_journal *j) { + if (!j) + return -EINVAL; + + return !j->on_network; +} diff --git a/src/shared/missing.h b/src/shared/missing.h index f58a609c7d..3777cf69b2 100644 --- a/src/shared/missing.h +++ b/src/shared/missing.h @@ -249,3 +249,7 @@ static inline int name_to_handle_at(int fd, const char *name, struct file_handle # error neither secure_getenv nor __secure_getenv are available # endif #endif + +#ifndef CIFS_MAGIC_NUMBER +#define CIFS_MAGIC_NUMBER 0xFF534D42 +#endif diff --git a/src/systemd/sd-journal.h b/src/systemd/sd-journal.h index 55281b1346..7241173035 100644 --- a/src/systemd/sd-journal.h +++ b/src/systemd/sd-journal.h @@ -124,6 +124,7 @@ int sd_journal_enumerate_unique(sd_journal *j, const void **data, size_t *l); void sd_journal_restart_unique(sd_journal *j); int sd_journal_get_fd(sd_journal *j); +int sd_journal_reliable_fd(sd_journal *j); int sd_journal_process(sd_journal *j); int sd_journal_wait(sd_journal *j, uint64_t timeout_usec); |