Changeset: 7c49f18c8f35 for MonetDB
URL: http://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=7c49f18c8f35
Modified Files:
monetdb5/misc/msabaoth.c
monetdb5/tools/Makefile.ag
Branch: default
Log Message:
sabaoth: fix running status for "own" databases
Since MT_lockf always succeeds when the same process already holds the
lock, a database cannot be determined to be crashed based on the result
of MT_lockf, when the database is looking at itself. This scenario was
handled by simply assuming that the database was running when it
happened to have the same name as the one that sabaoth was inited with.
For databases this is in general fine. However, when pseudo objects,
are registered like databases, and/or a single process has multiple
databases, this approach breaks down.
Each process that initialises sabaoth now, will generate an (unique)
UUID, that sabaoth writes in each database directory when it updates the
uplog file (registerStart). This way, getStatus can check per database
it sees, if the process associated with that database happens to be the
same as the one currently performing the getStatus query. As such, it
can determine the current running state based on the uplog file, with
the assumption that the process is still alive (or else it wouldn't be
querying at this point, would it?).
diffs (188 lines):
diff --git a/monetdb5/misc/msabaoth.c b/monetdb5/misc/msabaoth.c
--- a/monetdb5/misc/msabaoth.c
+++ b/monetdb5/misc/msabaoth.c
@@ -44,6 +44,7 @@
#include "msabaoth.h"
#include "mutils.h"
+#include "muuid.h"
#if defined(_MSC_VER) && _MSC_VER >= 1400
#define close _close
@@ -54,6 +55,8 @@
char *_sabaoth_internal_dbfarm = NULL;
/** the database which is "active" */
char *_sabaoth_internal_dbname = NULL;
+/** identifier of the current process */
+char *_sabaoth_internal_uuid = NULL;
/**
* Retrieves the dbfarm path plus an optional extra component added
@@ -115,6 +118,12 @@ msab_init(char *dbfarm, char *dbname)
if (_sabaoth_internal_dbname != NULL)
free(_sabaoth_internal_dbname);
+ /* this UUID is supposed to be unique per-process, we use it lateron
+ * to determine if a database is (started by) the current process,
+ * since locking always succeeds for the same process */
+ if (_sabaoth_internal_uuid == NULL)
+ _sabaoth_internal_uuid = generateUUID();
+
len = strlen(dbfarm);
_sabaoth_internal_dbfarm = strdup(dbfarm);
/* remove trailing slashes, newlines and spaces */
@@ -348,13 +357,19 @@ msab_wildRetreat(void)
return(tmp);
unlink(path);
+ if ((tmp = getDBPath(&path, PATHLENGTH, _sabaoth_internal_uuid)) !=
NULL)
+ return(tmp);
+ unlink(path);
+
return(NULL);
}
#define UPLOGFILE ".uplog"
/**
* Writes a start attempt to the sabaoth start/stop log. Examination of
- * the log at a later stage reveals crashes of the server.
+ * the log at a later stage reveals crashes of the server. In addition
+ * to updating the uplog file, it also leaves the unique signature of
+ * the current process behind.
*/
char *
msab_registerStart(void)
@@ -378,13 +393,23 @@ msab_registerStart(void)
fprintf(f, LLFMT "\t", (lng)time(NULL));
(void)fflush(f);
(void)fclose(f);
- return(NULL);
} else {
char buf[PATHLENGTH];
snprintf(buf, sizeof(buf), "failed to open file: %s (%s)",
strerror(errno), path);
return(strdup(buf));
}
+
+ /* we treat errors here (albeit being quite unlikely) as non-fatal,
+ * since they will cause wrong state information in the worst case
+ * lateron */
+ if ((tmp = getDBPath(&path, PATHLENGTH, _sabaoth_internal_uuid)) !=
NULL) {
+ free(tmp);
+ return(NULL);
+ }
+ fclose(fopen(path, "w"));
+
+ return(NULL);
}
/**
@@ -414,6 +439,12 @@ msab_registerStop(void)
strerror(errno), path);
return(strdup(buf));
}
+
+ /* remove server signature, it's no problem when it's left behind,
+ * but for the sake of keeping things clean ... */
+ if ((tmp = getDBPath(&path, PATHLENGTH, _sabaoth_internal_uuid)) !=
NULL)
+ return(tmp);
+ unlink(path);
}
/**
@@ -543,21 +574,38 @@ msab_getStatus(sabdb** ret, char *dbname
(void)fclose(f);
}
+
/* check the state of the server by looking at its gdk lock:
* - if we can lock it, the server has crashed or isn't running
* - if we can't open it because it's locked, the server is
* running
* - to distinguish between a crash and proper shutdown, consult
* the uplog
+ * - one exception to all above; if this is the same process, we
+ * cannot lock (it always succeeds), hence, if we have the
+ * same signature, we assume running if the uplog states so.
*/
- snprintf(buf, sizeof(buf), "%s/%s/%s", path, e->d_name,
".gdk_lock");
- if (_sabaoth_internal_dbname != NULL &&
- strcmp(_sabaoth_internal_dbname, e->d_name) ==
0)
+ snprintf(buf, sizeof(buf), "%s/%s/%s", path, e->d_name,
+ _sabaoth_internal_uuid);
+ if (stat(buf, &statbuf) != -1) {
+ /* database has the same process signature as ours,
which
+ * means, it must be us, rely on the uplog state */
+ snprintf(log, sizeof(log), "%s/%s/%s", path, e->d_name,
UPLOGFILE);
+ if ((f = fopen(log, "r")) != NULL) {
+ (void)fseek(f, -1, SEEK_END);
+ if (fread(data, 1, 1, f) != 1) {
+ /* the log is empty, assume no crash */
+ sdb->state = SABdbInactive;
+ } else if (data[0] == '\t') {
+ sdb->state = SABdbRunning;
+ } else { /* should be \n */
+ sdb->state = SABdbInactive;
+ }
+ (void)fclose(f);
+ }
+ } else if ((snprintf(buf, sizeof(buf), "%s/%s/%s", path,
e->d_name, ".gdk_lock") > 0) & /* no typo */
+ ((fd = MT_lockf(buf, F_TLOCK, 4, 1)) == -2))
{
- /* if we are the mserver that is running this database,
- * don't touch the lock! */
- sdb->state = SABdbRunning;
- } else if ((fd = MT_lockf(buf, F_TLOCK, 4, 1)) == -2) {
/* Locking failed; this can be because the lockfile
couldn't
* be created. Probably there is no Mserver running for
* that case also.
@@ -572,7 +620,7 @@ msab_getStatus(sabdb** ret, char *dbname
if ((f = fopen(log, "r")) != NULL) {
(void)fseek(f, -1, SEEK_END);
if (fread(data, 1, 1, f) != 1) {
- /* the log is corrupt/wrong, assume no
crash */
+ /* the log is empty, assume no crash */
sdb->state = SABdbInactive;
} else if (data[0] == '\n') {
sdb->state = SABdbInactive;
@@ -580,21 +628,17 @@ msab_getStatus(sabdb** ret, char *dbname
sdb->state = SABdbCrashed;
}
(void)fclose(f);
- } else {
- /* no uplog file? assume no crash */
- sdb->state = SABdbInactive;
- }
+ } /* cannot happen, we checked it before */
/* release the lock */
close(fd);
}
- snprintf(buf, sizeof(buf), "%s/%s/%s", path, e->d_name,
MAINTENANCEFILE);
- f = fopen(buf, "r");
- if (f != NULL) {
- (void)fclose(f);
+ snprintf(buf, sizeof(buf), "%s/%s/%s", path, e->d_name,
+ MAINTENANCEFILE);
+ if (stat(buf, &statbuf) == -1) {
+ sdb->locked = 0;
+ } else {
sdb->locked = 1;
- } else {
- sdb->locked = 0;
}
}
(void)closedir(d);
diff --git a/monetdb5/tools/Makefile.ag b/monetdb5/tools/Makefile.ag
--- a/monetdb5/tools/Makefile.ag
+++ b/monetdb5/tools/Makefile.ag
@@ -32,7 +32,8 @@ lib_monetdb5 = {
../../clients/mapilib/libmapi \
../../common/stream/libstream \
../../common/utils/libmcrypt \
- $(curl_LIBS) \
+ ../../common/utils/libmuuid \
+ $(UUID_LIBS) $(curl_LIBS) \
$(MATH_LIBS) $(SOCKET_LIBS) $(MALLOC_LIBS) $(PTHREAD_LIBS) \
$(DL_LIBS) $(READLINE_LIBS) $(openssl_LIBS) $(pcre_LIBS) \
$(LTLIBICONV) $(zlib_LIBS) $(libxml2_LIBS)
_______________________________________________
Checkin-list mailing list
[email protected]
http://mail.monetdb.org/mailman/listinfo/checkin-list
