Hi,
This is the patch to put multiple workers into autovacuum. This patch
applies after the recheck patch I just posted.
The main change is to have an array of Worker structs in shared memory;
each worker checks the current table of all other Workers, and skips a
table that's being vacuumed by any of them. It also rechecks the table
before vacuuming, which removes the problem of redundant vacuuming.
It also introduces the business of SIGUSR1 between workers and launcher.
The launcher keeps a database list in memory and schedules workers to
vacuum databases depending on that list. The actual database selected
may differ from what was in the schedule; in that case, the list is
reconstructed.
There are two main FIXMEs in this code:
1. have the list reconstruction and scheduling be smarter so that
databases are not ganged together in the schedule. The only difficulty
is keeping the sort order that the databases had.
2. have a way to clean up after failed workers filling up the Worker
array and thus starving other databases from vacuuming. I don't really
know a way to do this that works in all cases. The only idea I have so
far is that workers that started more than autovacuum_naptime seconds
ago are considered failed to start.
Neither of these is really minor, but I think they are solvable.
--
Alvaro Herrerahttp://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
*** 14recheck/src/backend/postmaster/autovacuum.c 2007-03-27 16:43:31.0 -0400
--- 12vacuum/src/backend/postmaster/autovacuum.c 2007-03-27 17:40:19.0 -0400
***
*** 52,57
--- 52,58
#include utils/syscache.h
+ static volatile sig_atomic_t got_SIGUSR1 = false;
static volatile sig_atomic_t got_SIGHUP = false;
static volatile sig_atomic_t avlauncher_shutdown_request = false;
***
*** 59,64
--- 60,66
* GUC parameters
*/
bool autovacuum_start_daemon = false;
+ int autovacuum_max_workers;
int autovacuum_naptime;
int autovacuum_vac_thresh;
double autovacuum_vac_scale;
***
*** 69,75
int autovacuum_vac_cost_delay;
int autovacuum_vac_cost_limit;
! /* Flag to tell if we are in the autovacuum daemon process */
static bool am_autovacuum_launcher = false;
static bool am_autovacuum_worker = false;
--- 71,77
int autovacuum_vac_cost_delay;
int autovacuum_vac_cost_limit;
! /* Flags to tell if we are in an autovacuum process */
static bool am_autovacuum_launcher = false;
static bool am_autovacuum_worker = false;
***
*** 86,91
--- 88,94
typedef struct autovac_dbase
{
Oid ad_datid;
+ TimestampTz ad_next_worker;
char *ad_name;
TransactionId ad_frozenxid;
PgStat_StatDBEntry *ad_entry;
***
*** 110,123
int at_vacuum_cost_limit;
} autovac_table;
typedef struct
{
! Oid process_db; /* OID of database to process */
! int worker_pid; /* PID of the worker process, if any */
} AutoVacuumShmemStruct;
static AutoVacuumShmemStruct *AutoVacuumShmem;
#ifdef EXEC_BACKEND
static pid_t avlauncher_forkexec(void);
static pid_t avworker_forkexec(void);
--- 113,158
int at_vacuum_cost_limit;
} autovac_table;
+ /*-
+ * This struct holds information about a single worker's whereabouts. We keep
+ * an array of these in shared memory, sized according to
+ * autovacuum_max_workers.
+ *
+ * wi_dboid OID of the database this worker is supposed to work on
+ * wi_tableoid OID of the table currently being vacuumed
+ * wi_workerpid PID of the running worker, 0 if not yet started
+ * wi_finished True when the worker is done and about to exit
+ *-
+ */
+ typedef struct
+ {
+ Oid wi_dboid;
+ Oid wi_tableoid;
+ int wi_workerpid;
+ bool wi_finished;
+ } WorkerInfo;
+
typedef struct
{
! pid_t av_launcherpid;
! WorkerInfo av_workers[1];
! /* VARIABLE LENGTH STRUCT */
} AutoVacuumShmemStruct;
+ /* Macro to iterate over all workers. Beware multiple evaluation of args! */
+ #define foreach_worker(_i, _worker) \
+ _worker = (WorkerInfo *) (AutoVacuumShmem + \
+ offsetof(AutoVacuumShmemStruct, av_workers)); \
+ for (_i = 0; _i autovacuum_max_workers; _i++, _worker += sizeof(WorkerInfo))
+
static AutoVacuumShmemStruct *AutoVacuumShmem;
+ /* number of currently free worker slots; only valid in the launcher */
+ static int free_workers;
+ /* the database list in the launcher, and the context that contains it */
+ static Dllist *DatabaseList = NULL;
+ static MemoryContext DatabaseListCxt = NULL;
+
#ifdef EXEC_BACKEND
static pid_t avlauncher_forkexec(void);
static pid_t avworker_forkexec(void);
***
*** 125,133
NON_EXEC_STATIC void AutoVacWorkerMain(int argc, char *argv[]);
NON_EXEC_STATIC void AutoVacLauncherMain(int argc, char *argv[]);
! static void
