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Add 'active_in' column to pg_replication_slots.

Browse source 
Right now it is visible whether a replication slot is active in any
session, but not in which.  Adding the active_in column, containing the
pid of the backend having acquired the slot, makes it much easier to
associate pg_replication_slots entries with the corresponding
pg_stat_replication/pg_stat_activity row.

This should have been done from the start, but I (Andres) dropped the
ball there somehow.

Author: Craig Ringer, revised by me Discussion:
CAMsr+YFKgZca5_7_ouaMWxA5PneJC9LNViPzpDHusaPhU9pA7g@mail.gmail.com
This commit is contained in:
Andres Freund 2015-04-21 11:51:06 +02:00
parent 528c2e44ab
commit d811c037ce
9 changed files with 47 additions and 28 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
contrib/test_decoding/expected/ddl.out
View file

@ -603,7 +603,7 @@ SELECT pg_drop_replication_slot('regression_slot');
/* check that the slot is gone */
SELECT * FROM pg_replication_slots;
slot_name | plugin | slot_type | datoid | database | active | xmin | catalog_xmin | restart_lsn
-----------+--------+-----------+--------+----------+--------+------+--------------+-------------
slot_name | plugin | slot_type | datoid | database | active | active_in | xmin | catalog_xmin | restart_lsn
-----------+--------+-----------+--------+----------+--------+-----------+------+--------------+-------------
(0 rows)

10
doc/src/sgml/catalogs.sgml
View file

@ -5400,6 +5400,16 @@
<entry>True if this slot is currently actively being used</entry>
</row>
<row>
<entry><structfield>active_in</structfield></entry>
<entry><type>integer</type></entry>
<entry></entry>
<entry>The process ID of the session using this slot if the slot
is currently actively being used. <literal>NULL</literal> if
inactive.
</entry>
</row>
<row>
<entry><structfield>xmin</structfield></entry>
<entry><type>xid</type></entry>

8
doc/src/sgml/logicaldecoding.sgml
View file

@ -62,10 +62,10 @@ postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', '
regression_slot | 0/16B1970
(1 row)
postgres=# SELECT * FROM pg_replication_slots;
slot_name | plugin | slot_type | datoid | database | active | xmin | catalog_xmin | restart_lsn
-----------------+---------------+-----------+--------+----------+--------+--------+--------------+-------------
regression_slot | test_decoding | logical | 12052 | postgres | f | | 684 | 0/16A4408
postgres=# SELECT slot_name, plugin, slot_type, database, active, restart_lsn FROM pg_replication_slots;
slot_name | plugin | slot_type | database | active | restart_lsn
-----------------+---------------+-----------+----------+--------+-------------
regression_slot | test_decoding | logical | postgres | f | 0/16A4408
(1 row)
postgres=# -- There are no changes to see yet

1
src/backend/catalog/system_views.sql
View file

@ -665,6 +665,7 @@ CREATE VIEW pg_replication_slots AS
L.datoid,
D.datname AS database,
L.active,
L.active_in,
L.xmin,
L.catalog_xmin,
L.restart_lsn

30
src/backend/replication/slot.c
View file

@ -262,7 +262,7 @@ ReplicationSlotCreate(const char *name, bool db_specific,
* be doing that. So it's safe to initialize the slot.
*/
Assert(!slot->in_use);
Assert(!slot->active);
Assert(slot->active_pid == 0);
slot->data.persistency = persistency;
slot->data.xmin = InvalidTransactionId;
slot->effective_xmin = InvalidTransactionId;
@ -291,8 +291,8 @@ ReplicationSlotCreate(const char *name, bool db_specific,
volatile ReplicationSlot *vslot = slot;
SpinLockAcquire(&slot->mutex);
Assert(!vslot->active);
vslot->active = true;
Assert(vslot->active_pid == 0);
vslot->active_pid = MyProcPid;
SpinLockRelease(&slot->mutex);
MyReplicationSlot = slot;
}
@ -314,7 +314,7 @@ ReplicationSlotAcquire(const char *name)
{
ReplicationSlot *slot = NULL;
int i;
bool active = false;
int active_pid = 0;
Assert(MyReplicationSlot == NULL);
@ -331,8 +331,9 @@ ReplicationSlotAcquire(const char *name)
volatile ReplicationSlot *vslot = s;
SpinLockAcquire(&s->mutex);
active = vslot->active;
vslot->active = true;
active_pid = vslot->active_pid;
if (active_pid == 0)
vslot->active_pid = MyProcPid;
SpinLockRelease(&s->mutex);
slot = s;
break;
@ -345,10 +346,11 @@ ReplicationSlotAcquire(const char *name)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("replication slot \"%s\" does not exist", name)));
if (active)
if (active_pid != 0)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_IN_USE),
errmsg("replication slot \"%s\" is already active", name)));
errmsg("replication slot \"%s\" is already active for pid %d",
name, active_pid)));
/* We made this slot active, so it's ours now. */
MyReplicationSlot = slot;
@ -363,7 +365,7 @@ ReplicationSlotRelease(void)
{
ReplicationSlot *slot = MyReplicationSlot;
Assert(slot != NULL && slot->active);
Assert(slot != NULL && slot->active_pid != 0);
if (slot->data.persistency == RS_EPHEMERAL)
{
@ -380,7 +382,7 @@ ReplicationSlotRelease(void)
volatile ReplicationSlot *vslot = slot;
SpinLockAcquire(&slot->mutex);
vslot->active = false;
vslot->active_pid = 0;
SpinLockRelease(&slot->mutex);
}
@ -460,7 +462,7 @@ ReplicationSlotDropAcquired(void)
bool fail_softly = slot->data.persistency == RS_EPHEMERAL;
SpinLockAcquire(&slot->mutex);
vslot->active = false;
vslot->active_pid = 0;
SpinLockRelease(&slot->mutex);
ereport(fail_softly ? WARNING : ERROR,
@ -477,7 +479,7 @@ ReplicationSlotDropAcquired(void)
* scanning the array.
*/
LWLockAcquire(ReplicationSlotControlLock, LW_EXCLUSIVE);
slot->active = false;
slot->active_pid = 0;
slot->in_use = false;
LWLockRelease(ReplicationSlotControlLock);
@ -749,7 +751,7 @@ ReplicationSlotsCountDBSlots(Oid dboid, int *nslots, int *nactive)
/* count slots with spinlock held */
SpinLockAcquire(&s->mutex);
(*nslots)++;
if (s->active)
if (s->active_pid != 0)
(*nactive)++;
SpinLockRelease(&s->mutex);
}
@ -1227,7 +1229,7 @@ RestoreSlotFromDisk(const char *name)
slot->candidate_restart_valid = InvalidXLogRecPtr;
slot->in_use = true;
slot->active = false;
slot->active_pid = 0;
restored = true;
break;

13
src/backend/replication/slotfuncs.c
View file

@ -158,7 +158,7 @@ pg_drop_replication_slot(PG_FUNCTION_ARGS)
Datum
pg_get_replication_slots(PG_FUNCTION_ARGS)
{
#define PG_GET_REPLICATION_SLOTS_COLS 8
#define PG_GET_REPLICATION_SLOTS_COLS 9
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
TupleDesc tupdesc;
Tuplestorestate *tupstore;
@ -206,7 +206,7 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
TransactionId xmin;
TransactionId catalog_xmin;
XLogRecPtr restart_lsn;
bool active;
pid_t active_pid;
Oid database;
NameData slot_name;
NameData plugin;
@ -227,7 +227,7 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
namecpy(&slot_name, &slot->data.name);
namecpy(&plugin, &slot->data.plugin);
active = slot->active;
active_pid = slot->active_pid;
}
SpinLockRelease(&slot->mutex);
@ -251,7 +251,12 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
else
values[i++] = database;
values[i++] = BoolGetDatum(active);
values[i++] = BoolGetDatum(active_pid != 0);
if (active_pid != 0)
values[i++] = Int32GetDatum(active_pid);
else
nulls[i++] = true;
if (xmin != InvalidTransactionId)
values[i++] = TransactionIdGetDatum(xmin);

2
src/include/catalog/pg_proc.h
View file

@ -5106,7 +5106,7 @@ DATA(insert OID = 3779 ( pg_create_physical_replication_slot PGNSP PGUID 12 1 0
DESCR("create a physical replication slot");
DATA(insert OID = 3780 ( pg_drop_replication_slot PGNSP PGUID 12 1 0 0 0 f f f f f f v 1 0 2278 "19" _null_ _null_ _null_ _null_ pg_drop_replication_slot _null_ _null_ _null_ ));
DESCR("drop a replication slot");
DATA(insert OID = 3781 ( pg_get_replication_slots PGNSP PGUID 12 1 10 0 0 f f f f f t s 0 0 2249 "" "{19,19,25,26,16,28,28,3220}" "{o,o,o,o,o,o,o,o}" "{slot_name,plugin,slot_type,datoid,active,xmin,catalog_xmin,restart_lsn}" _null_ pg_get_replication_slots _null_ _null_ _null_ ));
DATA(insert OID = 3781 ( pg_get_replication_slots PGNSP PGUID 12 1 10 0 0 f f f f f t s 0 0 2249 "" "{19,19,25,26,16,23,28,28,3220}" "{o,o,o,o,o,o,o,o,o}" "{slot_name,plugin,slot_type,datoid,active,active_in,xmin,catalog_xmin,restart_lsn}" _null_ pg_get_replication_slots _null_ _null_ _null_ ));
DESCR("information about replication slots currently in use");
DATA(insert OID = 3786 ( pg_create_logical_replication_slot PGNSP PGUID 12 1 0 0 0 f f f f f f v 2 0 2249 "19 19" "{19,19,25,3220}" "{i,i,o,o}" "{slot_name,plugin,slot_name,xlog_position}" _null_ pg_create_logical_replication_slot _null_ _null_ _null_ ));
DESCR("set up a logical replication slot");

4
src/include/replication/slot.h
View file

@ -84,8 +84,8 @@ typedef struct ReplicationSlot
/* is this slot defined */
bool in_use;
/* is somebody streaming out changes for this slot */
bool active;
/* Who is streaming out changes for this slot? 0 in unused slots. */
pid_t active_pid;
/* any outstanding modifications? */
bool just_dirtied;

3
src/test/regress/expected/rules.out
View file

@ -1396,10 +1396,11 @@ pg_replication_slots| SELECT l.slot_name,
l.datoid,
d.datname AS database,
l.active,
l.active_in,
l.xmin,
l.catalog_xmin,
l.restart_lsn
FROM (pg_get_replication_slots() l(slot_name, plugin, slot_type, datoid, active, xmin, catalog_xmin, restart_lsn)
FROM (pg_get_replication_slots() l(slot_name, plugin, slot_type, datoid, active, active_in, xmin, catalog_xmin, restart_lsn)
LEFT JOIN pg_database d ON ((l.datoid = d.oid)));
pg_roles| SELECT pg_authid.rolname,
pg_authid.rolsuper,