digoal
2021-08-01
PostgreSQL , InRecovery , standbyState
Move InRecovery and standbyState global vars to xlogutils.c.
author Heikki Linnakangas <heikki.linnakangas@iki.fi>
Sat, 31 Jul 2021 06:50:26 +0000 (09:50 +0300)
committer Heikki Linnakangas <heikki.linnakangas@iki.fi>
Sat, 31 Jul 2021 06:50:26 +0000 (09:50 +0300)
commit 317632f3073fc06047a42075eb5e28a9577a4f96
tree a9d01818156027ccafe91e2110feadb9c012b8d4 tree
parent 4fe8dcdff3af73f6ca16eb3edfa3339c7ee0d2c4 commit | diff
Move InRecovery and standbyState global vars to xlogutils.c.
They are used in code that runs both during normal operation and during
WAL replay, and needs to behave differently during replay. Move them to
xlogutils.c, because that's where we have other helper functions used by
redo routines.
Reviewed-by: Andres Freund
Discussion: https://www.postgresql.org/message-id/b3b71061-4919-e882-4857-27e370ab134a%40iki.fi
+/*
+ * Are we doing recovery from XLOG?
+ *
+ * This is only ever true in the startup process; it should be read as meaning
+ * "this process is replaying WAL records", rather than "the system is in
+ * recovery mode". It should be examined primarily by functions that need
+ * to act differently when called from a WAL redo function (e.g., to skip WAL
+ * logging). To check whether the system is in recovery regardless of which
+ * process you're running in, use RecoveryInProgress() but only after shared
+ * memory startup and lock initialization.
+ *
+ * This is updated from xlog.c, but lives here because it's mostly read by
+ * WAL redo functions.
+ */
+bool InRecovery = false;
+
+/* Are we in Hot Standby mode? Only valid in startup process, see xlogutils.h */
+HotStandbyState standbyState = STANDBY_DISABLED;
+
+/*
+ * Prior to 8.4, all activity during recovery was carried out by the startup
+ * process. This local variable continues to be used in many parts of the
+ * code to indicate actions taken by RecoveryManagers. Other processes that
+ * potentially perform work during recovery should check RecoveryInProgress().
+ * See XLogCtl notes in xlog.c.
+ */
+extern bool InRecovery;
+
+/*
+ * Like InRecovery, standbyState is only valid in the startup process.
+ * In all other processes it will have the value STANDBY_DISABLED (so
+ * InHotStandby will read as false).
+ *
+ * In DISABLED state, we're performing crash recovery or hot standby was
+ * disabled in postgresql.conf.
+ *
+ * In INITIALIZED state, we've run InitRecoveryTransactionEnvironment, but
+ * we haven't yet processed a RUNNING_XACTS or shutdown-checkpoint WAL record
+ * to initialize our primary-transaction tracking system.
+ *
+ * When the transaction tracking is initialized, we enter the SNAPSHOT_PENDING
+ * state. The tracked information might still be incomplete, so we can't allow
+ * connections yet, but redo functions must update the in-memory state when
+ * appropriate.
+ *
+ * In SNAPSHOT_READY mode, we have full knowledge of transactions that are
+ * (or were) running on the primary at the current WAL location. Snapshots
+ * can be taken, and read-only queries can be run.
+ */
+typedef enum
+{
+ STANDBY_DISABLED,
+ STANDBY_INITIALIZED,
+ STANDBY_SNAPSHOT_PENDING,
+ STANDBY_SNAPSHOT_READY
+} HotStandbyState;
+
+extern HotStandbyState standbyState;
+
+#define InHotStandby (standbyState >= STANDBY_SNAPSHOT_PENDING)
+
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