interim commit

repmgr.c

@@ -20,17 +20,43 @@
 #include "utils/builtins.h"
 #include "utils/timestamp.h"
 
+#include "voting.h"
+
 #define MAXFNAMELEN		64
+#define TRANCHE_NAME "repmgrd"
 
 PG_MODULE_MAGIC;
 
+typedef enum {
+	LEADER_NODE,
+	FOLLOWER_NODE,
+	CANDIDATE_NODE
+} NodeState;
+
+typedef struct repmgrdSharedState
+{
+	LWLockId	lock;			/* protects search/modification */
+	NodeState	node_state;
+	NodeVotingStatus voting_status;
+}	repmgrdSharedState;
+
+static repmgrdSharedState *shared_state = NULL;
+
+static shmem_startup_hook_type prev_shmem_startup_hook = NULL;
+
 
 void		_PG_init(void);
 void		_PG_fini(void);
 
+static void repmgr_shmem_startup(void);
+
 Datum		request_vote(PG_FUNCTION_ARGS);
 PG_FUNCTION_INFO_V1(request_vote);
 
+Datum		get_voting_status(PG_FUNCTION_ARGS);
+PG_FUNCTION_INFO_V1(get_voting_status);
+
+
 /*
  * Module load callback
  */
@@ -38,6 +64,25 @@ void
 _PG_init(void)
 {
 	elog(INFO, "repmgr init");
+
+	// error here?
+	if (!process_shared_preload_libraries_in_progress)
+		return;
+
+	RequestAddinShmemSpace(MAXALIGN(sizeof(repmgrdSharedState)));
+
+#if (PG_VERSION_NUM >= 90600)
+	RequestNamedLWLockTranche(TRANCHE_NAME, 1);
+#else
+	RequestAddinLWLocks(1);
+#endif
+
+	/*
+	 * Install hooks.
+	 */
+	prev_shmem_startup_hook = shmem_startup_hook;
+	shmem_startup_hook = repmgr_shmem_startup;
+
 }
 /*
  * Module unload callback
@@ -45,7 +90,47 @@ _PG_init(void)
 void
 _PG_fini(void)
 {
-	elog(INFO, "repmgr fini");
+	/* Uninstall hook */
+	shmem_startup_hook = prev_shmem_startup_hook;
+}
+
+
+/*
+ * shmem_startup hook: allocate or attach to shared memory,
+ */
+static void
+repmgr_shmem_startup(void)
+{
+	bool		found;
+
+	if (prev_shmem_startup_hook)
+		prev_shmem_startup_hook();
+
+	/* reset in case this is a restart within the postmaster */
+	shared_state = NULL;
+
+	/*
+	 * Create or attach to the shared memory state, including hash table
+	 */
+	LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);
+
+	shared_state = ShmemInitStruct("repmgrd shared state",
+								   sizeof(repmgrdSharedState),
+								   &found);
+
+	if (!found)
+	{
+		/* First time through ... */
+#if (PG_VERSION_NUM >= 90600)
+		shared_state->lock = &(GetNamedLWLockTranche(TRANCHE_NAME))->lock;
+#else
+		shared_state->lock = LWLockAssign();
+#endif
+
+		shared_state->voting_status = VS_NO_VOTE;
+	}
+
+	LWLockRelease(AddinShmemInitLock);
 }
 
 
@@ -58,3 +143,17 @@ request_vote(PG_FUNCTION_ARGS)
 
 	PG_RETURN_BOOL(true);
 }
+
+
+
+Datum
+get_voting_status(PG_FUNCTION_ARGS)
+{
+	NodeVotingStatus voting_status;
+
+	LWLockAcquire(shared_state->lock, LW_SHARED);
+	voting_status = shared_state->voting_status;
+	LWLockRelease(shared_state->lock);
+
+	PG_RETURN_INT32(voting_status);
+}