src/backend/utils/misc/gpexpand.c

/*-------------------------------------------------------------------------
 *
 * gpexpand.c
 *	  Helper functions for gpexpand.
 *
 *
 * Copyright (c) 2018-Present VMware, Inc. or its affiliates.
 *
 * src/backend/utils/misc/gpexpand.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#ifdef USE_INTERNAL_FTS
#include "catalog/gp_segment_configuration.h"
#endif
#include "catalog/gp_configuration_history.h"
#include "catalog/pg_auth_time_constraint.h"
#include "catalog/pg_description.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_shdescription.h"
#include "catalog/pg_stat_last_operation.h"
#include "catalog/pg_stat_last_shoperation.h"
#include "catalog/pg_statistic.h"
#include "cdb/cdbutil.h"
#include "cdb/cdbvars.h"
#include "postmaster/fts.h"
#include "storage/lock.h"
#include "utils/builtins.h"
#include "utils/rel.h"
#include "utils/relcache.h"
#include "utils/gpexpand.h"

static volatile int *gp_expand_version;

/*
 * Catalog lock.
 */
static LOCKTAG gp_expand_locktag =
{
	/* FIXME: how to fill the locktag? */
	.locktag_field1 = 0xdead,
	.locktag_field2 = 0xdead,
	.locktag_field3 = 0xdead,
	.locktag_field4 = 0xdd,
	.locktag_type = LOCKTAG_USERLOCK,
	.locktag_lockmethodid = USER_LOCKMETHOD,
};

int
GpExpandVersionShmemSize(void)
{
	return sizeof(*gp_expand_version);
}

void
GpExpandVersionShmemInit(void)
{
	if (IsUnderPostmaster)
		return;

	/* only postmaster initialize it */
	gp_expand_version = (volatile int*)ShmemAlloc(GpExpandVersionShmemSize());  
	*gp_expand_version = 0;
}

int
GetGpExpandVersion(void)
{
	return *gp_expand_version;
}

/*
 * Used by gpexpand to bump the gpexpand version once gpexpand started up
 * new segments and updated the gp_segment_configuration.
 *
 * a gpexpand version change also prevent concurrent changes to catalog
 * during gpexpand (see gp_expand_lock_catalog)
 *
 */
Datum
gp_expand_bump_version(PG_FUNCTION_ARGS)
{
	*gp_expand_version += 1;
	PG_RETURN_VOID();
}

/*
 * Lock the catalog lock in exclusive mode.
 *
 * This should only be called by gpexpand.
 */
Datum
gp_expand_lock_catalog(PG_FUNCTION_ARGS)
{
	(void) LockAcquire(&gp_expand_locktag, AccessExclusiveLock, false, false);

	PG_RETURN_VOID();
}

/*
 * Prevent catalog being changed during gpexpand.
 *
 * This should be called before any catalog changes.
 *
 * Will raise an error if gpexpand already in progress or complete.
 */
void
gp_expand_protect_catalog_changes(Relation relation)
{
	LockAcquireResult	acquired;
	int					oldVersion;
	int					newVersion;

	if (Gp_role != GP_ROLE_DISPATCH)
		/* only lock catalog updates on qd */
		return;

	if (RelationGetNamespace(relation) != PG_CATALOG_NAMESPACE)
		/* not catalog relations */
		return;

	switch (RelationGetRelid(relation))
	{
#ifdef USE_INTERNAL_FTS
		case GpSegmentConfigRelationId:
#endif
		case GpConfigHistoryRelationId:
		case DescriptionRelationId:
		case SharedDescriptionRelationId:
		case StatLastOpRelationId:
		case StatLastShOpRelationId:
		case StatisticRelationId:
		case AuthTimeConstraintRelationId:
			/* these catalog tables are only meaningful on qd */
			return;
	}

	/*
	 * The online expand util will hold this lock in AccessExclusiveLock mode.
	 * Acquire expand lock in dontWait mode. If the lock is not available,
	 * report error. Because online expand must be running, after that, the
	 * cluster size has been changed, and the catalog data has been copied
	 * to new segments, but this transaction gangs are still running on old
	 * segments. Any catalog changes won't be copied to new segment.
	 */
	/* FIXME: do not re-acquire the lock */
	acquired = LockAcquire(&gp_expand_locktag, AccessShareLock, false, true);
	if (acquired == LOCKACQUIRE_NOT_AVAIL)
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 errmsg("gpexpand in progress, catalog changes are disallowed.")));

	oldVersion = cdbcomponent_getCdbComponents()->expand_version;
	newVersion = GetGpExpandVersion();
	if (oldVersion != newVersion)
		ereport(FATAL,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 errmsg("cluster is expanded from version %d to %d, "
						"catalog changes are disallowed",
						oldVersion, newVersion)));
}