bind-9.10-threadsafe-mysql.patch

bind-9.10-threadsafe-mysql.patch

diff --git a/configure b/configure
index b4f2247..8b0bb26 100755
--- a/configure
+++ b/configure
@@ -20732,6 +20732,13 @@ $as_echo "not found" >&6; }
 	as_fn_error $? "MySQL was not found in any of $mysqldirs; use --with-dlz-mysql=/path" "$LINENO" 5
 fi
 
+if $use_threads
+then
+	mysqlclient_lib_name="mysqlclient_r"
+else
+	mysqlclient_lib_name="mysqlclient"
+fi
+
 case "$use_dlz_mysql" in
 	no)
 		{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
@@ -20749,9 +20756,9 @@ $as_echo "no" >&6; }
 	then
 		DLZ_DRIVER_INCLUDES="$DLZ_DRIVER_INCLUDES -I${mysql_include}"
 	fi
-	if test -n "-L${mysql_lib} -lmysqlclient -lz -lcrypt -lm"
+	if test -n "-L${mysql_lib} -l${mysqlclient_lib_name} -lz -lcrypt -lm"
 	then
-		DLZ_DRIVER_LIBS="$DLZ_DRIVER_LIBS -L${mysql_lib} -lmysqlclient -lz -lcrypt -lm"
+		DLZ_DRIVER_LIBS="$DLZ_DRIVER_LIBS -L${mysql_lib} -l${mysqlclient_lib_name} -lz -lcrypt -lm"
 	fi
 
 
diff --git a/contrib/dlz/config.dlz.in b/contrib/dlz/config.dlz.in
index 006c4d3..cb72619 100644
--- a/contrib/dlz/config.dlz.in
+++ b/contrib/dlz/config.dlz.in
@@ -191,6 +191,13 @@ then
 [MySQL was not found in any of $mysqldirs; use --with-dlz-mysql=/path])
 fi
 
+if $use_threads
+then
+	mysqlclient_lib_name="mysqlclient_r"
+else
+	mysqlclient_lib_name="mysqlclient"
+fi
+
 case "$use_dlz_mysql" in
 	no)
 		AC_MSG_RESULT(no)
@@ -198,7 +205,7 @@ case "$use_dlz_mysql" in
 	*)
 		DLZ_ADD_DRIVER(MYSQL, dlz_mysql_driver,
 				[-I${mysql_include}],
-				[-L${mysql_lib} -lmysqlclient -lz -lcrypt -lm])
+				[-L${mysql_lib} -l${mysqlclient_lib_name} -lz -lcrypt -lm])
 
 		AC_MSG_RESULT(
 [using mysql from ${mysql_lib} and ${mysql_include}])
diff --git a/contrib/dlz/drivers/dlz_mysql_driver.c b/contrib/dlz/drivers/dlz_mysql_driver.c
index 97deeab..2d618d0 100644
--- a/contrib/dlz/drivers/dlz_mysql_driver.c
+++ b/contrib/dlz/drivers/dlz_mysql_driver.c
@@ -75,6 +75,85 @@
 
 #include <mysql.h>
 
+#ifdef ISC_PLATFORM_USETHREADS
+#include <pthread.h>
+#include <unistd.h>
+
+static pthread_key_t thr_id_key;
+
+static void
+mysqldrv_thread_destructor(void *data)
+{
+	if (data != NULL) {
+		int *i = data;
+
+		if (*i) {
+			mysql_thread_end();
+		}
+
+		free(data);
+	}
+
+	pthread_setspecific(thr_id_key, NULL);
+}
+
+static void
+mysqldrv_mainthread_init(void)
+{
+	pthread_key_create(&thr_id_key, mysqldrv_thread_destructor);
+
+	int *i = malloc(sizeof(int));
+	*i = 0;
+
+	pthread_setspecific(thr_id_key, i);
+}
+
+static void
+mysqldrv_mainthread_end(void)
+{
+	void *data = pthread_getspecific(thr_id_key);
+
+	if (data != NULL)
+	{
+		free(data);
+		pthread_setspecific(thr_id_key, NULL);
+	}
+
+	pthread_key_delete(thr_id_key);
+}
+
+static void
+mysqldrv_thread_init(void)
+{
+	void *data = pthread_getspecific(thr_id_key);
+	if (data == NULL) {
+		if (mysql_thread_init()) {
+			return;
+		}
+
+		int *i = malloc(sizeof(int));
+		*i = 1;
+		pthread_setspecific(thr_id_key, i);
+	}
+}
+
+#define trylock_dbi(dbi) (isc_mutex_trylock(&(dbi)->instance_lock) == ISC_R_SUCCESS)
+#define unlock_dbi(dbi) (isc_mutex_unlock(&(dbi)->instance_lock))
+#else
+#define mysqldrv_mainthread_init()
+#define mysqldrv_mainthread_end()
+#define mysqldrv_thread_init()
+
+#define trylock_dbi(dbi) 1
+#define unlock_dbi(dbi) {}
+#endif
+
+typedef struct dbdata_array
+{
+	int count;
+	dbinstance_t **dbi;
+} dbdata_array_t;
+
 static dns_sdlzimplementation_t *dlz_mysql = NULL;
 
 #define dbc_search_limit 30
@@ -91,6 +170,31 @@ static dns_sdlzimplementation_t *dlz_mysql = NULL;
  * Private methods
  */
 
+#define dbc_search_limit 30
+
+static dbinstance_t *
+mysqldrv_find_avail_conn(void *dbdata)
+{
+	int count = 0;
+	int i;
+	dbdata_array_t *dbi_arr = (dbdata_array_t*)dbdata;
+	dbinstance_t **dbi = dbi_arr->dbi;
+
+	while (count < dbc_search_limit) {
+		for (i = 0; i < dbi_arr->count; ++i) {
+			if (trylock_dbi(dbi[i]))
+				return dbi[i];
+		}
+	}
+
+	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+		      DNS_LOGMODULE_DLZ, ISC_LOG_INFO,
+		      "Mysql driver unable to find available "
+		      "connection after searching %d times",
+		      count);
+	return NULL;
+}
+
 /*%
  * Allocates memory for a new string, and then constructs the new
  * string by "escaping" the input string.  The new string is
@@ -132,7 +236,8 @@ mysqldrv_escape_string(MYSQL *mysql, const char *instr) {
 static isc_result_t
 mysql_get_resultset(const char *zone, const char *record,
 		    const char *client, unsigned int query,
-		    void *dbdata, MYSQL_RES **rs)
+		    void *dbdata, MYSQL_RES **rs,
+		    dbinstance_t **r_dbi)
 {
 	isc_result_t result;
 	dbinstance_t *dbi = NULL;
@@ -147,7 +252,8 @@ mysql_get_resultset(const char *zone, const char *record,
 		REQUIRE(rs == NULL);
 
 	/* get db instance / connection */
-	dbi =  (dbinstance_t *) dbdata;
+	dbi = mysqldrv_find_avail_conn(dbdata);
+	*r_dbi = dbi;
 
 	/* if DBI is null, can't do anything else */
 	if (dbi == NULL) {
@@ -363,6 +469,11 @@ mysql_get_resultset(const char *zone, const char *record,
 	if (querystring  != NULL)
 		isc_mem_free(ns_g_mctx, querystring);
 
+	if (result != ISC_R_SUCCESS) {
+		unlock_dbi(dbi);
+		*r_dbi = NULL;
+	}
+
 	/* return result */
 	return result;
 }
@@ -374,7 +485,7 @@ mysql_get_resultset(const char *zone, const char *record,
  */
 
 static isc_result_t
-mysql_process_rs(dns_sdlzlookup_t *lookup, MYSQL_RES *rs)
+mysql_process_rs(dns_sdlzlookup_t *lookup, MYSQL_RES *rs, dbinstance_t *dbi)
 {
 	isc_result_t result = ISC_R_NOTFOUND;
 	MYSQL_ROW row;
@@ -446,7 +557,8 @@ mysql_process_rs(dns_sdlzlookup_t *lookup, MYSQL_RES *rs)
 					      "to allocate memory for "
 					      "temporary string");
 				mysql_free_result(rs);
-				return (ISC_R_FAILURE);	/* Yeah, I'd say! */
+				result = ISC_R_FAILURE;	/* Yeah, I'd say! */
+				goto cleanup;
 			}
 			/* copy field to tmpString */
 			strcpy(tmpString, safeGet(row[2]));
@@ -484,7 +596,8 @@ mysql_process_rs(dns_sdlzlookup_t *lookup, MYSQL_RES *rs)
 				      "dns_sdlz_putrr returned error. "
 				      "Error code was: %s",
 				      isc_result_totext(result));
-			return (ISC_R_FAILURE);
+			result = ISC_R_FAILURE;
+			goto cleanup;
 		}
 		row = mysql_fetch_row(rs);	/* get next row */
 	}
@@ -492,6 +605,11 @@ mysql_process_rs(dns_sdlzlookup_t *lookup, MYSQL_RES *rs)
 	/* free result set memory */
 	mysql_free_result(rs);
 
+cleanup:
+
+	if (dbi != NULL)
+		unlock_dbi(dbi);
+
 	/* return result code */
 	return result;
 }
@@ -509,13 +627,16 @@ mysql_findzone(void *driverarg, void *dbdata, const char *name,
 	isc_result_t result;
 	MYSQL_RES *rs = NULL;
 	my_ulonglong rows;
+	dbinstance_t *dbi = NULL;
 
 	UNUSED(driverarg);
 	UNUSED(methods);
 	UNUSED(clientinfo);
 
+	mysqldrv_thread_init();
+
 	/* run the query and get the result set from the database. */
-	result = mysql_get_resultset(name, NULL, NULL, FINDZONE, dbdata, &rs);
+	result = mysql_get_resultset(name, NULL, NULL, FINDZONE, dbdata, &rs, &dbi);
 	/* if we didn't get a result set, log an err msg. */
 	if (result != ISC_R_SUCCESS || rs == NULL) {
 		if (rs != NULL)
@@ -524,6 +645,10 @@ mysql_findzone(void *driverarg, void *dbdata, const char *name,
 			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
 			      "mysql driver unable to return "
 			      "result set for findzone query");
+
+		if (dbi != NULL)
+			unlock_dbi(dbi);
+
 		return (ISC_R_FAILURE);
 	}
 	/* count how many rows in result set */
@@ -531,9 +656,16 @@ mysql_findzone(void *driverarg, void *dbdata, const char *name,
 	/* get rid of result set, we are done with it. */
 	mysql_free_result(rs);
 
+	if (dbi != NULL)
+		unlock_dbi(dbi);
+
 	/* if we returned any rows, zone is supported. */
 	if (rows > 0) {
-		mysql_get_resultset(name, NULL, NULL, COUNTZONE, dbdata, NULL);
+		mysql_get_resultset(name, NULL, NULL, COUNTZONE, dbdata, NULL, &dbi);
+
+		if(dbi != NULL)
+			unlock_dbi(dbi);
+
 		return (ISC_R_SUCCESS);
 	}
 
@@ -549,9 +681,12 @@ mysql_allowzonexfr(void *driverarg, void *dbdata, const char *name,
 	isc_result_t result;
 	MYSQL_RES *rs = NULL;
 	my_ulonglong rows;
+	dbinstance_t *dbi = NULL;
 
 	UNUSED(driverarg);
 
+	mysqldrv_thread_init();
+
 	/* first check if the zone is supported by the database. */
 	result = mysql_findzone(driverarg, dbdata, name, NULL, NULL);
 	if (result != ISC_R_SUCCESS)
@@ -566,10 +701,10 @@ mysql_allowzonexfr(void *driverarg, void *dbdata, const char *name,
 	 * Run our query, and get a result set from the database.
 	 */
 	result = mysql_get_resultset(name, NULL, client, ALLOWXFR,
-				     dbdata, &rs);
+				     dbdata, &rs, &dbi);
 	/* if we get "not implemented", send it along. */
 	if (result == ISC_R_NOTIMPLEMENTED)
-		return result;
+		goto cleanup;
 	/* if we didn't get a result set, log an err msg. */
 	if (result != ISC_R_SUCCESS || rs == NULL) {
 		if (rs != NULL)
@@ -578,7 +713,8 @@ mysql_allowzonexfr(void *driverarg, void *dbdata, const char *name,
 			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
 			      "mysql driver unable to return "
 			      "result set for allow xfr query");
-		return (ISC_R_FAILURE);
+		result = ISC_R_FAILURE;
+		goto cleanup;
 	}
 	/* count how many rows in result set */
 	rows = mysql_num_rows(rs);
@@ -586,11 +722,20 @@ mysql_allowzonexfr(void *driverarg, void *dbdata, const char *name,
 	mysql_free_result(rs);
 
 	/* if we returned any rows, zone xfr is allowed. */
-	if (rows > 0)
-		return (ISC_R_SUCCESS);
+	if (rows > 0) {
+		result = ISC_R_SUCCESS;
+		goto cleanup;
+	}
 
 	/* no rows returned, zone xfr not allowed */
-	return (ISC_R_NOPERM);
+	result = ISC_R_NOPERM;
+
+cleanup:
+
+	if (dbi != NULL)
+		unlock_dbi(dbi);
+
+	return result;
 }
 
 /*%
@@ -611,14 +756,17 @@ mysql_allnodes(const char *zone, void *driverarg, void *dbdata,
 	char *tmpString;
 	char *endp;
 	int ttl;
+	dbinstance_t *dbi = NULL;
 
 	UNUSED(driverarg);
 
+	mysqldrv_thread_init();
+
 	/* run the query and get the result set from the database. */
-	result = mysql_get_resultset(zone, NULL, NULL, ALLNODES, dbdata, &rs);
+	result = mysql_get_resultset(zone, NULL, NULL, ALLNODES, dbdata, &rs, &dbi);
 	/* if we get "not implemented", send it along */
 	if (result == ISC_R_NOTIMPLEMENTED)
-		return result;
+		goto cleanup;
 	/* if we didn't get a result set, log an err msg. */
 	if (result != ISC_R_SUCCESS) {
 		if (rs != NULL)
@@ -627,7 +775,8 @@ mysql_allnodes(const char *zone, void *driverarg, void *dbdata,
 			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
 			      "mysql driver unable to return "
 			      "result set for all nodes query");
-		return (ISC_R_FAILURE);
+		result = ISC_R_FAILURE;
+		goto cleanup;
 	}
 
 	result = ISC_R_NOTFOUND;
@@ -673,7 +822,8 @@ mysql_allnodes(const char *zone, void *driverarg, void *dbdata,
 					      "to allocate memory for "
 					      "temporary string");
 				mysql_free_result(rs);
-				return (ISC_R_FAILURE);
+				result = ISC_R_FAILURE;
+				goto cleanup;
 			}
 			/* copy this field to tmpString */
 			strcpy(tmpString, safeGet(row[3]));
@@ -705,6 +855,11 @@ mysql_allnodes(const char *zone, void *driverarg, void *dbdata,
 	/* free result set memory */
 	mysql_free_result(rs);
 
+cleanup:
+
+	if (dbi != NULL)
+		unlock_dbi(dbi);
+
 	return result;
 }
 
@@ -718,14 +873,17 @@ mysql_authority(const char *zone, void *driverarg, void *dbdata,
 {
 	isc_result_t result;
 	MYSQL_RES *rs = NULL;
+	dbinstance_t *dbi = NULL;
 
 	UNUSED(driverarg);
 
+	mysqldrv_thread_init();
+
 	/* run the query and get the result set from the database. */
-	result = mysql_get_resultset(zone, NULL, NULL, AUTHORITY, dbdata, &rs);
+	result = mysql_get_resultset(zone, NULL, NULL, AUTHORITY, dbdata, &rs, &dbi);
 	/* if we get "not implemented", send it along */
 	if (result == ISC_R_NOTIMPLEMENTED)
-		return result;
+		goto error;
 	/* if we didn't get a result set, log an err msg. */
 	if (result != ISC_R_SUCCESS) {
 		if (rs != NULL)
@@ -734,13 +892,21 @@ mysql_authority(const char *zone, void *driverarg, void *dbdata,
 			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
 			      "mysql driver unable to return "
 			      "result set for authority query");
-		return (ISC_R_FAILURE);
+		result = ISC_R_FAILURE;
+		goto error;
 	}
 	/*
 	 * lookup and authority result sets are processed in the same
 	 * manner mysql_process_rs does the job for both functions.
 	 */
-	return mysql_process_rs(lookup, rs);
+	return mysql_process_rs(lookup, rs, dbi);
+
+error:
+
+	if (dbi != NULL)
+		unlock_dbi(dbi);
+
+	return result;
 }
 
 /*% if zone is supported, lookup up a (or multiple) record(s) in it */
@@ -751,13 +917,16 @@ mysql_lookup(const char *zone, const char *name, void *driverarg,
 {
 	isc_result_t result;
 	MYSQL_RES *rs = NULL;
+	dbinstance_t *dbi = NULL;
 
 	UNUSED(driverarg);
 	UNUSED(methods);
 	UNUSED(clientinfo);
 
+	mysqldrv_thread_init();
+
 	/* run the query and get the result set from the database. */
-	result = mysql_get_resultset(zone, name, NULL, LOOKUP, dbdata, &rs);
+	result = mysql_get_resultset(zone, name, NULL, LOOKUP, dbdata, &rs, &dbi);
 	/* if we didn't get a result set, log an err msg. */
 	if (result != ISC_R_SUCCESS) {
 		if (rs != NULL)
@@ -766,13 +935,21 @@ mysql_lookup(const char *zone, const char *name, void *driverarg,
 			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
 			      "mysql driver unable to return "
 			      "result set for lookup query");
-		return (ISC_R_FAILURE);
+		result = ISC_R_FAILURE;
+		goto error;
 	}
 	/*
 	 * lookup and authority result sets are processed in the same manner
 	 * mysql_process_rs does the job for both functions.
 	 */
-	return mysql_process_rs(lookup, rs);
+	return mysql_process_rs(lookup, rs, dbi);
+
+error:
+
+	if (dbi != NULL)
+		unlock_dbi(dbi);
+
+	return result;
 }
 
 /*%
@@ -786,7 +963,8 @@ mysql_create(const char *dlzname, unsigned int argc, char *argv[],
 	     void *driverarg, void **dbdata)
 {
 	isc_result_t result;
-	dbinstance_t *dbi = NULL;
+	dbinstance_t **dbi = NULL;
+	dbdata_array_t *res_arr = NULL;
 	char *tmp = NULL;
 	char *dbname = NULL;
 	char *host = NULL;
@@ -794,9 +972,10 @@ mysql_create(const char *dlzname, unsigned int argc, char *argv[],
 	char *pass = NULL;
 	char *socket = NULL;
 	int port;
+	int concount;
 	MYSQL *dbc;
 	char *endp;
-	int j;
+	int i, j;
 	unsigned int flags = 0;
 #if MYSQL_VERSION_ID >= 50000
         my_bool auto_reconnect = 1;
@@ -835,6 +1014,29 @@ mysql_create(const char *dlzname, unsigned int argc, char *argv[],
 		goto full_cleanup;
 	}
 
+	/* get connection count. Not required, must be >= 1 if specified */
+	tmp = getParameterValue(argv[1], "concount=");
+	if (tmp == NULL) {
+#ifdef ISC_PLATFORM_USETHREADS
+		concount = 9;
+#else
+		concount = 1;
+#endif
+	} else {
+		concount = strtol(tmp, &endp, 10);
+		isc_mem_free(ns_g_mctx, tmp);
+		if (*endp != '\0' || concount < 1) {
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+				      "Mysql driver concount "
+				      "must be a greater than 0.");
+			isc_mem_free(ns_g_mctx, tmp);
+			result = ISC_R_FAILURE;
+			goto full_cleanup;
+		}
+		isc_mem_free(ns_g_mctx, tmp);
+	}
+
 	/* get db port.  Not required, but must be > 0 if specified */
 	tmp = getParameterValue(argv[1], "port=");
 	if (tmp == NULL) {
@@ -853,58 +1055,6 @@ mysql_create(const char *dlzname, unsigned int argc, char *argv[],
 		isc_mem_free(ns_g_mctx, tmp);
 	}
 
-	/* how many queries were passed in from config file? */
-	switch(argc) {
-	case 4:
-		result = build_sqldbinstance(ns_g_mctx, NULL, NULL, NULL,
-					     argv[2], argv[3], NULL, &dbi);
-		break;
-	case 5:
-		result = build_sqldbinstance(ns_g_mctx, NULL, NULL, argv[4],
-					     argv[2], argv[3], NULL, &dbi);
-		break;
-	case 6:
-		result = build_sqldbinstance(ns_g_mctx, argv[5], NULL, argv[4],
-					     argv[2], argv[3], NULL, &dbi);
-		break;
-	case 7:
-		result = build_sqldbinstance(ns_g_mctx, argv[5],
-					     argv[6], argv[4],
-					     argv[2], argv[3], NULL, &dbi);
-		break;
-	case 8:
-		result = build_sqldbinstance(ns_g_mctx, argv[5],
-					     argv[6], argv[4],
-					     argv[2], argv[3], argv[7], &dbi);
-		break;
-	default:
-		/* not really needed, should shut up compiler. */
-		result = ISC_R_FAILURE;
-	}
-
-	/* unsuccessful?, log err msg and cleanup. */
-	if (result != ISC_R_SUCCESS) {
-		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
-			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
-			      "mysql driver could not create "
-			      "database instance object.");
-		result = ISC_R_FAILURE;
-		goto cleanup;
-	}
-
-	/* create and set db connection */
-	dbi->dbconn = mysql_init(NULL);
-
-	/* if db connection cannot be created, log err msg and cleanup. */
-	if (dbi->dbconn == NULL) {
-		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
-			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
-			      "mysql driver could not allocate "
-			      "memory for database connection");
-		result = ISC_R_FAILURE;
-		goto full_cleanup;
-	}
-
 	tmp = getParameterValue(argv[1], "compress=");
 	if (tmp != NULL) {
 		if (strcasecmp(tmp, "true") == 0)
@@ -932,42 +1082,120 @@ mysql_create(const char *dlzname, unsigned int argc, char *argv[],
 	pass = getParameterValue(argv[1], "pass=");
 	socket = getParameterValue(argv[1], "socket=");
 
+	mysqldrv_thread_init();
+
+
+	/* initialize result array */
+	dbi = malloc(sizeof(dbinstance_t*) * concount);
+	memset(dbi, 0, sizeof(dbinstance_t*) * concount);
+
+	for (i = 0; i < concount; ++i) {
+
+		/* how many queries were passed in from config file? */
+		switch(argc) {
+		case 4:
+			result = build_sqldbinstance(ns_g_mctx, NULL, NULL, NULL,
+						     argv[2], argv[3], NULL, &dbi[i]);
+			break;
+		case 5:
+			result = build_sqldbinstance(ns_g_mctx, NULL, NULL, argv[4],
+						     argv[2], argv[3], NULL, &dbi[i]);
+			break;
+		case 6:
+			result = build_sqldbinstance(ns_g_mctx, argv[5], NULL, argv[4],
+						     argv[2], argv[3], NULL, &dbi[i]);
+			break;
+		case 7:
+			result = build_sqldbinstance(ns_g_mctx, argv[5],
+						     argv[6], argv[4],
+						     argv[2], argv[3], NULL, &dbi[i]);
+			break;
+		case 8:
+			result = build_sqldbinstance(ns_g_mctx, argv[5],
+						     argv[6], argv[4],
+						     argv[2], argv[3], argv[7], &dbi[i]);
+			break;
+		default:
+			/* not really needed, should shut up compiler. */
+			result = ISC_R_FAILURE;
+		}
+
+		/* unsuccessful?, log err msg and cleanup. */
+		if (result != ISC_R_SUCCESS) {
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+				      "mysql driver could not create "
+				      "database instance object.");
+			result = ISC_R_FAILURE;
+			dbi[i] = NULL;
+			dbi[i]->dbconn = NULL;
+			goto full_cleanup;
+		}
+
+		/* create and set db connection */
+		dbi[i]->dbconn = mysql_init(NULL);
+
+		/* if db connection cannot be created, log err msg and cleanup. */
+		if (dbi[i]->dbconn == NULL) {
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+				      "mysql driver could not allocate "
+				      "memory for database connection");
+			result = ISC_R_FAILURE;
+			goto full_cleanup;
+		}
+
 #if MYSQL_VERSION_ID >= 50000
-	/* enable automatic reconnection. */
-        if (mysql_options((MYSQL *) dbi->dbconn, MYSQL_OPT_RECONNECT,
-			  &auto_reconnect) != 0) {
-		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
-			      DNS_LOGMODULE_DLZ, ISC_LOG_WARNING,
-			      "mysql driver failed to set "
-			      "MYSQL_OPT_RECONNECT option, continuing");
-	}
+		/* enable automatic reconnection. */
+	        if (mysql_options((MYSQL *) dbi[i]->dbconn, MYSQL_OPT_RECONNECT,
+				  &auto_reconnect) != 0) {
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_DLZ, ISC_LOG_WARNING,
+				      "mysql driver failed to set "
+				      "MYSQL_OPT_RECONNECT option, continuing");
+		}
 #endif
 
-	for (j=0; dbc == NULL && j < 4; j++)
-		dbc = mysql_real_connect((MYSQL *) dbi->dbconn, host,
-					 user, pass, dbname, port, socket,
-					 flags);
+		dbc = NULL;
+
+		for (j=0; dbc == NULL && j < 4; j++)
+			dbc = mysql_real_connect((MYSQL *) dbi[i]->dbconn, host,
+						 user, pass, dbname, port, socket,
+						 flags);
+
+		/* let user know if we couldn't connect. */
+		if (dbc == NULL) {
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
+				      "mysql driver failed to create "
+				      "database connection after 4 attempts");
+			result = ISC_R_FAILURE;
+			goto full_cleanup;
+		}
 
-	/* let user know if we couldn't connect. */
-	if (dbc == NULL) {
-		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
-			      DNS_LOGMODULE_DLZ, ISC_LOG_ERROR,
-			      "mysql driver failed to create "
-			      "database connection after 4 attempts");
-		result = ISC_R_FAILURE;
-		goto full_cleanup;
 	}
 
-	/* return db connection via dbdata */
-	*dbdata = dbi;
+	/* return db connections via dbdata */
+	res_arr = malloc(sizeof(dbdata_array_t));
+	res_arr->count = concount;
+	res_arr->dbi = dbi;
+	*dbdata = res_arr;
 
 	result = ISC_R_SUCCESS;
 	goto cleanup;
 
  full_cleanup:
 
-	if (dbi != NULL)
-		destroy_sqldbinstance(dbi);
+	if (dbi != NULL) {
+		for (i = 0; i < concount; ++i) {
+			if (dbi[i] != NULL) {
+				if (dbi[i]->dbconn != NULL)
+					mysql_close(dbi[i]->dbconn);
+				destroy_sqldbinstance(dbi[i]);
+			}
+		}
+		free(dbi);
+	}
 
  cleanup:
 
@@ -996,18 +1224,25 @@ mysql_create(const char *dlzname, unsigned int argc, char *argv[],
 static void
 mysql_destroy(void *driverarg, void *dbdata)
 {
-	dbinstance_t *dbi;
+	dbdata_array_t *dbi_arr = (dbdata_array_t*)dbdata;
+	dbinstance_t **dbi = dbi_arr->dbi;
+	int i;
 
 	UNUSED(driverarg);
 
-	dbi = (dbinstance_t *) dbdata;
+	mysqldrv_thread_init();
+
+	for (i = 0; i < dbi_arr->count; ++i) {
+		/* release DB connection */
+		if (dbi[i]->dbconn != NULL)
+			mysql_close((MYSQL *) dbi[i]->dbconn);
 
-	/* release DB connection */
-	if (dbi->dbconn != NULL)
-		mysql_close((MYSQL *) dbi->dbconn);
+		/* destroy DB instance */
+		destroy_sqldbinstance(dbi[i]);
+	}
 
-	/* destroy DB instance */
-	destroy_sqldbinstance(dbi);
+	free(dbi);
+	free(dbi_arr);
 }
 
 /* pointers to all our runtime methods. */
@@ -1044,6 +1279,14 @@ dlz_mysql_init(void) {
 		      DNS_LOGMODULE_DLZ, ISC_LOG_DEBUG(2),
 		      "Registering DLZ mysql driver.");
 
+	if (mysql_library_init(0, NULL, NULL)) {
+		UNEXPECTED_ERROR(__FILE__, __LINE__,
+				 "mysql_library_init() failed");
+		return ISC_R_UNEXPECTED;
+	}
+
+	mysqldrv_mainthread_init();
+
 	/* Driver is always threadsafe.  Because of the way MySQL handles
          * threads the MySQL driver can only be used when bind is run single
          * threaded.  Using MySQL with Bind running multi-threaded is not
@@ -1083,6 +1326,10 @@ dlz_mysql_clear(void) {
 	/* unregister the driver. */
 	if (dlz_mysql != NULL)
 		dns_sdlzunregister(&dlz_mysql);
+
+	mysql_library_end();
+
+	mysqldrv_mainthread_end();
 }
 
 #endif