p_usrloc: new parameter "mdb_availability_control" has been created.

- The new parameter "mdb_availability_control" overwrites the "write_on_db" parameter based on the availability of master database.

src/modules/p_usrloc/doc/p_usrloc_admin.xml

@@ -677,6 +677,26 @@ modparam("usrloc", "db_update_as_insert", 1)
 ...
 modparam("p_usrloc", "default_db_url", "mysql://ser:ser@localhost/ser")
 ...
+</programlisting>
+	    </example>
+	</section>
+
+	<section>
+		<title><varname>mdb_availability_control</varname>(str)</title>
+		<para>
+		  Checks the master database in certain time intervals specified by the <quote>retry_interval</quote> parameter. Overwrites the <quote>write_on_master_db</quote> parameter based on the reachability of master database. If the master db is unavailable then the aforementioned parameter will be deactivated.                        
+		</para>
+                <para>
+                <emphasis>
+                    Default value is <quote>0</quote>.
+                </emphasis>
+            </para>
+	    <example>
+		<title>Set <varname>mdb_availability_control</varname> parameter</title>
+		<programlisting format="linespecific">
+...
+modparam("p_usrloc", "mdb_availability_control", 1)
+...
 </programlisting>
 	    </example>
 	</section>

src/modules/p_usrloc/p_usrloc_mod.c

@@ -165,6 +165,7 @@ int policy               = DB_DEFAULT_POLICY;
 int db_write             = 0;
 int db_master_write      = 0;
 int alg_location         = 0;
+int mdb_availability_control = 0;
 
 int db_use_transactions  = 0;
 str db_transaction_level = str_init(DB_DEFAULT_TRANSACTION_LEVEL);
@@ -182,7 +183,7 @@ str default_db_type   = str_init(DEFAULT_DB_TYPE);
 str domain_db         = str_init(DEFAULT_DOMAIN_DB);
 int default_dbt       = 0;
 int expire            = 0;
-
+dbm_write_t *write_on_master_db_shared;
 
 /*! \brief
  * Exported functions
@@ -248,6 +249,7 @@ static param_export_t params[] = {
 	{"alg_location",         INT_PARAM, &alg_location },
     {"db_ops_ruid",          INT_PARAM, &default_p_usrloc_cfg.db_ops_ruid},
 	{"db_update_as_insert",  INT_PARAM, &default_p_usrloc_cfg.db_update_as_insert},
+	{"mdb_availability_control", INT_PARAM, &mdb_availability_control},
 	{0, 0, 0}
 };
 
@@ -307,6 +309,13 @@ static int mod_init(void)
 	}
 #endif
 
+	if((write_on_master_db_shared = shm_malloc(sizeof(dbm_write_t))) == NULL) {
+		LM_ERR("couldn't allocate shared memory.\n");
+		return -1;
+	} else {
+		write_on_master_db_shared->val = db_master_write;
+	}
+
 	if(ul_hash_size<=1)
 		ul_hash_size = 512;
 	else
@@ -395,10 +404,14 @@ static int mod_init(void)
 		LM_ERR("could not init database watch environment.\n");
 		return -1;
 	}
-	if(db_master_write){
+	if (lock_init(&write_on_master_db_shared->lock)==0){
+		LM_ERR("could not initialise lock\n");
+	}
+	if(write_on_master_db_shared->val){
 		/* register extra dummy timer to be created in init_db_check() */
 		register_dummy_timers(1);
 	}
+        check_master_db(db_master_write);
 	return 0;
 }
 

src/modules/p_usrloc/p_usrloc_mod.h

@@ -123,5 +123,11 @@ extern int connection_expires;
 extern int alg_location;
 
 extern int  max_loc_nr;
+typedef struct dbm_write {
+	int val;
+	gen_lock_t lock;
+} dbm_write_t;
+extern dbm_write_t *write_on_master_db_shared;
+extern int mdb_availability_control;
 
 #endif /* UL_MOD_H */

src/modules/p_usrloc/ul_db.c

@@ -60,7 +60,7 @@ int ul_db_init(void) {
 
 	memset(results, 0, sizeof(results));
 
-	if(db_master_write){
+	if(write_on_master_db_shared->val){
 		if(db_bind_mod(mdb.write.url, &mdb.write.dbf) < 0) {
 			LM_ERR("could not bind api for write db.\n");
 			return -1;
@@ -102,13 +102,16 @@ int ul_db_child_init(void) {
 	if(ul_db_child_locnr_init() == -1) return -1;
 
 	LM_INFO("location number is %d\n", max_loc_nr);
-	if(db_master_write){
+        lock_get(&write_on_master_db_shared->lock);
+	if(write_on_master_db_shared->val){
 		if((mdb.write.dbh  = mdb.write.dbf.init(mdb.write.url)) == NULL) {
 			LM_ERR("could not connect to sip master db (write).\n");
+			lock_release(&write_on_master_db_shared->lock);
 			return -1;
 		}
 		LM_INFO("write db connection for children initialized");
 	}
+	lock_release(&write_on_master_db_shared->lock);
 	return 0;
 }
 
@@ -146,10 +149,13 @@ int db_handle_error(ul_db_handle_t * handle, int no) {
 		LM_ERR("NULL pointer in parameter.\n");
 		return -1;
 	}
-
-	if(!db_master_write){
+
+	lock_get(&write_on_master_db_shared->lock);
+	if(!write_on_master_db_shared->val){
+		lock_release(&write_on_master_db_shared->lock);
 		return 0;
 	}
+	lock_release(&write_on_master_db_shared->lock);
 
 	query_len = 35 + reg_table.len
 			+ error_col.len * 2 + id_col.len;
@@ -372,9 +378,12 @@ int ul_db_query(str * table, str * first, str * second, db1_con_t *** _r_h,
 		LM_ERR("could not retrieve db handle.\n");
 		return -1;
 	}
-	if((ret = db_query(handle, _r_h, &f, table, _k, _op, _v, _c, _n, _nc, _o, _r, db_master_write)) < 0){
+	lock_get(&write_on_master_db_shared->lock);
+	if((ret = db_query(handle, _r_h, &f, table, _k, _op, _v, _c, _n, _nc, _o, _r, write_on_master_db_shared->val)) < 0){
+		lock_release(&write_on_master_db_shared->lock);
 		return ret;
 	}
+	lock_release(&write_on_master_db_shared->lock);
 	add_dbf(*_r, f);
 	return ret;
 }
@@ -392,25 +401,34 @@ int ul_db_free_result(db1_con_t ** dbh, db1_res_t * res){
 }
 
 int db_reactivate(ul_db_handle_t * handle, int no){
-	if(!db_master_write){
+	lock_get(&write_on_master_db_shared->lock);
+	if(!write_on_master_db_shared->val){
+		lock_release(&write_on_master_db_shared->lock);
 		LM_ERR("running in read only mode, abort.\n");
 		return -1;
 	}
+	lock_release(&write_on_master_db_shared->lock);
 	return db_failover_reactivate(&mdb.write.dbf, mdb.write.dbh, handle, no);
 }
 
 int db_reset_failover_time(ul_db_handle_t * handle, int no){
-	if(!db_master_write){
+	lock_get(&write_on_master_db_shared->lock);
+	if(!write_on_master_db_shared->val){
+		lock_release(&write_on_master_db_shared->lock);
 		LM_ERR("running in read only mode, abort.\n");
 		return -1;
 	}
+	lock_release(&write_on_master_db_shared->lock);
 	return db_failover_reset(&mdb.write.dbf, mdb.write.dbh, handle->id, no);
 }
 
 int ul_db_check(ul_db_handle_t * handle){
-	if(db_master_write){
+	lock_get(&write_on_master_db_shared->lock);
+	if(write_on_master_db_shared->val){
+		lock_release(&write_on_master_db_shared->lock);
 		return check_handle(&mdb.write.dbf, mdb.write.dbh, handle);
 	} else {
+		lock_release(&write_on_master_db_shared->lock);
 		LM_ERR("checking is useless in read-only mode\n");
 		return 0;
 	}

src/modules/p_usrloc/ul_db.h

@@ -56,6 +56,7 @@ typedef struct ul_master_db_set {
 } ul_master_db_set_t;
 
 extern int required_caps;
+extern ul_master_db_set_t mdb;
 
 int ul_db_init();
 

src/modules/p_usrloc/ul_db_watch.c

@@ -96,7 +96,10 @@ void check_dbs(unsigned int ticks, void *param){
 	ul_db_handle_list_t * tmp2, * new_element;
 	int found;
 	int i;
-
+
+	if(mdb_availability_control) {
+		check_master_db(db_master_write);
+	}
 	if(!list_lock){
 		return;
 	}
@@ -149,6 +152,25 @@ void check_dbs(unsigned int ticks, void *param){
 	lock_release(list_lock);
 }
 
+void check_master_db(int dbm_write_default) {
+	if(mdb_availability_control) {
+		if(mdb.write.dbh){
+			mdb.write.dbf.close(mdb.write.dbh);
+			mdb.write.dbh = NULL;
+		}
+
+		lock_get(&write_on_master_db_shared->lock);
+
+		if((mdb.write.dbh  = mdb.write.dbf.init(mdb.write.url)) == NULL) {
+			write_on_master_db_shared->val = 0;
+			LM_WARN("Master db is unavailable.\n");
+		} else {
+			write_on_master_db_shared->val = dbm_write_default;
+		}
+		lock_release(&write_on_master_db_shared->lock);
+	}
+}
+
 int ul_register_watch_db(int id){
 	ul_db_watch_list_t * new_id = NULL, * tmp;
 	if(!list_lock){

src/modules/p_usrloc/ul_db_watch.h

@@ -35,4 +35,6 @@ int ul_register_watch_db(int id);
 
 int ul_unregister_watch_db(int id);
 
+void check_master_db(int dbm_write_default);
+
 #endif