mysql add connection pool and keepalive thread

net/common/ccnet-db.c

@@ -12,12 +12,21 @@
 #include <sqlite3.h>
 #include <pthread.h>
 
+struct DBConnPool {
+    GPtrArray *connections;
+    pthread_mutex_t lock;
+    int max_connections;
+};
+typedef struct DBConnPool DBConnPool;
+
 struct CcnetDB {
     int type;
+    DBConnPool *pool;
 };
 
 typedef struct DBConnection {
-    /* Empty */
+    gboolean is_available;
+    DBConnPool *pool;
 } DBConnection;
 
 struct CcnetDBRow {
@@ -77,6 +86,97 @@ static int
 mysql_db_row_get_column_int (CcnetDBRow *row, int idx);
 static gint64
 mysql_db_row_get_column_int64 (CcnetDBRow *row, int idx);
+static gboolean
+mysql_db_connection_ping (DBConnection *vconn);
+static DBConnPool *
+
+init_conn_pool_common (int max_connections)
+{
+    DBConnPool *pool = g_new0(DBConnPool, 1);
+    pool->connections = g_ptr_array_sized_new (max_connections);
+    pthread_mutex_init (&pool->lock, NULL);
+    pool->max_connections = max_connections;
+
+    return pool;
+}
+
+static DBConnection *
+mysql_conn_pool_get_connection (CcnetDB *db)
+{
+    DBConnPool *pool = db->pool;
+    DBConnection *conn = NULL;
+
+    if (pool->max_connections == 0) {
+        conn = mysql_db_get_connection (db);
+        conn->pool = pool;
+        return conn;
+    }
+
+    pthread_mutex_lock (&pool->lock);
+
+    guint i, size = pool->connections->len;
+    for (i = 0; i < size; ++i) {
+        conn = g_ptr_array_index (pool->connections, i);
+        if (conn->is_available && mysql_db_connection_ping (conn)) {
+            conn->is_available = FALSE;
+            goto out;
+        }
+    }
+    conn = NULL;
+    if (size < pool->max_connections) {
+        conn = mysql_db_get_connection (db);
+        if (conn) {
+            conn->pool = pool;
+            conn->is_available = FALSE;
+            g_ptr_array_add (pool->connections, conn);
+        }
+    }
+
+out:
+    pthread_mutex_unlock (&pool->lock);
+    return conn;
+}
+
+static void
+mysql_conn_pool_release_connection (DBConnection *conn)
+{
+    if (!conn)
+        return;
+
+    if (conn->pool->max_connections == 0) {
+        mysql_db_release_connection (conn);
+        return;
+    }
+
+    pthread_mutex_lock (&conn->pool->lock);
+    conn->is_available = TRUE;
+    pthread_mutex_unlock (&conn->pool->lock);
+}
+
+#define KEEPALIVE_INTERVAL 30
+static void *
+mysql_conn_keepalive (void *arg)
+{
+    DBConnPool *pool = arg;
+    DBConnection *conn = NULL;
+
+    while (1) {
+        pthread_mutex_lock (&pool->lock);
+
+        guint i, size = pool->connections->len;
+        for (i = 0; i < size; ++i) {
+            conn = g_ptr_array_index (pool->connections, i);
+            if (conn->is_available) {
+                mysql_db_connection_ping (conn);
+            }
+        }
+        pthread_mutex_unlock (&pool->lock);
+
+        sleep (KEEPALIVE_INTERVAL);
+    }
+
+    return NULL;
+}
 
 CcnetDB *
 ccnet_db_new_mysql (const char *host,
@@ -96,8 +196,8 @@ ccnet_db_new_mysql (const char *host,
         return NULL;
     db->type = CCNET_DB_TYPE_MYSQL;
 
-    db_ops.get_connection = mysql_db_get_connection;
+    db_ops.get_connection = mysql_conn_pool_get_connection;
-    db_ops.release_connection = mysql_db_release_connection;
+    db_ops.release_connection = mysql_conn_pool_release_connection;
     db_ops.execute_sql_no_stmt = mysql_db_execute_sql_no_stmt;
     db_ops.execute_sql = mysql_db_execute_sql;
     db_ops.query_foreach_row = mysql_db_query_foreach_row;
@@ -106,6 +206,17 @@ ccnet_db_new_mysql (const char *host,
     db_ops.row_get_column_int = mysql_db_row_get_column_int;
     db_ops.row_get_column_int64 = mysql_db_row_get_column_int64;
 
+    db->pool = init_conn_pool_common (max_connections);
+
+    pthread_t tid;
+    int ret = pthread_create (&tid, NULL, mysql_conn_keepalive, db->pool);
+    if (ret != 0) {
+        ccnet_warning ("Failed to create mysql connection keepalive thread.\n");
+        return NULL;
+    }
+    pthread_detach (tid);
+
+
     return db;
 }
 
@@ -527,6 +638,14 @@ typedef struct MySQLDBConnection {
     MYSQL *db_conn;
 } MySQLDBConnection;
 
+static gboolean
+mysql_db_connection_ping (DBConnection *vconn)
+{
+    MySQLDBConnection *conn = (MySQLDBConnection *)vconn;
+
+    return (mysql_ping (conn->db_conn) == 0);
+}
+
 static CcnetDB *
 mysql_db_new (const char *host,
               int port,