ODBC transaction support

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@177320 65c4cc65-6c06-0410-ace0-fbb531ad65f3

CHANGES

@@ -94,6 +94,7 @@ Dialplan Functions
    of "core show function AES_ENCRYPT" from the CLI
  * Added AES_DECRYPT. For information on its use, please see the output
    of "core show function AES_DECRYPT" from the CLI
+ * func_odbc now supports database transactions across multiple queries.
 
 Applications
 ------------

configs/res_odbc.conf.sample

@@ -47,6 +47,13 @@ username => oscar
 password => thegrouch
 pre-connect => yes
 sanitysql => select count(*) from systables
+; forcecommit => no            ; Default to committing uncommitted transactions?
+; isolation => read_committed  ; Isolation level; supported levels are:
+                               ; read_uncommitted, read_committed, repeatable_read,
+                               ; serializable.  Note that not all databases support
+                               ; all isolation levels (e.g. Postgres only supports
+                               ; repeatable_read and serializable).  See database
+                               ; documentation for further information.
 ;
 ; Many databases have a default of '\' to escape special characters.  MS SQL
 ; Server does not.

funcs/func_odbc.c

@@ -2,6 +2,7 @@
  * Asterisk -- An open source telephony toolkit.
  *
  * Copyright (c) 2005, 2006 Tilghman Lesher
+ * Copyright (c) 2008 Digium, Inc.
  *
  * Tilghman Lesher <func_odbc__200508@the-tilghman.com>
  *
@@ -205,6 +206,7 @@ static int acf_odbc_write(struct ast_channel *chan, const char *cmd, char *s, co
 	struct acf_odbc_query *query;
 	char *t, varname[15];
 	int i, dsn, bogus_chan = 0;
+	int transactional = 0;
 	AST_DECLARE_APP_ARGS(values,
 		AST_APP_ARG(field)[100];
 	);
@@ -293,16 +295,32 @@ static int acf_odbc_write(struct ast_channel *chan, const char *cmd, char *s, co
 	}
 	pbx_builtin_setvar_helper(chan, "VALUE", NULL);
 
+	/*!\note
+	 * Okay, this part is confusing.  Transactions belong to a single database
+	 * handle.  Therefore, when working with transactions, we CANNOT failover
+	 * to multiple DSNs.  We MUST have a single handle all the way through the
+	 * transaction, or else we CANNOT enforce atomicity.
+	 */
 	for (dsn = 0; dsn < 5; dsn++) {
+		if (transactional) {
+			/* This can only happen second time through or greater. */
+			ast_log(LOG_WARNING, "Transactions do not work well with multiple DSNs for 'writehandle'\n");
+		}
+
 		if (!ast_strlen_zero(query->writehandle[dsn])) {
-			obj = ast_odbc_request_obj(query->writehandle[dsn], 0);
-			if (obj)
-				stmt = ast_odbc_direct_execute(obj, generic_execute, ast_str_buffer(buf));
+			if ((obj = ast_odbc_retrieve_transaction_obj(chan, query->writehandle[dsn]))) {
+				transactional = 1;
+			} else {
+				obj = ast_odbc_request_obj(query->writehandle[dsn], 0);
+				transactional = 0;
+			}
+			if (obj && (stmt = ast_odbc_direct_execute(obj, generic_execute, ast_str_buffer(buf)))) {
+				break;
+			}
 		}
-		if (stmt) {
-			status = "SUCCESS";
-			SQLRowCount(stmt, &rows);
-			break;
+
+		if (obj && !transactional) {
+			ast_odbc_release_obj(obj);
 		}
 	}
 
@@ -322,6 +340,9 @@ static int acf_odbc_write(struct ast_channel *chan, const char *cmd, char *s, co
 				break;
 			}
 		}
+	} else if (stmt) {
+		status = "SUCCESS";
+		SQLRowCount(stmt, &rows);
 	}
 
 	AST_RWLIST_UNLOCK(&queries);
@@ -338,7 +359,7 @@ static int acf_odbc_write(struct ast_channel *chan, const char *cmd, char *s, co
 		SQLCloseCursor(stmt);
 		SQLFreeHandle(SQL_HANDLE_STMT, stmt);
 	}
-	if (obj) {
+	if (obj && !transactional) {
 		ast_odbc_release_obj(obj);
 		obj = NULL;
 	}

include/asterisk/res_odbc.h

@@ -35,25 +35,30 @@
 
 typedef enum { ODBC_SUCCESS=0, ODBC_FAIL=-1} odbc_status;
 
+/*! \brief Flags for use with ast_odbc_request_obj2 */
+enum {
+	RES_ODBC_SANITY_CHECK = (1 << 0),
+	RES_ODBC_INDEPENDENT_CONNECTION = (1 << 1),
+};
+
 /*! \brief ODBC container */
 struct odbc_obj {
 	ast_mutex_t lock;
-	SQLHDBC  con;                   /* ODBC Connection Handle */
-	struct odbc_class *parent;      /* Information about the connection is protected */
-	struct timeval last_used;
+	SQLHDBC  con;                   /*!< ODBC Connection Handle */
+	struct odbc_class *parent;      /*!< Information about the connection is protected */
+	struct timeval last_used;       /*!< Used by idlecheck to determine if the connection should be renegotiated */
 #ifdef DEBUG_THREADS
 	char file[80];
 	char function[80];
 	int lineno;
 #endif
-	unsigned int used:1;
+	unsigned int used:1;            /*!< Is this connection currently in use? */
 	unsigned int up:1;
+	unsigned int tx:1;              /*!< Should this connection be unshared, regardless of the class setting? */
+	struct odbc_txn_frame *txf;     /*!< Reference back to the transaction frame, if applicable */
 	AST_LIST_ENTRY(odbc_obj) list;
 };
 
-/*!\brief These aren't used in any API calls, but they are kept in a common
- * location, simply for convenience and to avoid duplication.
- */
 struct odbc_cache_columns {
 	char *name;
 	SQLSMALLINT type;
@@ -106,6 +111,13 @@ int ast_odbc_smart_execute(struct odbc_obj *obj, SQLHSTMT stmt) __attribute__((d
  * thread which requests it.  Note that all connections should be released
  * when the thread is done by calling odbc_release_obj(), below.
  */
+#ifdef DEBUG_THREADS
+struct odbc_obj *_ast_odbc_request_obj2(const char *name, struct ast_flags flags, const char *file, const char *function, int lineno);
+#define ast_odbc_request_obj2(a, b)	_ast_odbc_request_obj2(a, b, __FILE__, __PRETTY_FUNCTION__, __LINE__)
+#else
+struct odbc_obj *ast_odbc_request_obj2(const char *name, struct ast_flags flags);
+#endif
+
 #ifdef DEBUG_THREADS
 struct odbc_obj *_ast_odbc_request_obj(const char *name, int check, const char *file, const char *function, int lineno);
 #define ast_odbc_request_obj(a, b)	_ast_odbc_request_obj(a, b, __FILE__, __PRETTY_FUNCTION__, __LINE__)
@@ -113,6 +125,18 @@ struct odbc_obj *_ast_odbc_request_obj(const char *name, int check, const char *
 struct odbc_obj *ast_odbc_request_obj(const char *name, int check);
 #endif
 
+/*!
+ * \brief Retrieve a stored ODBC object, if a transaction has been started.
+ * \param chan Channel associated with the transaction.
+ * \param objname Name of the database handle.  This name corresponds to the name passed
+ * to ast_odbc_request_obj2 (or formerly, to ast_odbc_request_obj).  Note that the
+ * existence of this parameter name explicitly allows for multiple transactions to be open
+ * at once, albeit to different databases.
+ * \retval A stored ODBC object, if a transaction was already started.
+ * \retval NULL, if no transaction yet exists.
+ */
+struct odbc_obj *ast_odbc_retrieve_transaction_obj(struct ast_channel *chan, const char *objname);
+
 /*! 
  * \brief Releases an ODBC object previously allocated by odbc_request_obj()
  * \param obj The ODBC object