Convert samples to use defer instead of just suggesting it

Author: ibmmqmet

samples/README.md

@@ -13,7 +13,7 @@ Where needed for the sample programs:
 
 * the default queue manager is "QM1"
 * the default queue is "DEV.QUEUE.1"
-* the default topic is "GO.TEST.TOPIC"
+* the default topic is "DEV.BASE.TOPIC"
 
 ## Description of sample programs
 Current samples in this directory include
@@ -25,10 +25,11 @@ Current samples in this directory include
 * amqsconn.go: How to programmatically connect as an MQ client to a remote queue manager.
 Allow use of a userid/password for authentication. There are no default values for this sample.
 * amqsprop.go: Set and extract message properties
-* amqsinq.go : Demonstrate the new InqMap API for inquiring object attributes
+* amqsinq.go : Demonstrate the new InqMap API for inquiring about object attributes
+* amqsset.go : Demonstrate how to set attributes of an MQ object using the MQSET verb
 
 Some trivial scripts run the sample programs in matching pairs:
-* putget.sh  : Run amqsput and then use the generated MsgId to get the same message
+* putget.sh  : Run amqsput and then use the generated MsgId to get the same message with amqsget
 * pubsub.sh  : Start amqssub and then run the amqspub program immediately
 
 The `mqitest` sample program in its own subdirectory is a more general demonstration
@@ -55,9 +56,9 @@ there is something waiting to receive the publications when they are made. The
 
 ## More information
 Comments in the programs explain what they are doing. For more detailed information about the
-MQ API, the functions, structures and constants, see the
-[MQ Knowledge Center](https://www.ibm.com/support/knowledgecenter/en/SSFKSJ_9.1.0/com.ibm.mq.ref.dev.doc/q089590_.htm)
+MQ API, the functions, structures, and constants, see the
+[MQ Knowledge Center](https://www.ibm.com/support/knowledgecenter/en/SSFKSJ_9.1.0/com.ibm.mq.ref.dev.doc/q089590_.htm).
 
-You can also find general MQ application development advice [here](https://www.ibm.com/support/knowledgecenter/en/SSFKSJ_9.1.0/com.ibm.mq.dev.doc/q022830_.htm)
+You can also find general MQ application development advice [here](https://www.ibm.com/support/knowledgecenter/en/SSFKSJ_9.1.0/com.ibm.mq.dev.doc/q022830_.htm).
 Information about development for procedural programming languages such as C in that
-site is most relevant for the interface exported by this Go package.
+documentation is most relevant for the interface exported by this Go package.

samples/amqsget.go

@@ -48,15 +48,17 @@ var qMgrObject ibmmq.MQObject
 var qObject ibmmq.MQObject
 
 func main() {
+	os.Exit(mainWithRc())
+}
+
+// The real main function is here to set a return code.
+func mainWithRc() int {
 	var msgId string
 
 	// The default queue manager and queue to be used. These can be overridden on command line.
 	qMgrName := "QM1"
 	qName := "DEV.QUEUE.1"
 
-	qMgrConnected := false
-	qOpened := false
-
 	fmt.Println("Sample AMQSGET.GO start")
 
 	// Get the queue and queue manager names from command line for overriding
@@ -82,8 +84,8 @@ func main() {
 	if err != nil {
 		fmt.Println(err)
 	} else {
-		qMgrConnected = true
 		fmt.Printf("Connected to queue manager %s\n", qMgrName)
+		defer disc(qMgrObject)
 	}
 
 	// Open of the queue
@@ -93,7 +95,7 @@ func main() {
 
 		// We have to say how we are going to use this queue. In this case, to GET
 		// messages. That is done in the openOptions parameter.
-		openOptions := ibmmq.MQOO_INPUT_EXCLUSIVE + ibmmq.MQOO_FAIL_IF_QUIESCING
+		openOptions := ibmmq.MQOO_INPUT_EXCLUSIVE
 
 		// Opening a QUEUE (rather than a Topic or other object type) and give the name
 		mqod.ObjectType = ibmmq.MQOT_Q
@@ -103,8 +105,8 @@ func main() {
 		if err != nil {
 			fmt.Println(err)
 		} else {
-			qOpened = true
 			fmt.Println("Opened queue", qObject.Name)
+			defer close(qObject)
 		}
 	}
 
@@ -119,9 +121,8 @@ func main() {
 
 		// The default options are OK, but it's always
 		// a good idea to be explicit about transactional boundaries as
-		// not all platforms behave the same way. It's also good practice to
-		// set the FAIL_IF_QUIESCING flag on all verbs.
-		gmo.Options = ibmmq.MQGMO_NO_SYNCPOINT | ibmmq.MQGMO_FAIL_IF_QUIESCING
+		// not all platforms behave the same way.
+		gmo.Options = ibmmq.MQGMO_NO_SYNCPOINT
 
 		// Set options to wait for a maximum of 3 seconds for any new message to arrive
 		gmo.Options |= ibmmq.MQGMO_WAIT
@@ -162,32 +163,33 @@ func main() {
 		}
 	}
 
-	// The usual tidy up at the end of a program is for queues to be closed,
-	// queue manager connections to be disconnected etc.
-	// In a larger Go program, we might move this to a defer() section to ensure
-	// it gets done regardless of other flows through the program.
-
-	// Close the queue if it was opened
-	if qOpened {
-		err = qObject.Close(0)
-		if err != nil {
-			fmt.Println(err)
-		} else {
-			fmt.Println("Closed queue")
-		}
+	// Exit with any return code extracted from the failing MQI call.
+	// Deferred disconnect will happen after the return
+	mqret := 0
+	if err != nil {
+		mqret = int((err.(*ibmmq.MQReturn)).MQCC)
 	}
+	return mqret
+}
 
-	// Disconnect from the queue manager
-	if qMgrConnected {
-		err = qMgrObject.Disc()
-		fmt.Printf("Disconnected from queue manager %s\n", qMgrName)
+// Disconnect from the queue manager
+func disc(qMgrObject ibmmq.MQQueueManager) error {
+	err := qMgrObject.Disc()
+	if err == nil {
+		fmt.Printf("Disconnected from queue manager %s\n", qMgrObject.Name)
+	} else {
+		fmt.Println(err)
 	}
+	return err
+}
 
-	// Exit with any return code extracted from the failing MQI call.
+// Close the queue if it was opened
+func close(object ibmmq.MQObject) error {
+	err := object.Close(0)
 	if err == nil {
-		os.Exit(0)
+		fmt.Println("Closed queue")
 	} else {
-		mqret := err.(*ibmmq.MQReturn)
-		os.Exit((int)(mqret.MQCC))
+		fmt.Println(err)
 	}
+	return err
 }

samples/amqsinq.go

@@ -39,7 +39,7 @@ var qMgrObject ibmmq.MQObject
 var object ibmmq.MQObject
 
 /*
- * This is an example of how to call MQINQ with the new "map" format for
+ * This is an example of how to call MQINQ with a "map" format for
  * responses
  */
 func inquire(obj ibmmq.MQObject, selectors []int32) {
@@ -60,15 +60,19 @@ func inquire(obj ibmmq.MQObject, selectors []int32) {
 	}
 }
 
+// Main function that simply calls a subfunction to ensure defer routines are called before os.Exit happens
 func main() {
+	os.Exit(mainWithRc())
+}
+
+// The real main function is here to set a return code.
+func mainWithRc() int {
 	var selectors []int32
 	// The default queue manager, a queue and a namelist to be used. These can be overridden on command line.
 	qMgrName := "QM1"
 	qName := "DEV.QUEUE.1"
 	nlName := "SYSTEM.DEFAULT.NAMELIST"
 
-	qMgrConnected := false
-
 	fmt.Println("Sample AMQSINQ.GO start")
 
 	// Get the object names from command line for overriding
@@ -91,8 +95,8 @@ func main() {
 	if err != nil {
 		fmt.Println(err)
 	} else {
-		qMgrConnected = true
 		fmt.Printf("Connected to queue manager %s\n", qMgrName)
+		defer disc(qMgrObject)
 	}
 
 	// Open an object
@@ -101,7 +105,7 @@ func main() {
 		mqod := ibmmq.NewMQOD()
 
 		// We have to say how we are going to use this object.
-		openOptions := ibmmq.MQOO_FAIL_IF_QUIESCING + ibmmq.MQOO_INQUIRE
+		openOptions := ibmmq.MQOO_INQUIRE
 		mqod.ObjectType = ibmmq.MQOT_Q_MGR
 		// Do not need the qmgr name when opening it
 
@@ -124,7 +128,7 @@ func main() {
 		mqod := ibmmq.NewMQOD()
 
 		// We have to say how we are going to use this object.
-		openOptions := ibmmq.MQOO_FAIL_IF_QUIESCING + ibmmq.MQOO_INQUIRE
+		openOptions := ibmmq.MQOO_INQUIRE
 		mqod.ObjectType = ibmmq.MQOT_Q
 		mqod.ObjectName = qName
 
@@ -149,7 +153,7 @@ func main() {
 		mqod := ibmmq.NewMQOD()
 
 		// We have to say how we are going to use this object.
-		openOptions := ibmmq.MQOO_FAIL_IF_QUIESCING + ibmmq.MQOO_INQUIRE
+		openOptions := ibmmq.MQOO_INQUIRE
 		mqod.ObjectType = ibmmq.MQOT_NAMELIST
 		mqod.ObjectName = nlName
 
@@ -166,17 +170,22 @@ func main() {
 		}
 	}
 
-	// Disconnect from the queue manager
-	if qMgrConnected {
-		err = qMgrObject.Disc()
-		fmt.Printf("Disconnected from queue manager %s\n", qMgrName)
+	// Exit with any return code extracted from the failing MQI call.
+	// Deferred disconnect will happen after the return
+	mqret := 0
+	if err != nil {
+		mqret = int((err.(*ibmmq.MQReturn)).MQCC)
 	}
+	return mqret
+}
 
-	// Exit with any return code extracted from the failing MQI call.
+// Disconnect from the queue manager
+func disc(qMgrObject ibmmq.MQQueueManager) error {
+	err := qMgrObject.Disc()
 	if err == nil {
-		os.Exit(0)
+		fmt.Printf("Disconnected from queue manager %s\n", qMgrObject.Name)
 	} else {
-		mqret := err.(*ibmmq.MQReturn)
-		os.Exit((int)(mqret.MQCC))
+		fmt.Println(err)
 	}
+	return err
 }

samples/amqsprop.go

@@ -176,15 +176,17 @@ func printProperties(getMsgHandle ibmmq.MQMessageHandle) {
 }
 
 func main() {
+	os.Exit(mainWithRc())
+}
+
+// The real main function is here to set a return code.
+func mainWithRc() int {
 	var putmqmd *ibmmq.MQMD
 
 	// The default queue manager and queue to be used. These can be overridden on command line.
 	qMgrName := "QM1"
 	qName := "DEV.QUEUE.1"
 
-	qMgrConnected := false
-	qOpened := false
-
 	fmt.Println("Sample AMQSPROP.GO start")
 
 	// Get the queue and queue manager names from command line for overriding
@@ -205,8 +207,8 @@ func main() {
 	if err != nil {
 		fmt.Println(err)
 	} else {
-		qMgrConnected = true
 		fmt.Printf("Connected to queue manager %s\n", qMgrName)
+		defer disc(qMgrObject)
 	}
 
 	// Open of the queue
@@ -216,7 +218,7 @@ func main() {
 
 		// We have to say how we are going to use this queue. In this case, to PUT and GET
 		// messages. That is done in the openOptions parameter.
-		openOptions := ibmmq.MQOO_OUTPUT + ibmmq.MQOO_FAIL_IF_QUIESCING + ibmmq.MQOO_INPUT_AS_Q_DEF
+		openOptions := ibmmq.MQOO_OUTPUT | ibmmq.MQOO_INPUT_AS_Q_DEF
 
 		// Opening a QUEUE (rather than a Topic or other object type) and give the name
 		mqod.ObjectType = ibmmq.MQOT_Q
@@ -226,8 +228,8 @@ func main() {
 		if err != nil {
 			fmt.Println(err)
 		} else {
-			qOpened = true
 			fmt.Println("Opened queue", qObject.Name)
+			defer close(qObject)
 		}
 	}
 
@@ -259,7 +261,7 @@ func main() {
 		putmqmd = ibmmq.NewMQMD()
 		pmo := ibmmq.NewMQPMO()
 
-		pmo.Options = ibmmq.MQPMO_NO_SYNCPOINT | ibmmq.MQPMO_FAIL_IF_QUIESCING
+		pmo.Options = ibmmq.MQPMO_NO_SYNCPOINT
 
 		// Set the handle that holds the properties
 		pmo.OriginalMsgHandle = putMsgHandle
@@ -281,7 +283,7 @@ func main() {
 		getmqmd := ibmmq.NewMQMD()
 		gmo := ibmmq.NewMQGMO()
 
-		gmo.Options = ibmmq.MQGMO_NO_SYNCPOINT | ibmmq.MQGMO_FAIL_IF_QUIESCING
+		gmo.Options = ibmmq.MQGMO_NO_SYNCPOINT
 
 		// Set options to not wait - we know the message is there since we just put it
 		gmo.Options |= ibmmq.MQGMO_NO_WAIT
@@ -312,37 +314,33 @@ func main() {
 		}
 	}
 
-	// The usual tidy up at the end of a program is for queues to be closed,
-	// queue manager connections to be disconnected etc.
-	// In a larger Go program, we might move this to a defer() section to ensure
-	// it gets done regardless of other flows through the program.
-
-	// Close the queue if it was opened
-	if qOpened {
-		err = qObject.Close(0)
-		if err != nil {
-			fmt.Println(err)
-		} else {
-			fmt.Println("Closed queue")
-		}
-
-		// Delete any created message handles
-		dmho := ibmmq.NewMQDMHO()
-		getMsgHandle.DltMH(dmho)
-		putMsgHandle.DltMH(dmho)
+	// Exit with any return code extracted from the failing MQI call.
+	// Deferred disconnect will happen after the return
+	mqret := 0
+	if err != nil {
+		mqret = int((err.(*ibmmq.MQReturn)).MQCC)
 	}
+	return mqret
+}
 
-	// Disconnect from the queue manager
-	if qMgrConnected {
-		err = qMgrObject.Disc()
-		fmt.Printf("Disconnected from queue manager %s\n", qMgrName)
+// Disconnect from the queue manager
+func disc(qMgrObject ibmmq.MQQueueManager) error {
+	err := qMgrObject.Disc()
+	if err == nil {
+		fmt.Printf("Disconnected from queue manager %s\n", qMgrObject.Name)
+	} else {
+		fmt.Println(err)
 	}
+	return err
+}
 
-	// Exit with any return code extracted from the failing MQI call.
+// Close the queue if it was opened
+func close(object ibmmq.MQObject) error {
+	err := object.Close(0)
 	if err == nil {
-		os.Exit(0)
+		fmt.Println("Closed queue")
 	} else {
-		mqret := err.(*ibmmq.MQReturn)
-		os.Exit((int)(mqret.MQCC))
+		fmt.Println(err)
 	}
+	return err
 }