Connection auto-recovery

Author: eduard93

RabbitMQ/Common.cls

@@ -45,8 +45,18 @@ Property Encoding As %String;
 /// See property AdditionalPaths in that class.
 Property ClassPath As %String(MAXLEN = 32000);
 
+/// How many times have we tried reconnecting
+/// empty - do not retry
+/// 0 - retry ad infinitum
+/// n - retry n times
+Property RetryCount As %Integer [ InitialExpression = 5 ];
+
+/// How frequently to retry access to the output system.
+/// Pause in seconds between retry attempts.
+Property RetryInterval As %Numeric(MINVAL = 0) [ InitialExpression = 5 ];
+
 /// These are the production settings for this object
-Parameter SETTINGS = "Host:Basic,Port:Basic,VirtualHost:Basic,Queue:Basic,Credentials:Basic:credentialsSelector,JGHost:Java Gateway,JGPort:Java Gateway,JGService:Java Gateway:selector?context={Ens.ContextSearch/ProductionItems?targets=0&productionName=@productionId},ClassPath:Basic,Encoding:Basic";
+Parameter SETTINGS = "Host:Basic,Port:Basic,VirtualHost:Basic,Queue:Basic,Credentials:Basic:credentialsSelector,JGHost:Java Gateway,JGPort:Java Gateway,JGService:Java Gateway:selector?context={Ens.ContextSearch/ProductionItems?targets=0&productionName=@productionId},ClassPath:Basic,Encoding:Basic,RetryCount:Alerting,RetryInterval:Alerting";
 
 /// Connect to running JGW 
 Method Connect() As %Status
@@ -87,14 +97,44 @@ Method ConnectToRabbitMQ() As %Status
 		Set pass = "guest"
 	}
 
+	Set port = $select(..Port="":-1, 1:..Port)
+	
 	Try {
-		Set ..API = ##class(isc.rabbitmq.API).%New(..JGW, ..Host, ..Port, user, pass, ..VirtualHost, ..Queue, $$$YES, ..Exchange)
+		Set ..API = ##class(isc.rabbitmq.API).%New(..JGW, ..Host, port, user, pass, ..VirtualHost, ..Queue, $$$YES, ..Exchange)
 	} Catch ex {
 		Set sc = $$$ADDSC(ex.AsStatus(),$g(%objlasterror))
 	}
 
 	Quit sc
 }
 
+Method IsOpen() As %Status
+{
+	#Dim sc As %Status = $$$OK 
+	Set retryCount = 1
+	Try {
+		While '..API.isOpen() {
+			If ..RetryCount = "" {
+				Set sc = $$$ERROR($$$GeneralError, "Connection problems. Consider specifying RetryCount and RetryInterval settings")
+			} ElseIf ((..RetryCount = 0) || (retryCount < ..RetryCount)) {
+				// wait and retry connecting
+				Set retryCount = retryCount + 1
+				Hang ..RetryInterval
+				
+				// reconnect happens in isOpen method			
+			} Else {
+				// we're out of reconnect attempts
+				Set sc = $$$ERROR($$$GeneralError, $$$FormatText("Connection still closed after %1 attempts at reconnecting.", ..RetryCount))
+			}
+			Quit:$$$ISERR(sc)
+		}
+	} Catch ex {
+		#Dim ex As %Exception.General
+		Set sc = ex.AsStatus()
+	}
+	
+	Quit sc
+}
+
 }
 

RabbitMQ/InboundAdapter.cls

@@ -28,21 +28,36 @@ Method OnTearDown() As %Status
 /// Get Messages from RabbitMQ queue.
 Method OnTask() As %Status
 {
-	Set sc = $$$OK
+	#Dim sc As %Status = $$$OK 
 
 	Set messageCount = 1
 
 	While messageCount > 0 {
+		Set sc = ..IsOpen()
+		Quit:$$$ISERR(sc)
+		
 		// List containing metainformation and possibly body (in the case of string interaction) of the RabbitMQ message 
 		#Dim messageList As %ListOfDataTypes 
 
-		If ..BodyClass = "" {
-			Set messageList = ..API.readMessageString()
-		} Else {
-			#Dim tempStream As %Library.GlobalBinaryStream
-			Set messageList = ##class(%ListOfDataTypes).%New()
-			For i=1:1:15 Do messageList.Insert("")
-			Set tempStream = ..API.readMessageStream(.messageList)
+		Set messageList = ##class(%ListOfDataTypes).%New()
+		For i=1:1:15 Do messageList.Insert("")
+
+		Try {
+			If ..BodyClass = "" {
+				Set messageList = ..API.readMessageString()
+			} Else {
+				#Dim tempStream As %Library.GlobalBinaryStream
+				Set tempStream = ..API.readMessageStream(.messageList)
+			}
+		} Catch ex {
+			#Dim ex As %Exception.General
+			If ($ZE["<ZJGTW>") {
+				Set sc = ..IsOpen()
+				Set:$$$ISERR(sc) sc = $$$ADDSC(sc, ex.AsStatus())
+			} Else {
+				Set sc = ex.AsStatus()
+			}
+			Quit:$$$ISERR(sc)
 		}
 
 		Set messageLength = messageList.GetAt(1)

RabbitMQ/OutboundAdapter.cls

@@ -36,10 +36,23 @@ Method SendMessage(message As %Stream.Object) As %Status
 		Do stream.Write(..EncodeMessageBody(message))
 	}
 
-	Try {
-		Do ..API.sendMessage(stream)
-	} Catch ex {
-		Set sc = ex.AsStatus()
+	#Dim attempts As %Integer = 0
+	
+	While attempts<2 {
+		Set attempts = attempts + 1
+		Try {
+			Do ..API.sendMessage(stream)
+			Return sc
+		} Catch ex {
+			#Dim ex As %Exception.General
+			If ($ZE["<ZJGTW>") {
+				Set sc = ..IsOpen()
+				Set:$$$ISERR(sc) sc = $$$ADDSC(sc, ex.AsStatus())
+			} Else {
+				Set sc = ex.AsStatus()
+			}
+			Return:$$$ISERR(sc) sc // quit if reconnect is unsuccessful or we got unknown exception 
+		}
 	}
 	Quit sc
 }
@@ -57,11 +70,24 @@ Method SendMessageToQueue(queue As %String, message As %Stream.Object) As %Statu
 	} Else {
 		Do stream.Write(..EncodeMessageBody(message))
 	}
+			
+	#Dim attempts As %Integer = 0
 
-	Try {
-		Do ..API.sendMessageToQueue(queue, stream)
-	} Catch ex {
-		Set sc = ex.AsStatus()
+	While attempts<2 {
+		Set attempts = attempts + 1
+		Try {
+			Do ..API.sendMessageToQueue(queue, stream)
+			Return sc
+		} Catch ex {
+			#Dim ex As %Exception.General
+			If ($ZE["<ZJGTW>") {
+				Set sc = ..IsOpen()
+				Set:$$$ISERR(sc) sc = $$$ADDSC(sc, ex.AsStatus())
+			} Else {
+				Set sc = ex.AsStatus()
+			}
+			Return:$$$ISERR(sc) sc // quit if reconnect is unsuccessful or we got unknown exception 
+		}
 	}
 	Quit sc
 }