I am using java API to interact with MQ.
When I try to get a message from an empty queue, I get exception.
Ok, but when I control it with try catch, I am expecting not prompted any error message in console.
but I get!!
try {
queue.get(getMessage, new MQGetMessageOptions());
return getMessage.readUTF();
} catch (Exception e) {
return "";
}
get in console as "MQJE001: Completion Code '2', Reason '2033'."
How can I disable this information output?
how can I check message availability or current queue size?
Thanks
First question: How can I disable this information output?
This link might help: Hide Java Output
Second question: How can I check message availability or current queue size?
MQQueue.getCurrentDepth() method will get you the current queue size. But you must note that this may not represent the correct queue depth at all times as messages could be consumed by other applications from the same queue. Actually you should not worry about queue depth. It is best practice to keep consuming messages and handle 2033 (MQJE001: MQRC_NO_MSG_AVAILABLE) exception which is thrown when there are no messages in the queue in your application.
Easiest method is using MQException.log=null line in your application.
Details bellow:
https://www.ibm.com/support/knowledgecenter/SSFKSJ_7.5.0/com.ibm.mq.dev.doc/q031000_.htm
Related
I am using C++/winRT UWP to discover and connect to Bluetooth Low Energy devices. I am using the advertisment watcher to look for advertisements from devices I can support. This works.
Then I pick one to connect to. The connection procedure is a little weird by my way of thinking but according to the microsoft docs one Calls this FromBluetoothAddressAsync() with the BluetoothAddress and two things happen; one gets the BluetoothLEDevice AND a connection attempt is made. One needs to register a handler for the connection status changed event BUT you can't do that until you get the BluetoothLEDevice.
Is there a timing issue causing the exception? Has the connection already happened BEFORE I get the BluetoothLEDevice object? Below is the code and below that is the log:
void BtleHandler::connectToDevice(BluetoothLEAdvertisementReceivedEventArgs eventArgs)
{
OutputDebugStringA("Connect to device called\n");
// My God this async stuff took me a while to figure out! See https://msdn.microsoft.com/en-us/magazine/mt846728.aspx
IAsyncOperation<Windows::Devices::Bluetooth::BluetoothLEDevice> async = // assuming the address type is how I am to behave ..
BluetoothLEDevice::FromBluetoothAddressAsync(eventArgs.BluetoothAddress(), BluetoothAddressType::Random);
bluetoothLEDevice = async.get();
OutputDebugStringA("BluetoothLEDevice returned\n");
bluetoothLEDevice.ConnectionStatusChanged({ this, &BtleHandler::onConnectionStatusChanged });
// This method not only gives you the device but it also initiates a connection
}
The above code generates the following log:
New advertisment/scanResponse with UUID 00001809-0000-1000-8000-00805F9B34FB
New ad/scanResponse with name Philips ear thermometer and UUID 00001809-0000-1000-8000-00805F9B34FB
Connect to device called
ERROR here--> onecoreuap\drivers\wdm\bluetooth\user\winrt\common\bluetoothutilities.cpp(509)\Windows.Devices.Bluetooth.dll!03BEFDD6: (caller: 03BFB977) ReturnHr(1) tid(144) 80070490 Element not found.
ERROR here--> onecoreuap\drivers\wdm\bluetooth\user\winrt\device\bluetoothledevice.cpp(428)\Windows.Devices.Bluetooth.dll!03BFB9B7: (caller: 03BFAF01) ReturnHr(2) tid(144) 80070490 Element not found.
BluetoothLEDevice returned
Exception thrown at 0x0F5CDF2F (WindowsBluetoothAdapter.dll) in BtleScannerTest.exe: 0xC0000005: Access violation reading location 0x00000000.
It sure looks like there is a timing issue. But if it is, I have no idea how to resolve it. I cannot register for the event if I don't have a BluetoothLEDevice object! I cannot figure out a way to get the BluetoothLEDevice object without invoking a connection.
================================ UPDATE =============================
Changed the methods to IAsyncAction and used co_await as suggested by #IInspectable. No difference. The problem is clearly that the registered handler is out of scope or something is wrong with it. I tried a get_strong() instead of a 'this' in the registration, but the compiler would not accept it (said identifier 'get_strong()' is undefined). However, if I commented out the registration, no exception is thrown but I still get these log messages
onecoreuap\drivers\wdm\bluetooth\user\winrt\common\bluetoothutilities.cpp(509)\Windows.Devices.Bluetooth.dll!0F27FDD6: (caller: 0F28B977) ReturnHr(3) tid(253c) 80070490 Element not found.
onecoreuap\drivers\wdm\bluetooth\user\winrt\device\bluetoothledevice.cpp(428)\Windows.Devices.Bluetooth.dll!0F28B9B7: (caller: 0F28AF01) ReturnHr(4) tid(253c) 80070490 Element not found.
But the program continues to run an I continue to discover and connect. But since I can't get the connection event it is kind of useless at this stage.
I hate my answer. But after asynching and co-routining everything under the sun, the problem is unsolvable by me:
This method
bluetoothLEDevice = co_await BluetoothLEDevice::FromBluetoothAddressAsync(eventArgs.BluetoothAddress(), BluetoothAddressType::Random);
returns NULL. That should not happen and there is not much I can do about it. I read that as a broken BLE API.
A BTLE Central should be able to do as follows
Discover a device if new then:
If user selects connect, connect to
the device
perform service discovery
read/write/enable
characteristics as needed
handle indications/notifications
If at any time the peripheral sends a security request or insufficient authentication error, start pairing
repeat the action that caused the insufficient authentication.
On disconnect, save the paired and bonded state if the device is pairable.
On rediscovery of the device, if unpaired (not a pairable device)
repeat above
If paired and bonded
start encryption
work with the device; no need to re-enable or do service discovery
========================= MORE INFO ===================================
This is what the log shows when the method is called
Connect to device called
onecoreuap\drivers\wdm\bluetooth\user\winrt\common\bluetoothutilities.cpp(509)\Windows.Devices.Bluetooth.dll!0496FDD6: (caller: 0497B977) ReturnHr(1) tid(3b1c) 80070490 Element not found.
onecoreuap\drivers\wdm\bluetooth\user\winrt\device\bluetoothledevice.cpp(428)\Windows.Devices.Bluetooth.dll!0497B9B7: (caller: 0497AF01) ReturnHr(2) tid(3b1c) 80070490 Element not found.
BluetoothLEDevice returned is NULL. Can't register
Since the BluetoothLEDevice is NULL, I do not attempt to register.
================= MORE INFO ===================
I should also add that taking an over-the-air sniff reveals that there is never a connection event. Though the method is supposed to initiate a connection as well as return the BluetoothLEDevice object, it ends up doing neither. My guess is that the method requires more pre-use setup of the system that only the DeviceWatcher does. The AdvertisementWatcher probably does not.
In BLE you always have to wait for every operation to complete.
I am not an expert in C++, but in C# the async connection procedure returns a bool if it was successful.
In C++ the IAsyncOperation does not have a return type, so there is no way to know if the connection procedure was successful or completed.
You will have to await the IAsyncOperation and make sure that you have a BluetoothLEDevice object, before you attach the event handler.
To await an IAsyncOperation there is a question/answer on how to await anIAsyncOperation:
How to wait for an IAsyncAction? How to wait for an IAsyncAction?
All,
I am using Change Feed Processor Library.Want to know the best way to handle service failure along with the exceptions/errors scenario's in ProcessChangesAsync method. Below are the events am referring to.
1) Service failure - Service having the processor library crashed in the middle of some operation. How to start the process from the same document(doc on failure instance)? is there any inbuilt mechanism where change feed will start with the last failed documents? E.g. Let assume,in current batch we have 10 docs.5 processed successfully and then service breaks because of network failure or by some other reasons.Will my process starts with 6th document once service is re-started? How to achieve this?
2) Exception and Errors- Any errors in ProcessChangesAsync method can be handle using try catch at the global level but how to persist those failure records and make them available for the next batch? Again,looking for any available inbuilt mechanism in change feed process.
1) The Processor Library, by default, checkpoints after a successful run of ProcessChangesAsync. In the latest library version, you can customize the Checkpointer to do manual checkpoints in case you need it. If for some reason the processor shuts down before checkpointing, then it will start processing next from the the last successful checkpoint stored in the Leases collection. In your case, it will start with the first document again, so you will never lose a change but you could experience double processing (this is an "at least once" model).
2) There is no built-in mechanism that you can leverage, handling exceptions within the ProcessChangesAsync is your responsibility. You could not only add a global try/catch but, in the case you are looping over the documents, add a try/catch inside the loop, to handle a failing document (maybe send it to queue for later analysis/post-process) without losing the batch. If you require logging for those errors (I'm assuming that's what you mean by persisting errors?), then the latest version is compatible with LibLog, so plugging your own custom logging is as simple as:
using Microsoft.Azure.Documents.ChangeFeedProcessor.Logging;
var hostName = "SampleHost";
var tracelogProvider = new TraceLogProvider(); //You can use any provider supported by LibLog
using (tracelogProvider.OpenNestedContext(hostName))
{
LogProvider.SetCurrentLogProvider(tracelogProvider);
// After this, create IChangeFeedProcessor instance and start/stop it.
}
Source
Extra info for the comments
To avoid exceptions halting the batch or causing a batch to be reprocessed, you can have handling like this:
public async Task ProcessChangesAsync(IChangeFeedObserverContext context, IReadOnlyList<Document> documents, CancellationToken cancellationToken)
{
try
{
foreach(var document in documents)
{
try
{
// Do your work for the document
}
catch(Exception ex)
{
// Something happened with the current document, handle it, send it to a queue / another storage to analyze, log it. This catch will make the loop continue with the next.
}
}
}
catch(Exception ex)
{
// Something unhandled happened, log it and avoid throwing it again so the next batch is processed
}
}
We have a Java class that listens to a database (Oracle) queue table and process it if there are records placed in that queue. It worked normally in UAT and development environments. Upon deployment in production, there are times when it cannot read a record from the queue. When a record is inserted, it cannot detect it and the records remain in the queue. This seldom happens but it happens. If I would give statistic, out of 30 records queued in a day, about 8 don't make it. We would need to restart the whole app for it to be able to read the records.
Here is a code snippet of my class..
public class SomeListener implements MessageListener{
public void onMessage(Message msg){
InputStream input = null;
try {
TextMessage txtMsg = (TextMessage) msg;
String text = txtMsg.getText();
input = new ByteArrayInputStream(text.getBytes());
} catch (Exception e1) {
// TODO Auto-generated catch block
logger.error("Parsing from the queue.... failed",e1);
e1.printStackTrace();
}
//process text message
}
}
Weird thing we cant find any traces of exceptions from the logs.
Can anyone help? by the way we set the receiveTimeout to 10 secs
We would need to restart the whole app for it to be able to read the records.
The most common reason for this is the listener thread is "stuck" in user code (//process text message). You can take a thread dump with jstack or jvisualvm or similar to see what the thread is doing.
Another possibility (with low volume apps like this) is the network (most likely a router someplace in the network) silently closes an idle socket because it has not been used for some time. If the container (actually the broker's JMS client library) doesn't know the socket is dead, it will never receive any more messages.
The solution to the first is to fix the code; the solution to the second is to enable some kind of heartbeat or keepalives on the connection so that the network/router does not close the socket when it has no "real" traffic on it.
You would need to consult your broker's documentation about configuring heartbeats/keepalives.
Is there anyway to log message contents when an exception occurs?
I looked at various logging extensions but they are just logging CorrelationId. And message contents are not available.
There is a CurrentMessge property in MessageContext, but that is not available at the time logger writes the exception.
I tried to handle PoisonMessage Event, which allows me to log the message contents.
public static void OnPoisonMessage(IBus bus, ReceivedTransportMessage receivedTransportMessage, Rebus.Bus.PoisonMessageInfo poisonMessageInfo) {
var message = new JsonMessageSerializer().Deserialize(receivedTransportMessage);
Log.Error("{#messageType} failed {#message}", message.Messages[0].GetType(), message);
}
This works great, but now I have two errors in the log one coming from my handler and the other coming from logger.
I am wondering if there is a better way to handle this requirement.
If your requirement is to simply log the message contents as JSON, I think you've found the right way to do it - at least that's the way I would have done it.
I'm curious though as to what problem you're solving by logging the message contents - you are aware of the fact that the failing message will end up in an error queue where you can inspect it?
If you're using MSMQ, you can inspect JSON-serialized messages using Rebus' Snoop-tool, which is a simple MSMQ inspector. It will also allow you to move the message back into the input queue where it failed ("return to source queue")
A good way to monitor your Rebus installation is to set up some kind of alerts when something arrives in an error queue, and then you can look at the message (which event includes the caught exceptions in a special header) and then resolve the situation from there.
I am trying to implement delayed queue with overriding of messages using Active MQ.
Each message is scheduled to be delivered with delay of x (say 60 seconds)
In between if same message is received again it should override previous message.
So even if I receive 10 messages say in x seconds. Only one message should be processed.
Is there clean way to accomplish this?
The question has two parts that need to be addressed separately:
Can a message be delayed in ActiveMQ?
Yes - see Delay and Schedule Message Delivery. You need to set <broker ... schedulerSupport="true"> in your ActiveMQ config, as well as setting the AMQ_SCHEDULED_DELAY property of the JMS message saying how long you want the message to be delayed (10000 in your case).
Is there any way to prevent the same message being consumed more than once?
Yes, but that's an application concern rather than an ActiveMQ one. It's often referred to as de-duplication or idempotent consumption. The simplest way if you only have one consumer is to keep track of messages received in a map, and check that map whether you receive a message. It it has been seen, discard.
For more complex use cases where you have multiple consumers on different machines, or you want that state to survive application restart, you will need to keep a table of messages seen in a database, and query it each time.
Please vote this answer up if it helps, as it encourages people to help you out.
Also according to method from ActiveMQ BrokerService class you should configure persistence to have ability to use scheduler functionality.
public boolean isSchedulerSupport() {
return this.schedulerSupport && (isPersistent() || jobSchedulerStore != null);
}
you can configure activemq broker to enable "schedulerSupport" with the following entry in your activemq.xml file located in conf directory of your activemq home directory.
<broker xmlns="http://activemq.apache.org/schema/core" brokerName="localhost" dataDirectory="${activemq.data}" schedulerSupport="true">
You can Override the BrokerService in your configuration
#Configuration
#EnableJms
public class JMSConfiguration {
#Bean
public BrokerService brokerService() throws Exception {
BrokerService brokerService = new BrokerService();
brokerService.setSchedulerSupport(true);
return brokerService;
}
}