We have a SQS listener, such as:
#MessageMapping("queueName")
void listen(String message) { ... }
This queue has redrive policy configured with an associated dead letter queue.
The problem is that the default Spring Cloud AWS implementation is deleting the message when polling it and wiring internally 3 retries for processing it, and failing afterwards.
I can see there is a SqsMessageDeletionPolicy enum with ALWAYS and ON_SUCCESS values, among others. I can't find in any documentation how can I change the QueueAttributes for that queue in order to change this behaviour.
Does anyone knows?
Seems like the solution is basically to use the SQS specific annotation instead of the generic one:
#SqsListener(value = "queueName", deletionPolicy = SqsMessageDeletionPolicy.ON_SUCCESS)
void listen(String message) { ... }
Accepted answer shows how to configure Deletion policy for single Queue,
If you want to set a Global deletion policy which will be used by all #SqsListener can be set by using a property:
cloud.aws.sqs.handler.default-deletion-policy=ON_SUCCESS
Related
I have an issue with an akka.net message send/Tell that ends up in the dead letter queue.
I developed a cluster based application using Akka.Cluster.Tools.PublishSubscribe with two ActorSystems each running in a 'console.application' on the same machine.
I start up one actor system with some actors. Then I start up my 2nd. application and immediatelly after I initialized the Actor system I publish the first Message Mediator.Tell(new Publish(Topics.Backend.SomeName, new MyInitialMessage())) to a Topic where the receiving actor is hosted in the 1st. application.
This message ends up in the dead letter queue always.
Ok now, instead of sending the message immediatelly I put in a delay of e.g 5sec. Then the message could be delivered properly.
This seems to me as a handshake problem.
Question: How do I find out when the 2nd. actor system is ready to receive any messages??
My current workaround is: I send scheduler based for each second a MyInitialMessage and wait for the first response message from my 2nd. application. Then I know my 2nd. app is now ready, handshake done.
But this seems to me just as a workaround. What would be a proper solution to this issue?
chris
Akka.Cluster.Tools.PublishSubscribe works over cluster. You need to await for cluster to become initialized before you'll be able to publish any messages. All of cluster operations are encapsulated in Cluster class that can be created from any actor system using Cluster.Get(actorSystem). In order to wait for cluster to initialize:
You can join to cluster programmatically by using await cluster.JoinAsync(address, cancellationToken) - you can use it to initialize both seed nodes (just make actor system join to itself) and new nodes. This will require to leave seed-nodes in your HOCON configuration empty.
If you're initializing cluster from configuration (using HOCON config file), you can register a callback function using cluster.RegisterOnMemberUp(callback) to postpone the rest of processing until local actor system successfully joined the cluster.
The fastest (in terms of performance and resource usage) way is to subscribe to cluster membership events from within a particular actor. In fact this is how other solutions described above are actually implemented under the hood.
class MyActor : ReceiveActor
{
readonly Cluster cluster = Akka.Cluster.Cluster.Get(Context.System);
public MyActor()
{
Receive<ClusterEvent.MemberUp>(up =>
{
if (up.Member.Address == cluster.SelfAddress)
{
Become(Ready);
}
});
}
protected override void PreStart()
{
cluster.Subscribe(Self, new[]{ typeof(ClusterEvent.IMemberEvent) });
}
protected override void PostStop()
{
// rember to unsubscribe once actor is stopping
cluster.Subscribe(Self);
}
void Ready()
{
// other receiver handlers
}
}
I want to restrict calls to a Feathers service method for externals calls with associateCurrentUser.
I also want to allow the server to call this service method without restricting it.
The use case is that through this service then clients use a lock table, all clients can see all locks, and occasionally the server should clear out abandoned rows in this table. Row abandonment can happen on network failures etc. When the server removes data then the normal Feathers remove events should be emitted to the clients.
I would imagine that this should be a mix of associateCurrentUser and disallow hooks but I can't even begin to experiment with this as I don't see how it would be put together.
How would one implement this, please?
Update:
I found this answer User's permissions in feathers.js API from Daff which implies that if the hook's context.params.provider is null then the call is internal, otherwise external. Can anyone confirm if this is really so in all cases, please?
It seems to be so from my own tests but I don't know if there are any special cases out there that might come and bite me down the line.
If the call is external params.provider will be set to the transport that has been used (currently either rest, socketio or primus, documented here, here and here).
If called internally on the server there is not really any magic. It will be whatever you pass as params. If you pass nothing it will be undefined if you pass (or merge with) hook.params in a hook it will be the same as what the original method was called with.
// `params` is an empty object so `params.provider` will be `undefined`
app.service('messages').find({})
// `params.provider` will be `server`
app.service('messages').find({ provider: 'server' })
// `params.provider` will be whatever the original hook was called with
function(hook) {
hook.app.service('otherservice').find(hook.params);
}
I'm using Dropwizard, which I'm hosting, along with a website, on the google cloud (GCE). This means that there are 2 locations currently active:
Some.IP.Address - UI
Some.IP.Address:8080 - Dropwizard server
When the UI tries to call anything from my dropwizard server, I get cross-site origin errors, which is understandable. However, this is posing a problem for me. How do I fix this? It would be great if I could somehow spoof the addresses so that I don't have to fully qualify the resource in the UI.
What I'm looking to do is this:
$.get('/provider/upload/display_information')
Or, if I have to fully qualify
$.get('http://Some.IP.Address:8080/provider/upload/display_information')
I tried setting Origin Filters in Dropwizard per this google groups thread (https://groups.google.com/forum/#!topic/dropwizard-user/ybDOTOxjlLI), but it doesn't seem to work.
In index.html that is served by the server at http://Some.IP.Address you might have a jQuery script that look as follows.
$.get('http://Some.IP.Address:8080/provider/upload/display_information', data, callback);
Of course your browser will not allow accessing http://Some.IP.Address:8080 due to the Same-Origin-Policy (SOP). The protocol (http, https) and the host as well as the port have to be the same.
To achieve Cross-Origin Resource Sharing (CORS) on Dropwizard, you have to add a CrossOriginFilter to the servlet environment. This filter will add some Access-Control-Headers to every response the server is sending. In the run method of your Dropwizard application write:
import org.eclipse.jetty.servlets.CrossOriginFilter;
public class SomeApplication extends Application<SomeConfiguration> {
#Override
public void run(TodoConfiguration config, Environment environment) throws Exception {
FilterRegistration.Dynamic filter = environment.servlets().addFilter("CORS", CrossOriginFilter.class);
filter.addMappingForUrlPatterns(EnumSet.allOf(DispatcherType.class), true, "/*");
filter.setInitParameter("allowedOrigins", "http://Some.IP.Address"); // allowed origins comma separated
filter.setInitParameter("allowedHeaders", "Content-Type,Authorization,X-Requested-With,Content-Length,Accept,Origin");
filter.setInitParameter("allowedMethods", "GET,PUT,POST,DELETE,OPTIONS");
filter.setInitParameter("preflightMaxAge", "5184000"); // 2 months
filter.setInitParameter("allowCredentials", "true");
// ...
}
// ...
}
This solution works for Dropwizard 0.7.0 and can be found on https://groups.google.com/d/msg/dropwizard-user/xl5dc_i8V24/gbspHyl4y5QJ.
This filter will add some Access-Control-Headers to every response. Have a look on http://www.eclipse.org/jetty/documentation/current/cross-origin-filter.html for a detailed description of the initialisation parameters of the CrossOriginFilter.
I have a simple accessor in my class:
public function get loggedIn():Boolean
{
var loggedIn:Boolean = somePrivateMethodToCheckStatus();
return loggedIn;
}
The API I'm now working with checks login status in an asynchronous fashion:
API_Class.addEventListener(API_Class.LOGIN_STATUS,onStatusCheck);
API_Class.checkLoginStatus();
function onStatusCheck(evt:API_Event):void
{
//evt.loggedIn == true or false
}
Is there a way I can perform this asynchronous request without exiting my accessor?
Simple answer: No, there is not. You will have to set up login verification in an asynchronous fashion.
I am a bit curious: Why is there a need to repeatedly poll the login status remotely? If your user logged in from within the Flash application, the status should be known. Same goes for logging out. If login and logout is handled from outside the Flash app, why not implement a notification mechanism (via JavaScript or socket connection)?
Also, if not being logged in prevents users from performing actions on the server, you could check for authorization on the server, whenever remote calls are made, and return an error if the session has expired. This would still be more efficient than repeatedly polling status info.
Not really, no. Flash runs in a single thread, and every function has to finish before events etc will be called.
One (sort of) solution would be to return three values; "yes", "no" and "pending". If it's pending the loggedIn()-method would start a check, and the client of that method should check again in a little while.
Another way would be to have the loggedIn-method send the answer to a callback instead. Eg "getLoggedInStatus(callback:Function)"
You may be interested in http://www.as3commons.org/as3-commons-eventbus/index.html
It is a handy lib that focuses on asynchronous jobs.
I am using NServiceBus for the first time and have a small, simple application where a user submits a form, the form fields are then sent to the queue, and the handler collects this data and writes it to the database using linq-to-sql.
Any changes within Component Services is a complete no-no as far as the DBA is concerned, so I'm now looking for an alternative to DTC (which is not enabled on the DB server), but using AsA_Server so that messages do not get purged.
I have tried removing AsA_Server after IConfigureThisEndpoint and specifying the configuration myself, but this doesn't seem to work (the console appears, page loads but nothing happens, it doesn't even stop at breakpoints.) AsA_Client does work, but as I understand it the messages will be purged at startup which I need to avoid.
Any suggestions?
Thanks,
OMK
EDIT: This has now been resolved by using wrapping the call to the database in a suppress transaction scope, which allows the database work to be done with no ambient transaction to enlist in:
using (TransactionScope sc = new TransactionScope(TransactionScopeOption.Suppress))
{
// code here
sc.Complete();
}
When you use AsA_Server, you are specifying you want durable queues and you will need to configure transactional queues.
With a transactional send/receive MSMQ requires you to send, transmit, receive, and process as part of one transaction. However, actually all these stages take place in their own transactions.
For example, the send transaction is complete when the sender sends a message onto their local MSMQ subsystem (even if the queue address is remote, the sender still sends to a local queue which acts as a kind of proxy to the remote queue).
The transmit transaction is complete when the MSMQ subsystem on the senders machine successfully transmits the message to the MSMQ subsystem on the receivers machine.
Even though this may all happen on one machine, I am guessing that your Handle() method is writing to a database on a different machine.
The problem here is that for the receive operation to complete satisfactorily from a transaction perspective, your call to the database must be successful. Only then will the message be de-queued from your input queue. This prevents any chance that the message is lost during processing failure.
However, in order to enforce that across the network you need to involve DTC to coordinate the distributed transaction to the database.
Bottom line, if you want durable queues in a distributed environment then you will need to use MSDTC.
Hope this helps.
There is an alternative. In your connection string you can add the option to not enlist in a distributed transaction and this will have your DB connection ignored in the DTC.
Of course, if this is set in the config then all database transactions for the application are ignored by the DTC rather than just a specific one.
Example:
<add key="DatabaseConnectionString" value="Data Source=SERVERNAME;Initial Catalog=DBNAME;Integrated Security=True;Enlist=False"/>
With NServiceBus 4.0 you can now do the following, which finally worked for me:
Configure.Transactions.Advanced(t =>
{
t.DisableDistributedTransactions();
t.DoNotWrapHandlersExecutionInATransactionScope();
});
When you use the As (AsA_Client, AsA_Server) interfaces, the configuration is applied after Init() so all the settings that you make there regarding MsmqTransport and UnicastBus are overriden.
It's possible to override those settings using IWantTheConfiguration in a IHandleProfile implementation. You get the Configuration after the default roles are applied but before the bus is started.
This way you can change the default profile settings and tailor them to your needs: deactivate transactions, enable impersonation...
Example:
public class DeactivateTransactions : IHandleProfile<Lite>, IWantTheEndpointConfig
{
private IConfigureThisEndpoint configure;
public IConfigureThisEndpoint Config
{
get { return configure; }
set
{
this.configure = value;
Configure.Instance.MsmqTransport()
.PurgeOnStartup(false)
.IsTransactional(false); // Or other changes
}
}
public void ProfileActivated()
{
}
}