I see WCF provides persession/percall/single instance modes and single/multiple/reentrant concurency model.
Currently I am using persession instance mode and multiple concurency mode for my service which creates one instance/service object for each client and serves on multiple threads requests from clients.
But actually I want to achive this:
I want to create multiple instances of service objects (not for each call like PerCall, but based on tag: for ex say guid) and I want the service to be re-entrant. Is it possible?
thank u for ur suggestions and ideas.
You need to create your own IInstanceProvider.
Related
We are using Hazelcast to store stuff in distributed maps. We are having a problem with remote servers and I need some feedback on what we can do to resolve the issue.
We create the server - WORKS
We create a new server (Hazelcast.newHazelcastInstance) inside our application's JVM. The hazelcast Config object we pass in has a bunch of custom serializers defined for all the types we are going to put in the maps. Our objects are a mixture of Protobufs, plain java objects, and a combination of the two. The server starts, we can put objects in the map and get objects back out later. We recently decided to start running Hazelcast in its own dedicated server so we tried the scenario below.
Server already exists externally, we connect as a client - DOESN'T WORK
Rather than creating our Hazelcast instance we connect to a remote instance that is already running. We pass in a config with all the same serializers we used before. We successfully connect to Hazelcast and we can put stuff in the map (works as far as I can tell) but we don't get anything back out. No events get fired letting our listeners know objects were added to a map.
I want to be able to connect to a Hazelcast instance that is already running outside of our JVM. It is not working for our use case and I am not sure how it is supposed to work.
Does the JVM running Hazelcast externally need in its class loader all of the class types we might put into the map? It seems like that might be where the problem is but wouldn't that make it very limiting to use Hazelcast?
How do you typically manage those class loader issues?
Assuming the above is true, is there a way to tell Hazelcast we will serialize the objects before even putting them in the map? Basically we would give Hazelcast an ID and byte array and that is all we would expect back in return. If so that would avoid the entire class loader issue I think we are running into. We do not need to be able to search on objects based on their fields. We just need to know as objects come and go and what their ID is.
#Jonathan, when using client-server architecture, unless you use queries or other operations that require data to be serialized on the cluster, members don't need to know anything about serialization. They just store already serialized data & serve it. If these listeners that you mentioned are on the client app, it should be working fine.
Hazelcast has a feature called User Code Deployment, https://docs.hazelcast.org/docs/3.11/manual/html-single/index.html#member-user-code-deployment-beta, but it's mainly for user classes. Serialization related config should be present on members or you should add that later & do a rolling restart.
If you can share some of the exceptions/setup etc, I can give specific answers as well.
I am trying to find a good way to horizontally scale a stateful NodeJS service.
The Problem
The problem is that most of the options I find online assume the service is stateless. The NodeJS cluster documentation says:
Node.js [Cluster] does not provide routing logic. It is, therefore important to design an application such that it does not rely too heavily on in-memory data objects for things like sessions and login.
https://nodejs.org/api/cluster.html
We are using Kubernetes so scaling across multiple machines would also be easy if my service was stateless, but it is not.
Current Setup
I have a list of objects that stay in memory, each object alone is a transaction boundary. Requests to this service always have the object ID in the url. Requests to the same object ID are put into a queue and processed one at a time.
Desired Setup
I would like to keep this interface to the external world but internally spread this list of objects across multiple nodes and based on the ID in the URL the request would be routed to the appropriate node.
What is the usual way to do it in NodeJS? I've seen people using the user session to make sure a given user always go to the same node, what I would like to do is the same thing but instead of using the user session using the ID in the url.
I am new to Service Fabric and currently I am struggling to find out how to access data from reliable collection (That is defined, and initialized in a Statefull Service context) from a WEB API (that is, also living in the Service fabric cluster, as a separate application). The problem is very basic and I am sure I am missing something very obvious. So apologies to the community if this sounds lame.
I have a large XML, a portions of which I want to expose via a WEB API endpoints as results from various queries . Searched for similar questions, but couldn't find a suitable answer.
Would be happy to see how an experienced SF developer would do such task.
EDIT I posted the solution i have came up with
After reading around and observing others issues and Azure's samples, I have implemented a solution. Posting here the gotchas I had, hoping that will help other devs that are new to Azure Service fabric (Disclaimer: I am still a newbie in Service Fabric, so comments and suggestions are highly appreciated):
First, pretty simple - I ended up with a stateful service and a WEB Api Stateless service in an azure service fabric application:
DataStoreService - Stateful service that is reading the large XMLs and stores them into Reliable dictionary (happens in the RunAsync method).
Web Api provides an /api/query endpoint that filters out the Collection of XElements that is stored in the rteliable dictionary and serialize it back to the requestor
3 Gotchas
1) How to get your hands on the reliable dictionary data from the Stateless service, i.e how to get an instance of the Stateful service from Stateless one :
ServiceUriBuilder builder = new ServiceUriBuilder("DataStoreService");
IDataStoreService DataStoreServiceClient = ServiceProxy.Create<IDataStoreService>(builder.ToUri(), new ServicePartitionKey("Your.Partition.Name"));
Above code is already giving you the instance. I.e - you need to use a service proxy. For that purpose you need:
define an interface that your stateful service will implement, and use it when invoking the Create method of ServiceProxy (IDataStoreService)
Pass the correct Partition Key to Create method. This article gives very good intro on Azure Service Bus partiotions
2) Registering of Replica listeners - in order to avoid errors saying
The primary or stateless instance for the partition 'a67f7afa-3370-4e6f-ae7c-15188004bfa1' has invalid address, this means that right address from the replica/instance is not registered in the system
, you need to register replica listeners as stated in this post :
public DataStoreService(StatefulServiceContext context)
: base(context)
{
configurationPackage = Context.CodePackageActivationContext.GetConfigurationPackageObject("Config");
}
3) Service fabric name spacing and referencing services - the ServiceUriBuilder class I took from the service-fabric-dotnet-web-reference-app. Basically you need something to generate an Uri of the form:
new Uri("fabric:/" + this.ApplicationInstance + "/" + this.ServiceInstance);,
where ServiceInstance is the name of the service you want to get instance of (DataStoreService in this case)
You can use WebAPI with OWIN to setup a communication listener and expose data from your reliable collections. See Build a web front end for your app for info on how to set that up. Take a look at the WordCount sample in the Getting started sample apps, which feeds a bunch of random words into a stateful service and keeps a count of the words processed. Hope that helps.
I am writing an application to serve facebook APIs; share, like etc.. I am keeping all those shared objects from my appliction in a database and I do not want to share the same object if it already been shared.
Considering I will deploy application on different servers there could be a case where both instance tries to insert the same object to table.
How can I manage this concurrency problem with blocking the applications fully ? I mean two threads will try to insert same object and they must sync but they should not block a 3rd thread where it is inserting totally different object.
If there's a way to derive primary key of data entry from data itself, database will resolve such concurrency issue by itself -- 2nd insert will fail with 'Primary Key constraint violation'. Perhaps, data supplied by Facebook API already have some unique ID?
Or, you can consider some distributed lock solution, for example, based on Hazelcast or on similar data grid. This would allow to have record state shared by different JVMs, so it will be possible to avoid unneeded INSERTS.
I have two identical sites which will consume RabbitMQ messages using the new Rabbit MQ client. The producer ideally should be able to designate the site either by queue name or routing key. The former I can do as a Publish parameter but the latter I have no access to. Furthermore, on the service side, the consumer appears only able to subscribe to convention-based queue names, i.e. mq.myrequest.inq and I don't seem to be able to take advantage of the routing key.
Is there a way I can publish and subscribe using my own routing key, or register the handler based on an explicit queue name, i.e mq.myrequest.site1.inq ?
There isn't. ServiceStack's RabbitMq support is conventionally based on Type names and is opinionated to function as a work queue. It was designed to be config-free and simple to use so automatically takes care of the details of which exchanges, routing keys and queue names to use.
If you need advanced or custom configuration it's best to instead use the underlying RabbitMQ.Client directly.