I am currently assigned the task of writing an application which will use JMS API to communicate using Apache qpid as the JMS provider.
so basically my application will have multiple instances of a server running.Each server will serve a set of unique desks.so each instance will only have data for the desks it is serving.
There will also be multiple instances of clients each configured by desk again.
Now when the client starts up, it will request the data for the desk it is serving to the servers.The request should only go to the server that has that desk data loaded and the response should only go back to the client who requested the data for that desk.
I am thinking of using queues for this.i am not sure if i should create only one request queue which will be used by all the servers or i should create seperate queues for each server.
For response ,I am planning to use temporary queues.
Not that the request from the client to the server is not very often.Say each client may send around 50 requests a day.
can someone please tell me if this is a good design?
Related
I have exposed a websocket enabled service endpoint through Azure Application Gateway and the service is hosted on azure service fabric. Client initiates a websocket connection with my endpoint and is able to exchange data. During certain message flows, my Web Socket enabled service calls other services hosted on the service fabric using azure service bus. These are handled in a completely async manner. Once the other services finish processing, they post a message to the service bus which my WebSocket service reads back.
The problem I am having is to route the messages back to the right service fabric node so that it can be pushed back to the client at the other end of the WebSocket connection
In the picture below, you can imagine each node containing multiple services including the web socket enabled service. Once the Websocket service posts a message to the service bus, the downstream services start processing and finally they post a message back to the service bus which the websocket service reads back. Here a random node will pick up the message and it might not have the relevent websocket connection to push the processed data back
Sample Design
I have looked at redis pubsub model and it looks like I have to maintain last message processed on the nodes. It also means, every node on the cluster will need to read the message and discard it if they don't have the websocket connection with the client. I am looking for any suggested design models for this kind of problem
I ran into a similar scenario and didn't like the idea of using a new external service (Redis/SQL Server) as a backplane that would simply duplicate each message/event across all nodes.
The solution I settled on was to lean on a property of actor proxies, using actor events to call-back to a specific instance of a stateless service. Creating an actor service to act as a pub/sub backplane.
The solution is summarised in this blog post and this GitHub repo. It's worth pointing out that the documentation states actor events are best effort. This hasn't really been an issue when the application is running as normal, I presume that during a deployment or failover, some events may get lost, however this could be mitigated with additional work.
It's also worth noting that your load balancing rules should maintain sticky connections between clients and back-end instances. You could create separate rules for websockets if you only wanted this to apply to them and not your regular HTTP traffic.
Whereas the corporate environment I am working in accepts the use of http(s) based request response patterns, which is OK for GraphQL Query and Mutation, they have issues with the use of websockets as needed for GraphQL Subscription and would prefer that the subscription is routed via IBM MQ.
Does anyone have any experience with this? I am thinking of using Apollo Server to serve up the GraphQL interface. Perhaps there is a front-end subscription solution that can be plugged in using IBM MQ? The back end data sources are Oracle databases.
Message queues are usually used to communicate between services while web sockets are how browsers can communicate with the server over a constant socket. This allows the server to send data to the client when a new event of a subscription arrived (classically browsers only supported "pull" and could only receive data when they asked for it). Browsers don't implement the MQ protocols you would need to directly subscribe to the MQ itself. I am not an expert on MQs but what is usually done is there is a subscription server that connects to the client via web socket. The subscription service then itself subscribes to the message queue and notifies relevant clients about their subscribed events. You can easily scale the subscription servers horizontally when you need additional resources.
I would like to figure out the best way to route messages from Kafka to web socket clients connected to a load balanced application server cluster. I understand that spring-kafka facilitates consuming and publishing messages to a kafka topic, but how does this work in a load balanced application server scenario when connecting to a distributed kafka topic. Here are the requirements that I would like to satisfy, with the overall goal of facilitating peer to peer messaging in an application with a very, very large volume of users:
Web clients can connect to a tomcat application server via web sockets connection via a load balancer.
Web client can send a message/notification to another client thats connected to different tomcat application server.
Messages are saved in the database and published to a kafka topic/partition that can be consumed by the appropriate web clients/users.
Kafka can be scaled to many brokers with many consumers.
I can see how this can be implemented quite easily in a single application server scenario where the consumer consumes all messages from a kafka topic and re-distributes via spring messaging/websockets. But I can't figure out how this would work in a load balanced application server scenario where there are consumers on each application server forming an overall consumer group for the kafka topic. Assuming that each of the application servers are are consuming sub-sets/partitions of the kafka topic, how do they know which server their intended recipients are connected to? And even if they knew which server their recipients were connected to, how would they route the message to them via websockets?
I considered that the application server load balancing could work by logging users with a particular routing key (users starts with 'A' etc) on to a specific application server, then only consuming messages for users starts with 'A' on that application server. But this seems like it would be difficult to maintain and would make autoscaling very difficult. This seems like it should be an common scenario to implement but I can't find any tools or approaches that fit this scenario.
Sounds like every single consumer should live in its own consumer group. This way all the available consumers are going to consume all the messages sent to the topic. Therefore all the connected websocket clients are going to be notified with those messages.
If you need more complex logic with those messages at
after consuming, e.g. filtering, routing, transforming, aggregating etc., you should consider to involve Spring Integration in you project: https://spring.io/projects/spring-integration
Broadcast to all the consumer may work, but the most efficient solution should route message to the node holds the websocket connection for the target user precisely. As i know, route in a distributed system can be done as follows:
Put the route information in a middleware，such as Redis; Or implement a service by yourself to keep track of all the ssesions. That is, solved in a centralized way.
Let the websocket server find route by themselves. In this circumstance, consensus algorithm like gossip should be taken into consideration.
As illustrated above, I need to build a Vert.x Java app that will be an HTTP server/virtual host (TLS Http traffic, Web socket traffic) that will redirect/channel specific domain traffic to other Vert.x Java apps running on the same server, each in it's own JVM.
I have been reading for days but I remain uncertain as to how to approach all aspects of the task.
What I DO know or have experience with:
Creating an HTTP server, etc
Using a Vert.x VirtualHost handler to "handle" incoming traffic for a
specific domain
What I DO NOT know:
How do I "re-direct" a domain's traffic to another Vert.x app (this
other Vert.x app would also be running on the same server, in its own
JVM).
- Naturally this "other" Vert.x app would need to respond to HTTP
requests, etc. What Vert.x mechanisms do I employ to accomplish this
aspect of the task?
Are any of the following concepts part of the solution? I'm unfamiliar with these concepts and how they may or may not form part of the solution.:
Running each Vert.x app using -cluster option?
Vert.x Streams?
Vert.x Pumps?
There are multiple ways to let your microservices communicate with each other, the fact that all your apps are running on the same server doesn't change much, but it makes number 2.) easy to configure
1.) Rest based client - server communication
Both host and apps have a webserver
When you handle the incoming requests on the host, you simply call another app with a HttpClient
Typically all services find each others address via service discovery.
Eg: each service registers his address in a central registry then other services use this central registry to find the addresses.
Note: this maybe an overkill for you and you can just configure the addresses of the other services.
2.) You start the vertx microservices in clustered mode
the eventbus is then shared among the services
For all incoming requests you send a broadcast on the eventbus
the responsible app replies to the message
For further reading you can checkout https://vertx.io/docs/vertx-hazelcast/java/#configcluster. You start your projects with -cluster option and define the clustering in an xml configuration. I think by default it finds the services via local broadcast.
3.) You use a message broker like RabbitMq etc.
All your apps connect to a central message broker
When a new request comes in to the host, it sends a message to the message broker
The responible app then listens to the relevant messages and replies
The host receives the reply from the message broker
There are already many existing vertx clients for certain message brokers like kafka, camel, zeromq:
https://github.com/vert-x3/vertx-awesome#integration
I have a setup of 2 WLS managed servers configured as part of a WLS cluster.
1) The requirement is to send requests to another system and receive responses using JMS as interface.
2) The request could originate from either of the Managed Servers. So the corresponding response should reach the managed server which originated the request.
3) The external system (to which requests are sent) should not be aware of how many managed servers are in the cluster (not a must have requirement)
How should JMS be configured for meeting these requirments?
Simple! Setup a response queue for each managed server and add a "reply-to" field in the messages you send to the other system. The other system will then ask the request where to send the reply. Deploy one Message Driven Bean (MDB) on each managed server (i.e. not on the cluster, one per managed server) to consume reply messages send to reply queues. Note that you might want to use clustered reply queues and persistent messages for load balancing and failover.
This is actually a combination of the Request-Reply and the Return Address patterns and is illustrated by the picture below: