I know it is possible to send messages from PostgreSQL to RabbitMQ, but is it possible to send messages from RabbitMQ to PostgreSQL.
Right now i am feeding RabbitMQ throught the amqp plugin with some data coming from a raspberry-pi using MQTT.
So yeah, i was wondering if it was possible to run a script or install another plugin in the database or if i would need something between the two to process the messages and converting it.
Thank you!
We need to write another service which will subscribe to rabbitmq message that service will insert the data into db. You can create service or any plugin which can consume messages from queue.
Related
I'd like to make a chat app, but I don't know how to send the messages in real time. Should I write them into a database, and retrive them on the other side, or should I use sockets for real time messaging? (I would use a database in both cases for reading old messages)
I would suggest using sockets for real time communication and execute job in background that would store these messages into database. Whenewer the user opens the conversation you can load recent messages from database. Otherwise I think there could be a problem with real time sync with the database. Hope this helps.
My Question centers around this slide from one of Rossen Stoyanchev webinars.
When using a simpleBroker I can send messages to individual users with the /user/** destination format that is picked up in UserDestination and converted. I can also use it to send to a specific session, or all sessions of a specific user.
This is also possible when using an External Broker like ActiveMQ or RabbitMQ as long as the sender is also able to use /user/** or its helper annotations #SentToUser etc.
But, if I am not processing these messages locally and I have another consumer connected to the External Message Broker (Apache Camel for example) How do handle User specific messages and also reply at a user and session level?
If the other consumer is in the same JVM you can have the "brokerMessagingTemplate" bean injected and use it to send messages to user-prefixed destinations.
For 4.2 we plan to support user destinations in a deployment with multiple web application servers connected to an External broker (see https://jira.spring.io/browse/SPR-11620). So if the other consumer is in a different JVM, then you could declare the #EnableWebSocketMessageBroker setup in that JVM as well or you could simple extend AbstractMessageBrokerConfiguration if you don't need the WebSocket client bits.
HTH
I am trying to design a Client Server kind of application in which my Server is a daemon that accepts client requests, send client's data over a serial channel to the other side(which is an MCU and its firmware will reply to the Server request over the same serial channel). My client can be a CLI application or any other system program.
My idea of design is -
Use message queues for communication between Client and Server since this is a local application and message queues are bidirectional and fast.
Implement a LIBRARY that acts as an interface between multiple clients and the server. This basically does the stuff of packetizing client data into a message(own defined protocol), create message queues, connect to server, send/receive data and then pass it to the respective client(using call backs). This library also exposes API that can be used by clients. Thus this library gives me the flexibility to add support for any new clients keeping the server program unchanged.
Server gets the data over serial from other side and passes it to the library over message queue. The library uses callbacks to send data to the client.
EDIT:
I am thinking of creating Message queues on the fly when any client requests arrive. If I do this, how does the Server daemon(which has already started at linux boot up) gets information about this message queue? Does the message queue has a name that is persistent across and used by other programs? I want to implement clients that will be blocked until it gets response from the server.
Could you guys please review this design and tell me whether my approach is correct. Please reply if you have any other recommendations.
Thanks in advance.
I created a working Google Channel AP and now I would like to send a message to all clients.
I have two servlets. The first creates the channel and tells the clients the userid and token. The second one is called by an http post and should send the message.
To send a message to a client, I use:
channelService.sendMessage(new ChannelMessage(channelUserId, "This is a server message!"));
This sends the message just to one client. How could I send this to all?
Have I to store every Id which I use to create a channel and send the message for every id? How could I pass the Ids to the second servlet?
Using Channel API it is not possible to create one channel and then having many subscribers to it. The server creates a unique channel for individual JavaScript clients, so if you have the same Client ID the messages will be received only by one.
If you want to send the same message to multiple clients, in short, you will have to keep a track of active clients and send the same message to all of them.
If that approach sounds scary and messy, consider using PubNub for your push notification messages, where you can easily create one channel and have many subscribers. To make it run on Google App Engine is not that hard, since they support almost any platform or device.
I know this is an old question, but I just finished an open source project that uses the Channel API to implement a publish/subscribe model, i.e. you can have multiple users subscribe to a single topic, and then all those subscribers will be notified when anyone publishes a message to the topic. It also has some nice features like automatic message persistence if desired, and "return receipts", where a subscriber can be notified whenever OTHER subscribers receive that message. See https://github.com/adevine/gaewebpubsub#gae-web-pubsub. Licensed under Apache 2.0 license.
could I send messages from one service to multiple service using service brokers?
Something like
BEGIN DIALOG CONVERSATION #dialog_handle
FROM SERVICE [SERVICE1]
TO SERVICE 'SERVICE2',**'SERVICE3'**
ON CONTRACT [MainContract]
Looking at the syntax, I do not think we could do this. What's the alternative?
Thanks and Regards
DEE
There is no publish-subscribe nor multicast built in into Service Broker. To send a message to multiple services you have to explicitly send it to each destination an o a separate dialog.
The typical solution is to send only one message from the application to a service that acts like a distributor. The distributor service receives this message and sends a copy of it to each interested service (Service2, Service3 etc). This way the application doesn't need to know upfront how many services it needs to send the message to, it just sends it to the distributor service.