I was wondering how to send messages to another user using Progress 4gl. We are trying to cut down on the PA speaker where I work and I want some way to notify a certain user/users of some predefined messages. I'm not sure if this is even possible with Progress, or if there is a message queue that can be used. If anyone has any samples, ideas or has done this before, please let me know. Thanks!!
You might find this helpful:
Following on from presentations in Boston and Finland, dot.r is
pleased to announce the open source Stomp project, available
immediately.
Download from either http://www.dotr.com or
https://bitbucket.org/jmls/stomp , the dot.r stomp programs allow you
to connect your progress session to any other application or service
that is connected to the same message broker.
Open source , free message brokers that support Stomp are :
Fuse (http://fusesource.com/products/fuse-mq-enterprise/)
[a Progress company now owned by Red Hat inc]
Fuse MQ Enterprise is a standards-based, open source messaging platform
that deploys with a very small footprint. The lack of license
fees combined with high-performance, reliable messaging that can be
used with any development environment provides a solution that
supports integration everywhere
ActiveMQ (http://activemq.apache.org/)
Apache ActiveMQ (tm) is the most popular and powerful open source messaging
and Integration Patterns server. Apache ActiveMQ is fast,
supports many Cross Language Clients and Protocols, comes with
easy to use Enterprise Integration Patterns and many advanced features
while fully supporting JMS 1.1 and J2EE 1.4.
Apache ActiveMQ is released under the Apache 2.0 License
RabbitMQ
RabbitMQ is a message broker. The principal idea is pretty simple: it
accepts and forwards messages. You can think about it as a post
office: when you send mail to the post box you're pretty sure that Mr.
Postman will eventually deliver the mail to your recipient. Using this
metaphor RabbitMQ is a post box, a post office and a postman.
The major difference between RabbitMQ and the post office is the fact
that it doesn't deal with paper, instead it accepts, stores and
forwards binary blobs of data - messages.
Please feel free to log any issues on the
https://bitbucket.org/jmls/stomp issue system, and fork the project in
order to commit back all those new features that you are going to add
...
dot.r Stomp uses the permissive MIT licence
(http://en.wikipedia.org/wiki/MIT_License)
Have fun, enjoy !
Julian
I tried it -- the code is dead-simple to install and run. And peeking inside the source is a pleasure.
ApacheMQ is pretty much painless to get going. This is a really, really easy way to get going with messaging.
If you are an old character-based fossil (such as myself) you might want to skip the GUI samples. You can send a message with:
/* stompQOut.p
*
*/
dotr.Stomp.Helper.SendMessage:ToQueue("myQueue","a test message")
And receive messages with:
/* stompQIn.p
*
*/
define variable stompClient as dotr.Stomp.StompClient no-undo.
define variable msgTxt as character no-undo format "x(60)".
stompClient = new dotr.Stomp.StompClient().
stompClient:Subscribe( this-procedure ).
stompClient:SubscribeToQueue( "myQueue" ).
pause 0 before-hide.
wait-for close of this-procedure.
procedure NewStompMessage:
define input parameter stompMessage as dotr.Stomp.StompMessage no-undo.
message string( stompMessage:Body ).
end.
Related
I'm looking for a way to implement basic Publish / Subscribe between applications written in different languages, to exchange events with JSON payloads.
WebSocket seems like the obvious choice for the transport, but you need an (arguably small) layer on top to implement some of the plumbing:
aggreeing on messages representing the pubsub domain "subscribe to a topic", "publish a message"
aggreeing on messages for the infra ("heartbeat", "authentication")
I was expecting to find an obvious standard for this, but there does not seem to be any.
WAMP is often refered to, but in my (short) experience, the implementations of server / clients libraries are not great
STOMP is often refered to, but in my (even shorter) experience, it's even worse
Phoenix Channels are nice, but they're restricted to Phoenix/Elixir world, and not standard (so the messages can be changed at any phoenix version without notice.)
So, is everyone using MQTT/WS (which require another broker components, rather than simple servers ?) Or gRPC ?
Is everyone just re-implementing it from scratch ? (It's one of those things that seems easy enough to do oneselves, but I guess you just end up with an half-baked, poorly-specified, broken version of the thing I'm looking for...)
Or is there something fundamentally broken with the idea of serving streams of data from a server over WS ?
There are two primary classes of WebSocket libraries; those that implement the protocol and leave the rest to the developer, and those that build on top of the protocol with various additional features commonly required by realtime messaging applications, such as restoring lost connections, pub/sub, and channels, authentication, authorization, etc.
The latter variety often requires that their own libraries be used on the client-side, rather than just using the raw WebSocket API provided by the browser. As such, it becomes crucial to make sure you’re happy with how they work and what they’re offering. You may find yourself locked into your chosen solution’s way of doing things once it has been integrated into your architecture, and any issues with reliability, performance, and extensibility may come back to bite you.
ws, faye-websockets, socket.io, μWebSockets and SocketCluster are some good open-source options.
The number of concurrent connections a server can handle is rarely the bottleneck when it comes to server load. Most decent WebSocket servers can support thousands of concurrent connections, but what’s the workload required to process and respond to messages once the WebSocket server process has handled receipt of the actual data?
Typically there will be all kinds of potential concerns, such as reading and writing to and from a database, integration with a game server, allocation and management of resources for each client, and so forth.
As soon as one machine is unable to cope with the workload, you’ll need to start adding additional servers, which means now you’ll need to start thinking about load-balancing, synchronization of messages among clients connected to different servers, generalized access to client state irrespective of connection lifespan or the specific server that the client is connected to – the list goes on and on.
There’s a lot involved when implementing support for the WebSocket protocol, not just in terms of client and server implementation details, but also with respect to support for other transports to ensure robust support for different client environments, as well as broader concerns, such as authentication and authorization, guaranteed message delivery, reliable message ordering, historical message retention, and so forth. A data stream network such as Ably Realtime would be a good option to use in such cases if you'd rather avoid re-inventing the wheel.
There's a nice piece on WebSockets, Pub/Sub, and all issues related to scaling that I'd recommend reading.
Full disclosure: I'm a Developer Advocate for Ably but I hope this genuinely answers your question.
I've been looking into sockjs-tornado recently and am working on a chat function for a social networking site. I'm trying to get a feel for common methods used in building scalable multiroom chat functionality. I'll outline a couple of the methods I've thought of and I'd like to get feedback. What methods are used in the real world? What are the advantages and disadvantages to these methods?
Prereqs:
running tornado
using sockjs-tornado lib
sockjs-client lib for js
Everything else is open.
Methods I've considered:
For loop
This seems like the simplest way to go. You create a user class that subscribes to certain room classes. The user sends a message class that contains a room id and the server redirects the message in the loop only to users that have subscribed to that room. This seems to me to be by far the worst because the complexity is obviously at least linear. (Imagine 500 users connected at once to 5 chat rooms each.)
Multi-tasking/multiple server instances
This also seems like a bad idea because you could have 500 server instances running at any time on... different ports? I'm really not sure on the implementation of this method.
Native support
Now granted, a lot of libraries have this built in such as socketio. However that's not an option due to the sole node.js support. (I'm on tornado server.) Socks in particular does not have built in support for multiple "rooms".
Conclusion
I'm looking for resources/case studies, and industry standards. Any help would be appreciated.
I would just use a message queue server like RabbitMQ with a fanout exchange as each "chat room".
You can see an example of using a fanout exchange in Python here.
The Pika AMQP library works with Tornado, too.
The advantage with using a message queueing system is that you can have users connected to different Tornado processes on different servers while still being in the same "room", giving you high availability on the HTTP layer.
RabbitMQ also has HA capabilities (although not the greatest).
I'm looking for an easy way to implement the XMPP server running with the following protocol:
https://developers.google.com/cloud-print/docs/rawxmpp
The only difference is that I must use X-GOOGLE-TOKEN authentication mechanism: https://stackoverflow.com/a/6211324/227244
The procedure is simple: I get the token from the data sent by a client, request user data based on this token and set the JID accordingly, appending some random chars to the resulting JID.
After that other clients with possibly different tokens, but same user account, connect to the XMPP resource and for clients who are subscribed the broadcast of push notifications is enabled.
What amount of the server code can be borrowed from the currently available implementations? I would avoid writing all of the server code myself, though the logic is pretty simple. I know there're ejabberd and prosody xmpp servers which implement lots of XEP. Which one is easier to add the custom handling mechanism to? Can you suggest other stable alternatives for the core xmpp server?
The way google has designed X-OAUTH2 is dead simple and straightforward to implement. Infact, there is no difference between how PLAIN and X-OAUTH2 mechanisms work. You can simply pick a standard PLAIN implementation and make it work for google X-OAUTH2 authentication mechanism with no extra effort.
I am author of Jaxl PHP library and I recently announced support for X-OAUTH2 inside the library. Here you can see exact lines of code I had to write to support this. The only relevant piece of code is:
switch($mechanism) {
case 'PLAIN':
case 'X-OAUTH2':
$stanza->t(base64_encode("\x00".$user."\x00".$pass));
break;
For X-OAUTH2 implementation $pass is nothing but your oauth token. In short, password field from PLAIN auth mechanism becomes oauth token for X-OAUTH2 mechanism. Rest all remains the same.
We have about about six systems (they are all internal systems) that we need to send data between. Currently we do not have a consistent way of doing this. We use SSIS, SQL Server linked servers to directly update databases, ODBC connections to directly update databases, text files, etc..
Our goals are:
1) Have a consistent way of connecting applications.
2) Have a central way of monitoring and logging the connections between
applications.
3) For the applications that offer web services we
would like to start using them instead of connectiong directly with
the database.
Whatever we use will need to be able to connect to web services, databases, flat files, and should also be able to accept data via a tcp connection.
Is Biztalk a good solution for this, or is it is overkill?
It really depends. For the architecture you're describing, it would seem a good fit. However, you will need to validate wether biztalk can communicate whith the systems you are trying to integrate. For example; when these systems use webservices, message queues or file based communication, that may be a good fit.
When you start with biztalk, you have to be willing to invest in hardware, software, en most of all in learning to use it.
regarding your points:
1) yes, if you make sure to encapsulate the system connectors correctly
2) yes, biztalk supports this with BAM
3) yes, that would match perfectly
From what you've described (6 systems), it is definitely a good time to investigate a more formalized approach to integration, as you've no doubt found that in a point to point / direct integration approach will result in a large number of permutations / spaghetti as each new system is added.
BizTalk supports both hub and spoke, and bus type topologies (with the ESB toolkit), either of which will reduce the number of interconnects between your systems.
To add to oɔɯǝɹ:
Yes - ultimately BizTalk converts everything to XML internally and you will use either visual maps or xslt to transform between message types.
Yes. Out of the box there are a lot of WMI and Perfmon counters you can use, plus BizTalk has a SCOM management pack to monitor BizTalk's Health. For you apps, BAM (either TPE for simple monitoring, but more advanced stuff can be done with the BAM API).
Yes - BizTalk supports all the common WCF binding types, and basic SOAP web services. BizTalk's messagebox can be used as a pub / sub engine which can allow you to 'hook' other processes into messages at a later stage.
Some caveats:
. BizTalk should be used for messages (e.g. Electronic Documents across the organisation), but not for bulk data synchronisation. SSIS is a better bet for really large data transfers / data migration / data synchronisation patterns.
. As David points out, there is a steep learning curve to BizTalk and the tool itself isn't free (requiring SQL and BizTalk licenses, and usually you will want to use a monitoring tool like SCOM as well.). To fast track this, you would need to send devs on BizTalk training, or bring in a BizTalk consultant.
. Microsoft seem to be focusing on Azure Service Bus, and there is speculation that BizTalk is going merged into Azure Service Bus at some point in future. If your enterprise strategy isn't entirely Microsoft, you might also want to consider products like NServiceBus and FUSE for an ESB.
You problem is a typical enterprise problem. Companies start of building isolated applications like HR, Web, Supply Chain, Inventory, Client management etc over number of years and once they reach a point these application cannot be living alone and they need to talk to each other, typically they start some hacked solution like data migration at database level.
But very soon they realize the problems like no clear visibility, poor management, no standards etc and they create a real spaghetti. The biggest threat is applications will become dependant on one another and you lose your agility to change anything. Any change to system will require heavy testing and long release cycle.
This is the kind of problem a middleware platform like BizTalk Server will solve for you. Lot of replies in the thread focused on cost of BizTalk server (some of the cost mentioned are not correct BTW). It's not a cheap product, but if you look at the role it play in your organisation as a central middleware platform connecting all the applications together and number of non-functional benefits you get out of the box like adapters to most of the third party products like SAP, Oracle, FTP, FILE, Web Services, etc, ability to scale your platform easily, performance, long running work flows, durability, compensation logic for long running workflows, throttling your environment etc., soon the cost factor will diminish.
My recommendation will be take a look at BizTalk, if you are new then engage with local Microsoft office. Either they can help or recommend a parter who can come and analyse your situation.
I would like to learn more about programming messaging applications and using message queues. Things like qpid, Amazon Queues, etc. Can you point me to some apps (preferably C++, open source if possible) so I can learn more.
Also, can you tell me the general guidelines one would use to decide whether ot not to use message queues. I am interesting in leanring about this just for the 'coolness' factor but I think it might be beneficial for me in the future.
RabbitMQ is the Message Queue that I am the most familiar with. It implements AMQP just like qpid. AMQP is a widely accepted wire protocol and there are many client libraries available such as C++, Java, Ruby, .Net, Python, etc.
If the distributed service is flaky and is not always online, you can use a rock solid message queue to persist the messages. The messages are then delivered when the distributed service comes back to life.
If the distributed service has low latency and the client service generates more requests than the distributed service can handle, a queue will hold the messages until the distributed service can process them while allowing the client to process uninhibited.
If requests need to be distributed to multiple services, an exchange will take care the important details such as delivering the message to each distributed service once and only once.
I don't recommend using message queues when you need a synchronous call to a remote service. Message queues are inherently asynchronous.
Not a programming language, but a useful tool when you're programming with message queues is Promela/Spin. It's designed to identify deadlocks or other concurrency issues that might arise from a distributed system. Certainly looking at the sort of issues it can help identify will give you an idea of the sort of problems you might encounter.
Not sure what its written in but Eclipse IDE seems to have some sort of message queue system. Whenever its busy (read, lagging... alot) you see a message saying "performing blank before user operation". Eclipse is Open Source. I am not sure where to download the source code.. but I believe it comes with the installation - http://www.eclipse.org/downloads/. latest is 3.6 (helios)