I'm stuck with jboss and blazeds clusterization.
What I have now is :
2 Jboss Instances, running in all mode
One load balancer with apache and mod_jk, as suggested by Jboss docs
A spring/flex integration app
A flex application that I do not want to throw errors when one of my JBoss instances falls
I find Adobe documentation really lacking, and being new at clustering, jgroups and balancing I cannot find how to deploy my app in clustered environment.
Actually this solution is working fine with remote calls. If one of jboss instances goes down the rpc gets routed to the other instance. What is not working are push messages, cause if client is connected to JBossA, and JBossA goes down, client displays an error message, stating that it can't reach JBossA, when it should failover to JBossB, without the user noticing anything.
From what I understood if configured correctly blazeds should tell flex client about failover servers upon connection. Then if flex client can't connect to the main server it goes to another. But the hard part for me is getting there.
Can someone point me to the right direction?
Thanks in advance
If you have an apache web server sitting between the clients and the JBoss servers, with mod_jk handling communication between apache and JBoss, then that should be your failover requirements met already.
mod_jk will detect if any of the JBoss servers fails, and send requests to the other one. As far as the clients are concerned, they see a single server, which is the apache server. They see nothing of the JBoss servers behind it.
I know nothing about BlazeDS clustering, but I'm guessing it has some form of manual failover mechanism, which it tells clients about a list of server addresses, and the clients pick one that works. This should only be necessary if you don't have a mod_jk middleman, so hopefully you can just ignore the blazeds clustering.
Things can, of course, get a lot more complicated, such as when you need to JBoss servers to commnunicate amongst themselves (e.g. session replication, clustered JMS, distributed caching, etc), but if you don't need any of that, then you can safely ignore it.
Related
We made a chat module in our project using socket.io. When the load is balanced and the manual deployed, if socket connections are switched to different servers, socket connections are disconnected and the messaging events are partially not processed. I solved the load balance problem with socket.io-redis library. It acts as a gateway and solves this problem thanks to redis.
Another problem is that when I deploy it manually, the pid of the servers changes and socketio connections are instantly disconnected on the client and then it is not connected even though it says connected.
Do you think that using tools such as Travis CI solves the problems in manual deploy process?
Another question is, if a system that goes to 3 servers with load balance then goes back to 2 servers, the socket connections will be closed again, what method may be required to solve this? I thought of separating the socket.io service from the monolithic structure and keeping it on a single server, and scaling the server vertically when the load increased.
We are using an Aws Elastic Beanstalk(EBS), it automatically performs load balance.
By default, applications in wildfly are deployed to localhost:8080/app. How to deploy application on dedicated port, i.e. open it on localhost:8282 without application name ending?
I need to change the port for certain application, not the default port.
I have not tried this, but AFAICT it should be possible to:
run a single Wildfly instance listening on multiple HTTP ports. This is, in theory at least, possible (ref: https://developer.jboss.org/thread/233414?start=0&tstart=0)
Configure undertow subsystem as a reverse proxy, and proxy your app to the other port/location (ref: http://www.mastertheboss.com/jboss-server/wildfly-8/configuring-a-reverse-proxy-with-undertow). That said, I have never used undertow for a reverse proxy and as such cannot speak for whether this really works.
Once you have done this, you have effectively just turned your Wildfly instance into an overly complex application server and reverse proxy in one. Ultimately however, the app in question would still be running on both ports, but you redirect the traffic using the proxy the way you would like.
The same proxy configuration in an Apache (ref: https://httpd.apache.org/docs/current/mod/mod_proxy.html#forwardreverse or https://www.leaseweb.com/labs/2014/12/tutorial-apache-2-4-transparent-reverse-proxy/) or NGINX (ref: https://www.nginx.com/resources/admin-guide/reverse-proxy/) would be IMHO less complex and better tested in countless production scenarios.
We have a Websphere app server with one cluster containing 2 servers. Each server contains our webapp. Each webapp/server talks to an single NCipher server though sockets. The NCipher server is listening for communications from each webapp/server on a common port.
If we reboot each of the Websphere servers in the cluster individually then we find that one connects straightaway but the other takes a variable amount of reboots before it connects. What I find confusing is why one connects immediately but the other doesn't.
What I have noticed is that connections are not being closed in the webapp. Not sure what impact this may have given that one of the servers is connecting fine once rebooted and the other doesn't.
Even though not closed I guess the connections do timeout, although closing them is definitely the correct thing to do.
Would anybody have any idea as to why this may be occuring ?
It seems that both service and server refer to some web based application. But is there any precise definition of the two terms?
A server offers one or more services. Server is also a more technical term, whereas service is more a term off the problem domain.
You also need to distinguish between:
Server as hardware (see post from Dan D)
Server as software (eg. Apache HTTP server)
You can find more elaborate definiton on Wikipedia:
Service
Server
This is regardless of client-server or P2P models.
A server provides services to one or more clients, and a server(hardware) is a computer. A server(hardware) can be anything from a home computer to a big server-rack with a lot of processor power.
From the view of a computer, a server(software) is just a set of services which is available to clients on the network.
Some well known services are web-server, mail-server. ftp-server. notice they are called xxx-server because such programs consist of a client and server part. The postfix is mainly to distinguish whether we are talking about the client or the server.
So at what moment do we call something a server? We do it when a computer shares some service/content on the network, which is accessible by clients. In other words, when we make a server as defined for software.
Regarding the P2P model: every one is both a client and a server, hence called servent. The above apply to the server part of a P2P network, just remember that it also can be a client.
Futher reading:
Client-Server model
P2P
a server is a piece of hardware or on a virtual machine
a service is a process that provides services normally over the network and runs on a server
but a server can also refer to a web server which is actual a service but it's sort of like one as it hosts services
i think those are reasonable working definitions
I think a simpler way to define both besides the definition of the server being a piece of hardware, a server in the software sense is a service that serves data. In other words you interact with a server with a request and you should get a response back. It "serves" data.
A service does not need interaction and is pretty much just a random process that keeps running doing the same thing, but a server is a service because it is basically a process that keep waiting for a request to come in so that it can return a response.
"A service is a component that performs operations in the background without a user interface."
~ Android Developers
Services don't just run on servers
Shell services
Services can run from the shell. Unix refers to services as Daemons (pronounced "demons"), and Windows refers to them as services.
Client-side services
Services can run client-side. Mozilla (and other browsers) support Web Workers which run in a background thread. Client-side frameworks, like Angular, support services as well.
Does anyone have experience deploying GWT apps to EC2?
If I were to install tomcat or apache on a ec2 instance, could I have users connect directly to a url pointing there?
Would that be cost effective, or would java hosting services be best?
Is there any downside to hosting the edge HTTP server on a regular hosting service and have that direct requests to EC2? Performance ever an issue here?
Other answers are correct but I just wanted to share the fact that we are are developing a product that is 100% EC2/S3 based and also have a pure GWT front end.
We use maven2 for builds and the excellent gwt-maven plugin. This makes it easy to produce a WAR package of our web application as output. We use Jetty but Tomcat would work just as well.
We have pound (a http accelerator/load balancer) running on the VM listening for http & https, which then forwards to requests to lighttpd (static) or jetty (app). This also simplifies SSL certificates because pound handles SSL. I've found Java servers have always been a pain to configure with SSL certs.
Yes, you can host pretty much whatever you want, as you effectively have a dedicated Linux machine at your command.
As I last recall, the basic rate for an EC2 instance, on their "low end box" worked out to around $75/month, so you can use that as a benchmark against other vendors. That also assumed that the machine is up 24x7 (since you pay for it by the hour).
The major downside of an EC2 instance is simply that it can "go away" at any time, and when it does, any data written to your instance will "go away" as well.
That means you need to set it up so that you can readily restart the server, but also you need to offline any data that you generate and wish to keep (either to one of Amazons other services, like S3, or to some other external service). That will incur some extra costs depending on volume.
Finally, you will also be billed for any traffic to the service.
The thing to compare it against is another "Virtual Server" from some other vendor. There is a lot of interesting things that can be done with EC2, but it may well be easier to go with a dedicated Virtual hosting service if you're just using a single machine.
Others have given good answers. I would have to add that you need to spend programmer time getting to know EC2's quirks and addressing them (e.g. with EBS). It's not completely trivial, and though it is useful knowledge to have and may be worth it for that reason alone, if you want to get up and running quickly with just a few servers, you should probably look at other hosted options.
On the other hand, if you plan to scale up massively enough (eventually hosting many servers on EC2) then I would highly recommend it. You have to architect a few things, but you need to do that anyways. The flexibility of on-demand computing, and the generally low price, makes this a killer platform once you reach a certain scale of operation.
You definitely can host an http server in EC2, but you need to take into consideration the following:
As mentioned before the cost can be much higher than alternative hosting solutions
Your instance (the machine you've started in EC2) can go off unexpectedly. There is no guarantee from Amazon for 24x7 availability. This mean that the data you've stored in local storage will be lost and when you've start a new instance, it will get a new IP.
To successfully host a server in EC2, you therefore need to employ some other services from Amazon. You need Elastic IP, so that you can circumvent the new IP address problem. You can also use Elastic Block Storage. This is a service that will allow you to mount in your machine a disk, that will not go away when your instance is lost.