For some performance issue, i need to process one kind of request in a dedicated node. For example, I need to process all request like http://hostname/report* on node1. So, I added a rule in load balancer to redirect http://hostname/report* to http://node1name/report*. But node1 ask me to login again. And I was logged in http://hostname/ already. How can I directly access without login again?
As #JoseK mentioned, it looks like you don't have session replication and failover configured between the servers. You will need all of your application servers to be inside the same WebLogic cluster and you will also have to pick their secondary session replication node to be the destination for in-memory replication. You can dictate this by assigning the dedicated node to a specific machine, which is then selected as the secondary replication target for all cluster members.
Also, for session replication to work, all objects within your session have to be/implement serializable.
Related
We are trying to prevent our application startups from just spinning if we cannot reach the remote cluster. From what I've read Force Server Mode states
In this case, discovery will happen as if all the nodes in topology
were server nodes.
What i want to know is:
Does this client then permanently act as a server which would run computes and store caching data?
If connection to the cluster does not happen at first, a later connection to an establish cluster cause issue with consistency? What would be the expect behavior with a Topology version mismatch? Id their potential for a split brain scenario?
No, it's still a client node, but behaves as a server on discovery protocol level. For example, it can start without any server nodes running.
Client node can never cause data inconsistency as it never stores the data. This does not depend forceServerMode flag.
Currently I have the following setup:
Hardware load balancer directing traffic to two physical servers each with 2 instances of weblogic running.
Works ok. I'd like to be able to shutdown one of the servers without dropping active sessions. Right now if I shutdown one of the physical servers any traffic that was going there gets bounced back to a login screen.
I'm looking for the simplest way of accomplishing this with the smallest performance hit.
Things I've considered so far:
1. See if I can somehow store the session information on the Load Balancer and through some Load Balancer magic have it notice a server is dead and try another one with the same session information (not sure this is possible)
2. Configure weblogic clustering. Not sure what the performance hit would be. Im guessing this is what I'll end up with, but still fishing for alternatives.
3. ?
What I currently have is an overly designed DR solution (which was the requirement), but I'd like to move it more in the direction of HA (for the flexibility)
edit Also is it worthwhile to create 2 clusters and replicate the sessions between them (I was thinking one cluster per site, sites are close enough). This would cover the event of one cluster failing.
You could try setting up a JDBC Session Storage pointing (of course) both instances to the same datasource without setting up a cluster, but I think the right approach would be setting up a Weblogic Cluster.
A nice thing about clustering Weblogic Servers is that - (from the link above, emphasis mine):
Sessions can be shared across clustered WebLogic Servers. Note that session persistence is no longer a requirement in a WebLogic Cluster. Instead, you can use in-memory replication of state. For more information, see Using WebLogic Server Clusters.
We've got a write up of this on our blog http://blog.c2b2.co.uk/2012/10/basic-clustering-with-weblogic-12c-and.html which provides step by step instructions on setting up web session failover in a cluster.
Clusters are not heavyweight assuming you don't store huge amounts of data in the cluster as it will be replicated.
Does REDIS has built-in mechanism that will use slave when master is down?
Can I use virtual IP to direct to master and when Master is down is it possible to direct to slave?
As per the documentaion:
elect the slave to master using the SLAVEOF NO ONE command, and shut down your master.
But how the application will know about the changed IP?
mysql has a third party utility that is called MMM (master master replication with monitor). Is there such an utility for REDIS?
You can use a virtual IP in a load balancer, though this is not built in to Redis. Any quality hardware or software load balancer should be able to do it. For example you can use "balance" or HAProxy to front the VIP and use a script or rules that checks the status of Redis instances to see which is master and sets that as the destination in the load balancer (LB).
Going this route would require one or more additional servers (or VMs depending on your setup) but it would provide you with a configuration that has clients talking to a single IP and being clueless about which server they need to talk to on the back end. How you update the LB with which server to talk to is dependent on what LB you use. Fortunately, none of them would need to know or handle the Redis protocol; they are just balancing a port.
When I go this route I go with a Slave-VIP and a Master-VIP. The slave-VIP load balances across all Redis instances, whereas the Master-VIP only has the current master enabled. If your write load is very heavy you can leave the current master out of the Slave-VIP pool. Otherwise I would leave it in; that eliminates the need for failover updating of the Slave-VIP pool.
Hi I have a application that is deploy on two weblogic app servers
recently we have issue that for certain cases the user session returned is null. Developer feedback is that it could be caused by the session not replicating to the other server.
How do we prove if this is really the case?
Are you using a single session store that both application servers can access via some communication protocol? If not, then it is definitely the case. Think about it, if your weblogic servers are storing the session in memory anywhere, and having users pass their session id via cookies, than the other server has no way of accessing the memory on the other machine. Unless you are using sticky load balancing. Are you?
There's 2 concepts to consider here - Session stickiness and session replication.
Session Stickiness is a mechanism where weblogic server ensures that if a request from a user with session A goes to server 1 then the next request from user with session A will go to server 1 only.
This is achieved by configuring a hardware loadbalancer (like F5) which is capable of providing session stickiness. or configuring weblogic proxy installed on apache/iis/weblogic.
The first time a request reached WLS managed server, it responds with a session id and appends to it the JVM id of the server (this is the primary id), if the managed server is part of a cluster, it also attaches a secondary server jvm id (the secondary server is the server where the session is being replicated)
The proxy maintains a table of all JVM id's and corresponding IP of managed server, it also checks periodically if the servers are up and running or not.
The next time when another request passes the proxy with existing session id and a primary jvm id, the proxy parses this and tries to send the request to that server, if it cannot within some time it tries to send to secondary server.
Session Replication - This is enabled by default when you configure a WLS cluster with 2 or more managed server. Each time any data is updates to a session, its data is replication in a secondary server too.
So in your case if your application users are loosing session or getting redirected to login page between normal usage, then check that the session did not get invalidated because of a timeout, if you have defined a cluster and using WLS proxy then check the proxy debug output to make sure the primary and secondary server are being appended to the session id.
Finally there's a simple example in the sample application deployment of wls that you can use to test session replication and failover functionality.
So to prove why session is getting lost,
1) check server log to see if session got invalidated because of timeout,
2) if using wlproxy, enable debug, and the next time the issue happens check in the proxy log if the request was sent to a different server, and if that server is not the secondary server.
I have a Glassfish v2u2 cluster with two instances and I want to to fail-over between them. Every document that I read on this subject says that I should use a load balancer in front of Glassfish, like Apache httpd. In this scenario failover works, but I again have a single point of failure.
Is Glassfish able to do that fail-over without a load balancer in front?
The we solved this is that we have two IP addresses which both respond to the URL. The DNS provider (DNS Made Easy) will round robin between the two. Setting the timeout low will ensure that if one server fails the other will answer. When one server stops responding, DNS Made Easy will only send the other host as the server to respond to this URL. You will have to trust the DNS provider, but you can buy service with extremely high availability of the DNS lookup
As for high availability, you can have cluster setup which allows for session replication so that the user won't loose more than potentially one request which fails.
Hmm.. JBoss can do failover without a load balancer according to the docs (http://docs.jboss.org/jbossas/jboss4guide/r4/html/cluster.chapt.html) Chapter 16.1.2.1. Client-side interceptor.
As far as I know glassfish the cluster provides in-memory session replication between nodes. If I use Suns Glassfish Enterprise Application Server I can use HADB which promisses 99.999% of availability.
No, you can't do it at the application level.
Your options are:
Round-robin DNS - expose both your servers to the internet and let the client do the load-balancing - this is quite attractive as it will definitely enable fail-over.
Use a different layer 3 load balancing system - such as "Windows network load balancing" , "Linux Network Load balancing" or the one I wrote called "Fluffy Linux cluster"
Use a separate load-balancer that has a failover hot spare
In any of these cases you still need to ensure that your database and session data etc, are available and in sync between the members of your cluster, which in practice is much harder.