Weblogic interview Questions
1.how can achive high availbulity
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2. load balancer
1. Cluster
cluster means group of members to appear to cllint to be one.
why we use cluster
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1.load balancing : load must be balanced among the cluster , we use round rabin algoritham
2.High avavibulity : at a given point of time i have a member to server your request.
3.failover : if one member in the cluster is not responding , then request move to another member
4.scalability : adding or removing member in cluster
Types of cluster
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1.vertical : member of cluster resides in same machine
2.Harizontal : member of cluster resides in more than one machine
modes of communication
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1.we have 2 types of communication
2.communication do via heartbeats
3.heartbeat throshed value : 3 sec
1. unicast --> one to one
2.multicast --> one to many
oracle recomends alwayes unicast.
What is the difference between unicast and multicast messaging modes in cluste
Say you have three servers (MS-1,MS-2,MS-3) in a cluster. If they have to communicate with each other, then they have to ping (i.e. heartbeats ) the cluster master for informing it that they are alive. If MS-1 is the master then MS-2 and MS-3 would send the ping to MS-1
Multicast:
In Multicast, there is no cluster master. Instead each server has to ping each other to inform everyone that they are alive. So MS-1 would send the ping to MS-2 & MS-3 and at the same time MS-2 would send the ping to MS-1 & MS-3 and MS-3 would ping MS-1 & MS-3. Thus, in multicast there are more pings sent which makes the congestion in sending the pings much heavier compared to unicast. Because of this, WLS recommends using Unicast instead for less congestion in the network
Dynamic cluster
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1. when the load increases on a node/cluster , it will automatically create new managed server there.
2. max no of managed servers supported per cluster is 8
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