java ee - How does weblogic clustering work? -

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i'm new weblogic.

i've read http://download.oracle.com/docs/cd/e11035_01/wls100/cluster/overview.html , searched topic on internet still had hard time understanding of weblogic's clustering concepts.

can confirm/correct understandings below?

  • a cluster contains 1 or more logical servers can reside on 1 or many physical servers
  • when deploying j2ee app cluster, tied 1 server in cluster
  • external users of deployed app aren't aware of clustering
  • the log file of app located on server it's deployed
  • if server hosting app fails, it's okay because app in cluster , server pick work?
  • if server hosting app fails, happens logging?

maybe got whole concept wrong. point me correct directions?

thanks much.

i think should understand concept of domain first.

the domain parent of cluster. contains typically 1 admin , 1 or more managed servers. cluster grouping of or of these managed servers within domain.

hope diagram here helps understanding.

once configure domain , cluster on development environment, you'll know more it.

now here answers specific questions

•a cluster contains 1 or more logical servers can reside on 1 or many physical servers

true. let's clarify mean 'logical' servers. in cluster typically have 2 or more managed servers. these servers run in own jvms , can started independently , serve requests independently. each server have unique ip:port address, , can directly accessed browser. these server instances can reside on multiple physical servers.

•when deploying j2ee app cluster, tied 1 server in cluster

no not tied 1 server. when deploy j2ee app cluster, deployed in turn each server in cluster. jndi cluster-wide , each server maintains local copy of jndi.

you can object (say ejb) via jndi on cluster or on individual server. see what types of objects can clustered.

•external users of deployed app aren't aware of clustering

true.

but in case should have apache web server or load balancer or dns server takes request browser, , internally maps 1 of servers in cluster. if dont have of these, have define cluster address dns name or ip address client. see section "avoiding listen address problems " on http://download.oracle.com/docs/cd/e13222_01/wls/docs103/cluster/setup.html#wp682940

•the log file of app located on server it's deployed

true, 1 weblogic log per server.

•if server hosting app fails, it's okay because app in cluster , server pick work?

not default, have configure failover , replication. a huge topic needs separate reading

•if server hosting app fails, happens logging?

logging stops. you'll see shutdown or heartbeat errors in log, or outofmemory or whatever reason failure. you'll have restart server - , logging continues in new file (depending on logging settings)


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