{"id":3333,"date":"2011-10-28T12:53:15","date_gmt":"2011-10-28T17:53:15","guid":{"rendered":"http:\/\/jianmingli.com\/wp\/?p=3333"},"modified":"2011-10-28T12:53:15","modified_gmt":"2011-10-28T17:53:15","slug":"weblogic-11g-clustering-failover-and-replication-in-a-cluster","status":"publish","type":"post","link":"https:\/\/jianmingli.com\/wp\/?p=3333","title":{"rendered":"WebLogic 11g Clustering: Failover and Replication in a Cluster"},"content":{"rendered":"

How WebLogic Server Detects Server Failures<\/h2><\/span>\n

* By monitoring IP sockets between peer server instances.
\n– Unexpected IP socket closure marks server as “failed”.
\n* By monitoring server heartbeats.
\n– Each server instance broadcasts heartbeat messages to other members in the cluster.
\n– Heartbeat interval defaults to 10 second.
\n– Three missed heartbeats marked the server as “failed”.<\/p>\n

Replication and Failover for Servlets and JSPs<\/h2><\/span>\n

* Via hardware load balancers.
\n* Via proxy plug-ins.<\/p>\n

HTTP Session State Replication Mechanisms<\/h3><\/span>\n

* In-memory replication:
\n– Session state is copies from one server instance to another.
\n– Primary server creates primary session state.
\n– A session state replica is copied to another server instance in the cluster.
\n– Replica is kept up-to-date so that it can be used in case of primary server failure.
\n– Requires web applications be deployed homogeneously on all nodes in a cluster.
\n* File-based or JDBC-based persistence:
\n– JDBC-based persistence is used for HTTP session state replication within a WAN.
\n* Coherence Web
\n– Not a replace ment for in-memory state replication.
\n– Use
\n~ when an application has large HTTP session state objects.
\n~ when running into memory constraints due to storing HTTP session object data.
\n~ have an existing Coherence cluster available and want to off-load HTTP session state to it.<\/p>\n

Programming Considerations for Clustered Servlets and JSPs<\/h2><\/span>\n

* Session data must be serializable.
\n* Use setAttribute()<\/em> and removeAttribute()<\/em> to change session state.
\n* Consider serialization overhead.
\n* Control frame access to session data.
\n– In a given frameset, ensure that only one frame creates and modifies session data.
\n– Always create the session in a frame of the first frameset your application uses.
\n– Access the session data only in framesets other than the first frameset.<\/p>\n

Using Replication Groups<\/h2><\/span>\n

* A replication group is a preferred list of clustered servers to be used for storing session state replicas<\/em>.
\n* Ranking server instances for session replication<\/p>\n

\r\nRank    Is a member of preferred rep grp    Resides on same different machine\r\n1         yes                                              yes\r\n2         yes                                              no\r\n3         no                                               yes\r\n4         no                                               no\r\n<\/pre>\n
Accessing Clustered Servlets and JSPs Using a Proxy<\/h2><\/span>\n
* Use cookie if allowed.
\n* Use URL rewriting if cookie not allowed.
\n– Enable by setting url-rewriting-enabled parameter to true <\/strong>in weblogic.xml. This is default <\/em>behavior.<\/p>\n
Accessing Clustered Servlets and JSPs with Load Balancing Hardware<\/h2><\/span>\n
* Clients do not use the cookie information to actively locate a server after a failure. Load balancer does it for them.
\n– Client side cookies or URL rewriting is recorded for history use only.<\/p>\n
Session State Replication Across Clusters in a MAN\/WAN<\/h2><\/span>\n
\"\"<\/a><\/h4><\/span>\n
Network Requirements for Cross-cluster Replication<\/h3><\/span>\n
* Must include global and local hardware load balancers.
\n– Global load balancer: responsible for cluster level load balancing and cluster affinity.
\n– Local load balancer: responsible for load balancing and server affinity within a cluster.<\/p>\n
Configuration Requirements for Cross-Cluster Replication<\/h3><\/span>\n
* A replication channel must be configured to communicate session state information from the primary to the secondary cluster.
\n– replication channel is created on all cluster members and has the same name
\n* Cross-cluster replication requires that each cluster be assigned to a different domain.
\n* Each domain should be set up and configured identically:
\n– domain configuration
\n– cluster and server configuration
\n– number of servers in clusters
\n– Application deployment
\n* Must enable trust between both domains.
\n* for WAN cross-cluster replication, must create a data source to maintain session state.<\/p>\n
Replication and Failover for EJBs and RMIs<\/h2><\/span>\n
* Failover is accomplished using the object’s replica-aware stub.<\/p>\n
Failover and JDBC Connections<\/h2><\/span>\n
* Failover of JDBC connections are not supported.
\n– server dies, then all JDBC connections also die.
\n* Use multi data source.<\/p>\n
References<\/h2><\/span>\n
* Application Failover and Replication in a Cluster<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
How WebLogic Server Detects Server Failures * By monitoring IP sockets between peer server instances. – Unexpected IP socket closure marks server as “failed”. * By monitoring server heartbeats. – Each server instance broadcasts heartbeat messages to other members in … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[104],"tags":[],"class_list":["post-3333","post","type-post","status-publish","format-standard","hentry","category-weblogic11g"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p8cRUO-RL","_links":{"self":[{"href":"https:\/\/jianmingli.com\/wp\/index.php?rest_route=\/wp\/v2\/posts\/3333","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jianmingli.com\/wp\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/jianmingli.com\/wp\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/jianmingli.com\/wp\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/jianmingli.com\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3333"}],"version-history":[{"count":5,"href":"https:\/\/jianmingli.com\/wp\/index.php?rest_route=\/wp\/v2\/posts\/3333\/revisions"}],"predecessor-version":[{"id":3676,"href":"https:\/\/jianmingli.com\/wp\/index.php?rest_route=\/wp\/v2\/posts\/3333\/revisions\/3676"}],"wp:attachment":[{"href":"https:\/\/jianmingli.com\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3333"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/jianmingli.com\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3333"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/jianmingli.com\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3333"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}