Hi All, As mentioned, an extensible point "org.wso2.broker.coordination.HaStrategy" has been introduced, which can be implemented to provide variations upon which HA support will be based.
Any new/custom implementation would have to notify the listeners listening on node state changes (when a node state changes from active to passive or passive to active). Currently the modules listening on state changes are as follows: - broker-core - broker-transport - broker-rest-runner All nodes will start up in "passive" mode, and only change state to "active" on notification by the HA strategy. This requires that the listeners are registered prior to starting the HA strategy (identification of the active node). *Default RDBMS Coordinator Election based HA Strategy * With the default HA strategy (RdbmsHaStrategy - implemented based on the RDBMS based coordinator election approach [1]), the possible coordination node states are mapped to active/passive as follows: - COORDINATOR - Active - CANDIDATE - Passive - ELECTION - Passive Thus notification of the HA listeners happens when: - election is triggered and the node was previously the coordinator node (active → passive) - election resulted in the node becoming the coordinator node (passive → active) [1] https://github.com/wso2/message-broker/pull/74 Feedback/suggestions would be highly appreciated. Thank you, Maryam On Fri, Jan 12, 2018 at 6:41 PM, Maryam Ziyad <[email protected]> wrote: > Hi Asanka, > > Renamed "haConfig" to "failover" based on the offline discussion. > > Thank you, > Maryam > > On Tue, Dec 19, 2017 at 7:05 PM, Asanka Abeyweera <[email protected]> > wrote: > >> Hi Maryam, >> >> Shall we rename the "haConfig" to "ha-clustering"? I'm not sure if we >> should use camel case in the yaml config. >> >> On Tue, Dec 19, 2017 at 4:42 PM, Maryam Ziyad <[email protected]> wrote: >> >>> Hi All, >>> >>> We are currently working on introducing $subject [1]. Please find below >>> a high level description of the approach. >>> >>> An extension point (HaStrategy) will be introduced, allowing >>> straightforward introduction of different implementations of identification >>> of the active node, where the only requirements would be that these >>> approaches extend the common class and invoke particular methods when the >>> node state changes. >>> >>> The broker-core and broker-transport (broker-amqp) modules would >>> introduce listeners to receive notifications of node states changes >>> (active/passive), and change behaviour accordingly. >>> >>> >>> >>> >>> *Configuration* >>> >>> The HA related configuration would be specified in the broker.yaml file >>> including whether HA is enabled and the HA strategy to use. >>> >>> haConfig: >>> enabled: true >>> strategy: org.wso2.broker.coordination.rdbms.RdbmsHaStrategy >>> >>> >>> The basic/initial HA strategy implementation will be the >>> RdbmsHaStrategy based on the RDBMS based coordinator election approach >>> previously introduced for MB 3.2.0. [2, 3]. If HA enabled is set to true >>> but no strategy is specified, the RdbmsHaStrategy will be used. >>> >>> >>> *RDBMS Coordinator Election based HA Strategy (RdbmsHaStrategy)* >>> >>> The RDBMS based coordinator election algorithm would be extended to >>> provide HA support, by specifying the node elected as coordinator to always >>> be the active node, while the other node(s) will be considered passive. The >>> RDBMS coordinator election based approach, which would also be the default >>> HA strategy, would require the nodes in the HA group to share the same >>> database. All MB nodes pointing to this shared database will be considered >>> as MBs belonging to the same group, and at any given point only one of the >>> nodes will be considered active. >>> >>> Feedback on the approach would be highly appreciated. >>> >>> [1] https://github.com/wso2/message- >>> <https://github.com/wso2/message-broker/issues/87>*when*broker/issues/87 >>> <https://github.com/wso2/message-broker/issues/87> >>> [2] Mail: "[Architecture] RDBMS based coordinator election algorithm for >>> MB" >>> [3] https://github.com/wso2/andes/pullwhen/668 >>> <https://github.com/wso2/andes/pull/668> >>> >>> Thank you, >>> Maryam >>> >>> -- >>> *Maryam Ziyad Mohamed* >>> Software Engineer | WSO2 >>> [image: http://wso2.com/signature] <http://wso2.com/signature> >>> >>> _______________________________________________ >>> Architecture mailing list >>> [email protected] >>> https://mail.wso2.org/cgi-bin/mailman/listinfo/architecture >>> >>> >> >> >> -- >> Asanka Abeyweera >> Associate Technical Lead >> WSO2 Inc. >> >> Phone: +94 712228648 <+94%2071%20222%208648> >> Blog: a5anka.github.io >> >> <https://wso2.com/signature> >> >> _______________________________________________ >> Architecture mailing list >> [email protected] >> https://mail.wso2.org/cgi-bin/mailman/listinfo/architecture >> >> > > > -- > *Maryam Ziyad Mohamed* > Software Engineer | WSO2 > [image: http://wso2.com/signature] <http://wso2.com/signature> > -- *Maryam Ziyad Mohamed* Software Engineer | WSO2 [image: http://wso2.com/signature] <http://wso2.com/signature>
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