Hi All,
BPEL processes in ode are executed by first writing the process initiating
message to the database and running a job (a separate thread ) against it
which will try to execute the process definition against the message and
current process state. Ode job scheduler is what does the loading of jobs
from the job table for execution.Usually, all the jobs scheduled from a
given BPS node is loaded and executed by that node itself. However, in case
of a long running process, where there can be waiting activities or timer
jobs, there will be jobs that are not loaded immediately. These jobs
are scheduled against a node id identifying the running ode instance. In
our current cluster implementation, if a node goes down, these jobs will
remain there until the node is restarted. In order to solve this problem
,we though of using the hazel-cast cluster which is already available and
used.
Ode scheduler has a heartbeat method, which should be called in the cluster
implementation periodically by each node in order to tell the scheduler
that each node is alive. A separate task is executed to monitor the
availability/staleness of the nodes periodically by maintaining a list of
known nodes and nodes that have not updated the heartbeat.
Job redistribution has two problems.
1. If all the nodes in the cluster try to redistribute the jobs of a stale
node, there will be dead locks since these are db operations. Hence we need
to elect a node in the cluster which will do the job redistribution.
In hazelcast, we can select the leader by obtaining the oldest member
of the cluster and treating it as the leader.
2. We need a way to implement the heartbeat method.
Initially we though of using the membership listeners available from carbon
clustering. However, it seems when nodes are added/removed, all nodes does
not get notified. Hence we though of using the periodic task running in the
scheduler to do the member availability check and update the heartbeat
using the hazel-cast cluster.
@Hasitha - Please add anything i missed.
Regards
Nandika
--
Nandika Jayawardana
Senior Technical Lead
WSO2 Inc ; http://wso2.com
lean.enterprise.middleware
_______________________________________________
Dev mailing list
[email protected]
http://wso2.org/cgi-bin/mailman/listinfo/dev
