Hi Ramith, Sure. Actually, I was talking with SameeraR to take over this and create a common component which has the required coordination functionality. The idea is to create a component, where the providers can be plugged in, such as the RDBMS based one, ZK, or any other container specific provider that maybe out there.
Cheers, Anjana. On Mon, Nov 7, 2016 at 12:38 PM, Ramith Jayasinghe <ram...@wso2.com> wrote: > this might require some work.. shall we have a chat? > > On Thu, Nov 3, 2016 at 3:52 PM, Anjana Fernando <anj...@wso2.com> wrote: > >> Ping! .. >> >> On Wed, Nov 2, 2016 at 5:03 PM, Anjana Fernando <anj...@wso2.com> wrote: >> >>> Hi, >>> >>> On Wed, Nov 2, 2016 at 3:14 PM, Asanka Abeyweera <asank...@wso2.com> >>> wrote: >>> >>>> Hi Anjana, >>>> >>>> Currently, the implementation is part of the MB code (not a common >>>> component). >>>> >>> >>> Okay, can we please get it as a common component. >>> >>> Cheers, >>> Anjana. >>> >>> >>>> >>>> On Wed, Nov 2, 2016 at 3:00 PM, Anjana Fernando <anj...@wso2.com> >>>> wrote: >>>> >>>>> Hi Asanka/Ramith, >>>>> >>>>> So for C5 based Streaming Analytics solution, we need coordination >>>>> functionality there as well. Is the functionality mentioned here created >>>>> as >>>>> a common component or baked in to the MB code? .. if so, can we please get >>>>> it implemented it as a generic component, so other products can also use >>>>> it. >>>>> >>>>> Cheers, >>>>> Anjana. >>>>> >>>>> On Tue, Aug 9, 2016 at 3:10 PM, Anjana Fernando <anj...@wso2.com> >>>>> wrote: >>>>> >>>>>> Great! .. >>>>>> >>>>>> Cheers, >>>>>> Anjana. >>>>>> >>>>>> On Tue, Aug 9, 2016 at 1:49 PM, Asanka Abeyweera <asank...@wso2.com> >>>>>> wrote: >>>>>> >>>>>>> Hi Anjana, >>>>>>> >>>>>>> Thank you for the suggestion. We have already done a similar thing. >>>>>>> We have added a backoff time after creating the leader entry and check >>>>>>> if >>>>>>> the leader entry is the entry created by self before informing the >>>>>>> leader >>>>>>> change. >>>>>>> >>>>>>> On Tue, Aug 9, 2016 at 12:27 PM, Anjana Fernando <anj...@wso2.com> >>>>>>> wrote: >>>>>>> >>>>>>>> I see, thanks for the clarification, looks good! .. I think small >>>>>>>> thing to consider is, to avoid the situation where, the current leader >>>>>>>> goes >>>>>>>> away, and two other competes to become the leader, and the first one >>>>>>>> and >>>>>>>> the second one checks (reads) the table to check the last heartbeat and >>>>>>>> figures out that the leader is outdated at the same time, and then >>>>>>>> first >>>>>>>> one delete the entry and puts his one, and after that, second one will >>>>>>>> also >>>>>>>> delete the existing one and put his one, so both will think they >>>>>>>> became the >>>>>>>> leader, due to the condition that both succeeded in adding the entry >>>>>>>> without an error. So this can probably be fixed by checking back after >>>>>>>> a >>>>>>>> bit of time if the current node is actually me, which probabilistically >>>>>>>> will work well, if that time period is sufficient big enough than a >>>>>>>> typical >>>>>>>> database transaction required by a node to do the earlier operations. >>>>>>>> Or >>>>>>>> else, we should make sure the database transaction level used in this >>>>>>>> scenario is at least REPEATABLE_READ, where when we read the record, it >>>>>>>> will lock it throughout the transaction. So some DBMSs does not support >>>>>>>> REPEATABLE_READ, where in that case, we should be able to use >>>>>>>> SERIALIZABLE, >>>>>>>> which most of them support. >>>>>>>> >>>>>>>> Cheers, >>>>>>>> Anjana. >>>>>>>> >>>>>>>> On Tue, Aug 9, 2016 at 11:11 AM, Maninda Edirisooriya < >>>>>>>> mani...@wso2.com> wrote: >>>>>>>> >>>>>>>>> Hi Anjana, >>>>>>>>> >>>>>>>>> After having an offline chat with Asanka what I understood was >>>>>>>>> that the leader election was done completely via the database but >>>>>>>>> with no >>>>>>>>> network communication. The leader is mentioned in the database first. >>>>>>>>> Then >>>>>>>>> the leader updates the node data periodically in the database. If >>>>>>>>> some node >>>>>>>>> realizes the data in the DB are outdated that means the leader was >>>>>>>>> disconnected. Then that node will look at the created timestamp of the >>>>>>>>> leader entry. If that is not very recent that means there was no new >>>>>>>>> leader >>>>>>>>> elected recently. So he will try to update the leader entry with his >>>>>>>>> ID. As >>>>>>>>> I understand there the leader entry is using the leader ID and the >>>>>>>>> timestamp as the primary key. Even several nodes try to do it >>>>>>>>> simultaneously only one node will successfully be able to update the >>>>>>>>> entry >>>>>>>>> with the help of atomicity provided by the DB. Others members will >>>>>>>>> note the >>>>>>>>> timestamp of the leader was updated so will accept the first one who >>>>>>>>> updates as the leader. Even after the leader is elected, the leader >>>>>>>>> will >>>>>>>>> only notify node data via updating DB instead of network calls. Other >>>>>>>>> nodes >>>>>>>>> will just observe it and check the latest timestmps of the entry. >>>>>>>>> >>>>>>>>> >>>>>>>>> *Maninda Edirisooriya* >>>>>>>>> Senior Software Engineer >>>>>>>>> >>>>>>>>> *WSO2, Inc.*lean.enterprise.middleware. >>>>>>>>> >>>>>>>>> *Blog* : http://maninda.blogspot.com/ >>>>>>>>> *E-mail* : mani...@wso2.com >>>>>>>>> *Skype* : @manindae >>>>>>>>> *Twitter* : @maninda >>>>>>>>> >>>>>>>>> On Tue, Aug 9, 2016 at 10:13 AM, Anjana Fernando <anj...@wso2.com> >>>>>>>>> wrote: >>>>>>>>> >>>>>>>>>> Hi, >>>>>>>>>> >>>>>>>>>> I just noticed this thread. I've some concerns on this >>>>>>>>>> implementations. First of all, I don't think the statement mentioned >>>>>>>>>> here >>>>>>>>>> saying an external service such as ZooKeeper doesn't work, is >>>>>>>>>> correct. >>>>>>>>>> Because, if you have a ZK cluster (it is suppose to be used as a >>>>>>>>>> cluster), >>>>>>>>>> you will not have any issues. All the nodes have a list of endpoints >>>>>>>>>> to all >>>>>>>>>> the ZK nodes and they connect to those, and ZK has a quorum based >>>>>>>>>> mechanism >>>>>>>>>> in keeping its state. So this makes sure, all the users have a single >>>>>>>>>> version of the ZK data. >>>>>>>>>> >>>>>>>>>> Also, I guess the fundamental problem here in the split brain >>>>>>>>>> situation is, we need one external entity taking the decision (e.g. >>>>>>>>>> ZK >>>>>>>>>> cluster), because it should have oversight to the whole environment. >>>>>>>>>> I >>>>>>>>>> don't see how this RDBMS mechanism would solve that. Because, what >>>>>>>>>> it gives >>>>>>>>>> is a central location of state persistence. But the decisions of >>>>>>>>>> making who >>>>>>>>>> is the leader is taken by the users, which can be problematic. Where >>>>>>>>>> when >>>>>>>>>> we have a network partition scenario in that occasion, two groups of >>>>>>>>>> users >>>>>>>>>> will be overriding each other in the centralized RDBMS data >>>>>>>>>> repeatedly and >>>>>>>>>> it will go on forever, where in the ZK situation, there will be only >>>>>>>>>> one >>>>>>>>>> leader, and the guys in the other partition simply won't be able to >>>>>>>>>> reach >>>>>>>>>> the leader, until its network issues are sorted. >>>>>>>>>> >>>>>>>>>> So I also think, as Imesh mentioned, creating a coordination >>>>>>>>>> algorithm from scratch may not be a wise decision, and we should use >>>>>>>>>> proven >>>>>>>>>> technology/libraries to do that. And on a side note, the main reason >>>>>>>>>> for >>>>>>>>>> not using ZK for this earlier was because of the hassle of bringing >>>>>>>>>> up >>>>>>>>>> another set of servers when our products are clustered, and we knew >>>>>>>>>> that >>>>>>>>>> the split brain scenario will occur in HZ, but maybe now we should >>>>>>>>>> give an >>>>>>>>>> extension point probably to plug into an external service if for some >>>>>>>>>> applications the split brain scenario is a show stopper. >>>>>>>>>> >>>>>>>>>> Cheers, >>>>>>>>>> Anjana. >>>>>>>>>> >>>>>>>>>> On Tue, Aug 9, 2016 at 4:45 AM, Kasun Indrasiri <ka...@wso2.com> >>>>>>>>>> wrote: >>>>>>>>>> >>>>>>>>>>> Hi Ramith/Asanka, >>>>>>>>>>> >>>>>>>>>>> ESB/DSS natask impl is also based on HZ. I guess if this model >>>>>>>>>>> works for the MB, we should make it generic for all such >>>>>>>>>>> coordination >>>>>>>>>>> requirements. (Thinking about using this in ESB 5.1)? >>>>>>>>>>> >>>>>>>>>>> On Fri, Aug 5, 2016 at 3:58 AM, Sajini De Silva <saj...@wso2.com >>>>>>>>>>> > wrote: >>>>>>>>>>> >>>>>>>>>>>> Hi Maninda, >>>>>>>>>>>> >>>>>>>>>>>> Locking the database will be supported by some databases but >>>>>>>>>>>> there will be huge performance impact. So we cannot use that >>>>>>>>>>>> approach. If >>>>>>>>>>>> this approach cannot be adapted the only thing we can do is queue >>>>>>>>>>>> wise >>>>>>>>>>>> load balancing through slot coordinator. But in this case we cannot >>>>>>>>>>>> guarantee that load balance will be equally distributed since some >>>>>>>>>>>> queues >>>>>>>>>>>> can be loaded while some will be idle. Also we cannot have >>>>>>>>>>>> multiple slot >>>>>>>>>>>> coordinators having same queue as it may cause several >>>>>>>>>>>> complications such >>>>>>>>>>>> as, same slot is assigned to two nodes by different subscribers, >>>>>>>>>>>> message >>>>>>>>>>>> duplication etc. Actually this slot architecture was discussed in a >>>>>>>>>>>> separate mail thread before it is implemented. >>>>>>>>>>>> >>>>>>>>>>>> Thanks >>>>>>>>>>>> >>>>>>>>>>>> On Fri, Aug 5, 2016 at 3:12 PM, Maninda Edirisooriya < >>>>>>>>>>>> mani...@wso2.com> wrote: >>>>>>>>>>>> >>>>>>>>>>>>> Hi Sajini, >>>>>>>>>>>>> >>>>>>>>>>>>> Yes that is what I meant. As the number of slots are >>>>>>>>>>>>> proportional to the number of messages passing through the >>>>>>>>>>>>> cluster, slot >>>>>>>>>>>>> delivery should not be handled by the coordinator when there is >>>>>>>>>>>>> only one >>>>>>>>>>>>> coordinator in the cluster which is a bottleneck for scaling >>>>>>>>>>>>> messages >>>>>>>>>>>>> passing through the cluster. If there is only a single >>>>>>>>>>>>> coordinator, it >>>>>>>>>>>>> should handle operations that are not proportional to messages >>>>>>>>>>>>> throughput >>>>>>>>>>>>> of the cluster. Then only the tasks like subscriber adding / >>>>>>>>>>>>> removing >>>>>>>>>>>>> should be handled by the coordinator. As this is not the current >>>>>>>>>>>>> implementation, we can consider multiple coordinator approach. >>>>>>>>>>>>> Then the >>>>>>>>>>>>> number of coordinators should be scalable with the message >>>>>>>>>>>>> throughout. I am >>>>>>>>>>>>> not sure whether locking the database per transaction would >>>>>>>>>>>>> achieve this >>>>>>>>>>>>> coordinator scalability in the multiple coordinator >>>>>>>>>>>>> implementation. >>>>>>>>>>>>> >>>>>>>>>>>>> Thanks. >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> *Maninda Edirisooriya* >>>>>>>>>>>>> Senior Software Engineer >>>>>>>>>>>>> >>>>>>>>>>>>> *WSO2, Inc.*lean.enterprise.middleware. >>>>>>>>>>>>> >>>>>>>>>>>>> *Blog* : http://maninda.blogspot.com/ >>>>>>>>>>>>> *E-mail* : mani...@wso2.com >>>>>>>>>>>>> *Skype* : @manindae >>>>>>>>>>>>> *Twitter* : @maninda >>>>>>>>>>>>> >>>>>>>>>>>>> On Fri, Aug 5, 2016 at 2:42 PM, Sajini De Silva < >>>>>>>>>>>>> saj...@wso2.com> wrote: >>>>>>>>>>>>> >>>>>>>>>>>>>> Hi Maninda, >>>>>>>>>>>>>> >>>>>>>>>>>>>> On Fri, Aug 5, 2016 at 2:28 PM, Maninda Edirisooriya < >>>>>>>>>>>>>> mani...@wso2.com> wrote: >>>>>>>>>>>>>> >>>>>>>>>>>>>>> @Sajini, >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> But the number of slots are proportional to the number of >>>>>>>>>>>>>>> messages pass through the MB which needs to be handled by the >>>>>>>>>>>>>>> coordinator. >>>>>>>>>>>>>>> That is what I meant by "information related to meta data of >>>>>>>>>>>>>>> messages pass >>>>>>>>>>>>>>> through a single coordinator". Ideally after the senders and >>>>>>>>>>>>>>> receivers are >>>>>>>>>>>>>>> subscribed to the cluster, coordinator should have nothing to >>>>>>>>>>>>>>> do until they >>>>>>>>>>>>>>> are removed or changed. >>>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> Even though it is possible to have multiple coordinators >>>>>>>>>>>>>> after having en effort (Lock the database for a whole >>>>>>>>>>>>>> transaction or the >>>>>>>>>>>>>> work load distribution as described by Ramith) , coordinator may >>>>>>>>>>>>>> have >>>>>>>>>>>>>> different work to do other than subscriber adding and removing. >>>>>>>>>>>>>> As I said >>>>>>>>>>>>>> earlier our MB message distribution system is based on slot >>>>>>>>>>>>>> architecture >>>>>>>>>>>>>> and slots will managed by the coordinator. You can read [1] to >>>>>>>>>>>>>> understand >>>>>>>>>>>>>> more about slot architecture in MB. >>>>>>>>>>>>>> >>>>>>>>>>>>>> [1] http://sajinid.blogspot.com/2015/03/wso2-message-broker- >>>>>>>>>>>>>> 300-slot-based.html >>>>>>>>>>>>>> >>>>>>>>>>>>>> Thanks >>>>>>>>>>>>>> >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> @Ramith, >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> +1 for multiple coordinators by partitioning the cluster >>>>>>>>>>>>>>> which maintains the simplicity and correctness of the algorithm >>>>>>>>>>>>>>> than >>>>>>>>>>>>>>> compromising simplicity with a less important factor like >>>>>>>>>>>>>>> "delivering a >>>>>>>>>>>>>>> good mix of messages". >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Thanks. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> *Maninda Edirisooriya* >>>>>>>>>>>>>>> Senior Software Engineer >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> *WSO2, Inc.*lean.enterprise.middleware. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> *Blog* : http://maninda.blogspot.com/ >>>>>>>>>>>>>>> *E-mail* : mani...@wso2.com >>>>>>>>>>>>>>> *Skype* : @manindae >>>>>>>>>>>>>>> *Twitter* : @maninda >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> On Fri, Aug 5, 2016 at 2:05 PM, Ramith Jayasinghe < >>>>>>>>>>>>>>> ram...@wso2.com> wrote: >>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> @Imesh, >>>>>>>>>>>>>>>> We can prove that doing leader election using a lib (where >>>>>>>>>>>>>>>> we maintain cluster state in another place, a.k.a DB) will not >>>>>>>>>>>>>>>> solve our >>>>>>>>>>>>>>>> original problem (this also relates to our past experience >>>>>>>>>>>>>>>> with both the >>>>>>>>>>>>>>>> zookeeper and hazelcast). >>>>>>>>>>>>>>>> We can make this implementation a common component if >>>>>>>>>>>>>>>> other products have a use of it. BPS might be able to use it >>>>>>>>>>>>>>>> since their >>>>>>>>>>>>>>>> data is also in the database. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> @Malaka: >>>>>>>>>>>>>>>> VFS scenario can't be solved by relying on this >>>>>>>>>>>>>>>> implementation. why? you can have the access to DB but not VFS >>>>>>>>>>>>>>>> resources/file (and vice versa). this is the same point we >>>>>>>>>>>>>>>> explained before. >>>>>>>>>>>>>>>> in Ntask implementation, if tasks are stored in the >>>>>>>>>>>>>>>> database then using this implementation makes sense. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> @Akila, >>>>>>>>>>>>>>>> implementing (distributed) a queue algorithm is >>>>>>>>>>>>>>>> non-trivial. Having one coordinator (single source of truth) >>>>>>>>>>>>>>>> keeps things >>>>>>>>>>>>>>>> simple hence it's a conscious design decision we agreed during >>>>>>>>>>>>>>>> the initial >>>>>>>>>>>>>>>> stages. However, possible extension to this scheme is to have >>>>>>>>>>>>>>>> multiple >>>>>>>>>>>>>>>> coordinators ( each responsible for coordinating a subset of >>>>>>>>>>>>>>>> queues in the >>>>>>>>>>>>>>>> cluster), that will be some what similar to kafka. >>>>>>>>>>>>>>>> Even if its preferable to have no coordinator at-all, (to >>>>>>>>>>>>>>>> decide how messages are disseminated in the cluster) that >>>>>>>>>>>>>>>> will make us >>>>>>>>>>>>>>>> give up desired behaviour such as delivering a good mix of >>>>>>>>>>>>>>>> messages (from >>>>>>>>>>>>>>>> different publishers) to consumers in a cluster. having said >>>>>>>>>>>>>>>> this, we have >>>>>>>>>>>>>>>> an ongoing research on how to improve the algorithm and we >>>>>>>>>>>>>>>> like to try out >>>>>>>>>>>>>>>> both these approaches. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> On Fri, Aug 5, 2016 at 1:31 PM, Malaka Silva < >>>>>>>>>>>>>>>> mal...@wso2.com> wrote: >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> The same issue with Hazelcast can be experienced with ESB >>>>>>>>>>>>>>>>> inbounds (running on top of NTASK) and VFS distribution locks. >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> The idea of only single worker works at a given time >>>>>>>>>>>>>>>>> breaks if there is a Hazelcast heart beat fails. This will >>>>>>>>>>>>>>>>> make two workers >>>>>>>>>>>>>>>>> to work in parallel. >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> Also with distributed locking there is no guarantee that >>>>>>>>>>>>>>>>> file is only process only by one worker. >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> So in the case of network fail >>>>>>>>>>>>>>>>> with DB >>>>>>>>>>>>>>>>> make sense to stop processing until it's recovered. >>>>>>>>>>>>>>>>> Also making this component generic ESB can reuse. >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> On Fri, Aug 5, 2016 at 9:21 AM, Asitha Nanayakkara < >>>>>>>>>>>>>>>>> asi...@wso2.com> wrote: >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> Hi Imesh, >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> On Fri, Aug 5, 2016 at 7:33 AM, Imesh Gunaratne < >>>>>>>>>>>>>>>>>> im...@wso2.com> wrote: >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> On Fri, Aug 5, 2016 at 7:31 AM, Imesh Gunaratne < >>>>>>>>>>>>>>>>>>> im...@wso2.com> wrote: >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>> You can see here [3] how K8S has implemented leader >>>>>>>>>>>>>>>>>>>> election feature for the products deployed on top of that >>>>>>>>>>>>>>>>>>>> to utilize. >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> Correction: Please refer [4]. >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>> On Thu, Aug 4, 2016 at 7:27 PM, Asanka Abeyweera < >>>>>>>>>>>>>>>>>>>>> asank...@wso2.com> wrote: >>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>> Hi Imesh, >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>> We are not implementing this to overcome a limitation >>>>>>>>>>>>>>>>>>>>>> in the coordination algorithm available in the >>>>>>>>>>>>>>>>>>>>>> Hazlecast. We are >>>>>>>>>>>>>>>>>>>>>> implementing this since we need an RDBMS based >>>>>>>>>>>>>>>>>>>>>> coordination algorithm (not >>>>>>>>>>>>>>>>>>>>>> a network based algorithm). >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>> Are you saying that database connections do not use >>>>>>>>>>>>>>>>>>>> the same network used by Hazelcast? >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>> The reason is, a network based election algorithm will >>>>>>>>>>>>>>>>>>>>>> always elect multiple leaders when the network is >>>>>>>>>>>>>>>>>>>>>> partitioned. But if we >>>>>>>>>>>>>>>>>>>>>> use a RDBMS based algorithm this will not happen. >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>> I do not think your argument is correct. If there is a >>>>>>>>>>>>>>>>>>>> problem with the network, it may apply to both Hazelcast >>>>>>>>>>>>>>>>>>>> based solution >>>>>>>>>>>>>>>>>>>> and database based solution. >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> Yes, if the same network interface is used network >>>>>>>>>>>>>>>>>> partion will cause all types of connections to be >>>>>>>>>>>>>>>>>> partitioned. But user can >>>>>>>>>>>>>>>>>> use multiple network interfaces for database, Hazelcast and >>>>>>>>>>>>>>>>>> thrift. >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> Following is the scenario we are trying to solve in MB. >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> In MB all the details related to messages, subscriptions, >>>>>>>>>>>>>>>>>> queues, topics etc are stored in database. And we operate >>>>>>>>>>>>>>>>>> depending on that >>>>>>>>>>>>>>>>>> information. If the MB node can't connect to the database >>>>>>>>>>>>>>>>>> that means the >>>>>>>>>>>>>>>>>> node is ineffective in the cluster until it can make a >>>>>>>>>>>>>>>>>> database connection. >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> We have seen instances where Hazelcast cluster get >>>>>>>>>>>>>>>>>> partitioned for some time period in networks, Reasons were, >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> 1. Due to heavy load Hazelcast couldn't process or >>>>>>>>>>>>>>>>>> send (some times both) hearbeats, hence a network >>>>>>>>>>>>>>>>>> partition for Hazelcast >>>>>>>>>>>>>>>>>> cluster >>>>>>>>>>>>>>>>>> 2. An actual network partition of Hazelcast cluster >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> In both scenarios the database connection was working. In >>>>>>>>>>>>>>>>>> that case we get two coordinators elected through Hazelcast >>>>>>>>>>>>>>>>>> and working on >>>>>>>>>>>>>>>>>> the same database to deliver the messages. this leads to >>>>>>>>>>>>>>>>>> inconsistencies in >>>>>>>>>>>>>>>>>> the cluster behavior (for instances duplicate message >>>>>>>>>>>>>>>>>> delivery, corrupred >>>>>>>>>>>>>>>>>> subscription states etc) . >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> Since the point of interest for MB is the database, we >>>>>>>>>>>>>>>>>> decided to do the coordinator election through database as >>>>>>>>>>>>>>>>>> well. If the >>>>>>>>>>>>>>>>>> node can't connect to the database, then the MB won't >>>>>>>>>>>>>>>>>> operate anyway. >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> Regards, >>>>>>>>>>>>>>>>>> Asitha >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>> [4] http://blog.kubernetes.io/ >>>>>>>>>>>>>>>>>>>> 2016/01/simple-leader-election-with-Kubernetes.html >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>> Thanks >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>> On Thu, Aug 4, 2016 at 7:16 PM, Imesh Gunaratne < >>>>>>>>>>>>>>>>>>>>>> im...@wso2.com> wrote: >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>> Hi Asanka, >>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>> Do we really need to implement a leader election >>>>>>>>>>>>>>>>>>>>>>> algorithm on our own? AFAIU this is a complex problem >>>>>>>>>>>>>>>>>>>>>>> which has been >>>>>>>>>>>>>>>>>>>>>>> already solved by several algorithms [1]. IMO it would >>>>>>>>>>>>>>>>>>>>>>> be better to go >>>>>>>>>>>>>>>>>>>>>>> ahead with an existing well established implementation >>>>>>>>>>>>>>>>>>>>>>> on etcd [1] or >>>>>>>>>>>>>>>>>>>>>>> Consul [2]. >>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>> Those provide HTTP APIs for clients to make leader >>>>>>>>>>>>>>>>>>>>>>> election calls. [3] is a client library written in >>>>>>>>>>>>>>>>>>>>>>> Node.js for etcd based >>>>>>>>>>>>>>>>>>>>>>> leader election. >>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>> [1] https://www.projectcalico. >>>>>>>>>>>>>>>>>>>>>>> org/using-etcd-for-elections >>>>>>>>>>>>>>>>>>>>>>> [2] https://www.consul.io/docs >>>>>>>>>>>>>>>>>>>>>>> /guides/leader-election.html >>>>>>>>>>>>>>>>>>>>>>> [3] https://www.npmjs.com/package/etcd-leader >>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>> Thanks >>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>> On Wed, Aug 3, 2016 at 5:12 PM, Asanka Abeyweera < >>>>>>>>>>>>>>>>>>>>>>> asank...@wso2.com> wrote: >>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>> Hi Maninda, >>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>> Since we are using RDBMS to poll the node status, >>>>>>>>>>>>>>>>>>>>>>>> the cluster will not end up in situation 1,2 or 3. >>>>>>>>>>>>>>>>>>>>>>>> With this approach we >>>>>>>>>>>>>>>>>>>>>>>> consider a node unreachable when it cannot access the >>>>>>>>>>>>>>>>>>>>>>>> database. Therefore >>>>>>>>>>>>>>>>>>>>>>>> an unreachable node can never be the leader. >>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>> As you have mentioned, we are currently using the >>>>>>>>>>>>>>>>>>>>>>>> RDBMS as an atomic global variable to create the >>>>>>>>>>>>>>>>>>>>>>>> coordinator entry. >>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>> On Tue, Aug 2, 2016 at 5:22 PM, Maninda >>>>>>>>>>>>>>>>>>>>>>>> Edirisooriya <mani...@wso2.com> wrote: >>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>> Hi Asanka, >>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>> As I understand the accuracy of electing the >>>>>>>>>>>>>>>>>>>>>>>>> leader correctly is dependent on the election >>>>>>>>>>>>>>>>>>>>>>>>> mechanism with RDBMS because >>>>>>>>>>>>>>>>>>>>>>>>> there can be edge cases like, >>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>> 1. Unreachable leader activates during the >>>>>>>>>>>>>>>>>>>>>>>>> election process: Then who becomes the leader? >>>>>>>>>>>>>>>>>>>>>>>>> 2. The elected leader becomes unreachable before >>>>>>>>>>>>>>>>>>>>>>>>> the election is completed: Then will there be a >>>>>>>>>>>>>>>>>>>>>>>>> situation where there is no >>>>>>>>>>>>>>>>>>>>>>>>> leader? >>>>>>>>>>>>>>>>>>>>>>>>> 3. A leader and a set of nodes are disconnected >>>>>>>>>>>>>>>>>>>>>>>>> from the other part of the cluster and while the >>>>>>>>>>>>>>>>>>>>>>>>> leader is trying to remove >>>>>>>>>>>>>>>>>>>>>>>>> unreachable members other part is calling an election >>>>>>>>>>>>>>>>>>>>>>>>> to make a leader: Who >>>>>>>>>>>>>>>>>>>>>>>>> will win? >>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>> RDBMS based election algorithm should handle such >>>>>>>>>>>>>>>>>>>>>>>>> cases without bringing the cluster to an inconsistent >>>>>>>>>>>>>>>>>>>>>>>>> state or dead lock in >>>>>>>>>>>>>>>>>>>>>>>>> all concurrent cases. If all these kind of cases >>>>>>>>>>>>>>>>>>>>>>>>> cannot be handled isn't it >>>>>>>>>>>>>>>>>>>>>>>>> better to keep the current hazelcast clustering and >>>>>>>>>>>>>>>>>>>>>>>>> use the RDBMS only to >>>>>>>>>>>>>>>>>>>>>>>>> handle the split brain scenario? In other words when >>>>>>>>>>>>>>>>>>>>>>>>> a new hazelcast leader >>>>>>>>>>>>>>>>>>>>>>>>> is elected it should be updated in the RDBMS. If >>>>>>>>>>>>>>>>>>>>>>>>> another split party has >>>>>>>>>>>>>>>>>>>>>>>>> already elected a leader, the node who is going to >>>>>>>>>>>>>>>>>>>>>>>>> write it to RDBMS should >>>>>>>>>>>>>>>>>>>>>>>>> avoid updating it. Simply, the RDBMS can be used as >>>>>>>>>>>>>>>>>>>>>>>>> an atomic global >>>>>>>>>>>>>>>>>>>>>>>>> variable to keep the leader name by modifying the >>>>>>>>>>>>>>>>>>>>>>>>> hazelcast clustering. >>>>>>>>>>>>>>>>>>>>>>>>> WDYT? >>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>> Thanks. >>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>> *Maninda Edirisooriya* >>>>>>>>>>>>>>>>>>>>>>>>> Senior Software Engineer >>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>> *WSO2, Inc.*lean.enterprise.middleware. >>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>> *Blog* : http://maninda.blogspot.com/ >>>>>>>>>>>>>>>>>>>>>>>>> *E-mail* : mani...@wso2.com >>>>>>>>>>>>>>>>>>>>>>>>> *Skype* : @manindae >>>>>>>>>>>>>>>>>>>>>>>>> *Twitter* : @maninda >>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>> On Thu, Jul 28, 2016 at 4:38 PM, Asanka Abeyweera >>>>>>>>>>>>>>>>>>>>>>>>> <asank...@wso2.com> wrote: >>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> Hi Akila, >>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> Let me explain the issue in a different way. >>>>>>>>>>>>>>>>>>>>>>>>>> Let's assume the MB nodes are using two different >>>>>>>>>>>>>>>>>>>>>>>>>> network interfaces for >>>>>>>>>>>>>>>>>>>>>>>>>> Hazelcast communication and database communication. >>>>>>>>>>>>>>>>>>>>>>>>>> With such a >>>>>>>>>>>>>>>>>>>>>>>>>> configuration, there can be failures only in the >>>>>>>>>>>>>>>>>>>>>>>>>> network interface used for >>>>>>>>>>>>>>>>>>>>>>>>>> Hazelcast communication in some nodes. When this >>>>>>>>>>>>>>>>>>>>>>>>>> happens, there will be two >>>>>>>>>>>>>>>>>>>>>>>>>> or more Hazelcast clusters due to the network >>>>>>>>>>>>>>>>>>>>>>>>>> segmentation, and as a result >>>>>>>>>>>>>>>>>>>>>>>>>> there will be multiple coordinators. Since every >>>>>>>>>>>>>>>>>>>>>>>>>> node still have access to >>>>>>>>>>>>>>>>>>>>>>>>>> the database, multiple coordinators can affect the >>>>>>>>>>>>>>>>>>>>>>>>>> correctness of the data >>>>>>>>>>>>>>>>>>>>>>>>>> stored in the DB. But if we used a RDBMS based >>>>>>>>>>>>>>>>>>>>>>>>>> approach we won't have >>>>>>>>>>>>>>>>>>>>>>>>>> multiple coordinators due to a network partition in >>>>>>>>>>>>>>>>>>>>>>>>>> Hazelcast. This is one >>>>>>>>>>>>>>>>>>>>>>>>>> advantage we get from this approach. >>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> Even when we use Zookeeper or RAFT the same issue >>>>>>>>>>>>>>>>>>>>>>>>>> will be there since we are using different >>>>>>>>>>>>>>>>>>>>>>>>>> interfaces for Hazelcast >>>>>>>>>>>>>>>>>>>>>>>>>> communication and DB communication. >>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> On Thu, Jul 28, 2016 at 2:56 PM, Akila Ravihansa >>>>>>>>>>>>>>>>>>>>>>>>>> Perera <raviha...@wso2.com> wrote: >>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>> Hi, >>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>> What's the advantage of using RDBMS (even as an >>>>>>>>>>>>>>>>>>>>>>>>>>> alternative) to implement a leader/coordinator >>>>>>>>>>>>>>>>>>>>>>>>>>> election? If the network >>>>>>>>>>>>>>>>>>>>>>>>>>> connection to DB fails then this will be a single >>>>>>>>>>>>>>>>>>>>>>>>>>> point of failure. I don't >>>>>>>>>>>>>>>>>>>>>>>>>>> think we can scale RDBMS instances and expect the >>>>>>>>>>>>>>>>>>>>>>>>>>> election algorithm to >>>>>>>>>>>>>>>>>>>>>>>>>>> work. That would be reducing this problem to >>>>>>>>>>>>>>>>>>>>>>>>>>> another problem (electing >>>>>>>>>>>>>>>>>>>>>>>>>>> coordinator RDBMS instance). >>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>> IMHO it would be better to look at Zookeeper >>>>>>>>>>>>>>>>>>>>>>>>>>> Atomic Broadcast (ZAB) [1] or RAFT leader election >>>>>>>>>>>>>>>>>>>>>>>>>>> [2] algorithms which >>>>>>>>>>>>>>>>>>>>>>>>>>> have already proven results. >>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>> [1] https://cwiki.apache.org/c >>>>>>>>>>>>>>>>>>>>>>>>>>> onfluence/display/ZOOKEEPER/Zab1.0 >>>>>>>>>>>>>>>>>>>>>>>>>>> [2] http://libraft.io/ >>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>> Thanks. >>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>> On Thu, Jul 28, 2016 at 1:42 PM, Nandika >>>>>>>>>>>>>>>>>>>>>>>>>>> Jayawardana <nand...@wso2.com> wrote: >>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>> +1 to make it a common component . We have the >>>>>>>>>>>>>>>>>>>>>>>>>>>> clustering implementation for BPEL component based >>>>>>>>>>>>>>>>>>>>>>>>>>>> on hazelcast. If the >>>>>>>>>>>>>>>>>>>>>>>>>>>> coordination is available at RDBMS level, we can >>>>>>>>>>>>>>>>>>>>>>>>>>>> remove hazelcast >>>>>>>>>>>>>>>>>>>>>>>>>>>> dependancy. >>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>> Regards >>>>>>>>>>>>>>>>>>>>>>>>>>>> Nandika >>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>> On Thu, Jul 28, 2016 at 1:28 PM, Hasitha >>>>>>>>>>>>>>>>>>>>>>>>>>>> Aravinda <hasi...@wso2.com> wrote: >>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>> Can we make it a common component, which is >>>>>>>>>>>>>>>>>>>>>>>>>>>>> not hard coupled with MB. BPS has the same >>>>>>>>>>>>>>>>>>>>>>>>>>>>> requirement. >>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>> Thanks, >>>>>>>>>>>>>>>>>>>>>>>>>>>>> Hasitha. >>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>> On Thu, Jul 28, 2016 at 9:47 AM, Asanka >>>>>>>>>>>>>>>>>>>>>>>>>>>>> Abeyweera <asank...@wso2.com> wrote: >>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Hi All, >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> In MB, we have used a coordinator based >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> approach to manage distributed messaging >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> algorithm in the cluster. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Currently Hazelcast is used to elect the >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> coordinator. But one issue we >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> faced with Hazelcast is, during a network >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> segmentation (split brain), >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Hazelcast can elect two or more coordinators in >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> the cluster. This affects >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> the correctness of the distributed messaging >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> algorithm since there are some >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> tables in the database that should only be >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> edited by a single node (i.e. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> coordinator). >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> As a solution to this problem we have >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> implemented minimum node count based approach >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> [1] to deactivate set of >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> partitioned nodes to stop multiple nodes >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> becoming coordinators until the >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> network segmentation issue is fixed. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> As an alternative solution, we are thinking >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> of implementing an RDBMS based approach to elect >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> the coordinator node in >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> the cluster. By doing this we can make sure that >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> even during a network >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> segmentation only one node will be elected as >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> the coordinator node since >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> the election is happening through the database. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> The algorithm will use a polling mechanism to >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> check the validity of the nodes. To make the >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> election algorithm scalable, >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> only the coordinator node will be checking >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> status of all the nodes in the >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> cluster and it will inform other nodes through >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> database when a member is >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> added/left. The nodes will be only checking for >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> the status of the >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> coordinator node. When a node detect that >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> coordinator is invalid it will go >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> for a election to elect a new coordinator. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> We are currently working on a POC to test how >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> this works with MB's slot based messaging >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> algorithm. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> thoughts? >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> [1] https://wso2.org/jira/browse/MB-1664 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Asanka Abeyweera >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Senior Software Engineer >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> WSO2 Inc. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Phone: +94 712228648 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Blog: a5anka.github.io >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> <https://wso2.com/signature> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> ______________________________ >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> _________________ >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Architecture mailing list >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Architecture@wso2.org >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> https://mail.wso2.org/cgi-bin/ >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> mailman/listinfo/architecture >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>>>>>>>>>>>>>> Hasitha Aravinda, >>>>>>>>>>>>>>>>>>>>>>>>>>>>> Associate Technical Lead, >>>>>>>>>>>>>>>>>>>>>>>>>>>>> WSO2 Inc. >>>>>>>>>>>>>>>>>>>>>>>>>>>>> Email: hasi...@wso2.com >>>>>>>>>>>>>>>>>>>>>>>>>>>>> Mobile : +94 718 210 200 >>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>> ______________________________ >>>>>>>>>>>>>>>>>>>>>>>>>>>>> _________________ >>>>>>>>>>>>>>>>>>>>>>>>>>>>> Architecture mailing list >>>>>>>>>>>>>>>>>>>>>>>>>>>>> Architecture@wso2.org >>>>>>>>>>>>>>>>>>>>>>>>>>>>> https://mail.wso2.org/cgi-bin/ >>>>>>>>>>>>>>>>>>>>>>>>>>>>> mailman/listinfo/architecture >>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>>>>>>>>>>>>> Nandika Jayawardana >>>>>>>>>>>>>>>>>>>>>>>>>>>> WSO2 Inc ; http://wso2.com >>>>>>>>>>>>>>>>>>>>>>>>>>>> lean.enterprise.middleware >>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>> _______________________________________________ >>>>>>>>>>>>>>>>>>>>>>>>>>>> Architecture mailing list >>>>>>>>>>>>>>>>>>>>>>>>>>>> Architecture@wso2.org >>>>>>>>>>>>>>>>>>>>>>>>>>>> https://mail.wso2.org/cgi-bin/ >>>>>>>>>>>>>>>>>>>>>>>>>>>> mailman/listinfo/architecture >>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>>>>>>>>>>>> Akila Ravihansa Perera >>>>>>>>>>>>>>>>>>>>>>>>>>> WSO2 Inc.; http://wso2.com/ >>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>> Blog: http://ravihansa3000.blogspot.com >>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>> _______________________________________________ >>>>>>>>>>>>>>>>>>>>>>>>>>> Architecture mailing list >>>>>>>>>>>>>>>>>>>>>>>>>>> Architecture@wso2.org >>>>>>>>>>>>>>>>>>>>>>>>>>> https://mail.wso2.org/cgi-bin/ >>>>>>>>>>>>>>>>>>>>>>>>>>> mailman/listinfo/architecture >>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>>>>>>>>>>> Asanka Abeyweera >>>>>>>>>>>>>>>>>>>>>>>>>> Senior Software Engineer >>>>>>>>>>>>>>>>>>>>>>>>>> WSO2 Inc. >>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> Phone: +94 712228648 >>>>>>>>>>>>>>>>>>>>>>>>>> Blog: a5anka.github.io >>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> <https://wso2.com/signature> >>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> _______________________________________________ >>>>>>>>>>>>>>>>>>>>>>>>>> Architecture mailing list >>>>>>>>>>>>>>>>>>>>>>>>>> Architecture@wso2.org >>>>>>>>>>>>>>>>>>>>>>>>>> https://mail.wso2.org/cgi-bin/ >>>>>>>>>>>>>>>>>>>>>>>>>> mailman/listinfo/architecture >>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>>>>>>>>> Asanka Abeyweera >>>>>>>>>>>>>>>>>>>>>>>> Senior Software Engineer >>>>>>>>>>>>>>>>>>>>>>>> WSO2 Inc. >>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>> Phone: +94 712228648 >>>>>>>>>>>>>>>>>>>>>>>> Blog: a5anka.github.io >>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>> <https://wso2.com/signature> >>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>> _______________________________________________ >>>>>>>>>>>>>>>>>>>>>>>> Architecture mailing list >>>>>>>>>>>>>>>>>>>>>>>> Architecture@wso2.org >>>>>>>>>>>>>>>>>>>>>>>> https://mail.wso2.org/cgi-bin/ >>>>>>>>>>>>>>>>>>>>>>>> mailman/listinfo/architecture >>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>>>>>>>> *Imesh Gunaratne* >>>>>>>>>>>>>>>>>>>>>>> Software Architect >>>>>>>>>>>>>>>>>>>>>>> WSO2 Inc: http://wso2.com >>>>>>>>>>>>>>>>>>>>>>> T: +94 11 214 5345 M: +94 77 374 2057 >>>>>>>>>>>>>>>>>>>>>>> W: https://medium.com/@imesh TW: @imesh >>>>>>>>>>>>>>>>>>>>>>> lean. enterprise. middleware >>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>> _______________________________________________ >>>>>>>>>>>>>>>>>>>>>>> Architecture mailing list >>>>>>>>>>>>>>>>>>>>>>> Architecture@wso2.org >>>>>>>>>>>>>>>>>>>>>>> https://mail.wso2.org/cgi-bin/ >>>>>>>>>>>>>>>>>>>>>>> mailman/listinfo/architecture >>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>>>>>>> Asanka Abeyweera >>>>>>>>>>>>>>>>>>>>>> Senior Software Engineer >>>>>>>>>>>>>>>>>>>>>> WSO2 Inc. >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>> Phone: +94 712228648 >>>>>>>>>>>>>>>>>>>>>> Blog: a5anka.github.io >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>> <https://wso2.com/signature> >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>> _______________________________________________ >>>>>>>>>>>>>>>>>>>>>> Architecture mailing list >>>>>>>>>>>>>>>>>>>>>> Architecture@wso2.org >>>>>>>>>>>>>>>>>>>>>> https://mail.wso2.org/cgi-bin/ >>>>>>>>>>>>>>>>>>>>>> mailman/listinfo/architecture >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>>>>>> Ramith Jayasinghe >>>>>>>>>>>>>>>>>>>>> Technical Lead >>>>>>>>>>>>>>>>>>>>> WSO2 Inc., http://wso2.com >>>>>>>>>>>>>>>>>>>>> lean.enterprise.middleware >>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>> E: ram...@wso2.com >>>>>>>>>>>>>>>>>>>>> P: +94 772534930 >>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>> _______________________________________________ >>>>>>>>>>>>>>>>>>>>> Architecture mailing list >>>>>>>>>>>>>>>>>>>>> Architecture@wso2.org >>>>>>>>>>>>>>>>>>>>> https://mail.wso2.org/cgi-bin/ >>>>>>>>>>>>>>>>>>>>> mailman/listinfo/architecture >>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>>>>> *Imesh Gunaratne* >>>>>>>>>>>>>>>>>>>> Software Architect >>>>>>>>>>>>>>>>>>>> WSO2 Inc: http://wso2.com >>>>>>>>>>>>>>>>>>>> T: +94 11 214 5345 M: +94 77 374 2057 >>>>>>>>>>>>>>>>>>>> W: https://medium.com/@imesh TW: @imesh >>>>>>>>>>>>>>>>>>>> lean. enterprise. middleware >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>>>> *Imesh Gunaratne* >>>>>>>>>>>>>>>>>>> Software Architect >>>>>>>>>>>>>>>>>>> WSO2 Inc: http://wso2.com >>>>>>>>>>>>>>>>>>> T: +94 11 214 5345 M: +94 77 374 2057 >>>>>>>>>>>>>>>>>>> W: https://medium.com/@imesh TW: @imesh >>>>>>>>>>>>>>>>>>> lean. enterprise. middleware >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> _______________________________________________ >>>>>>>>>>>>>>>>>>> Architecture mailing list >>>>>>>>>>>>>>>>>>> Architecture@wso2.org >>>>>>>>>>>>>>>>>>> https://mail.wso2.org/cgi-bin/ >>>>>>>>>>>>>>>>>>> mailman/listinfo/architecture >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>>> *Asitha Nanayakkara* <http://asitha.github.io/> >>>>>>>>>>>>>>>>>> Senior Software Engineer >>>>>>>>>>>>>>>>>> WSO2, Inc. <http://wso2.com/> >>>>>>>>>>>>>>>>>> Mob: +94 77 853 0682 >>>>>>>>>>>>>>>>>> [image: https://wso2.com/signature] >>>>>>>>>>>>>>>>>> <https://wso2.com/signature> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> _______________________________________________ >>>>>>>>>>>>>>>>>> Architecture mailing list >>>>>>>>>>>>>>>>>> Architecture@wso2.org >>>>>>>>>>>>>>>>>> https://mail.wso2.org/cgi-bin/ >>>>>>>>>>>>>>>>>> mailman/listinfo/architecture >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> Best Regards, >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> Malaka Silva >>>>>>>>>>>>>>>>> Senior Technical Lead >>>>>>>>>>>>>>>>> M: +94 777 219 791 >>>>>>>>>>>>>>>>> Tel : 94 11 214 5345 >>>>>>>>>>>>>>>>> Fax :94 11 2145300 >>>>>>>>>>>>>>>>> Skype : malaka.sampath.silva >>>>>>>>>>>>>>>>> LinkedIn : http://www.linkedin.com/pub/ >>>>>>>>>>>>>>>>> malaka-silva/6/33/77 >>>>>>>>>>>>>>>>> Blog : http://mrmalakasilva.blogspot.com/ >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> WSO2, Inc. >>>>>>>>>>>>>>>>> lean . enterprise . middleware >>>>>>>>>>>>>>>>> https://wso2.com/signature >>>>>>>>>>>>>>>>> http://www.wso2.com/about/team/malaka-silva/ >>>>>>>>>>>>>>>>> <http://wso2.com/about/team/malaka-silva/> >>>>>>>>>>>>>>>>> https://store.wso2.com/store/ >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> Don't make Trees rare, we should keep them with care >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> _______________________________________________ >>>>>>>>>>>>>>>>> Architecture mailing list >>>>>>>>>>>>>>>>> Architecture@wso2.org >>>>>>>>>>>>>>>>> https://mail.wso2.org/cgi-bin/ >>>>>>>>>>>>>>>>> mailman/listinfo/architecture >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>> Ramith Jayasinghe >>>>>>>>>>>>>>>> Technical Lead >>>>>>>>>>>>>>>> WSO2 Inc., http://wso2.com >>>>>>>>>>>>>>>> lean.enterprise.middleware >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> E: ram...@wso2.com >>>>>>>>>>>>>>>> P: +94 772534930 >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> _______________________________________________ >>>>>>>>>>>>>>>> Architecture mailing list >>>>>>>>>>>>>>>> Architecture@wso2.org >>>>>>>>>>>>>>>> https://mail.wso2.org/cgi-bin/mailman/listinfo/architecture >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> -- >>>>>>>>>>>>>> Sajini De SIlva >>>>>>>>>>>>>> Senior Software Engineer; WSO2 Inc.; http://wso2.com , >>>>>>>>>>>>>> Email: saj...@wso2.com >>>>>>>>>>>>>> Blog: http://sajinid.blogspot.com/ >>>>>>>>>>>>>> Git hub profile: https://github.com/sajinidesilva >>>>>>>>>>>>>> >>>>>>>>>>>>>> Phone: +94 712797729 >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> -- >>>>>>>>>>>> Sajini De SIlva >>>>>>>>>>>> Senior Software Engineer; WSO2 Inc.; http://wso2.com , >>>>>>>>>>>> Email: saj...@wso2.com >>>>>>>>>>>> Blog: http://sajinid.blogspot.com/ >>>>>>>>>>>> Git hub profile: https://github.com/sajinidesilva >>>>>>>>>>>> >>>>>>>>>>>> Phone: +94 712797729 >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> _______________________________________________ >>>>>>>>>>>> Architecture mailing list >>>>>>>>>>>> Architecture@wso2.org >>>>>>>>>>>> https://mail.wso2.org/cgi-bin/mailman/listinfo/architecture >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> -- >>>>>>>>>>> Kasun Indrasiri >>>>>>>>>>> Director, Integration Technologies >>>>>>>>>>> WSO2, Inc.; http://wso2.com >>>>>>>>>>> lean.enterprise.middleware >>>>>>>>>>> >>>>>>>>>>> cell: +1 650 450 2293 >>>>>>>>>>> Blog : http://kasunpanorama.blogspot.com/ >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> -- >>>>>>>>>> *Anjana Fernando* >>>>>>>>>> Associate Director / Architect >>>>>>>>>> WSO2 Inc. | http://wso2.com >>>>>>>>>> lean . enterprise . middleware >>>>>>>>>> >>>>>>>>>> _______________________________________________ >>>>>>>>>> Architecture mailing list >>>>>>>>>> Architecture@wso2.org >>>>>>>>>> https://mail.wso2.org/cgi-bin/mailman/listinfo/architecture >>>>>>>>>> >>>>>>>>>> >>>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> -- >>>>>>>> *Anjana Fernando* >>>>>>>> Associate Director / Architect >>>>>>>> WSO2 Inc. | http://wso2.com >>>>>>>> lean . enterprise . middleware >>>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> -- >>>>>>> Asanka Abeyweera >>>>>>> Senior Software Engineer >>>>>>> WSO2 Inc. >>>>>>> >>>>>>> Phone: +94 712228648 >>>>>>> Blog: a5anka.github.io >>>>>>> >>>>>>> <https://wso2.com/signature> >>>>>>> >>>>>> >>>>>> >>>>>> >>>>>> -- >>>>>> *Anjana Fernando* >>>>>> Associate Director / Architect >>>>>> WSO2 Inc. | http://wso2.com >>>>>> lean . enterprise . middleware >>>>>> >>>>> >>>>> >>>>> >>>>> -- >>>>> *Anjana Fernando* >>>>> Associate Director / Architect >>>>> WSO2 Inc. | http://wso2.com >>>>> lean . enterprise . middleware >>>>> >>>> >>>> >>>> >>>> -- >>>> Asanka Abeyweera >>>> Senior Software Engineer >>>> WSO2 Inc. >>>> >>>> Phone: +94 712228648 >>>> Blog: a5anka.github.io >>>> >>>> <https://wso2.com/signature> >>>> >>> >>> >>> >>> -- >>> *Anjana Fernando* >>> Associate Director / Architect >>> WSO2 Inc. | http://wso2.com >>> lean . enterprise . middleware >>> >> >> >> >> -- >> *Anjana Fernando* >> Associate Director / Architect >> WSO2 Inc. | http://wso2.com >> lean . enterprise . middleware >> > > > > -- > Ramith Jayasinghe > Technical Lead > WSO2 Inc., http://wso2.com > lean.enterprise.middleware > > E: ram...@wso2.com > P: +94 772534930 > -- *Anjana Fernando* Associate Director / Architect WSO2 Inc. | http://wso2.com lean . enterprise . middleware
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