Hi yang,
+1 for this proposal. Queryable state is a very common usage in our scenarios when we debug and query the realtime status in streaming process like CEP. And we’ve done a lot to improve the “user experience” of this feature like exposing the taskmanager’s proxy port in TaskManagerInfo. I’m looking forward to a more detailed and deeper discussion and I’d like to contribute back to the community on this. Best Regards, Jiayi Liao Original Message Sender:vino [hidden email] Recipient:[hidden email]@flink.apache.org Date:Friday, Apr 26, 2019 16:41 Subject:Re: [DISCUSS] Improve Queryable State and introduce aQueryServerProxy component Hi Paul, Thanks for your reply. You are right, currently, the queryable state has few users. And I totally agree with you, it makes the streaming works more like a DB. About the architecture and the problem you concern: yes, it maybe affect the JobManager if they are deployed together. I think it's important to guarantee the JobManager's available and stability, and the QueryProxyServer is just a secondary service component. So when describing the role of the QueryProxyServer, I mentioned SLA policy, I think it's a solution. But the detail may need to be discussed. About starting queryable state client with a cmd, I think it's a good idea and valuable. Best, Vino. Paul Lam [hidden email] 于2019年4月26日周五 下午3:31写道: Hi Vino, Thanks a lot for bringing up the discussion! Queryable state has been at beta version for a long time, and due to its complexity and instability I think there are not many users, but there’s a great value in it which makes state as database one step closer. WRT the architecture, I’d vote for opt 3, because it fits the cloud architecture the most and avoids putting more burdens on JM (sometimes the queries could be slow and resources intensive). My concern is that on many cluster frameworks the container resources are limited (IIUC, the JM and QS are running in the same container), would JM gets killed if QS eats up too much memory? And a minor suggestion: can we introduce a cmd script to setup a QueryableStateClient? That would be easier for users who wants to try out this feature. Best, Paul Lam 在 2019年4月26日,11:09,vino yang [hidden email] 写道: Hi Quan, Thanks for your reply. Actually, I did not try this way. But, there are two factors we should consider: 1. The local state storage is not equals to RocksDB, otherwise Flink does not need to provide a queryable state client. What's more, querying the RocksDB is still an address-explicit action. 2. IMO, the proposal's more valuable suggestion is to make the queryable state's architecture more reasonable, let it encapsulated more details and improve its scalability. Best, Vino Shi Quan [hidden email] 于2019年4月26日周五 上午10:38写道: Hi, How about take states from RocksDB directly, in this case, TM host is unnecessary. Best Quan Shi ________________________________ From: vino yang [hidden email] Sent: Thursday, April 25, 2019 10:18:20 PM To: dev; user Cc: Stefan Richter; Aljoscha Krettek; [hidden email] Subject: [DISCUSS] Improve Queryable State and introduce a QueryServerProxy component Hi all, I want to share my thought with you about improving the queryable state and introducing a QueryServerProxy component. I think the current queryable state's client is hard to use. Because it needs users to know the TaskManager's address and proxy's port. Actually, some business users who do not have good knowledge about the Flink's inner or runtime in production. However, sometimes they need to query the values of states. IMO, the reason caused this problem is because of the queryable state's architecture. Currently, the queryable state clients interact with query state client proxy components which host on each TaskManager. This design is difficult to encapsulate the point of change and exposes too much detail to the user. My personal idea is that we could introduce a really queryable state server, named e.g. QueryStateProxyServer which would delegate all the query state request and query the local registry then redirect the request to the specific QueryStateClientProxy(runs on each TaskManager). The server is the users really want to care about. And it would make the users ignorant to the TaskManagers' address and proxies' port. The current QueryStateClientProxy would become QueryStateProxyClient. Generally speaking, the roles of the QueryStateProxyServer list below: * works as all the query client's proxy to receive all the request and send response; * a router to redirect the real query requests to the specific proxy client; * maintain route table registry (state - TaskManager, TaskManager-proxy client address) * more fine-granted control, such as cache result, ACL, TTL, SLA(rate limit) and so on About the implementation, there are three opts: opt 1: Let the JobManager acts as the query proxy server. * pros: reuse the exists JM, do not need to introduce a new process can reduce the complexity; * cons: would make JM heavy burdens, depends on the query frequency, may impact on the stability [Screen Shot 2019-04-25 at 5.12.07 PM.png] opt 2: Introduce a new component which runs as a single process and acts as the query proxy server: * pros: reduce the burdens and make the JM more stability * cons: introduced a new component will make the implementation more complexity [Screen Shot 2019-04-25 at 5.14.05 PM.png] opt 3 (suggestion comes from Stefan Richter): Combining the two opts, the query server could run as a single entry point(process) and integrate with JobManager. If we keep it well encapsulated, the only difference would be how we register new TMs with the query server in the different scenarios, in JM we might have this information already, in standalone e.g. the TMs be started with the query server address to register. This would give the convenience to start QS with the JM and the flexibility for power user to reduce load on their JM. IMO, the queryable state is a very valuable feature. It can let users query some real-time measure results. I hope it will get the attention of the community. It is just a roughly thought. If it is valuable to the community, I will give a design draft. What's your opinion? Any feedback and comment are welcome! Best, Vino. |
Hi Jiayi,
Thanks for your reply and glad to hear that you have taken some effort for it, the potential contribution is also welcome. I also want to explore it in depth. Currently, let's listen to the community's opinions. Best, Vino. bupt_ljy <[hidden email]> 于2019年4月26日周五 下午9:54写道: > Hi yang, > +1 for this proposal. Queryable state is a very common usage in our > scenarios when we debug and query the realtime status in streaming process > like CEP. And we’ve done a lot to improve the “user experience” of this > feature like exposing the taskmanager’s proxy port in TaskManagerInfo. > I’m looking forward to a more detailed and deeper discussion and I’d like > to contribute back to the community on this. > > > Best Regards, > Jiayi Liao > > > Original Message > Sender:vino [hidden email] > Recipient:[hidden email]@flink.apache.org > Date:Friday, Apr 26, 2019 16:41 > Subject:Re: [DISCUSS] Improve Queryable State and introduce > aQueryServerProxy component > > > Hi Paul, Thanks for your reply. You are right, currently, the queryable > state has few users. And I totally agree with you, it makes the streaming > works more like a DB. About the architecture and the problem you concern: > yes, it maybe affect the JobManager if they are deployed together. I think > it's important to guarantee the JobManager's available and stability, and > the QueryProxyServer is just a secondary service component. So when > describing the role of the QueryProxyServer, I mentioned SLA policy, I > think it's a solution. But the detail may need to be discussed. About > starting queryable state client with a cmd, I think it's a good idea and > valuable. Best, Vino. Paul Lam [hidden email] 于2019年4月26日周五 > 下午3:31写道: Hi Vino, Thanks a lot for bringing up the discussion! > Queryable state has been at beta version for a long time, and due to its > complexity and instability I think there are not many users, but there’s a > great value in it which makes state as database one step closer. WRT the > architecture, I’d vote for opt 3, because it fits the cloud architecture > the most and avoids putting more burdens on JM (sometimes the queries > could be slow and resources intensive). My concern is that on many cluster > frameworks the container resources are limited (IIUC, the JM and QS are > running in the same container), would JM gets killed if QS eats up too > much memory? And a minor suggestion: can we introduce a cmd script to > setup a QueryableStateClient? That would be easier for users who wants to > try out this feature. Best, Paul Lam 在 2019年4月26日,11:09,vino yang > [hidden email] 写道: Hi Quan, Thanks for your reply. > Actually, I did not try this way. But, there are two factors we should > consider: 1. The local state storage is not equals to RocksDB, > otherwise Flink does not need to provide a queryable state client. What's > more, querying the RocksDB is still an address-explicit action. 2. > IMO, the proposal's more valuable suggestion is to make the queryable > state's architecture more reasonable, let it encapsulated more details > and improve its scalability. Best, Vino Shi Quan > [hidden email] 于2019年4月26日周五 上午10:38写道: Hi, How about take > states from RocksDB directly, in this case, TM host is unnecessary. > Best Quan Shi ________________________________ From: vino yang > [hidden email] Sent: Thursday, April 25, 2019 10:18:20 PM To: > dev; user Cc: Stefan Richter; Aljoscha Krettek; [hidden email] > Subject: [DISCUSS] Improve Queryable State and introduce a > QueryServerProxy component Hi all, I want to share my thought with > you about improving the queryable state and introducing a > QueryServerProxy component. I think the current queryable state's > client is hard to use. Because it needs users to know the TaskManager's > address and proxy's port. Actually, some business users who do not have > good knowledge about the Flink's inner or runtime in production. > However, sometimes they need to query the values of states. IMO, the > reason caused this problem is because of the queryable state's > architecture. Currently, the queryable state clients interact with query > state client proxy components which host on each TaskManager. This > design is difficult to encapsulate the point of change and exposes too > much detail to the user. My personal idea is that we could introduce > a really queryable state server, named e.g. QueryStateProxyServer which > would delegate all the query state request and query the local registry > then redirect the request to the specific QueryStateClientProxy(runs on > each TaskManager). The server is the users really want to care about. > And it would make the users ignorant to the TaskManagers' address and > proxies' port. The current QueryStateClientProxy would become > QueryStateProxyClient. Generally speaking, the roles of the > QueryStateProxyServer list below: * works as all the query client's > proxy to receive all the request and send response; * a router to > redirect the real query requests to the specific proxy client; * > maintain route table registry (state - TaskManager, TaskManager-proxy > client address) * more fine-granted control, such as cache result, ACL, > TTL, SLA(rate limit) and so on About the implementation, there are > three opts: opt 1: Let the JobManager acts as the query proxy > server. * pros: reuse the exists JM, do not need to introduce a new > process can reduce the complexity; * cons: would make JM heavy burdens, > depends on the query frequency, may impact on the stability [Screen > Shot 2019-04-25 at 5.12.07 PM.png] opt 2: Introduce a new component > which runs as a single process and acts as the query proxy server: > * pros: reduce the burdens and make the JM more stability * cons: > introduced a new component will make the implementation more complexity > [Screen Shot 2019-04-25 at 5.14.05 PM.png] opt 3 (suggestion comes > from Stefan Richter): Combining the two opts, the query server could > run as a single entry point(process) and integrate with JobManager. > If we keep it well encapsulated, the only difference would be how we > register new TMs with the query server in the different scenarios, in JM > we might have this information already, in standalone e.g. the TMs be > started with the query server address to register. This would give the > convenience to start QS with the JM and the flexibility for power user to > reduce load on their JM. IMO, the queryable state is a very valuable > feature. It can let users query some real-time measure results. I hope it > will get the attention of the community. It is just a roughly > thought. If it is valuable to the community, I will give a design draft. > What's your opinion? Any feedback and comment are welcome! Best, > Vino. |
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