[DISCUSS] Improve Queryable State and introduce a QueryServerProxy component

[vino yang]

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

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

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.

[Georgi Stoyanov]

Hi Vino,

 

I was investigating the current architecture and AFAIK the first proposal will be a lot easier to implement, cause currently JM has the information about the states (where, which etc thanks to KvStateLocationRegistry. Correct me if I’m wrong)

We are using the feature and it’s indeed not very cool to iterate trough ports, check which TM is the responsible one etc etc.

 

It will be very useful if someone from the committers joins the topic and give us some insights what’s going to happen with that feature.

 

 

Kind Regards,

Georgi

 

 

 

From: vino yang <[hidden email]>
Sent: Thursday, April 25, 2019 5:18 PM
To: dev <[hidden email]>; user <[hidden email]>
Cc: Stefan Richter <[hidden email]>; Aljoscha Krettek <[hidden email]>; [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

 

 

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

 

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.

 

[vino yang]

Hi Georgi,

Thanks for your feedback. And glad to hear you are using queryable state.

I agree that implementation of option 1 is easier than others. However, when we design the new architecture we need to consider more aspects .e.g. scalability. So it seems option 3 is more suitable. Actually, some committers such as Stefan, Gordon and Aljoscha have given me feedback and direction.

Currently, I am writing the design document. If it is ready to be presented. I will copy to this thread and we can discuss further details.

----
Best,
Vino

On 2019-06-07 19:03 , [hidden email] Wrote:

Hi Vino,

 

I was investigating the current architecture and AFAIK the first proposal will be a lot easier to implement, cause currently JM has the information about the states (where, which etc thanks to KvStateLocationRegistry. Correct me if I’m wrong)

We are using the feature and it’s indeed not very cool to iterate trough ports, check which TM is the responsible one etc etc.

 

It will be very useful if someone from the committers joins the topic and give us some insights what’s going to happen with that feature.

 

 

Kind Regards,

Georgi

 

 

 

From: vino yang <[hidden email]>
Sent: Thursday, April 25, 2019 5:18 PM
To: dev <[hidden email]>; user <[hidden email]>
Cc: Stefan Richter <[hidden email]>; Aljoscha Krettek <[hidden email]>; [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

 

 

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

 

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.

 

[vino yang]

Hi all,

In the past, I have tried to further refine the design of this topic thread and wrote a design document to give more detailed design images and text description, so that it is more conducive to discussion.[1]

Note: The document is not yet completed, for example, the "Implementation" section is missing. Therefore, it is still in an open discussion state. I will improve the rest while listening to the opinions of the community.

Welcome and appreciate more discussions and feedback.

Best,

Vino

[1]: https://docs.google.com/document/d/181qYVIiHQGrc3hCj3QBn1iEHF4bUztdw4XO8VSaf_uI/edit?usp=sharing

yanghua1127 <[hidden email]> 于2019年6月7日周五 下午11:32写道：

Hi Georgi,

Thanks for your feedback. And glad to hear you are using queryable state.

I agree that implementation of option 1 is easier than others. However, when we design the new architecture we need to consider more aspects .e.g. scalability. So it seems option 3 is more suitable. Actually, some committers such as Stefan, Gordon and Aljoscha have given me feedback and direction.

Currently, I am writing the design document. If it is ready to be presented. I will copy to this thread and we can discuss further details.

----
Best,
Vino

On 2019-06-07 19:03 , [hidden email] Wrote:

Hi Vino,

 

I was investigating the current architecture and AFAIK the first proposal will be a lot easier to implement, cause currently JM has the information about the states (where, which etc thanks to KvStateLocationRegistry. Correct me if I’m wrong)

We are using the feature and it’s indeed not very cool to iterate trough ports, check which TM is the responsible one etc etc.

 

It will be very useful if someone from the committers joins the topic and give us some insights what’s going to happen with that feature.

 

 

Kind Regards,

Georgi

 

 

 

From: vino yang <[hidden email]>
Sent: Thursday, April 25, 2019 5:18 PM
To: dev <[hidden email]>; user <[hidden email]>
Cc: Stefan Richter <[hidden email]>; Aljoscha Krettek <[hidden email]>; [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

 

 

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

 

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.