option 2 is probably not feasible, as checkpoint may take a long time or may fail.
Option 1 might work, although it complicates the job recovery and checkpoint. After checkpoint completion, we need to clean up those control signals stored in HA service. On Tue, Jun 8, 2021 at 1:14 AM 刘建刚 <liujiangangp...@gmail.com> wrote: > Thanks for the reply. It is a good question. There are multi choices as > follows: > > 1. We can persist control signals in HighAvailabilityServices and replay > them after failover. > 2. Only tell the users that the control signals take effect after they > are checkpointed. > > > Steven Wu [via Apache Flink User Mailing List archive.] < > ml+s2336050n44278...@n4.nabble.com> 于2021年6月8日周二 下午2:15写道： > > > > > I can see the benefits of control flow. E.g., it might help the old (and > > inactive) FLIP-17 side input. I would suggest that we add more details of > > some of the potential use cases. > > > > Here is one mismatch with using control flow for dynamic config. Dynamic > > config is typically targeted/loaded by one specific operator. Control > flow > > will propagate the dynamic config to all operators. not a problem per se > > > > Regarding using the REST api (to jobmanager) for accepting control > > signals from external system, where are we going to persist/checkpoint > the > > signal? jobmanager can die before the control signal is propagated and > > checkpointed. Did we lose the control signal in this case? > > > > > > On Mon, Jun 7, 2021 at 11:05 PM Xintong Song <[hidden email] > > <http:///user/SendEmail.jtp?type=node&node=44278&i=0>> wrote: > > > >> +1 on separating the effort into two steps: > >> > >> 1. Introduce a common control flow framework, with flexible > >> interfaces for generating / reacting to control messages for various > >> purposes. > >> 2. Features that leverating the control flow can be worked on > >> concurrently > >> > >> Meantime, keeping collecting potential features that may leverage the > >> control flow should be helpful. It provides good inputs for the control > >> flow framework design, to make the framework common enough to cover the > >> potential use cases. > >> > >> My suggestions on the next steps: > >> > >> 1. Allow more time for opinions to be heard and potential use cases > >> to be collected > >> 2. Draft a FLIP with the scope of common control flow framework > >> 3. We probably need a poc implementation to make sure the framework > >> covers at least the following scenarios > >> 1. Produce control events from arbitrary operators > >> 2. Produce control events from JobMaster > >> 3. Consume control events from arbitrary operators downstream > >> where the events are produced > >> > >> > >> Thank you~ > >> > >> Xintong Song > >> > >> > >> > >> On Tue, Jun 8, 2021 at 1:37 PM Yun Gao <[hidden email] > >> <http:///user/SendEmail.jtp?type=node&node=44278&i=1>> wrote: > >> > >>> Very thanks Jiangang for bringing this up and very thanks for the > >>> discussion! > >>> > >>> I also agree with the summarization by Xintong and Jing that control > >>> flow seems to be > >>> a common buidling block for many functionalities and dynamic > >>> configuration framework > >>> is a representative application that frequently required by users. > >>> Regarding the control flow, > >>> currently we are also considering the design of iteration for the > >>> flink-ml, and as Xintong has pointed > >>> out, it also required the control flow in cases like detection global > >>> termination inside the iteration > >>> (in this case we need to broadcast an event through the iteration body > >>> to detect if there are still > >>> records reside in the iteration body). And regarding whether to > >>> implement the dynamic configuration > >>> framework, I also agree with Xintong that the consistency guarantee > >>> would be a point to consider, we > >>> might consider if we need to ensure every operator could receive the > >>> dynamic configuration. > >>> > >>> Best, > >>> Yun > >>> > >>> > >>> > >>> ------------------------------------------------------------------ > >>> Sender:kai wang<[hidden email] > >>> <http:///user/SendEmail.jtp?type=node&node=44278&i=2>> > >>> Date:2021/06/08 11:52:12 > >>> Recipient:JING ZHANG<[hidden email] > >>> <http:///user/SendEmail.jtp?type=node&node=44278&i=3>> > >>> Cc:刘建刚<[hidden email] > >>> <http:///user/SendEmail.jtp?type=node&node=44278&i=4>>; Xintong Song > >>> [via Apache Flink User Mailing List archive.]<[hidden email] > >>> <http:///user/SendEmail.jtp?type=node&node=44278&i=5>>; user<[hidden > >>> email] <http:///user/SendEmail.jtp?type=node&node=44278&i=6>>; > dev<[hidden > >>> email] <http:///user/SendEmail.jtp?type=node&node=44278&i=7>> > >>> Theme:Re: Add control mode for flink > >>> > >>> > >>> > >>> I'm big +1 for this feature. > >>> > >>> 1. Limit the input qps. > >>> 2. Change log level for debug. > >>> > >>> in my team, the two examples above are needed > >>> > >>> JING ZHANG <[hidden email] > >>> <http:///user/SendEmail.jtp?type=node&node=44278&i=8>> 于2021年6月8日周二 > >>> 上午11:18写道： > >>> > >>>> Thanks Jiangang for bringing this up. > >>>> As mentioned in Jiangang's email, `dynamic configuration framework` > >>>> provides many useful functions in Kuaishou, because it could update > job > >>>> behavior without relaunching the job. The functions are very popular > in > >>>> Kuaishou, we also see similar demands in maillist [1]. > >>>> > >>>> I'm big +1 for this feature. > >>>> > >>>> Thanks Xintong and Yun for deep thoughts about the issue. I like the > >>>> idea about introducing control mode in Flink. > >>>> It takes the original issue a big step closer to essence which also > >>>> provides the possibility for more fantastic features as mentioned in > >>>> Xintong and Jark's response. > >>>> Based on the idea, there are at least two milestones to achieve the > >>>> goals which were proposed by Jiangang: > >>>> (1) Build a common control flow framework in Flink. > >>>> It focuses on control flow propagation. And, how to integrate the > >>>> common control flow framework with existing mechanisms. > >>>> (2) Builds a dynamic configuration framework which is exposed to users > >>>> directly. > >>>> We could see dynamic configuration framework is a top application > >>>> on the underlying control flow framework. > >>>> It focuses on the Public API which receives configuration > updating > >>>> requests from users. Besides, it is necessary to introduce an API > >>>> protection mechanism to avoid job performance degradation caused by > too > >>>> many control events. > >>>> > >>>> I suggest splitting the whole design into two after we reach a > >>>> consensus on whether to introduce this feature because these two > sub-topic > >>>> all need careful design. > >>>> > >>>> > >>>> [ > >>>> > http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Dynamic-configuration-of-Flink-checkpoint-interval-td44059.html > >>>> ] > >>>> > >>>> Best regards, > >>>> JING ZHANG > >>>> > >>>> 刘建刚 <[hidden email] > >>>> <http:///user/SendEmail.jtp?type=node&node=44278&i=9>> 于2021年6月8日周二 > >>>> 上午10:01写道： > >>>> > >>>>> Thanks Xintong Song for the detailed supplement. Since flink is > >>>>> long-running, it is similar to many services. So interacting with it > or > >>>>> controlling it is a common desire. This was our initial thought when > >>>>> implementing the feature. In our inner flink, many configs used in > yaml can > >>>>> be adjusted by dynamic to avoid restarting the job, for examples as > follow: > >>>>> > >>>>> 1. Limit the input qps. > >>>>> 2. Degrade the job by sampling and so on. > >>>>> 3. Reset kafka offset in certain cases. > >>>>> 4. Stop checkpoint in certain cases. > >>>>> 5. Control the history consuming. > >>>>> 6. Change log level for debug. > >>>>> > >>>>> > >>>>> After deep discussion, we realize that a common control flow > >>>>> will benefit both users and developers. Dynamic config is just one > of the > >>>>> use cases. For the concrete design and implementation, it relates > with many > >>>>> components, like jobmaster, network channel, operators and so on, > which > >>>>> needs deeper consideration and design. > >>>>> > >>>>> Xintong Song [via Apache Flink User Mailing List archive.] <[hidden > >>>>> email] <http:///user/SendEmail.jtp?type=node&node=44278&i=10>> > >>>>> 于2021年6月7日周一 下午2:52写道： > >>>>> > >>>>>> Thanks Jiangang for bringing this up, and Steven & Peter for the > >>>>>> feedback. > >>>>>> > >>>>>> I was part of the preliminary offline discussions before this > >>>>>> proposal went public. So maybe I can help clarify things a bit. > >>>>>> > >>>>>> In short, despite the phrase "control mode" might be a bit > >>>>>> misleading, what we truly want to do from my side is to make the > concept of > >>>>>> "control flow" explicit and expose it to users. > >>>>>> > >>>>>> ## Background > >>>>>> Jiangang & his colleagues at Kuaishou maintain an internal version > of > >>>>>> Flink. One of their custom features is allowing dynamically changing > >>>>>> operator behaviors via the REST APIs. He's willing to contribute > this > >>>>>> feature to the community, and came to Yun Gao and me for > suggestions. After > >>>>>> discussion, we feel that the underlying question to be answered is > how do > >>>>>> we model the control flow in Flink. Dynamically controlling jobs > via REST > >>>>>> API can be one of the features built on top of the control flow, > and there > >>>>>> could be others. > >>>>>> > >>>>>> ## Control flow > >>>>>> Control flow refers to the communication channels for sending > >>>>>> events/signals to/between tasks/operators, that changes Flink's > behavior in > >>>>>> a way that may or may not affect the computation logic. Typical > control > >>>>>> events/signals Flink currently has are watermarks and checkpoint > barriers. > >>>>>> > >>>>>> In general, for modeling control flow, the following questions > should > >>>>>> be considered. > >>>>>> 1. Who (which component) is responsible for generating the control > >>>>>> messages? > >>>>>> 2. Who (which component) is responsible for reacting to the > messages. > >>>>>> 3. How do the messages propagate? > >>>>>> 4. When it comes to affecting the computation logics, how should the > >>>>>> control flow work together with the exact-once consistency. > >>>>>> > >>>>>> 1) & 2) may vary depending on the use cases, while 3) & 4) probably > >>>>>> share many things in common. A unified control flow model would help > >>>>>> deduplicate the common logics, allowing us to focus on the use case > >>>>>> specific parts. > >>>>>> > >>>>>> E.g., > >>>>>> - Watermarks: generated by source operators, handled by window > >>>>>> operators. > >>>>>> - Checkpoint barrier: generated by the checkpoint coordinator, > >>>>>> handled by all tasks > >>>>>> - Dynamic controlling: generated by JobMaster (in reaction to the > >>>>>> REST command), handled by specific operators/UDFs > >>>>>> - Operator defined events: The following features are still in > >>>>>> planning, but may potentially benefit from the control flow model. > (Please > >>>>>> correct me if I'm wrong, @Yun, @Jark) > >>>>>> * Iteration: When a certain condition is met, we might want to > >>>>>> signal downstream operators with an event > >>>>>> * Mini-batch assembling: Flink currently uses special watermarks > >>>>>> for indicating the end of each mini-batch, which makes it tricky to > deal > >>>>>> with event time related computations. > >>>>>> * Hive dimension table join: For periodically reloaded hive > tables, > >>>>>> it would be helpful to have specific events signaling that a > reloading is > >>>>>> finished. > >>>>>> * Bootstrap dimension table join: This is similar to the previous > >>>>>> one. In cases where we want to fully load the dimension table before > >>>>>> starting joining the mainstream, it would be helpful to have an > event > >>>>>> signaling the finishing of the bootstrap. > >>>>>> > >>>>>> ## Dynamic REST controlling > >>>>>> Back to the specific feature that Jiangang proposed, I personally > >>>>>> think it's quite convenient. Currently, to dynamically change the > behavior > >>>>>> of an operator, we need to set up a separate source for the control > events > >>>>>> and leverage broadcast state. Being able to send the events via > REST APIs > >>>>>> definitely improves the usability. > >>>>>> > >>>>>> Leveraging dynamic configuration frameworks is for sure one possible > >>>>>> approach. The reason we are in favor of introducing the control > flow is > >>>>>> that: > >>>>>> - It benefits not only this specific dynamic controlling feature, > but > >>>>>> potentially other future features as well. > >>>>>> - AFAICS, it's non-trivial to make a 3rd-party dynamic configuration > >>>>>> framework work together with Flink's consistency mechanism. > >>>>>> > >>>>>> Thank you~ > >>>>>> > >>>>>> Xintong Song > >>>>>> > >>>>>> > >>>>>> > >>>>>> On Mon, Jun 7, 2021 at 11:05 AM 刘建刚 <[hidden email] > >>>>>> <http:///user/SendEmail.jtp?type=node&node=44245&i=0>> wrote: > >>>>>> > >>>>>>> Thank you for the reply. I have checked the post you mentioned. The > >>>>>>> dynamic config may be useful sometimes. But it is hard to keep data > >>>>>>> consistent in flink, for example, what if the dynamic config will > take > >>>>>>> effect when failover. Since dynamic config is a desire for users, > maybe > >>>>>>> flink can support it in some way. > >>>>>>> > >>>>>>> For the control mode, dynamic config is just one of the control > >>>>>>> modes. In the google doc, I have list some other cases. For > example, > >>>>>>> control events are generated in operators or external services. > Besides > >>>>>>> user's dynamic config, flink system can support some common dynamic > >>>>>>> configuration, like qps limit, checkpoint control and so on. > >>>>>>> > >>>>>>> It needs good design to handle the control mode structure. Based on > >>>>>>> that, other control features can be added easily later, like > changing log > >>>>>>> level when job is running. In the end, flink will not just process > data, > >>>>>>> but also interact with users to receive control events like a > service. > >>>>>>> > >>>>>>> Steven Wu <[hidden email] > >>>>>>> <http:///user/SendEmail.jtp?type=node&node=44245&i=1>> > 于2021年6月4日周五 > >>>>>>> 下午11:11写道： > >>>>>>> > >>>>>>>> I am not sure if we should solve this problem in Flink. This is > >>>>>>>> more like a dynamic config problem that probably should be solved > by some > >>>>>>>> configuration framework. Here is one post from google search: > >>>>>>>> > https://medium.com/twodigits/dynamic-app-configuration-inject-configuration-at-run-time-using-spring-boot-and-docker-ffb42631852a > >>>>>>>> > >>>>>>>> On Fri, Jun 4, 2021 at 7:09 AM 刘建刚 <[hidden email] > >>>>>>>> <http:///user/SendEmail.jtp?type=node&node=44245&i=2>> wrote: > >>>>>>>> > >>>>>>>>> Hi everyone, > >>>>>>>>> > >>>>>>>>> Flink jobs are always long-running. When the job is > running, > >>>>>>>>> users may want to control the job but not stop it. The control > reasons can > >>>>>>>>> be different as following: > >>>>>>>>> > >>>>>>>>> 1. > >>>>>>>>> > >>>>>>>>> Change data processing’ logic, such as filter condition. > >>>>>>>>> 2. > >>>>>>>>> > >>>>>>>>> Send trigger events to make the progress forward. > >>>>>>>>> 3. > >>>>>>>>> > >>>>>>>>> Define some tools to degrade the job, such as limit input qps, > >>>>>>>>> sampling data. > >>>>>>>>> 4. > >>>>>>>>> > >>>>>>>>> Change log level to debug current problem. > >>>>>>>>> > >>>>>>>>> The common way to do this is to stop the job, do > >>>>>>>>> modifications and start the job. It may take a long time to > recover. In > >>>>>>>>> some situations, stopping jobs is intolerable, for example, the > job is > >>>>>>>>> related to money or important activities.So we need some > >>>>>>>>> technologies to control the running job without stopping the job. > >>>>>>>>> > >>>>>>>>> > >>>>>>>>> We propose to add control mode for flink. A control mode based on > >>>>>>>>> the restful interface is first introduced. It works by these > steps: > >>>>>>>>> > >>>>>>>>> > >>>>>>>>> 1. The user can predefine some logic which supports config > >>>>>>>>> control, such as filter condition. > >>>>>>>>> 2. Run the job. > >>>>>>>>> 3. If the user wants to change the job's running logic, just > >>>>>>>>> send a restful request with the responding config. > >>>>>>>>> > >>>>>>>>> Other control modes will also be considered in the future. More > >>>>>>>>> introduction can refer to the doc > >>>>>>>>> > https://docs.google.com/document/d/1WSU3Tw-pSOcblm3vhKFYApzVkb-UQ3kxso8c8jEzIuA/edit?usp=sharing > >>>>>>>>> . If the community likes the proposal, more discussion is needed > and a more > >>>>>>>>> detailed design will be given later. 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