Re: Deploying Flink on Kubernetes with fractional CPU and different limits and requests

Wed, 01 Sep 2021 01:24:10 -0700


Hi,everyone
I have some other ideas for kubernetes resource Settings, as described by WangYang in [flink-15648], which increase the CPU limit by a certain percentage to provide more computational performance for jobs. Should we consider the alternative of shrinking the request to start more jobs, which would improve cluster resource utilization? For example, for some low-traffic tasks, we can even set the CPU request to 0 in extreme cases. Both limit enlargement and Request shrinkage may be required

Best,
Lz
On 09/1/2021 16:06，Denis Cosmin NUTIU<dnu...@bitdefender.com> wrote：
Hi Yang,

I have limited Flink internals knowledge, but I can try to implement FLINK-15648 and open up a PR on GitHub or send the patch via email. How does that sound?
I'll sign the ICLA and switch to my personal address.

Sincerely,
Denis

On Wed, 2021-09-01 at 13:48 +0800, Yang Wang wrote:
Great. If no one wants to work on this ticket FLINK-15648, I will try to get this done in the next major release cycle(1.15).

Best,
Yang

Denis Cosmin NUTIU <dnu...@bitdefender.com> 于2021年8月31日周二 下午4:59写道：
Hi everyone,

Thanks for getting back to me! 

>  I think it would be nice if the task manager pods get their values from the configuration file only if the pod templates don’t specify any resources. That was the goal of supporting pod templates, right? Allowing more custom scenarios without letting the configuration options get bloated.

I think that's correct. In the current behavior Flink will override the resources settings "The memory and cpu resources(including requests and limits) will be overwritten by Flink configuration options. All other resources(e.g. ephemeral-storage) will be retained.'[1]. After reading the comments from FLINK-15648[2], I'm not sure that it can be done in a clean manner with pod templates.

> I think it is a good improvement to support different resource requests and limits. And it is very useful especially for the CPU resource since it heavily depends on the upstream workloads.

I agree with you! I have limited knowledge of Flink internals but the kubernetes.jobmanager.limit-factor and kubernetes.taskmanager.limit-factor seems to be the right way to do it.


From: Yang Wang <danrtsey...@gmail.com>
Sent: Tuesday, August 31, 2021 6:04 AM
To: Alexis Sarda-Espinosa <alexis.sarda-espin...@microfocus.com>
Cc: Denis Cosmin NUTIU <dnu...@bitdefender.com>; matth...@ververica.com <matth...@ververica.com>; user@flink.apache.org <user@flink.apache.org>
Subject: Re: Deploying Flink on Kubernetes with fractional CPU and different limits and requests
 
Hi all,

I think it is a good improvement to support different resource requests and limits. And it is very useful 
especially for the CPU resource since it heavily depends on the upstream workloads.

Actually, we(alibaba) have introduced some internal config options to support this feature. WDYT?
// The prefix of Kubernetes resource limit factor. It should not be less than 1. The resource
// could be cpu, memory, ephemeral-storage and all other types supported by Kubernetes.
public static final String KUBERNETES_JOBMANAGER_RESOURCE_LIMIT_FACTOR_PREFIX =
        "kubernetes.jobmanager.limit-factor.";
public static final String KUBERNETES_TASKMANAGER_RESOURCE_LIMIT_FACTOR_PREFIX =
        "kubernetes.taskmanager.limit-factor.";

BTW, we already have an old ticket for this feature[1].



Best,
Yang

Alexis Sarda-Espinosa <alexis.sarda-espin...@microfocus.com> 于2021年8月26日周四 下午10:04写道：

I think it would be nice if the task manager pods get their values from the configuration file only if the pod templates don’t specify any resources. That was the goal of supporting pod templates, right? Allowing more custom scenarios without letting the configuration options get bloated.

 

Regards,

Alexis.

 

From: Denis Cosmin NUTIU <dnu...@bitdefender.com>
Sent: Donnerstag, 26. August 2021 15:55
To: matth...@ververica.com
Cc: user@flink.apache.org; danrtsey...@gmail.com
Subject: Re: Deploying Flink on Kubernetes with fractional CPU and different limits and requests

 

Hi Matthias,

 

Thanks for getting back to me and for your time!

 

We have some Flink jobs deployed on Kubernetes and running kubectl top pod gives the following result:

 

NAME                                                            CPU(cores)   MEMORY(bytes)
aa-78c8cb77d4-zlmpg                  8m           1410Mi
aa-taskmanager-2-2                   32m          1066Mi
bb-5f7b65f95c-jwb7t          7m           1445Mi
bb-taskmanager-2-2           32m          1016Mi
cc-54d967b55d-b567x       11m          514Mi
cc-taskmanager-4-1        11m          496Mi
dd-6fbc6b8666-krhlx   10m          535Mi
dd-taskmanager-2-2    12m          522Mi
xx-6845cf7986-p45lq     53m          526Mi
xx-taskmanager-5-2      11m          507Mi

 

During low workloads the jobs consume just about 100m CPU and during high workloads the CPU consumption increases to 500m-1000m. Having the ability to specify requests and limit separately would give us more deployment flexibility.

 

Sincerely,

Denis

 

On Thu, 2021-08-26 at 14:22 +0200, Matthias Pohl wrote:

Hi Denis,

I did a bit of digging: It looks like there is no way to specify them independently. You can find documentation about pod templates for TaskManager and JobManager [1]. But even there it states that for cpu and memory, the resource specs are overwritten by the Flink configuration. The code also reveals that limit and requests are set using the same value [2].

 

I'm going to pull Yang Wang into this thread. I'm wondering whether there is a reason for that or whether it makes sense to create a Jira issue introducing more specific configuration parameters for limit and requests.

 

Best,
Matthias

 

 

On Thu, Aug 26, 2021 at 11:17 AM Denis Cosmin NUTIU <dnu...@bitdefender.com> wrote:

Hello,

I've developed a Flink job and I'm trying to deploy it on a Kubernetes
cluster using Flink Native.

Setting kubernetes.taskmanager.cpu=0.5 and
kubernetes.jobmanager.cpu=0.5 sets the requests and limits to 500m,
which is correct, but I'd like to set the requests and limits to
different values, something like:

resources:
  requests:
    memory: "1048Mi"
    cpu: "100m"
  limits:
    memory: "2096Mi"
    cpu: "1000m"

I've tried using pod templates from Flink 1.13 and manually patching
the Kubernetes deployment file, the jobmanager gets spawned with the
correct reousrce requests and limits but the taskmanagers get spawned
with the defaults:   

Limits:
      cpu:     1
      memory:  1728Mi
    Requests:
      cpu:     1
      memory:  1728Mi

Is there any way I could set the requests/limits for the CPU/Memory to
different values when deploying Flink in Kubernetes? If not, would it
make sense to request this as a feature?

Thanks in advance!

Denis

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