Reuse the http request object for http probes

[SergeyKanzhelev]

Today we construct the request object for every http request for the http probes. This involves concatenating some strings, setting headers, etc.

Probes are simple http get requests that are executed synchronously (for a single probe) and has no request body.

The optimization may be to reuse the request object for all probe executions. This likely save some cpu and memory for the kubelet process.

Some code references:

• DoProbe is executed today on each probe execution.
• New request are being created for each execution.
• New object will need to be stored in worker that for http probes will hold the http request object. This object will need to encapsulate the logic of runProbe method of the prober.

I'm marking this issue as a good first issue, as the issue doesn't require deep knowledge of Kubernetes. However it is not an easy issue, a few parts of code will be affected and change needs to be done very carefully.

Please review code and make sure you understand the task before self-assigning the issue.

Implementation notes

1. If you can send the small benchmark results on probes with and without this optimization, it will be a good starting point. Note, for the benchmark, each probe can run once a second, not more often. But the number of probes is virtually unlimited since we are not defining the limit on number of containers per Pod. Realistically we are talking about 110 pods (max) with maybe 2 containers each, with 3 probes each (660 probes).
2. Code change may be big. So make sure to help reviewers to review the code. One idea may be to split implementation into multiple commits to simplify the review. First, creating the object encapsulating the logic of runProbe, second storing and initializing this object in worker, and third, actual reusing of the request object.

/sig node
/good-first-issue
/help-wanted
/area kubelet

[k8s-ci-robot]

@SergeyKanzhelev:
This request has been marked as suitable for new contributors.

Guidelines

Please ensure that the issue body includes answers to the following questions:

• Why are we solving this issue?
• To address this issue, are there any code changes? If there are code changes, what needs to be done in the code and what places can the assignee treat as reference points?
• Does this issue have zero to low barrier of entry?
• How can the assignee reach out to you for help?

For more details on the requirements of such an issue, please see here and ensure that they are met.

If this request no longer meets these requirements, the label can be removed
by commenting with the /remove-good-first-issue command.

In response to this:

Today we construct the request object for every http request for the http probes. This involves concatenating some strings, setting headers, etc.

Probes are simple http get requests that are executed synchronously (for a single probe) and has no request body.

The optimization may be to reuse the request object for all probe executions. This likely save some cpu and memory for the kubelet process.

Some code references:

• DoProbe is executed today on each probe execution.
• New request are being created for each execution.
• New object will need to be stored in worker that for http probes will hold the http request object. This object will need to encapsulate the logic of runProbe method of the prober.

I'm marking this issue as a good first issue, as the issue doesn't require deep knowledge of Kubernetes. However it is not an easy issue, a few parts of code will be affected and change needs to be done very carefully.

Please review code and make sure you understand the task before self-assigning the issue.

Implementation notes

1. If you can send the small benchmark results on probes with and without this optimization, it will be a good starting point. Note, for the benchmark, each probe can run once a second, not more often. But the number of probes is virtually unlimited since we are not defining the limit on number of containers per Pod. Realistically we are talking about 110 pods (max) with maybe 2 containers each, with 3 probes each (660 probes).
2. Code change may be big. So make sure to help reviewers to review the code. One idea may be to split implementation into multiple commits to simplify the review. First, creating the object encapsulating the logic of runProbe, second storing and initializing this object in worker, and third, actual reusing of the request object.

/sig node
/good-first-issue
/help-wanted
/area kubelet

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[k8s-ci-robot]

This issue is currently awaiting triage.

If a SIG or subproject determines this is a relevant issue, they will accept it by applying the triage/accepted label and provide further guidance.

The triage/accepted label can be added by org members by writing /triage accepted in a comment.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[XDRAGON2002]

Hi @SergeyKanzhelev!
I'm a new contributor and would like to contribute to the project.

Since this is a good first issue, I suppose this would be a good starting point for contributing?

I would like to take this up.

Could you help me out in getting started with this if so?

[VishalPraneeth]

Hello @SergeyKanzhelev @thockin
I'm a beginner to open-source and want to work on this good-first-issue
Can you please guide me on how to proceed with this
I've gone through the Contributing.md guidelines and have basic programming knowledge in Golang

[SergeyKanzhelev]

@XDRAGON2002, @VishalPraneeth thank you for your interest. Please look at code references I posted in original issue for a good starting points to understand the task.

[Sajiyah-Salat]

I completely understand the issue. And you have explained it very well. Till now I have contributed in 4 prs in kubernetes in which 2 were merged. I know golang but still I am afraid that I dont know how can I start? Can you please help me with that.

[rayowang]

/assign

[rayowang]

Just recently, I checked kubelet-related issues and saw this code as well. I will use the object pool to complete the reuse of related objects. @SergeyKanzhelev

[aroradaman]

Hi @SergeyKanzhelev
I tweaked the prober and did some CPU-memory profiling and compared them, overall saved 32.MB of RAM and 2.27sec CPU time by running 500 probers concurrently for 2 minutes and probing every second.

Benchmarking function: https://github.com/daman1807/kubernetes/blob/11f6565bf092128deaf9e3b080e4e9e4b92dc07b/pkg/probe/http/benchmark_test.go

Modification in prober for this benchmarking:
https://github.com/daman1807/kubernetes/blob/11f6565bf092128deaf9e3b080e4e9e4b92dc07b/pkg/probe/http/http.go#L65-L93