[Feature]: Visualize Critical Path of a trace

[ramumanam]

This is filed as an intern project for the LFX Mentorship. Please refer to jaegertracing/jaeger#4453. Apply here.

Requirement

Have an ability to view critical path for a given trace.

Problem

A call graph can have multiple spans, but not all spans really contribute to the latency computation. Critical path is the longest chain of dependent tasks in a microservice dependency graph( i.e.,specific sequence of spans from the root to a leaf) . Reducing the critical path length is necessary to reduce the end-to-end latency of a request. Hence, a latency optimization effort benefits by prioritizing the services that are on the critical path. A tool to help identify the critical path of any trace I choose to investigate is beneficial for developers.

Tools like "Lightstep observability" are already having this feature. This effort will be a feature parity for jaeger with other tools.

Proposal

Jaeger already supports a bunch of different analysis views of a trace. It would be useful if Jaeger UI would allow a developer to view the critical path of the trace in the same context.

We propose adding a new option under that dropdown labeled “Critical path”. A critical path is a specific sequence of spans from the root to a leaf. The algorithm to compute the critical path can be run in real-time even in the browser. Once the critical path is computed, it needs to be presented to the developer.

The critical path could be rendered in either (or both) of the formats - tabular and flamegraph.
For efficiency, we may want to re-use the tabular and flame graph trace analysis views already available in Jaeger.

Open questions

No response

[yurishkuro]

do you have a design suggestion how to display it?

[ramumanam]

Hey @yurishkuro , I wanted to leverage existing flamegraph view, screenshot below

[yurishkuro]

Changing this particular view will be more difficult since we use a 3rd party library (pyroscope) for drawing flamegraphs. I am also not sure this is the best representation of the critical path. Your description said "A critical path is a specific sequence of spans from the root to a leaf", but it's not correct because critical path may descend into different sub-trees of the call graph. I thought you wanted a display similar to Lightstep where CP is shown on top of the Gantt chart view.

[ramumanam]

Hey @yurishkuro,
what Am I trying to do here

• I am going to leverage CRISP algorithm to compute critical path for a given jaeger trace.
• I am not proposing modifying any existing flamegraph page. Instead, I am going to add a new page which will display the above computed critical path in both tabular and flamegraph representation.

Also to inform you I am not just proposing this feature request but I am also willing to do the implementation.

[ramumanam]

Hi @yurishkuro, I am attaching the following screenshots which gives an overview on what we are planning to do.
step1: Display an option "Trace Critical Path" on the dropdown as shown

step2: On clicking "Trace Critical Path", computed critical path for the given trace should be rendered as follows

[haanhvu]

Hey @ramumanam I'd love to work on this project under LFX mentorship term 2. As I am learning go, I believe this project will be a great opportunity for me to apply my skills and gain hands-on experience. Looking forward to contributing to the project's success.

Could you provide me with some resources to get started with initially so that I can get myself familiarized with the project and its needs!

I don't participate in this project. But I think you can start by learning Critical Path Analysis. For example this blog from Uber might be a good resource: https://www.uber.com/en-VN/blog/crisp-critical-path-analysis-for-microservice-architectures/

[ramumanam]

Hey @ramumanam I'd love to work on this project under LFX mentorship term 2. As I am learning go, I believe this project will be a great opportunity for me to apply my skills and gain hands-on experience. Looking forward to contributing to the project's success.

Could you provide me with some resources to get started with initially so that I can get myself familiarized with the project and its needs!

FYI this project needs to get implemented using javascript React library

[mugishasam123]

Hey @ramumanam , I am very interested in working on this project as a part of the LFX Mentorship program. I have prior experience working with Javascript, and Typescript and I believe this project would provide an excellent opportunity for me to enhance my skills and gain more practical experience in this field.

I am excited to learn more about the project and would appreciate any information or resources you can provide to help me prepare for the mentorship. Thank you for considering my application.