blog: distributed tracing in ceph using jaeger blog 2021

Signed-off-by: Deepika Upadhyay <[email protected]>

src/en/news/blog/2021/distributed-tracing-in-ceph-using-jaeger/index.md

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+# Distributed Tracing using Jaeger in Ceph
+
+Distributed systems like Ceph can be a nightmare to debug because they do not have a single point of failure. To address this, we have been working on adding a standard distributed tracing solution, Jaeger, to Ceph. Jaeger is a distributed tracing open-source library and a project under CNCF. Jaeger will provide more visibility into Ceph’s distributed background processes and help users identify abnormalities, hence, “**making Ceph more transparent”.**
+
+This blog presents an opportunity to learn about using tracing for debugging Ceph - perfect for those looking to identify performance bottlenecks, latency optimization and abnormalities in distributed transactions.
+
+We are happy to announce initial support for Jaeger in the Pacific release of Ceph!
+
+**How Does It Work?**
+
+[Jaeger](https://www.jaegertracing.io/docs)(tracing backend) along with [Opentracing](https://opentracing.io/docs/supported-tracers/)(API) provides ready-to-use tracing services for distributed systems and is becoming a widely used, de facto standard because of its simplicity.
+
+Jaeger is responsible for the collection of spans. These spans are made with the use of smart pointers. They include a timestamp, TraceID, and other meta info, like a specific tag/log associated with the span, to be uniquely identified across the distributed system. These are then correlated to generate visualizations(trace) of the lifetime of a request.
+
+![images/image1.png](images/image1.png)
+<p align = "center">
+credits: jaeger documentation
+</p>
+
+## Let's try it out!
+
+Let's take a look into tracing the core functions involved in Ceph's input-output transactions. Please skip the next section if you have the jaeger backend set up for working with Ceph.
+
+For information on how to set it up, please refer to the documentation: [https://docs.ceph.com/en/latest/dev/developer_guide/jaegertracing/](https://docs.ceph.com/en/latest/dev/developer_guide/jaegertracing/)
+
+## Deploying Jaeger Services
+
+We are going to use vstart for getting started with tracing.
+
+For this please ensure you have:
+
+1. Ceph compiled with `WITH_JAEGER=ON`.
+2. deployed jaeger backend services - to deploy the Jaeger Backend service using the vstart development cluster you just need to pass the `--jaeger` option.
+
+```
+$ ../src/vstart.sh --jaeger
+```
+
+By following the above steps, you should be able to set up all the Jaeger services and access the JaegerUI at [http://localhost:16686](http://localhost:16686/).
+
+Read more: [https://www.jaegertracing.io/docs/1.20/getting-started/#all-in-one](https://www.jaegertracing.io/docs/1.20/getting-started/#all-in-one)
+
+![images/image10.png](images/image10.png)
+
+(JaegerUI at [http://localhost:16686](http://localhost:16686/) )
+
+If for some reason you are not able to access JaegerUI, retry manually running Jaeger services using:
+
+```
+$ docker run -d --name jaeger \
+-e COLLECTOR_ZIPKIN_HTTP_PORT=9411 \
+-p 5775:5775/udp \
+-p 6831:6831/udp \
+-p 6832:6832/udp \
+-p 5778:5778 \
+-p 16686:16686 \
+-p 14268:14268 \
+-p 14250:14250 \
+-p 9411:9411 \
+jaegertracing/all-in-one:1.20
+```
+## Tracing Core Services
+
+Now that we have Jaeger Services up and running, let's take a look into Ceph’s core services tracing.
+
+Ceph currently can trace operations in the OSD I/O path and we'll be it demonstrating here:
+
+We'll perform a simple write operation, for which we are using rados bench write. You can use any other available write interface of your choice.
+
+
+```
+[ideepika@vossi03 build]$ bin/ceph osd pool create test; //create a pool
+[ideepika@vossi03 build]$ bin/rados -p test bench 5 write --no-cleanup //perform a rados bench write for 5 sec
+```
+
+On refreshing the JaegerUI ([http://localhost:16686](http://localhost:16686/)), you should be able to see osd-services in the services field, which specify the traced OSD processes in a lifetime of a request.
+
+![images/image4.gif](images/image4.gif)
+
+![images/image8.png](images/image8.png)
+
+Right below is the Operations field, which lists the spans collected, clicking on which shall give you traces containing it.
+
+![images/image5.png](images/image5.png)
+
+we see a list of the traces gathered by our recent write operation, and an x(time)-y(duration) graph with traces as data points.
+
+![images/image3.gif](images/image3.gif)
+
+![images/image2.png](images/image2.png)
+
+when you click on any of the traces, it should expand into all the spans and metadata stored in them.
+
+![images/image6.gif](images/image6.gif)
+
+We can store Ceph's metadata in the form of tags and logs while creating a span, as seen below; logs field carrying Ceph's relevant metadata.
+
+![images/image9.png](images/image9.png)
+
+There you have your internal processes visualized!
+
+**Exporting Traces as JSON**
+
+These traces are portable! They can be converted into JSON output, which can be rendered on other systems using the JaegerUI.
+
+![images/image7.png](images/image7.png)
+
+**Demo**
+
+<iframe
+  width="560"
+  height="315"
+  src="https://youtu.be/GVXlBL6vtVY"
+  title="Quick Demo of using JaegerUI for Ceph"
+  frameborder="0"
+  allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture"
+  allowfullscreen
+></iframe>
+
+**What’s Next**
+
+This project is still a work in progress, however with the orchestration of the right information as real-time traces, we will be having an end-to-end tracing, which can make debugging much easier, so understanding the internals of Ceph!
+
+We look forward to improving the observability of Ceph overall.
+
+We have some tasks lined up for improving tracing support, extending tracing support to clients( RGW, CephFS, RBD) and integration with OSD traces, improving deployment strategies for always-on monitoring of high-level traces.
+
+If this sounds exciting to you, we welcome contributions in the form of PRs!
+
+Please feel free to reach out over the [email protected]  or IRC #ceph-devel on OFTC for queries!