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https://github.com/ceph/ceph
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75 lines
3.1 KiB
ReStructuredText
75 lines
3.1 KiB
ReStructuredText
JAEGER- DISTRIBUTED TRACING
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===========================
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Jaeger + Opentracing provides ready to use tracing services for distributed
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systems and is becoming the widely used standard because of their simplicity and
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standardization.
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We use a modified `jaeger-cpp-client
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<https://github.com/ceph/jaeger-client-cpp>`_ the backend provided to the
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Opentracing API, which is responsible for the collection of spans, these spans
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are made with the use of smart pointers that carry the timestamp, TraceID and other
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meta info like a specific tag/log associated with the span to uniquely identify
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it across the distributed system.
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BASIC ARCHITECTURE AND TERMINOLOGY
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----------------------------------
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* TRACE: A trace shows the data/execution path through a system.
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* SPAN: A single unit of a trace, it is a data structure that stores
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information like operation name, timestamps, ordering in a trace.
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* JAEGER CLIENT: language-specific implementations of the OpenTracing API.
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* JAEGER AGENT: a daemon that listens for spans sent over User Datagram Protocol.
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The agent is meant to be placed on the same host as the instrumented
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application. (acts like a sidecar listener)
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* JAEGER COLLECTOR: Jaeger agent sends the spans to this daemon which then
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stitches the spans together to form a trace(if enabled, also persists a database
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for these traces)
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* JAEGER QUERY AND CONSOLE FRONTEND: UI based frontend to checkout the jaeger
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traces, navigate to http://localhost:16686 (if using default `all-in-one
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docker <https://www.jaegertracing.io/docs/1.22/getting-started/#all-in-one>`_ to access the Jaeger UI.
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HOW TO GET STARTED USING TRACING?
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---------------------------------
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Enabling jaegertracing with Ceph needs deployment Jaeger daemons + compiling
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Ceph with Jaeger, orchestrated to be used in vstart cluster for developers, this
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uses a jaeger `all-in-one docker
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<https://www.jaegertracing.io/docs/1.22/getting-started/#all-in-one>`_ which
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isn't recommended for production, but for testing purposes. Let's look at all the
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steps needed:
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1. Update system with Jaeger dependencies, using install-deps::
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$ WITH_JAEGER=true ./install-deps.sh
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2. Compile Ceph with Jaeger enabled:
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- for precompiled build::
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$ cd build
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$ cmake -DWITH_JAEGER=ON ..
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- for fresh compilation using do_cmake.sh::
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$ ./do_cmake.sh -DWITH_JAEGER=ON && ninja vstart
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3. After successful compiling, start a vstart cluster with `--jaeger` which
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will deploy `jaeger all-in-one <https://www.jaegertracing.io/docs/1.20/getting-started/#all-in-one>`_
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using container deployment services(docker/podman)::
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$ MON=1 MGR=0 OSD=1 ../src/vstart.sh --with-jaeger
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if the deployment is unsuccessful, you can deploy `all-in-one
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<https://www.jaegertracing.io/docs/1.20/getting- started/#all-in-one>`_
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service manually and start vstart cluster without jaeger as well.
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4. Test the traces using rados-bench write::
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$ bin/rados -p test bench 5 write --no-cleanup
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.. seealso::
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`using-jaeger-cpp-client-for-distributed-tracing-in-ceph <https://medium.com/@deepikaupadhyay/using-jaeger-cpp-client-for-distributed-tracing-in-ceph-8b1f4906ca2>`_
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