src/jaegertracing: add README.md for jaegertracing

Signed-off-by: Deepika Upadhyay <dupadhya@redhat.com>

src/jaegertracing/README.md

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+
+This guide provides the steps for anyone who is interested in getting started with end to end tracing using Jaeger and Opentracing libraries. 
+
+Note: Right now support is available for using Jaeger in development environment on centos8 or Ubuntu(Bionic or Focal)
+
+## Jaeger & Opentracing : 
+Jaeger along with Opentracing provides a standard solution for tracing the complex background transactions in Ceph. 
+Opentracing is the framework which in this case works with Jaeger backend, consisting of an agent which listens for any span, upon receiving one sends them to the collector. 
+The spans gathered by the collectors are weived together to form traces, which can then be rendered on Jaeger UI. 
+![Architecture](https://www.jaegertracing.io/img/architecture-v1.png)
+
+## Steps: 
+The instructions work ideally for Ubuntu 18.04(Bionic), and have been tested on Fedora 31 as well as Centos8. 
+
+### Installing Jaeger dependencies :
+
+1. rerun: 
+
+```
+$ ./install_deps.sh
+```
+this will install all the distro package available dependencies that are additionally required for Jaeger.
+
+Note: you should use boost v1.72+ and above for depedencies to work properly.
+Note: for Bionic(Ubuntu 18.04) yaml-cpp v0.6.0+ is not available, the following instruction will help in building it from source: 
+
+2. For enabling Jaeger, either create a new build for ceph using: 
+```
+$ ./do_cmake.sh -DWITH_JAEGER=ON
+```
+or rerun cmake from `build/` using  
+```
+$ cmake -DWITH_JAEGER=ON ..
+```
+<!-- sudo apt-get install automake bison flex g++ git libevent-dev libssl-dev libtool make pkg-config> -->
+
+### Pull Jaeger UI docker image
+```
+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 9411:9411 \
+  jaegertracing/all-in-one:1.12
+```
+<Note add port details here>
+
+Test if tracing is working fine:
+
+start a vstart cluster: 
+```
+MDS=0 MGR=1 OSD=1 MON=1 ../src/vstart.sh -n --without-dashboard --memstore  
+```
+perform a write operation using RADOS bench, use the following commands : 
+```
+// creating a pool
+    $ bin/ceph osd pool create test 8
+// writing to it
+    $ bin/rados -p test bench 5 write --no-cleanup
+```
+You can then navigate to http://localhost:16686 to access the Jaeger UI to see the traces. 
+
+### Tracer configuration
+
+Based on the usecase, the tracer can be configured by passing suitable parameter in form of a yaml file( generally present in `$(ceph-dir)/src/jaegertracing` )
+
+
+TODO: elaborate more about config.yaml
+
+
+valid config parameters: 
+https://www.jaegertracing.io/docs/1.16/client-features/
+
+ <!-- TODO: 
+ 1. add traced path details
+ 2. tracer config options recommended
+ 
+ 
+ Note: how to add new tracepath(functional summary in a blog to publish on ceph)
+ either here or on tracker: common debugging issues
+ -->