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diff --git a/src/ceph/doc/dev/blkin.rst b/src/ceph/doc/dev/blkin.rst new file mode 100644 index 0000000..8e0320f --- /dev/null +++ b/src/ceph/doc/dev/blkin.rst @@ -0,0 +1,167 @@ +========================= + Tracing Ceph With BlkKin +========================= + +Ceph can use Blkin, a library created by Marios Kogias and others, +which enables tracking a specific request from the time it enters +the system at higher levels till it is finally served by RADOS. + +In general, Blkin implements the Dapper_ tracing semantics +in order to show the causal relationships between the different +processing phases that an IO request may trigger. The goal is an +end-to-end visualisation of the request's route in the system, +accompanied by information concerning latencies in each processing +phase. Thanks to LTTng this can happen with a minimal overhead and +in realtime. The LTTng traces can then be visualized with Twitter's +Zipkin_. + +.. _Dapper: http://static.googleusercontent.com/media/research.google.com/el//pubs/archive/36356.pdf +.. _Zipkin: http://zipkin.io/ + + +Installing Blkin +================ + +You can install Markos Kogias' upstream Blkin_ by hand.:: + + cd blkin/ + make && make install + +or build distribution packages using DistroReadyBlkin_, which also comes with +pkgconfig support. If you choose the latter, then you must generate the +configure and make files first.:: + + cd blkin + autoreconf -i + +.. _Blkin: https://github.com/marioskogias/blkin +.. _DistroReadyBlkin: https://github.com/agshew/blkin + + +Configuring Ceph with Blkin +=========================== + +If you built and installed Blkin by hand, rather than building and +installing packages, then set these variables before configuring +Ceph.:: + + export BLKIN_CFLAGS=-Iblkin/ + export BLKIN_LIBS=-lzipkin-cpp + +Since there are separate lttng and blkin changes to Ceph, you may +want to configure with something like:: + + ./configure --with-blkin --without-lttng --with-debug + + +Testing Blkin +============= + +It's easy to test Ceph's Blkin tracing. Let's assume you don't have +Ceph already running, and you compiled Ceph with Blkin support but +you did't install it. Then launch Ceph with the ``vstart.sh`` script +in Ceph's src directgory so you can see the possible tracepoints.:: + + cd src + OSD=3 MON=3 RGW=1 ./vstart.sh -n + lttng list --userspace + +You'll see something like the following::: + + UST events: + ------------- + PID: 8987 - Name: ./ceph-osd + zipkin:timestamp (loglevel: TRACE_WARNING (4)) (type: tracepoint) + zipkin:keyval (loglevel: TRACE_WARNING (4)) (type: tracepoint) + ust_baddr_statedump:soinfo (loglevel: TRACE_DEBUG_LINE (13)) (type: tracepoint) + + PID: 8407 - Name: ./ceph-mon + zipkin:timestamp (loglevel: TRACE_WARNING (4)) (type: tracepoint) + zipkin:keyval (loglevel: TRACE_WARNING (4)) (type: tracepoint) + ust_baddr_statedump:soinfo (loglevel: TRACE_DEBUG_LINE (13)) (type: tracepoint) + + ... + +Next, stop Ceph so that the tracepoints can be enabled.:: + + ./stop.sh + +Start up an LTTng session and enable the tracepoints.:: + + lttng create blkin-test + lttng enable-event --userspace zipkin:timestamp + lttng enable-event --userspace zipkin:keyval + lttng start + +Then start up Ceph again.:: + + OSD=3 MON=3 RGW=1 ./vstart.sh -n + +You may want to check that ceph is up.:: + + ./ceph status + +Now put something in usin rados, check that it made it, get it back, and remove it.:: + + ./rados mkpool test-blkin + ./rados put test-object-1 ./vstart.sh --pool=test-blkin + ./rados -p test-blkin ls + ./ceph osd map test-blkin test-object-1 + ./rados get test-object-1 ./vstart-copy.sh --pool=test-blkin + md5sum vstart* + ./rados rm test-object-1 --pool=test-blkin + +You could also use the example in ``examples/librados/`` or ``rados bench``. + +Then stop the LTTng session and see what was collected.:: + + lttng stop + lttng view + +You'll see something like::: + + [13:09:07.755054973] (+?.?????????) scruffy zipkin:timestamp: { cpu_id = 5 }, { trace_name = "Main", service_name = "MOSDOp", port_no = 0, ip = "0.0.0.0", trace_id = 7492589359882233221, span_id = 2694140257089376129, parent_span_id = 0, event = "Message allocated" } + [13:09:07.755071569] (+0.000016596) scruffy zipkin:keyval: { cpu_id = 5 }, { trace_name = "Main", service_name = "MOSDOp", port_no = 0, ip = "0.0.0.0", trace_id = 7492589359882233221, span_id = 2694140257089376129, parent_span_id = 0, key = "Type", val = "MOSDOp" } + [13:09:07.755074217] (+0.000002648) scruffy zipkin:keyval: { cpu_id = 5 }, { trace_name = "Main", service_name = "MOSDOp", port_no = 0, ip = "0.0.0.0", trace_id = 7492589359882233221, span_id = 2694140257089376129, parent_span_id = 0, key = "Reqid", val = "client.4126.0:1" } + ... + + +Install Zipkin +=============== +One of the points of using Blkin is so that you can look at the traces +using Zipkin. Users should run Zipkin as a tracepoints collector and +also a web service, which means users need to run three services, +zipkin-collector, zipkin-query and zipkin-web. + +Download Zipkin Package:: + + wget https://github.com/twitter/zipkin/archive/1.1.0.tar.gz + tar zxf 1.1.0.tar.gz + cd zipkin-1.1.0 + bin/collector cassandra & + bin/query cassandra & + bin/web & + +Check Zipkin:: + + bin/test + Browse http://${zipkin-web-ip}:8080 + + +Show Ceph's Blkin Traces in Zipkin-web +====================================== +Blkin provides a script which translates lttng result to Zipkin +(Dapper) semantics. + +Send lttng data to Zipkin:: + + python3 babeltrace_zipkin.py ${lttng-traces-dir}/${blkin-test}/ust/uid/0/64-bit/ -p ${zipkin-collector-port(9410 by default)} -s ${zipkin-collector-ip} + +Example:: + + python3 babeltrace_zipkin.py ~/lttng-traces-dir/blkin-test-20150225-160222/ust/uid/0/64-bit/ -p 9410 -s 127.0.0.1 + +Check Ceph traces on webpage:: + + Browse http://${zipkin-web-ip}:8080 + Click "Find traces" |