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https://github.com/ceph/ceph
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170 lines
5.9 KiB
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170 lines
5.9 KiB
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=========================
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Tracing Ceph With BlkKin
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=========================
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Ceph can use Blkin, a library created by Marios Kogias and others,
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which enables tracking a specific request from the time it enters
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the system at higher levels till it is finally served by RADOS.
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In general, Blkin implements the Dapper_ tracing semantics
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in order to show the causal relationships between the different
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processing phases that an IO request may trigger. The goal is an
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end-to-end visualisation of the request's route in the system,
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accompanied by information concerning latencies in each processing
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phase. Thanks to LTTng this can happen with a minimal overhead and
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in realtime. The LTTng traces can then be visualized with Twitter's
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Zipkin_.
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.. _Dapper: http://static.googleusercontent.com/media/research.google.com/el//pubs/archive/36356.pdf
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.. _Zipkin: https://zipkin.io/
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Installing Blkin
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================
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You can install Markos Kogias' upstream Blkin_ by hand.::
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cd blkin/
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make && make install
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or build distribution packages using DistroReadyBlkin_, which also comes with
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pkgconfig support. If you choose the latter, then you must generate the
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configure and make files first.::
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cd blkin
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autoreconf -i
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.. _Blkin: https://github.com/marioskogias/blkin
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.. _DistroReadyBlkin: https://github.com/agshew/blkin
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Configuring Ceph with Blkin
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===========================
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If you built and installed Blkin by hand, rather than building and
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installing packages, then set these variables before configuring
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Ceph.::
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export BLKIN_CFLAGS=-Iblkin/
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export BLKIN_LIBS=-lzipkin-cpp
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Blkin support in Ceph is disabled by default, so you may
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want to configure with something like::
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./do_cmake -DWITH_BLKIN=ON
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Config option for blkin must be set to true in ceph.conf to get
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traces from rbd through OSDC and OSD::
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rbd_blkin_trace_all = true
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Testing Blkin
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=============
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It's easy to test Ceph's Blkin tracing. Let's assume you don't have
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Ceph already running, and you compiled Ceph with Blkin support but
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you did't install it. Then launch Ceph with the ``vstart.sh`` script
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in Ceph's src directgory so you can see the possible tracepoints.::
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cd src
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OSD=3 MON=3 RGW=1 ./vstart.sh -n
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lttng list --userspace
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You'll see something like the following:::
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UST events:
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-------------
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PID: 8987 - Name: ./ceph-osd
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zipkin:timestamp (loglevel: TRACE_WARNING (4)) (type: tracepoint)
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zipkin:keyval_integer (loglevel: TRACE_WARNING (4)) (type: tracepoint)
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zipkin:keyval_string (loglevel: TRACE_WARNING (4)) (type: tracepoint)
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lttng_ust_tracelog:TRACE_DEBUG (loglevel: TRACE_DEBUG (14)) (type: tracepoint)
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PID: 8407 - Name: ./ceph-mon
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zipkin:timestamp (loglevel: TRACE_WARNING (4)) (type: tracepoint)
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zipkin:keyval_integer (loglevel: TRACE_WARNING (4)) (type: tracepoint)
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zipkin:keyval_string (loglevel: TRACE_WARNING (4)) (type: tracepoint)
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lttng_ust_tracelog:TRACE_DEBUG (loglevel: TRACE_DEBUG (14)) (type: tracepoint)
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...
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Next, stop Ceph so that the tracepoints can be enabled.::
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./stop.sh
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Start up an LTTng session and enable the tracepoints.::
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lttng create blkin-test
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lttng enable-event --userspace zipkin:timestamp
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lttng enable-event --userspace zipkin:keyval_integer
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lttng enable-event --userspace zipkin:keyval_string
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lttng start
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Then start up Ceph again.::
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OSD=3 MON=3 RGW=1 ./vstart.sh -n
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You may want to check that ceph is up.::
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./ceph status
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Now put something in usin rados, check that it made it, get it back, and remove it.::
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./rados mkpool test-blkin
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./rados put test-object-1 ./vstart.sh --pool=test-blkin
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./rados -p test-blkin ls
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./ceph osd map test-blkin test-object-1
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./rados get test-object-1 ./vstart-copy.sh --pool=test-blkin
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md5sum vstart*
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./rados rm test-object-1 --pool=test-blkin
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You could also use the example in ``examples/librados/`` or ``rados bench``.
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Then stop the LTTng session and see what was collected.::
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lttng stop
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lttng view
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You'll see something like:::
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[15:33:08.884275486] (+0.000225472) ubuntu zipkin:timestamp: { cpu_id = 53 }, { trace_name = "op", service_name = "Objecter", port_no = 0, ip = "0.0.0.0", trace_id = 5485970765435202833, span_id = 5485970765435202833, parent_span_id = 0, event = "osd op reply" }
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[15:33:08.884614135] (+0.000002839) ubuntu zipkin:keyval_integer: { cpu_id = 10 }, { trace_name = "", service_name = "Messenger", port_no = 6805, ip = "0.0.0.0", trace_id = 7381732770245808782, span_id = 7387710183742669839, parent_span_id = 1205040135881905799, key = "tid", val = 2 }
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[15:33:08.884616431] (+0.000002296) ubuntu zipkin:keyval_string: { cpu_id = 10 }, { trace_name = "", service_name = "Messenger", port_no = 6805, ip = "0.0.0.0", trace_id = 7381732770245808782, span_id = 7387710183742669839, parent_span_id = 1205040135881905799, key = "entity type", val = "client" }
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Install Zipkin
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===============
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One of the points of using Blkin is so that you can look at the traces
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using Zipkin. Users should run Zipkin as a tracepoints collector and
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also a web service. The executable jar runs a collector on port 9410 and
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the web interface on port 9411
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Download Zipkin Package::
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git clone https://github.com/openzipkin/zipkin && cd zipkin
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wget -O zipkin.jar 'https://search.maven.org/remote_content?g=io.zipkin.java&a=zipkin-server&v=LATEST&c=exec'
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java -jar zipkin.jar
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Show Ceph's Blkin Traces in Zipkin-web
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======================================
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Download babeltrace-zipkin project. This project takes the traces
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generated with blkin and sends them to a Zipkin collector using scribe::
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git clone https://github.com/vears91/babeltrace-zipkin
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cd babeltrace-zipkin
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Send lttng data to Zipkin::
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python3 babeltrace_zipkin.py ${lttng-traces-dir}/${blkin-test}/ust/uid/0/64-bit/ -p ${zipkin-collector-port(9410 by default)} -s ${zipkin-collector-ip}
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Example::
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python3 babeltrace_zipkin.py ~/lttng-traces-dir/blkin-test-20150225-160222/ust/uid/0/64-bit/ -p 9410 -s 127.0.0.1
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Check Ceph traces on webpage::
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Browse http://${zipkin-collector-ip}:9411
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Click "Find traces"
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