doc/dev/blkin.rst
if you compile code, please use -DWITH_LTTNG option (default: ON)::
./do_cmake -DWITH_LTTNG=ON
If your Ceph deployment is package-based (YUM, DNF, APT) vs containerized, install the required software packages according to the module which you want to track， otherwise, it may cause a coredump due to missing *tp.solibrary files::
librbd-devel
librgw-devel
librados-devel
Config option for tracing must be set to true in ceph.conf. Following options are currently available::
bluestore_tracing event_tracing (-DWITH_EVENTTRACE) osd_function_tracing (-DWITH_OSD_INSTRUMENT_FUNCTIONS) osd_objectstore_tracing (actually filestore tracing) rbd_tracing osd_tracing rados_tracing rgw_op_tracing rgw_rados_tracing
Start LTTng daemon::
lttng-sessiond --daemonize
Run vstart cluster with enabling trace options::
../src/vstart.sh -d -n -l -e -o "osd_tracing = true"
List available tracepoints::
lttng list --userspace
You will get something like::
PID: 100859 - Name: /path/to/ceph-osd pg:queue_op (loglevel: TRACE_DEBUG_LINE (13)) (type: tracepoint) osd:do_osd_op_post (loglevel: TRACE_DEBUG_LINE (13)) (type: tracepoint) osd:do_osd_op_pre_unknown (loglevel: TRACE_DEBUG_LINE (13)) (type: tracepoint) osd:do_osd_op_pre_copy_from (loglevel: TRACE_DEBUG_LINE (13)) (type: tracepoint) osd:do_osd_op_pre_copy_get (loglevel: TRACE_DEBUG_LINE (13)) (type: tracepoint) ...
Create tracing session, enable tracepoints and start trace::
lttng create trace-test lttng enable-event --userspace osd:* lttng start
Perform some Ceph operation::
rados bench -p ec 5 write
Stop tracing and view result::
lttng stop lttng view
Destroy tracing session::
lttng destroy
.. deprecated:: This feature was deprecated in the Squid release and will be removed in a later release.
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: https://zipkin.io/
Use -DWITH_BLKIN option (which requires -DWITH_LTTNG)::
./do_cmake -DWITH_LTTNG=ON -DWITH_BLKIN=ON
Config option for blkin must be set to true in ceph.conf. Following options are currently available::
rbd_blkin_trace_all osd_blkin_trace_all osdc_blkin_trace_all
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 didn't install it. Then launch Ceph with the vstart.sh script
in Ceph's src directory so you can see the possible tracepoints.::
OSD=3 MON=3 RGW=1 ../src/vstart.sh -n -o "rbd_blkin_trace_all" lttng list --userspace
You'll see something like the following:::
PID: 8987 - Name: ./ceph-osd zipkin:timestamp (loglevel: TRACE_WARNING (4)) (type: tracepoint) zipkin:keyval_integer (loglevel: TRACE_WARNING (4)) (type: tracepoint) zipkin:keyval_string (loglevel: TRACE_WARNING (4)) (type: tracepoint) lttng_ust_tracelog:TRACE_DEBUG (loglevel: TRACE_DEBUG (14)) (type: tracepoint)
PID: 8407 - Name: ./ceph-mon zipkin:timestamp (loglevel: TRACE_WARNING (4)) (type: tracepoint) zipkin:keyval_integer (loglevel: TRACE_WARNING (4)) (type: tracepoint) zipkin:keyval_string (loglevel: TRACE_WARNING (4)) (type: tracepoint) lttng_ust_tracelog:TRACE_DEBUG (loglevel: TRACE_DEBUG (14)) (type: tracepoint)
...
Next, stop Ceph so that the tracepoints can be enabled.::
../src/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_integer lttng enable-event --userspace zipkin:keyval_string lttng start
Then start up Ceph again.::
OSD=3 MON=3 RGW=1 ../src/vstart.sh -n -o "rbd_blkin_trace_all"
You may want to check that ceph is up.::
ceph status
Now put something in using rados, check that it made it, get it back, and remove it.::
ceph osd pool create test-blkin rados put test-object-1 ../src/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:::
[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" } [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 } [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" }
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. The executable jar runs a collector on port 9410 and the web interface on port 9411
Download Zipkin Package::
git clone https://github.com/openzipkin/zipkin && cd zipkin wget -O zipkin.jar 'https://search.maven.org/remote_content?g=io.zipkin.java&a=zipkin-server&v=LATEST&c=exec' java -jar zipkin.jar
Or, launch docker image::
docker run -d -p 9411:9411 openzipkin/Zipkin
Download babeltrace-zipkin project. This project takes the traces generated with blkin and sends them to a Zipkin collector using scribe::
git clone https://github.com/vears91/babeltrace-zipkin cd babeltrace-zipkin
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-collector-ip}:9411 Click "Find traces"