crimson
Crimson is the code name of crimson-osd, which is the next generation ceph-osd. It targets fast networking devices, fast storage devices by leveraging state of the art technologies like DPDK and SPDK, for better performance. And it will keep the support of HDDs and low-end SSDs via BlueStore. Crimson will try to be backward compatible with classic OSD.
Building Crimson
Crimson is not enabled by default. To enable it:
$ WITH_SEASTAR=true ./install-deps.sh
$ mkdir build && cd build
$ cmake -DWITH_SEASTAR=ON ..
Please note, ASan is enabled by default if crimson is built from a source cloned using git.
Running Crimson
As you might expect, crimson is not featurewise on par with its predecessor yet.
object store backend
At the moment, crimson-osd
offers both native and alienized object store
backends. The native object store backends perform IO using seastar reactor.
They are:
- cyanstore
CyanStore is modeled after memstore in classic OSD.
- seastore
Seastore is still under active development.
While the alienized object store backends are backed by a thread pool, which is a proxy of the alien store adaptor running in SeaStar. The proxy issues requests to object stores running in alien threads, i.e., worker threads not managed by the Seastar framework. They are:
- memstore
The memory backed object store
- bluestore
The object store used by classic OSD by default.
daemonize
Unlike ceph-osd
, crimson-osd
does not daemonize itself even if the
daemonize
option is enabled. Because, to read this option, crimson-osd
needs to ready its config sharded service, but this sharded service lives
in the seastar reactor. If we fork a child process and exit the parent after
starting the Seastar engine, that will leave us with a single thread which is
the replica of the thread calls fork(). This would unnecessarily complicate
the code, if we would have tackled this problem in crimson.
Since a lot of GNU/Linux distros are using systemd nowadays, which is able to
daemonize the application, there is no need to daemonize by ourselves. For
those who are using sysvinit, they can use start-stop-daemon
for daemonizing
crimson-osd
. If this is not acceptable, we can whip up a helper utility
to do the trick.
logging
Currently, crimson-osd
uses the logging utility offered by Seastar. see
src/common/dout.h
for the mapping between different logging levels to
the severity levels in Seastar. For instance, the messages sent to derr
will be printed using logger::error()
, and the messages with debug level
over 20
will be printed using logger::trace()
.
ceph |
seastar |
< 0 |
error |
0 |
warn |
[1, 6) |
info |
[6, 20] |
debug |
> 20 |
trace |
Please note, crimson-osd
does not send the logging message to specified log_file
. It writes
the logging messages to stdout and/or syslog. Again, this behavior can be
changed using --log-to-stdout
and --log-to-syslog
command line
options. By default, log-to-stdout
is enabled, and the latter disabled.
vstart.sh
To facilitate the development of crimson, following options would be handy when
using vstart.sh
,
--crimson
start
crimson-osd
instead ofceph-osd
--nodaemon
do not daemonize the service
--redirect-output
redirect the stdout and stderr of service to
out/$type.$num.stdout
.--osd-args
pass extra command line options to crimson-osd or ceph-osd. It's quite useful for passing Seastar options to crimson-osd. For instance, you could use
--osd-args "--memory 2G"
to set the memory to use. Please refer the output of:crimson-osd --help-seastar
for more Seastar specific command line options.
--cyanstore
use the CyanStore as the object store backend.
--bluestore
use the alienized BlueStore as the object store backend. This is the default setting, if not specified otherwise.
--memstore
use the alienized MemStore as the object store backend.
So, a typical command to start a single-crimson-node cluster is:
$ MGR=1 MON=1 OSD=1 MDS=0 RGW=0 ../src/vstart.sh -n -x \
--without-dashboard --cyanstore \
--crimson --redirect-output \
--osd-args "--memory 4G"
Where we assign 4 GiB memory, a single thread running on core-0 to crimson-osd.
You could stop the vstart cluster using:
$ ../src/stop.sh --crimson
Metrics and Tracing
Crimson offers three ways to report the stats and metrics:
pg stats reported to mgr
Crimson collects the per-pg, per-pool, and per-osd stats in a MPGStats message, and send it over to mgr, so that the mgr modules can query them using the MgrModule.get() method.
asock command
an asock command is offered for dumping the metrics:
$ ceph tell osd.0 dump_metrics
$ ceph tell osd.0 dump_metrics reactor_utilization
Where reactor_utilization is an optional string allowing us to filter the dumped metrics by prefix.
Prometheus text protocol
the listening port and address can be configured using the command line options of --prometheus_port see Prometheus for more details.
Profiling Crimson
fio
crimson-store-nbd
exposes configurable FuturizedStore
internals as an
NBD server for use with fio.
To use fio to test crimson-store-nbd
,
You will need to install
libnbd
, and compile fio likeapt-get install libnbd-dev git clone git://git.kernel.dk/fio.git cd fio ./configure --enable-libnbd make
Build
crimson-store-nbd
cd build ninja crimson-store-nbd
Run the
crimson-store-nbd
server with a block device. Please specify the path to the raw device, like/dev/nvme1n1
in place of the created file for testing with a block device.export disk_img=/tmp/disk.img export unix_socket=/tmp/store_nbd_socket.sock rm -f $disk_img $unix_socket truncate -s 512M $disk_img ./bin/crimson-store-nbd \ --device-path $disk_img \ --smp 1 \ --mkfs true \ --type transaction_manager \ --uds-path ${unix_socket} &
in which,
--smp
how many CPU cores are used
--mkfs
initialize the device first
--type
which backend to use. If
transaction_manager
is specified, SeaStore'sTransactionManager
andBlockSegmentManager
are used to emulate a block device. Otherwise, this option is used to choose a backend ofFuturizedStore
, where the whole "device" is divided into multiple fixed-size objects whose size is specified by--object-size
. So, if you are only interested in testing the lower-level implementation of SeaStore like logical address translation layer and garbage collection without the object store semantics,transaction_manager
would be a better choice.
Create an fio job file named
nbd.fio
[global] ioengine=nbd uri=nbd+unix:///?socket=${unix_socket} rw=randrw time_based runtime=120 group_reporting iodepth=1 size=512M [job0] offset=0
Test the crimson object store using the fio compiled just now
./fio nbd.fio
CBT
We can use cbt for performing perf tests:
$ git checkout master
$ make crimson-osd
$ ../src/script/run-cbt.sh --cbt ~/dev/cbt -a /tmp/baseline ../src/test/crimson/cbt/radosbench_4K_read.yaml
$ git checkout yet-another-pr
$ make crimson-osd
$ ../src/script/run-cbt.sh --cbt ~/dev/cbt -a /tmp/yap ../src/test/crimson/cbt/radosbench_4K_read.yaml
$ ~/dev/cbt/compare.py -b /tmp/baseline -a /tmp/yap -v
19:48:23 - INFO - cbt - prefill/gen8/0: bandwidth: (or (greater) (near 0.05)):: 0.183165/0.186155 => accepted
19:48:23 - INFO - cbt - prefill/gen8/0: iops_avg: (or (greater) (near 0.05)):: 46.0/47.0 => accepted
19:48:23 - WARNING - cbt - prefill/gen8/0: iops_stddev: (or (less) (near 0.05)):: 10.4403/6.65833 => rejected
19:48:23 - INFO - cbt - prefill/gen8/0: latency_avg: (or (less) (near 0.05)):: 0.340868/0.333712 => accepted
19:48:23 - INFO - cbt - prefill/gen8/1: bandwidth: (or (greater) (near 0.05)):: 0.190447/0.177619 => accepted
19:48:23 - INFO - cbt - prefill/gen8/1: iops_avg: (or (greater) (near 0.05)):: 48.0/45.0 => accepted
19:48:23 - INFO - cbt - prefill/gen8/1: iops_stddev: (or (less) (near 0.05)):: 6.1101/9.81495 => accepted
19:48:23 - INFO - cbt - prefill/gen8/1: latency_avg: (or (less) (near 0.05)):: 0.325163/0.350251 => accepted
19:48:23 - INFO - cbt - seq/gen8/0: bandwidth: (or (greater) (near 0.05)):: 1.24654/1.22336 => accepted
19:48:23 - INFO - cbt - seq/gen8/0: iops_avg: (or (greater) (near 0.05)):: 319.0/313.0 => accepted
19:48:23 - INFO - cbt - seq/gen8/0: iops_stddev: (or (less) (near 0.05)):: 0.0/0.0 => accepted
19:48:23 - INFO - cbt - seq/gen8/0: latency_avg: (or (less) (near 0.05)):: 0.0497733/0.0509029 => accepted
19:48:23 - INFO - cbt - seq/gen8/1: bandwidth: (or (greater) (near 0.05)):: 1.22717/1.11372 => accepted
19:48:23 - INFO - cbt - seq/gen8/1: iops_avg: (or (greater) (near 0.05)):: 314.0/285.0 => accepted
19:48:23 - INFO - cbt - seq/gen8/1: iops_stddev: (or (less) (near 0.05)):: 0.0/0.0 => accepted
19:48:23 - INFO - cbt - seq/gen8/1: latency_avg: (or (less) (near 0.05)):: 0.0508262/0.0557337 => accepted
19:48:23 - WARNING - cbt - 1 tests failed out of 16
Where we compile and run the same test against two branches. One is master
, another is yet-another-pr
branch.
And then we compare the test results. Along with every test case, a set of rules is defined to check if we have
performance regressions when comparing two set of test results. If a possible regression is found, the rule and
corresponding test results are highlighted.
Hacking Crimson
Seastar Documents
See Seastar Tutorial . Or build a browsable version and start an HTTP server:
$ cd seastar
$ ./configure.py --mode debug
$ ninja -C build/debug docs
$ python3 -m http.server -d build/debug/doc/html
You might want to install pandoc
and other dependencies beforehand.
Debugging Crimson
Debugging with GDB
The tips for debugging Scylla also apply to Crimson.
Human-readable backtraces with addr2line
When a seastar application crashes, it leaves us with a serial of addresses, like:
Segmentation fault.
Backtrace:
0x00000000108254aa
0x00000000107f74b9
0x00000000105366cc
0x000000001053682c
0x00000000105d2c2e
0x0000000010629b96
0x0000000010629c31
0x00002a02ebd8272f
0x00000000105d93ee
0x00000000103eff59
0x000000000d9c1d0a
/lib/x86_64-linux-gnu/libc.so.6+0x000000000002409a
0x000000000d833ac9
Segmentation fault
seastar-addr2line
offered by Seastar can be used to decipher these
addresses. After running the script, it will be waiting for input from stdin,
so we need to copy and paste the above addresses, then send the EOF by inputting
control-D
in the terminal:
$ ../src/seastar/scripts/seastar-addr2line -e bin/crimson-osd
0x00000000108254aa
0x00000000107f74b9
0x00000000105366cc
0x000000001053682c
0x00000000105d2c2e
0x0000000010629b96
0x0000000010629c31
0x00002a02ebd8272f
0x00000000105d93ee
0x00000000103eff59
0x000000000d9c1d0a
0x00000000108254aa
[Backtrace #0]
seastar::backtrace_buffer::append_backtrace() at /home/kefu/dev/ceph/build/../src/seastar/src/core/reactor.cc:1136
seastar::print_with_backtrace(seastar::backtrace_buffer&) at /home/kefu/dev/ceph/build/../src/seastar/src/core/reactor.cc:1157
seastar::print_with_backtrace(char const*) at /home/kefu/dev/ceph/build/../src/seastar/src/core/reactor.cc:1164
seastar::sigsegv_action() at /home/kefu/dev/ceph/build/../src/seastar/src/core/reactor.cc:5119
seastar::install_oneshot_signal_handler<11, &seastar::sigsegv_action>()::{lambda(int, siginfo_t*, void*)#1}::operator()(int, siginfo_t*, void*) const at /home/kefu/dev/ceph/build/../src/seastar/src/core/reactor.cc:5105
seastar::install_oneshot_signal_handler<11, &seastar::sigsegv_action>()::{lambda(int, siginfo_t*, void*)#1}::_FUN(int, siginfo_t*, void*) at /home/kefu/dev/ceph/build/../src/seastar/src/core/reactor.cc:5101
?? ??:0
seastar::smp::configure(boost::program_options::variables_map, seastar::reactor_config) at /home/kefu/dev/ceph/build/../src/seastar/src/core/reactor.cc:5418
seastar::app_template::run_deprecated(int, char**, std::function<void ()>&&) at /home/kefu/dev/ceph/build/../src/seastar/src/core/app-template.cc:173 (discriminator 5)
main at /home/kefu/dev/ceph/build/../src/crimson/osd/main.cc:131 (discriminator 1)
Please note, seastar-addr2line
is able to extract the addresses from
the input, so you can also paste the log messages like:
2020-07-22T11:37:04.500 INFO:teuthology.orchestra.run.smithi061.stderr:Backtrace:
2020-07-22T11:37:04.500 INFO:teuthology.orchestra.run.smithi061.stderr: 0x0000000000e78dbc
2020-07-22T11:37:04.501 INFO:teuthology.orchestra.run.smithi061.stderr: 0x0000000000e3e7f0
2020-07-22T11:37:04.501 INFO:teuthology.orchestra.run.smithi061.stderr: 0x0000000000e3e8b8
2020-07-22T11:37:04.501 INFO:teuthology.orchestra.run.smithi061.stderr: 0x0000000000e3e985
2020-07-22T11:37:04.501 INFO:teuthology.orchestra.run.smithi061.stderr: /lib64/libpthread.so.0+0x0000000000012dbf
Unlike classic OSD, crimson does not print a human-readable backtrace when it handles fatal signals like SIGSEGV or SIGABRT. And it is more complicated when it comes to a stripped binary. So before planting a signal handler for those signals in crimson, we could to use script/ceph-debug-docker.sh to parse the addresses in the backtrace:
# assuming you are under the source tree of ceph
$ ./src/script/ceph-debug-docker.sh --flavor crimson master:27e237c137c330ebb82627166927b7681b20d0aa centos:8
....
[root@3deb50a8ad51 ~]# wget -q https://raw.githubusercontent.com/scylladb/seastar/master/scripts/seastar-addr2line
[root@3deb50a8ad51 ~]# dnf install -q -y file
[root@3deb50a8ad51 ~]# python3 seastar-addr2line -e /usr/bin/crimson-osd
# paste the backtrace here