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Print a histogram of the number of async work items in the shard's
outgoing smp queues.
Example:
(gdb) scylla smp-queues
10747 17 -> 3 ++++++++++++++++++++++++++++++++++++++++
721 17 -> 19 ++
247 17 -> 20 +
233 17 -> 10 +
210 17 -> 14 +
205 17 -> 4 +
204 17 -> 5 +
198 17 -> 16 +
197 17 -> 6 +
189 17 -> 11 +
181 17 -> 1 +
179 17 -> 13 +
176 17 -> 2 +
173 17 -> 0 +
163 17 -> 8 +
1 17 -> 9 +
Useful for identifying the target shard, when `scylla task_histogram`
indicates a high number of async work items.
To produce the histogram the command goes over all virtual objects in
memory and identifies the source and target queues of each
`seastar::smp_message_queue::async_work_item` object. Practically the
source queue will always be that of the current shard. As this scales
with the number of virtual objects in memory, it can take some time to
run. An alternative implementation would be to instead read the actual
smp queues, but the code of that is scary so I went for the simpler and
more reliable solution.
Signed-off-by: Botond Dénes <bdenes@scylladb.com>
Message-Id: <20191028132456.37796-1-bdenes@scylladb.com>
Scylla
Quick-start
To get the build going quickly, Scylla offers a frozen toolchain which would build and run Scylla using a pre-configured Docker image. Using the frozen toolchain will also isolate all of the installed dependencies in a Docker container. Assuming you have met the toolchain prerequisites, which is running Docker in user mode, building and running is as easy as:
$ ./tools/toolchain/dbuild ./configure.py
$ ./tools/toolchain/dbuild ninja build/release/scylla
$ ./tools/toolchain/dbuild ./build/release/scylla --developer-mode 1
Please see HACKING.md for detailed information on building and developing Scylla.
Note: GCC >= 8.1.1 is required to compile Scylla.
Running Scylla
- Run Scylla
./build/release/scylla
- run Scylla with one CPU and ./tmp as data directory
./build/release/scylla --datadir tmp --commitlog-directory tmp --smp 1
- For more run options:
./build/release/scylla --help
Scylla APIs and compatibility
By default, Scylla is compatible with Apache Cassandra and its APIs - CQL and Thrift. There is also experimental support for the API of Amazon DynamoDB, but being experimental it needs to be explicitly enabled to be used. For more information on how to enable the experimental DynamoDB compatibility in Scylla, and the current limitations of this feature, see Alternator and Getting started with Alternator.
Documentation
Documentation can be found in ./docs and on the wiki. There is currently no clear definition of what goes where, so when looking for something be sure to check both. Seastar documentation can be found here. User documentation can be found here.
Building Fedora RPM
As a pre-requisite, you need to install Mock on your machine:
# Install mock:
sudo yum install mock
# Add user to the "mock" group:
usermod -a -G mock $USER && newgrp mock
Then, to build an RPM, run:
./dist/redhat/build_rpm.sh
The built RPM is stored in /var/lib/mock/<configuration>/result directory.
For example, on Fedora 21 mock reports the following:
INFO: Done(scylla-server-0.00-1.fc21.src.rpm) Config(default) 20 minutes 7 seconds
INFO: Results and/or logs in: /var/lib/mock/fedora-21-x86_64/result
Building Fedora-based Docker image
Build a Docker image with:
cd dist/docker
docker build -t <image-name> .
Run the image with:
docker run -p $(hostname -i):9042:9042 -i -t <image name>