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The materialized views flow control mechanism works by adding a certain delay to each client request, designed to slow down the client to the rate at we can complete the background view work. Until now we could observe this mechanism only indirectly, in whether or not it succeeded to keep the view backlog bounded; But we had no way to directly observe the delay that we decided to add. In fact, we had a bug where this delay was constantly zero, and we didn't even notice :-) So in this patch we add a new metric, scylla_storage_proxy_coordinator_last_mv_flow_control_delay The metric is a floating point number, in units of seconds. This metric is somewhat peculiar that it always contains the *last* delay used for some request - unlike other metrics it doesn't measure the "current" value of something. Moreover, it can jump wildly because there is no guarantee that each request's delay will be identical (in particular, different requests may involve different base replicas which have different view backlogs, so decide on different delays). In the future we may want to supplement this metric with some sort of delay histogram. But even this simple metric is already useful to debug certain scenarios and understand if the materialized-views flow control is working or not. Signed-off-by: Nadav Har'El <nyh@scylladb.com> Message-Id: <20190227133630.26328-1-nyh@scylladb.com>
Scylla
Quick-start
$ git submodule update --init --recursive
$ sudo ./install-dependencies.sh
$ ./configure.py --mode=release
$ ninja-build -j4 # Assuming 4 system threads.
$ ./build/release/scylla
$ # Rejoice!
Please see HACKING.md for detailed information on building and developing Scylla.
Note: GCC >= 8.1.1 is require to compile Scylla.
Note: See frozen toolchain for a way to build and run on an older distribution.
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
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>