697b16414a
In each gossip round, i.e., gossiper::run(), we do:
1) send syn message
2) peer node: receive syn message, send back ack message
3) process ack message in handle_ack_msg
apply_state_locally
mark_alive
send_gossip_echo
handle_major_state_change
on_restart
mark_alive
send_gossip_echo
mark_dead
on_dead
on_join
apply_new_states
do_on_change_notifications
on_change
4) send back ack2 message
5) peer node: process ack2 message
apply_state_locally
At the moment, syn is "wait" message, it times out in 3 seconds. In step
3, all the registered gossip callbacks are called which might take
significant amount of time to complete.
In order to reduce the gossip round latency, we make syn "no-wait" and
do not run the handle_ack_msg insdie the gossip::run(). As a result, we
will not get a ack message as the return value of a syn message any
more, so a GOSSIP_DIGEST_ACK message verb is introduced.
With this patch, the gossip message exchange is now async. It is useful
when some nodes are down in the cluster. We will not delay the gossip
round, which is supposed to run every second, 3*n seconds (n = 1-3,
since it talks to 1-3 peer nodes in each gossip round) or even
longer (considering the time to run gossip callbacks).
Later, we can make talking to the 1-3 peer nodes in parallel to reduce
latency even more.
Refs: #900
#Scylla
##Building Scylla
In addition to required packages by Seastar, the following packages are required by Scylla.
Submodules
Scylla uses submodules, so make sure you pull the submodules first by doing:
git submodule init
git submodule update --recursive
Building and Running Scylla on Fedora
- Installing required packages:
sudo yum install yaml-cpp-devel lz4-devel zlib-devel snappy-devel jsoncpp-devel thrift-devel antlr3-tool antlr3-C++-devel libasan libubsan gcc-c++ gnutls-devel ninja-build ragel libaio-devel cryptopp-devel xfsprogs-devel numactl-devel hwloc-devel libpciaccess-devel libxml2-devel python3-pyparsing
- Build Scylla
./configure.py --mode=release --with=scylla --disable-xen
ninja-build build/release/scylla -j2 # you can use more cpus if you have tons of RAM
- 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>
Contributing to Scylla
Do not send pull requests.
Send patches to the mailing list address scylladb-dev@googlegroups.com. Be sure to subscribe.
In order for your patches to be merged, you must sign the Contributor's License Agreement, protecting your rights and ours. See http://www.scylladb.com/opensource/cla/.