Doozer
What Is It?
Doozer is a highly-available, completely consistent
store for small amounts of extremely important data.
When the data changes, it can notify connected clients
immediately (no polling), making it ideal for
infrequently-updated data for which clients want
real-time updates. Doozer is good for name service,
database master elections, and configuration data shared
between several machines. See When Should I Use It?,
below, for details.
See the mailing list to discuss doozer with
other users and developers.
Quick Start
-
Download doozerd
-
Unpack the archive and put
doozerdin yourPATH -
Repeat for doozer
-
Start a doozerd with a WebView listening on
:8080$ doozerd -w ":8080" -
Set a key and read it back
$ echo "hello, world", doozer add /message $ doozer get /message hello, world -
Open http://localhost:8080 and see your message
How Does It Work?
Doozer is a network service. A handful of machines
(usually three, five, or seven) each run one doozer
server process. These processes communicate with each
other using a standard fully-consistent distributed
consensus algorithm. Clients dial in to one or more of
the doozer servers, issue commands, such as GET, SET,
and WATCH, and receive responses.
(insert network diagram here)
Each doozerd process has a complete copy of the
datastore and serves both read and write requests; there
is no distinguished "master" or "leader". Doozer is
designed to store data that fits entirely in memory; it
never writes data to permanent files. A separate tool
provides durable storage for backup and recovery.
When Should I Use It?
Here are some example scenarios:
-
Name Service
You have a set of machines that serve incoming HTTP
requests. Due to hardware failure, occasionally one
of these machines will fail and you replace it with a
new machine at a new network address. A change to DNS
data would take time to reach all clients, because
the TTL of the old DNS record would cause it to
remain in client caches for some time.Instead of DNS, you could use Doozer. Clients can
subscribe to the names they are interested in, and
they will get notified when any of those names’
addresses change. -
Database Master Election
You are deploying a MySQL system. You want it to have
high availability, so you add slaves on separate
physical machines. When the master fails, you might
promote one slave to become the new master. At any
given time, clients need to know which machine is the
master, and the slaves must coordinate with each
other during failover.You can use doozer to store the address of the
current master and all information necessary to
coordinate failover. -
Configuration
You have processes on several different machines, and
you want them all to use the same config file, which
you must occasionally update. It is important that
they all use the same configuration.Store the config file in doozer, and have the
processes read their configuration directly from
doozer.
What can I do with it?
We have a detailed description of the data model.
For ways to manipulate or read the data, see the protocol spec.
Try out doozer's fault-tolerance with some fire drills.
Similar Projects
Doozer is similar to the following pieces of software:
- Apache Zookeeper http://zookeeper.apache.org/
- Google Chubby http://research.google.com/archive/chubby.html
Hacking on Doozer
License and Authors
Doozer is distributed under the terms of the MIT
License. See LICENSE for details.
Doozer was created by Blake Mizerany and Keith Rarick.
Type git shortlog -s for a full list of contributors.