This project provides transactional support for HBase (or any other key-value store) using Snapshot Isolation.
Omid is composed by a server (the Status Oracle) and several clients. The server contains all the information needed to manage transactions and replicates it to the clients which just contact the server when they want to start a transaction or commit it.
The server uses BookKeeper as a Writer Ahead Log where it dumps all its state. In case of crash it is possible to restart the server without losing any commit information.
Omid uses Maven for its build system. We are using a temporary repository for zookeeper and bookkeeper packages to ease the installation procedure
Then to compile omid:
$ tar jxvf omid-1.0-SNAPSHOT.tar.bz2 $ cd omid-1.0-SNAPSHOT $ mvn install
Tests should run cleanly.
You need to run four components before running the transactional client. They are bookkeeper, zookeeper, omid tso and hbase. Bookkeeper is needed by the TSO. Zookeeper is needed by bookkeeper and hbase. The TSO is needed by hbase. Hence, the order of starting should be: 1. Zookeeper 2. Bookkeeper 3. TSO 4. Hbase
Zookeeper & Bookkeeper
For simplicity we've included a utility script which starts zookeeper and bookkeeper. Run:
$ bin/omid.sh bktest
Omid doesn't use anything special in zookeeper or bookkeeper, so you can use any install for these. However, if you are running this anywhere but localhost, you need to update the setting for hbase and TSO. See the hbase docs for changing the zookeeper quorum. For TSO, you need to modify bin/omid.sh.
To start the TSO, run:
$ bin/omid.sh tso
To benchmark the TSO alone, run:
$ bin/omid.sh tsobench
We've included a utility script to start a HBase cluster on your local machine. Run:
$ bin/omid.sh tran-hbase
For running in a cluster
The public api is in
src/main/java/com/yahoo/omid/client/TransactionalTable.java src/main/java/com/yahoo/omid/client/TransactionState.java src/main/java/com/yahoo/omid/client/TransactionManager.java
For an example of usage, look in
Logging can be adjusted in src/main/resource/log4j.properties.