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authorShawn O. Pearce2011-03-02 18:23:30 -0500
committerShawn O. Pearce2011-05-05 13:21:12 -0400
commitde8946c0c2c63907c0b14f2d9c419ac338b60588 (patch)
tree09976f8a6dfd58605953db19d6434e7d613c0b7f /
parent87455127a33fba9ebfdab9e2a611d4148c7501a4 (diff)
Store Git on any DHT is a storage provider implementation for JGit that permits storing the Git repository in a distributed hashtable, NoSQL system, or other database. The actual underlying storage system is undefined, and can be plugged in by implementing 7 small interfaces: * Database * RepositoryIndexTable * RepositoryTable * RefTable * ChunkTable * ObjectIndexTable * WriteBuffer The storage provider interface tries to assume very little about the underlying storage system, and requires only three key features: * key -> value lookup (a hashtable is suitable) * atomic updates on single rows * asynchronous operations (Java's ExecutorService is easy to use) Most NoSQL database products offer all 3 of these features in their clients, and so does any decent network based cache system like the open source memcache product. Relying only on key equality for data retrevial makes it simple for the storage engine to distribute across multiple machines. Traditional SQL systems could also be used with a JDBC based spi implementation. Before submitting this change I have implemented six storage systems for the spi layer: * Apache HBase[1] * Apache Cassandra[2] * Google Bigtable[3] * an in-memory implementation for unit testing * a JDBC implementation for SQL * a generic cache provider that can ride on top of memcache All six systems came in with an spi layer around 1000 lines of code to implement the above 7 interfaces. This is a huge reduction in size compared to prior attempts to implement a new JGit storage layer. As this package shows, a complete JGit storage implementation is more than 17,000 lines of fairly complex code. A simple cache is provided in storage.dht.spi.cache. Implementers can use CacheDatabase to wrap any other type of Database and perform fast reads against a network based cache service, such as the open source memcached[4]. An implementation of CacheService must be provided to glue this spi onto the network cache. [1] [2] [3] [4] Change-Id: I0aa4072781f5ccc019ca421c036adff2c40c4295 Signed-off-by: Shawn O. Pearce <>
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