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资源说明：Simple JRuby script for one-way CouchDB 0.8.1 replication
h1. Jpotatoe: A simple JRuby script for one-way CouchDB 0.8.1 replication This script is a modified version of potatoe.rb, an example Ruby script that demonstrated basic CouchDB replication through the DbUpdateNotificationProcess hook (couchdb.ini) setting. The original potatoe.rb script is found in this blog post: "http://blog.idearise.com/2008/09/08/couchdb-081/":http://blog.idearise.com/2008/09/08/couchdb-081/ The original potatoe.rb script did not do batch updates or timed updates. The Jpotatoe script does both and is meant to be used with JRuby. However, I don't think this script is a good way for real heavy CouchDB replication. It hasn't been tested with major loads, and there is no notion of how it may behave. Furthermore, it just doesn't seem right to do major replication this way instead of doing it through a built-in CouchDB service or a message queue. So, why is this here? Hopefully, it will help anyone, who is thinking about doing replication this way, to see what might be wrong with such an approach. In any case, it might just be a waste of time. ;-) h2. Caveats and TODO * It is not known how JRuby startup times may affect any CouchDB update messages that are already being sent before the script process is ready to accept those messages. * CouchDB fires another "database update" message after a successful replication. This means that during its periodic time check the script may call for a subsequent replication even if there are no other database updates. * A CouchDB "database update" message doesn't always mean a document was updated...See the previous point about CouchDB sending a database update message after a successful replication. * The script spawns a thread for each replication HTTP POST. * The thread locks are not on a "transaction" that includes the replication; they are on the minimum shared resource. This means that additional database updates may occur before replication has begun and will be end up as part of that replication. * The script doesn't handle batch sizes or times for different databases. * CouchDB replication may be completely different in the future! h2. Example Usage Batch size is the number of database updates that the script will wait for before starting the replication process. A database update doesn't always mean that a document was updated! The script will also start the replication process every X seconds to make sure that the target database is updated every so often.replicate_url = "http://192.168.0.4:5984/_replicate" source = "http://192.168.0.4:5984/" # with trailing slash target = "http://192.168.0.2:5984/" # with trailing slash databases = { "mytestdb" => 0 } # { "name_in_quotes" => default_update_count } config = { :replicate_url => replicate_url, :source => source, :target => target, :databases => databases, :batch_size => 50, :x_seconds => 1800 } Jpotatoe.new(config).watch
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