Just a quick note – I’m in the process of publishing a book, Clojure Recipes. You can see it for presale on Amazon here.
Introduction
This post shows you how to setup Datomic running on Cassandra using Virtualbox VMs from scratch. This is non-trivial and if everything goes well, will probably take a couple of hours.
Note that this are my notes from going through this process, so there will definitely be room for improvement, either a simpler way to do things or a better way to explain what is going on.
Assumptions
- This has been written for a Macbook Pro Retina running MacOS X 10.9.3 (Mavericks) with 16GB of RAM. You’ll need to make a judgment as to whether your setup is similar enough for these steps to apply to your system.
- VirtualBox uses the language ‘guest’ to describe the client virtual machine running. This is not to be confused with the ‘guest login’ (which we won’t use anyway)
Pre-requisites
- you need at least 9G free on your hard drive
- you need at least 2.5G free RAM (running three virtual machines)
- to actually do this – you need a datomic pro evaluation key – you can get this by registering on the my.datomic.com site – and then under Account click
Send licence keyand underDownloads– and also get the latest version of Datomic Pro.
Outline
This has the following steps:
Note that steps A-J are here.
K. Setting Up Datomic
L. Running Datomic
Process Steps
Note that steps 1-53 are here:
K. Setting Up Datomic:
54. Expand the datomic download
unzip datomic-pro-0.9.4384.zip -d datomic-pro-0.9.4384
cd datomic-pro-0.9.4384
55. Provision a keyspace and table for datomic from the datomic directory:
/home/cassandra/apache-cassandra-2.0.3/bin/cqlsh -f bin/cql/cassandra-keyspace.cql -u cassandra -p cassandra
56. Copy the cassandra transactor sample into the config directory
cd config/samples
cp cassandra-template.properties ..
cd ..
57. Modify the cassandra template to setup the properties of our local instance.
nano cassandra-template.properties
cd ..
58. Copy the licence key you downloaded (at step 16) into the file under the property entry
licence-key=
59. Set the following property entries
cassandra-host=localhost
60. Start the datomic transactor with the new cassandra template properties we just created:
bin/transactor config/cassandra-template.properties
Ensure you get a result like:
System started datomic:case://localhost:9042/datomic.datomic/<DB-NAME>
Note this down – this will be the URI to connect.
L. Running Datomic
61. In a new command prompt in the datomic-pro directory run:
bin/shell
Ensure you get the prompt
Datomic Java Shell
62. Run through the following commands from the datomic tutorial: http://docs.datomic.com/tutorial.html
String uri = "datomic:cass://localhost:9042/datomic.datomic/seattle";
Peer.createDatabase(uri);
conn = Peer.connect(uri);
63. Load up the schema
schema_rdr = new FileReader("samples/seattle/seattle-schema.dtm");
schema_tx = Util.readAll(schema_rdr).get(0);
txResult = conn.transact(schema_tx).get();
64. Add some seed data
data_rdr = new FileReader("samples/seattle/seattle-data0.dtm");
data_tx = Util.readAll(data_rdr).get(0);
txResult = conn.transact(data_tx).get();
65. Query the database
db = conn.db();
for (Object result : results) {
entity = db.entity(result.get(0));
System.out.println(entity.get(":community/name"));
}
Voila – you have a Datomic database running on Cassandra across three nodes!