NodeJS Bindings for Cassandra
Currently the driver has full CQL support and a growing support for thrift (non-cql) commands. If you would like to contribute, please contact Russ Bradberry <[email protected]>
If you have any questions regarding the driver, please visit our google group
npm install helenus
Ensure cassandra is running on localhost:9160.
make test
For coverage
make test-cov
var helenus = require('helenus'),
pool = new helenus.ConnectionPool({
hosts : ['localhost:9160'],
keyspace : 'helenus_test',
user : 'test',
password : 'test1233',
timeout : 3000
//cqlVersion : '3.0.0' // specify this if you're using Cassandra 1.1 and want to use CQL 3
});
//optionally you can supply the 'getHost' parameter to the connection pool options which will
// allow you to override the default random host decision
//if you don't listen for error, it will bubble up to `process.uncaughtException`
//pools act just like connection objects, so you don't have to worry about api
//differences when using either the pool or the connection
pool.on('error', function(err){
console.error(err.name, err.message);
});
//makes a connection to the pool, this will return once there is at least one
//valid connection, other connections may still be pending
pool.connect(function(err, keyspace){
if(err){
throw(err);
} else {
//to use cql, access the pool object once connected
//the first argument is the CQL string, the second is an `Array` of items
//to interpolate into the format string, the last is the callback
//for formatting specific see `http://nodejs.org/docs/latest/api/util.html#util.format`
//results is an array of row objects
pool.cql("SELECT col FROM cf_one WHERE key = ?", ['key123'], function(err, results){
console.log(err, results);
});
//NOTE:
//- You can always skip quotes around placeholders, they are added automatically.
//- In CQL 3 you cannot use placeholders for ColumnFamily names or Column names.
}
});If you do not want to use CQL, you can make calls using the thrift driver
pool.connect(function(err, keyspace){
if(err){
throw(err);
}
//first retreive the column family from the server
//helenus will cache column families it has already seen
keyspace.get('my_cf', function(err, cf){
if(err){
throw(err);
}
//insert something into the column family
cf.insert('foo', {'bar':'baz'}, function(err){
if(err){
throw(err);
}
//get what we just put in
//the driver will return a helenus.Row object just like CQL
cf.get('foo', {consistency:helenus.ConsistencyLevel.ONE} function(err, row){
if(err){
throw(err);
}
row.get('bar').value // => baz
});
});
});
});Currently Helenus supports the following command for the thrift side of the driver:
- connection.createKeyspace
- connection.dropKeyspace
- keyspace.createColumnFamily
- keyspace.dropColumnFamily
- columnFamily.insert
- columnFamily.get
- columnFamily.getIndexed
- columnFamily.remove
- columnFamily.truncate
The following support is going to be added in later releases:
- columnFamily.rowCount
- columnFamily.columnCount
- columnfamily.increment
- SuperColumns
- CounterColumns
- Better composite support
The Helenus Row object acts like an array but contains some helper methods to make your life a bit easier when dealing with dynamic columns in Cassandra
Returns the number of columns in the row
This will return the column at index N
results.forEach(function(row){
//gets the 5th column of each row
console.log(row[5]);
});
This will return the column with a specific name
results.forEach(function(row){
//gets the column with the name 'foo' of each row
console.log(row.get('foo'));
});
This is wrapper function of Array.forEach which return name,value,ts,ttl of column from row as callback params.
results.forEach(function(row){
//all row of result
row.forEach(function(name,value,ts,ttl){
//all column of row
console.log(name,value,ts,ttl);
});
});
Slices columns in the row based on their numeric index, this allows you to get columns x through y, it returns a Helenus row object of columns that match the slice.
results.forEach(function(row){
//gets the first 5 columns of each row
console.log(row.slice(0,5));
});
Slices the columns based on part of their column name. returns a Helenus row of columns that match the slice
results.forEach(function(row){
//gets all columns that start with a, b, c, or d
console.log(row.nameSlice('a','e'));
});
Columns are returned as objects with the following structure:
{
name: 'Foo', //The column name
value: 'bar', //The column value
timestamp: Date(), //The date object of the timestamp for the column
ttl: 123456 //The ttl (in milliseconds) for the columns
}Helenus supports using a custom consistency level. By default, when using the thrift client reads and writes will both use QUORUM. When using the thrift driver, you simply pass a custom level in the options:
cf.insert(key, values, {consistency : helenus.ConsistencyLevel.ANY}, callback);- Russell Bradberry - @devdazed
- Matthias Eder - @matthiase
- Christoph Tavan - @ctavan
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