## Node.js CQL Driver for Apache Cassandra
Node.js CQL driver for Apache Cassandra with a small dependency tree written in pure javascript.
The driver uses Cassandra's binary protocol which was introduced in Cassandra version 1.2.
Installation
$ npm install node-cassandra-cql
Features
- Connection pooling to multiple hosts
- Load balancing and automatic failover
- Plain Old Javascript: no need to generate thrift files
- Long and uuid support
- Row and field streaming
Using it
//Creating a new connection pool to multiple hosts.var cql = ;var client = hosts: 'host1:9042' 'host2:9042' keyspace: 'keyspace1';//Readingclient; //Writingclient; //Streaming query rowsclient; //Streaming fieldclient; //The whole result set as a streamclient ;
API
Client
The Client
maintains a pool of opened connections to the hosts to avoid several time-consuming steps that are involved with the setup of a CQL binary protocol connection (socket connection, startup message, authentication, ...).
The Client is the recommended driver class to interact with Cassandra nodes.
new Client(options)
Constructs a new client object.
options
is an object with these slots, only hosts
is required:
hosts: Array of string in host:port format. Port is optional (default 9042).
keyspace: Name of keyspace to use.
username: User for authentication.
password: Password for authentication.
staleTime: Time in milliseconds before trying to reconnect to a node.
maxExecuteRetries: Maximum amount of times an execute can be retried
using another connection, in case the server is unhealthy.
getAConnectionTimeout: Maximum time in milliseconds to wait for a connection from the pool.
poolSize: Number of connections to open for each host (default 1)
client.connect([callback])
Connects / warms up the pool.
It ensures the pool is connected. It is not required to call it, internally the driver will call to connect
when executing a query.
The optional callback
parameter will be executed when the pool is connected. If the pool is already connected, it will be called instantly.
client.execute(query, [params], [consistency], callback)
Executes a CQL query.
The query
is the cql query to execute, with ?
placeholders as parameters.
Use one of the values defined in types.consistencies
for consistency
, defaults to quorum.
Callback should take two arguments err and result.
The driver will replace the placeholders with the params
, stringified into the query.
client.executeAsPrepared(query, [params], [consistency], callback)
Prepares (the first time) and executes the prepared query.
To execute a prepared query, the params
are binary serialized. Using prepared statements increases performance, especially for repeated queries.
In the case the query is already being prepared on a host, it queues the executing of a prepared statement on that host until the preparing finished (the driver will not issue a request to prepare statement more than once).
Use one of the values defined in types.consistencies
for consistency
, defaults to quorum.
Callback should take two arguments err and result.
client.eachRow(query, [params], [consistency], rowCallback, endCallback)
Prepares (the first time), executes the prepared query and streams the rows as soon as they are received.
It executes rowCallback(n, row)
per each row received, where n
is the index of the row.
It executes endCallback(err, rowLength)
when all rows have been received or there is an error retrieving the row.
Use one of the values defined in types.consistencies
for consistency
, defaults to quorum.
client.streamField(query, [params], [consistency], rowCallback, [endCallback])
Prepares (the first time), executes the prepared query and streams the last field of each row.
It executes rowCallback(n, row, streamField)
per each row as soon as the first chunk of the last field is received, where n
is the index of the row.
The stream
is a Readable Streams2 object that contains the raw bytes of the field value.
It can be piped downstream and provides automatic pause/resume logic (it buffers when not read).
The row
object is similar to the one provided on eachRow
, except that it does not contain the definition of the last column.
Use one of the values defined in types.consistencies
for consistency
, defaults to quorum.
It executes endCallback(err, rowLength)
when all rows have been received or there is an error retrieving the row.
client.stream(query, [params], [consistency], [callback])
Returns a Readable Streams2 object in objectMode
.
When a row can be read from the stream, it will emit a readable
event.
It can be piped downstream and provides automatic pause/resume logic (it buffers when not read).
Prepares (the first time), executes the prepared query.
Use one of the values defined in types.consistencies
for consistency
, defaults to quorum.
It executes callback(err)
when all rows have been received or there is an error retrieving the row.
client.shutdown([callback])
Disconnects the pool.
Closes all connections in the pool. Normally, it should be called once in your application lifetime.
The optional callback
parameter will be executed when the pool is disconnected.
Connection
In the case that you need lower level fine-grained control you could use the Connection
class.
It represents a connection to a Cassandra node. The consumer has to take care of open and close it.
new Connection(options)
Constructs a new connection object.
open(callback)
Establishes a connection, authenticates and sets a keyspace.
close(callback)
Closes the connection to a Cassandra node.
execute(query, args, consistency, callback)
Executes a CQL query.
prepare(query, callback)
Prepares a CQL query.
executePrepared(queryId, args, consistency, callback)
Executes a previously prepared query (determined by the queryId).
types
The types
module contains field definitions that are useful to interact with Cassandra nodes.
consistencies
Object that contains the CQL consistencies defined as properties. For example: consistencies.one
, consistencies.quorum
, ...
dataTypes
Object that contains all the CQL data types defined as properties.
responseErrorCodes
Object containing all the possible response error codes returned by Cassandra defined as properties.
Long()
Constructs a 64-bit two's-complement integer. See Long API Documentation.
timeuuid()
Function to generate a uuid v1. It uses node-uuid module to generate and accepts the same arguments.
uuid()
Function to generate a uuid v4. It uses node-uuid module to generate and accepts the same arguments.
Logging
Instances of Client()
and Connection()
are EventEmitter
's and emit log
events:
client;
The level
being passed to the listener can be info
or error
.
Data types
Cassandra's bigint data types are parsed as Long.
List / Set datatypes are encoded from / decoded to Javascript Arrays.
Map datatype are encoded from / decoded to Javascript objects with keys as props.
Decimal and Varint are not parsed yet, they are yielded as byte Buffers.
Check the documentation for data type support →
FAQ
How can specify the target data type of a query parameter?
The driver tries to guess the target data type, if you want to set the target data type use a param object with the hint and value properties.
All the cassandra data types are defined in the object types.dataTypes
.
For example:
//hint as stringvar keyParam = value: key hint: 'int';client; //hint using dataTypesvar keyParam = value: key hint: typesdataTypesint;client;
Should I shutdown the pool after executing a query?
No, you should only call client.shutdown
once in your application lifetime.
License
node-cassandra-cql is distributed under the MIT license.
Contributions
Feel free to join in to help this project grow!
Check the Issue tracker, there are issues even marked "New Contributors Welcome" :)
Acknowledgements
FrameReader and FrameWriter are based on node-cql3's FrameBuilder and FrameParser.