Thrift Pool

A module that wraps thrift interfaces in connection pooling logic to make them more resilient.

The node thrift code exposes a service and types file. The node thrift client also exposes interfaces to create connections to the thrift server. There is no way to use the node thrift library to do connection pooling or to create new connections if existing connections fail.

This library takes in a thrift service and wraps the methods with connection pooling logic (based on node-pool).

Installation

npm install node-thrift-pool

Usage

var thrift = require('thrift'),
  Service = require('./gen-nodejs/Service'),
  Types = require('./gen-nodejs/types'),
  thriftPool = require('node-thrift-pool');

var thrift_client = thriftPool(thrift, Service, {host: "localhost", port: 9090});

/*
 * thrift_client is now an initialized thrift client that uses connection pooling behind the scenes
 * thrift_client.method(function(err, returned_data){console.log(err, returned_data)});
 */

Supported pooling options

Options to use when creating pool, defaults match those used by node-pool.

host - Required - The host of the thrift server to connect to
port - Required - The port of the thrift server to connect to
log - Default: false - true/false or function
max_connections - Default: 1 - Max number of connections to keep open at any given time
min_connections - Default: 0 - Min number of connections to keep open at any given time
idle_timeout - Default: 30000 - Time (ms) to wait until closing idle connections
ttl - Default: undefined - Time (+/-50%) (ms) past which to destroy the connection. For more explanation, see below
ssl - Default: false - Whether to use SSL/TLS

ttl

When using load balancers such as Amazon's ELB service, a common deploy strategy is to deploy new instances with new versions of your code, attach them to the load balancer, and detach the old ones. This doesn't work very well with persistent connections, however. New connections go to the new servers, but any open connections to the old servers remain and are eventually closed by the server when the servers turn off. This causes any in-flight requests on those connections to error with Error: Thrift-pool: Connection closed.

The ttl option treats any connection older than ttl (+/-50%) as invalid, so if something tries to acquite it, they'll get a more recent connection instead. If you set this time lower than the connection drain timeout of your load balancer, you can guarantee that all connections to the old servers are closed before the servers are stopped.

We use some amount of randomness (+/- 50%) of this time to ensure that all of your connections are not marked invalid simultaneously.

As an example, we have our connection drain timeout set to five minutes, so when you're removing instances from the ELB, any connections older than five minutes are just cut off. Based on that, we set our ttl to two minutes, and guarantee that all connections will be destroyed sometime after one to three minutes.

Thrift options - optional

All thrift options are supported and can be passed in as an object in addition to the pooling options.

var thrift_options = {
    timeout: 250
};
var thrift_client = thriftPool(thrift, Service, {host: "localhost", port: 9090}, thrift_options);

Note: If the timeout option is passed in the thrift_options object, a timeout listener will be added to the connection.

If the timeout event is emitted on a connection while it is in the pool, the connection will be invalidated and treated the same way as if an error or close event had been emitted.
If the timeout event is emitted after the connection is acquired a timeout error will be returned: new Error "Connection timeout".

Development

After making any changes, please add or run any required tests. Tests are located in the test directory, and can be run via npm:

npm test

The debug package is used to simplify debugging. To turn on logging: export DEBUG=thrift-pool
Source hosted at GitHub
Report issues, questions, feature requests on GitHub Issues

Pull requests are welcome! Please ensure your patches are well tested. Please create separate branches for separate features/patches.