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seaport

service registry and port assignment for clusters

crane

example

simple service

First spin up the seaport server:

$ seaport 9090
seaport listening on :9090

then obtain a port for a server called 'web':

server.js:

var seaport = require('seaport');
var ports = seaport.connect('localhost', 9090, { secret : 'beep boop' });
var http = require('http');

var server = http.createServer(function (req, res) {
    res.end('beep boop\r\n');
});

ports.service('web@1.2.3', function (port, ready) {
    server.listen(port, ready);
});

now just get() that 'web' service!

client.js:

var seaport = require('seaport');
var ports = seaport.connect(9090, { secret : 'beep boop' });
var request = require('request');

ports.get('web@1.2.x', function (ps) {
    var u = 'http://' + ps[0].host + ':' + ps[0].port;
    request(u).pipe(process.stdout);
});

output:

$ node server.js &
[1] 6012
$ node client.js
beep boop

and if you spin up client.js before server.js then it still works because get() queues the response!

command-line usage

Usage:

  OPTIONS

    --secret   Use a service password for seaport connections.

  seaport port OPTIONS

    Create seaport server.

  seaport host:port show OPTIONS

    Show the port map from the server at host:port.

  seaport host:port service name@version OPTIONS -- [COMMAND...]

    Register a service. COMMAND will get an assigned port to use as
    its last argument. If COMMAND exits it will be restarted.

  seaport host:port query name@version OPTIONS

    Query the server for services matching the name@version pattern.
    The version may contain semver patterns to specify a range.
    Prints out a JSON array of host:port strings.

methods

var seaport = require('seaport')

All the parameters that take a role parameter can be intelligently versioned with semvers by specifying a version in the role parameter after an '@' character.

var ports = seaport.connect(...)

Connect to the seaport service at ....

ports.get(role, cb)

Request an array of host/port objects through cb(services) that fulfill role.

If there are no such services then the callback cb will get queued until some service fulfilling role gets allocated.

ports.service(role, meta={}, cb)

Create a service fulfilling the role of role.

Receive a callback cb(port, ready) with the allocated port and ready() function to call and re-assume the port every time the seaport service connection gets interrupted.

You can optionally supply a metadata object meta that will be merged into the result objects available when you call .get() or .query(). If you supply 'host' or 'port' keys they will be overwritten.

ports.allocate(role, meta={}, cb)

Request a port to fulfil a role. cb(port, ready) fires with the result.

Call ready() when your service is ready to start accepting connections.

If cb.length === 1 then ready() will be fired automatically.

You can optionally supply a metadata object meta that will be merged into the result objects available when you call .get() or .query(). If you supply 'host' or 'port' keys they will be overwritten.

ports.free(port, cb)

Give a port back. cb(alloc) fires when complete. You will get back the alloc object that you would have gotten if you'd queried the service directly.

If port is an object, you can free ports on other services besides the presently connected host by passing in a host field in addition to a port field.

ports.assume(role, port or meta={}, cb)

Dictate to the server what port you are listening on. This is useful for re-establishing a route without restarting the server.

You can optionally supply a metadata object meta that will be merged into the result objects available when you call .get() or .query(). If you use meta you must supply meta.port as the port argument.

Other keys used by seaport like 'host' will be overwritten.

ports.query(role, cb)

Get the services that satisfy the role role in cb(services). Everything after the '@' in role will be treated as a semver. If the semver is invalid (but not undefined) the algorithm will resort to exact matches.

Services are just objects that look like: { host : '1.2.3.4', port : 5678 }. Services can also include metadata that you've given them.

ports.on(eventName, cb)

Subscribe to events ('free', 'allocate', and 'assume') from the remote seaport server. ports will also emit local 'up', 'down', and 'reconnect' events from the upnode connection.

ports acts like a regular EventEmitter except that data won't be sent for remote events until you start listening for them.

Note that you won't get events while the seaport server is down so you should probably listen for the 'up' event from ports and then call ports.query() if you are trying to keep a local cache of registry entries.

server methods

Instead of using the command-line tool to spin up a seaport server, you can use these api methods:

var server = seaport.createServer()

Create a new dnode seaport server.

The server emits 'allocate', 'assume', and 'free' events when clients allocate, assume, and free ports.

install

To get the seaport library, with npm do:

npm install seaport

To get the seaport command, do:

npm install -g seaport

license

MIT

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