lepu-test-platform-web/node_modules/bonjour/lib/registry.js

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'use strict'
var dnsEqual = require('dns-equal')
var flatten = require('array-flatten')
var Service = require('./service')
var REANNOUNCE_MAX_MS = 60 * 60 * 1000
var REANNOUNCE_FACTOR = 3
module.exports = Registry
function Registry (server) {
this._server = server
this._services = []
}
Registry.prototype.publish = function (opts) {
var service = new Service(opts)
service.start = start.bind(service, this)
service.stop = stop.bind(service, this)
service.start({ probe: opts.probe !== false })
return service
}
Registry.prototype.unpublishAll = function (cb) {
teardown(this._server, this._services, cb)
this._services = []
}
Registry.prototype.destroy = function () {
this._services.forEach(function (service) {
service._destroyed = true
})
}
function start (registry, opts) {
if (this._activated) return
this._activated = true
registry._services.push(this)
if (opts.probe) {
var service = this
probe(registry._server.mdns, this, function (exists) {
if (exists) {
service.stop()
service.emit('error', new Error('Service name is already in use on the network'))
return
}
announce(registry._server, service)
})
} else {
announce(registry._server, this)
}
}
function stop (registry, cb) {
if (!this._activated) return // TODO: What about the callback?
teardown(registry._server, this, cb)
var index = registry._services.indexOf(this)
if (index !== -1) registry._services.splice(index, 1)
}
/**
* Check if a service name is already in use on the network.
*
* Used before announcing the new service.
*
* To guard against race conditions where multiple services are started
* simultaneously on the network, wait a random amount of time (between
* 0 and 250 ms) before probing.
*
* TODO: Add support for Simultaneous Probe Tiebreaking:
* https://tools.ietf.org/html/rfc6762#section-8.2
*/
function probe (mdns, service, cb) {
var sent = false
var retries = 0
var timer
mdns.on('response', onresponse)
setTimeout(send, Math.random() * 250)
function send () {
// abort if the service have or is being stopped in the meantime
if (!service._activated || service._destroyed) return
mdns.query(service.fqdn, 'ANY', function () {
// This function will optionally be called with an error object. We'll
// just silently ignore it and retry as we normally would
sent = true
timer = setTimeout(++retries < 3 ? send : done, 250)
timer.unref()
})
}
function onresponse (packet) {
// Apparently conflicting Multicast DNS responses received *before*
// the first probe packet is sent MUST be silently ignored (see
// discussion of stale probe packets in RFC 6762 Section 8.2,
// "Simultaneous Probe Tiebreaking" at
// https://tools.ietf.org/html/rfc6762#section-8.2
if (!sent) return
if (packet.answers.some(matchRR) || packet.additionals.some(matchRR)) done(true)
}
function matchRR (rr) {
return dnsEqual(rr.name, service.fqdn)
}
function done (exists) {
mdns.removeListener('response', onresponse)
clearTimeout(timer)
cb(!!exists)
}
}
/**
* Initial service announcement
*
* Used to announce new services when they are first registered.
*
* Broadcasts right away, then after 3 seconds, 9 seconds, 27 seconds,
* and so on, up to a maximum interval of one hour.
*/
function announce (server, service) {
var delay = 1000
var packet = service._records()
server.register(packet)
;(function broadcast () {
// abort if the service have or is being stopped in the meantime
if (!service._activated || service._destroyed) return
server.mdns.respond(packet, function () {
// This function will optionally be called with an error object. We'll
// just silently ignore it and retry as we normally would
if (!service.published) {
service._activated = true
service.published = true
service.emit('up')
}
delay = delay * REANNOUNCE_FACTOR
if (delay < REANNOUNCE_MAX_MS && !service._destroyed) {
setTimeout(broadcast, delay).unref()
}
})
})()
}
/**
* Stop the given services
*
* Besides removing a service from the mDNS registry, a "goodbye"
* message is sent for each service to let the network know about the
* shutdown.
*/
function teardown (server, services, cb) {
if (!Array.isArray(services)) services = [services]
services = services.filter(function (service) {
return service._activated // ignore services not currently starting or started
})
var records = flatten.depth(services.map(function (service) {
service._activated = false
var records = service._records()
records.forEach(function (record) {
record.ttl = 0 // prepare goodbye message
})
return records
}), 1)
if (records.length === 0) return cb && cb()
server.unregister(records)
// send goodbye message
server.mdns.respond(records, function () {
services.forEach(function (service) {
service.published = false
})
if (cb) cb.apply(null, arguments)
})
}