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replicate.js
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replicate.js
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var framedHash = require('framed-hash')
var collect = require('stream-collector')
var xtend = require('xtend')
var lexint = require('lexicographic-integer')
var pump = require('pump')
var pumpify = require('pumpify')
var parallel = require('parallel-transform')
var multiplex = require('multiplex')
var through = require('through2')
var after = require('after-all')
var messages = require('./messages')
var FILE = messages.CONTENT.FILE
module.exports = function (self, opts) {
var fetchingBlobs = []
var blobs = self._index.blobs
var finalize = function (cb) {
self.flush(cb)
}
var onoperation = function (id, stream) {
var op = self._index.operations.createValueStream({
gt: id + '!',
lt: id + '!~',
valueEncoding: 'binary'
})
graphOut.cork() // cork to add a bit of flow control since we won't resolve graph nodes until blob is done anyways
pump(op, stream, function () {
graphOut.uncork()
})
plex.emit('push-operation', op)
}
var onfile = function (id, stream) {
if (!self._index.blobs) return stream.destroy(new Error('no blob store attached'))
var file = self._index.blobs.createReadStream(id)
graphOut.cork() // cork to add a bit of flow control since we won't resolve graph nodes until blob is done anyways
pump(file, stream, function () {
graphOut.uncork()
})
plex.emit('push-file', file)
}
var onflow = function (stream) {
stream.on('data', function (data) {
data = data.toString()
if (data === 'cork') graphOut.cork()
else graphOut.uncork()
})
}
var plex = multiplex(function (stream, id) {
if (id === 'flow') return onflow(stream)
if (id.indexOf('operation/') > -1) return onoperation(id.slice(10), stream)
if (id.indexOf('file/') > -1) return onfile(id.slice(5), stream)
stream.destroy(new Error('Unknown channel'))
})
plex.progress = {
puts: 0,
deletes: 0,
files: 0
}
var fetchBlob = function (filename, key, cb) {
if (!blobs) return cb()
blobs.exists(key, function (_, exists) {
if (exists) return cb()
if (fetchingBlobs.indexOf(key) > -1) return cb() // skip
fetchingBlobs.push(key)
var stream = plex.createStream('file/' + key, {chunked: true})
var file = blobs.createWriteStream(filename)
pump(stream, file, function (err) {
if (err) return cb(err)
var i = fetchingBlobs.indexOf(key)
fetchingBlobs.splice(i, 1)
cb()
})
plex.emit('pull-file', file)
})
}
var hasOperation = function (key, cb) {
if (!key) return cb(null, true)
self._index.operations.get(key + '!00', function (err) {
if (err) return cb(null, false)
cb(null, true)
})
}
var flowStream = plex.createStream('flow')
var corking = false
// we currently handle readable backpressure
// by corking the graph stream using the flow channel.
// we should fix the multiplex stream per channel backpressure
// instead since this is more or less a hack
var buf = through.obj({highWaterMark: 1000000})
var update = function () {
var len = Math.max(buf._readableState.length, queue._readableState.length)
if (len > 128 && !corking) {
corking = true
flowStream.write('cork')
} else if (len < 64 && corking) {
corking = false
flowStream.write('uncork')
}
}
var queue = parallel(16, function (node, cb) {
update()
var commit = messages.Commit.decode(node.value)
var hash = framedHash('sha256')
plex.progress.puts += commit.puts
plex.progress.deletes += commit.deletes
plex.progress.files += commit.files
plex.emit('progress')
var onbatch = function (batch) {
var wrap = new Array(batch.length)
var next = after(function (err) {
update()
if (err) return cb(err)
cb(null, node)
})
for (var i = 0; i < wrap.length; i++) {
if (commit.files) {
var op = messages.Operation.decode(batch[i])
if (op.content === FILE) fetchBlob(op.key, messages.File.decode(op.value).key, next())
}
hash.update(batch[i])
wrap[i] = {type: 'put', key: lexint.pack(i, 'hex'), value: batch[i]}
}
var digest = hash.digest('hex')
if (digest !== commit.operations) return next()(new Error('Operation checksum mismatch'))
for (var j = 0; j < wrap.length; j++) wrap[j].key = digest + '!' + wrap[j].key
self._index.operations.batch(wrap, next())
}
hasOperation(commit.operations, function (err, exists) {
if (err) return cb(err)
if (exists) return cb(null, node)
var op = plex.createStream('operation/' + commit.operations)
collect(op, function (err, batch) {
if (err) return plex.destroy(err)
onbatch(batch)
})
})
})
var graph = self._index.log.replicate(xtend(opts, { finalize: finalize, process: pumpify.obj(buf, queue) }))
var graphOut = plex.createStream('graph')
var graphIn = plex.receiveStream('graph')
pump(graphIn, graph, graphOut)
graph.on('error', function (err) {
plex.destroy(err)
})
graph.on('metadata', function (value) {
plex.emit('metadata', value)
})
graph.on('push', function () {
plex.emit('push')
})
graph.on('pull', function () {
plex.emit('pull')
})
graph.on('finish', function () {
plex.end()
})
return plex
}