transaction stub

lib/multiplexer.js

@@ -1,16 +0,0 @@
-/*
-module.exports = function() {
-	local_store()
-	for each uplink
-		status = uplink_store()
-		if (status == 201) {
-			succeess.push(uplink)
-		} else {
-			bail()
-		}
-
-	bail:
-		local_revert()
-		uplink_revert()
-};
-*/

lib/transaction.js

@@ -0,0 +1,46 @@
+var async = require('async')
+
+// 
+// Function performs a certain task on a multiple uplinks
+// and reverts changes if something fails
+//
+// uplinks - list of uplinks not counting local
+// localAction, localRollback - function(cb)
+// remoteAction, remoteRollback - function(uplink, cb)
+//
+module.exports = function(uplinks, localAction, localRollback, remoteAction, remoteRollback, callback) {
+	var uplink_ids = uplinks.map(function(_, i) {
+		return i
+	})
+
+	localAction(function(err) {
+		if (err) return callback(err)
+		async.map(uplink_ids, function(i, cb) {
+			remoteAction(uplinks[i], function(err) {
+				cb(null, err)
+			})
+		}, function(err, res) {
+			var return_err = err
+
+			// let err be first non-null element in the array
+			for (var i=0; i<res.length; i++) {
+				if (return_err) break
+				return_err = res[i]
+			}
+
+			if (!return_err) return callback()
+
+			async.map(uplink_ids, function(i, cb) {
+				if (res[i]) return cb()
+				remoteRollback(uplinks[i], function() {
+					cb()
+				})
+			}, function(err) {
+				localRollback(function() {
+					callback(return_err)
+				})
+			})
+		})
+	})
+}
+

test/transaction.js

@@ -0,0 +1,74 @@
+var transaction = require('../lib/transaction')
+var assert = require('assert')
+
+function call_back(cb, value) {
+	setTimeout(function() {
+		cb(value)
+	}, Math.random()*30)
+}
+
+function test(uplinks, cb) {
+	var calls = []
+	var local = uplinks.shift()
+	transaction(
+		uplinks.map(
+			function(x, i) {return [i, x]}
+		),
+		function localAction(cb) {
+			calls.push('l')
+			call_back(cb, !local ? 'l' : null)
+		},
+		function localRollback(cb) {
+			calls.push('lb')
+			call_back(cb, true)
+		},
+		function remoteAction(remote, cb) {
+			calls.push('r'+remote[0])
+			call_back(cb, !remote[1] ? 'r'+remote[0] : null)
+		},
+		function remoteRollback(remote, cb) {
+			calls.push('rb'+remote[0])
+			call_back(cb, true)
+		},
+		function callback(err) {
+			cb(err, calls)
+		}
+	)
+}
+
+// everything is fine
+test([true, true, true, true, true], function(err, calls) {
+	assert.deepEqual(err, undefined)
+	assert.deepEqual(calls, [ 'l', 'r0', 'r1', 'r2', 'r3' ])
+})
+
+// local throws errors - don't call remotes
+test([false, true, true, true, true], function(err, calls) {
+	assert.deepEqual(err, 'l')
+	assert.deepEqual(calls, ['l'])
+})
+
+// remote fails, call all rollbacks
+test([true, true, true, false, true], function(err, calls) {
+	assert.deepEqual(err, 'r2')
+	assert.deepEqual(calls, [ 'l', 'r0', 'r1', 'r2', 'r3', 'rb0', 'rb1', 'rb3', 'lb' ])
+})
+
+// no remotes
+test([true], function(err, calls) {
+	assert.deepEqual(err, undefined)
+	assert.deepEqual(calls, [ 'l' ])
+})
+
+// all remotes fail
+test([true, false, false, false, false], function(err, calls) {
+	assert.deepEqual(err, 'r0')
+	assert.deepEqual(calls, [ 'l', 'r0', 'r1', 'r2', 'r3', 'lb' ])
+})
+
+// mix
+test([true, true, false, true, false], function(err, calls) {
+	assert.deepEqual(err, 'r1')
+	assert.deepEqual(calls, [ 'l', 'r0', 'r1', 'r2', 'r3', 'rb0', 'rb2', 'lb' ])
+})
+