From 486511e0caa1f8423155ba95fbaafbf0602e1c43 Mon Sep 17 00:00:00 2001
From: MaciejBaj <macie.baj@gmail.com>
Date: Sun, 21 Jan 2018 16:05:12 +0100
Subject: [PATCH 01/17] Create synchronousTasksSequence and add forging and
 sync process into

---
 app.js                          | 11 +++++++-
 modules/delegates.js            | 16 ++++++-----
 modules/loader.js               | 49 +++++++++++++++++----------------
 test/system/synchronousTasks.js |  0
 4 files changed, 45 insertions(+), 31 deletions(-)
 create mode 100644 test/system/synchronousTasks.js

diff --git a/app.js b/app.js
index 5df230699f3..af0661ed49b 100644
--- a/app.js
+++ b/app.js
@@ -332,6 +332,15 @@ d.run(function () {
 			cb(null, sequence);
 		}],
 
+		synchronousTasksSequence: ['logger', function (scope, cb) {
+			var sequence = new Sequence({
+				onWarning: function (current) {
+					scope.logger.warn('Synchronous tasks queue', current);
+				}
+			});
+			cb(null, sequence);
+		}],
+
 		/**
 		 * Once config, public, genesisblock, logger, build and network are completed,
 		 * adds configuration to `network.app`.
@@ -498,7 +507,7 @@ d.run(function () {
 		 * at leats will contain the required elements.
 		 * @param {nodeStyleCallback} cb - Callback function with resulted load.
 		 */
-		modules: ['network', 'connect', 'config', 'logger', 'bus', 'sequence', 'dbSequence', 'balancesSequence', 'db', 'logic', 'cache', function (scope, cb) {
+		modules: ['network', 'connect', 'config', 'logger', 'bus', 'sequence', 'dbSequence', 'balancesSequence', 'synchronousTasksSequence', 'db', 'logic', 'cache', function (scope, cb) {
 
 			var tasks = {};
 
diff --git a/modules/delegates.js b/modules/delegates.js
index 1178a85f4ea..aa13c1d6f30 100644
--- a/modules/delegates.js
+++ b/modules/delegates.js
@@ -25,6 +25,7 @@ __private.loaded = false;
 __private.blockReward = new BlockReward();
 __private.keypairs = {};
 __private.tmpKeypairs = {};
+__private.forgeAttemptInterval = 1000;
 
 /**
  * Initializes library with scope content and generates a Delegate instance.
@@ -46,6 +47,7 @@ function Delegates (cb, scope) {
 		network: scope.network,
 		schema: scope.schema,
 		balancesSequence: scope.balancesSequence,
+		synchronousTasksSequence: scope.synchronousTasksSequence,
 		logic: {
 			transaction: scope.logic.transaction,
 		},
@@ -598,15 +600,15 @@ Delegates.prototype.onBlockchainReady = function () {
 				library.logger.error('Failed to load delegates', err);
 			}
 
-			async.series([
-				__private.forge,
-				modules.transactions.fillPool
-			], function () {
-				return setImmediate(cb);
-			});
+			library.synchronousTasksSequence.add(function (sequenceCb) {
+				async.series([
+					__private.forge,
+					modules.transactions.fillPool
+				], sequenceCb);
+			}, cb);
 		}
 
-		jobsQueue.register('delegatesNextForge', nextForge, 1000);
+		jobsQueue.register('delegatesNextForge', nextForge, __private.forgeAttemptInterval);
 	});
 };
 
diff --git a/modules/loader.js b/modules/loader.js
index 0bb9835f35f..44d6d50de61 100644
--- a/modules/loader.js
+++ b/modules/loader.js
@@ -44,6 +44,7 @@ function Loader (cb, scope) {
 		bus: scope.bus,
 		genesisblock: scope.genesisblock,
 		balancesSequence: scope.balancesSequence,
+		synchronousTasksSequence: scope.synchronousTasksSequence,
 		logic: {
 			transaction: scope.logic.transaction,
 			account: scope.logic.account,
@@ -609,30 +610,32 @@ __private.sync = function (cb) {
 	__private.isActive = true;
 	__private.syncTrigger(true);
 
-	async.series({
-		getPeersBefore: function (seriesCb) {
-			library.logger.debug('Establishing broadhash consensus before sync');
-			return modules.transport.getPeers({limit: constants.maxPeers}, seriesCb);
-		},
-		loadBlocksFromNetwork: function (seriesCb) {
-			return __private.loadBlocksFromNetwork(seriesCb);
-		},
-		updateSystem: function (seriesCb) {
-			return modules.system.update(seriesCb);
-		},
-		getPeersAfter: function (seriesCb) {
-			library.logger.debug('Establishing broadhash consensus after sync');
-			return modules.transport.getPeers({limit: constants.maxPeers}, seriesCb);
-		}
-	}, function (err) {
-		__private.isActive = false;
-		__private.syncTrigger(false);
-		__private.blocksToSync = 0;
+	library.synchronousTasksSequence.add(function (sequenceCb) {
+		async.series({
+			getPeersBefore: function (seriesCb) {
+				library.logger.debug('Establishing broadhash consensus before sync');
+				return modules.transport.getPeers({limit: constants.maxPeers}, seriesCb);
+			},
+			loadBlocksFromNetwork: function (seriesCb) {
+				return __private.loadBlocksFromNetwork(seriesCb);
+			},
+			updateSystem: function (seriesCb) {
+				return modules.system.update(seriesCb);
+			},
+			getPeersAfter: function (seriesCb) {
+				library.logger.debug('Establishing broadhash consensus after sync');
+				return modules.transport.getPeers({limit: constants.maxPeers}, seriesCb);
+			}
+		}, function (err) {
+			__private.isActive = false;
+			__private.syncTrigger(false);
+			__private.blocksToSync = 0;
 
-		library.logger.info('Finished sync');
-		library.bus.message('syncFinished');
-		return setImmediate(cb, err);
-	});
+			library.logger.info('Finished sync');
+			library.bus.message('syncFinished');
+			return setImmediate(sequenceCb, err);
+		});
+	}, cb);
 };
 
 /* 
diff --git a/test/system/synchronousTasks.js b/test/system/synchronousTasks.js
new file mode 100644
index 00000000000..e69de29bb2d

From 3a1bdfcd020278d77373d7112e278ffe0133c393 Mon Sep 17 00:00:00 2001
From: MaciejBaj <macie.baj@gmail.com>
Date: Sun, 21 Jan 2018 16:35:14 +0100
Subject: [PATCH 02/17] Add synchronousTasksSequence to test/common/application

---
 test/common/application.js | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/test/common/application.js b/test/common/application.js
index 401df446830..d2849d90c50 100644
--- a/test/common/application.js
+++ b/test/common/application.js
@@ -160,6 +160,14 @@ function __init (initScope, done) {
 				});
 				cb(null, sequence);
 			}],
+			synchronousTasksSequence: ['logger', function (scope, cb) {
+				var sequence = new Sequence({
+					onWarning: function (current) {
+						scope.logger.warn('Synchronous tasks queue', current);
+					}
+				});
+				cb(null, sequence);
+			}],
 			ed: function (cb) {
 				cb(null, require('../../helpers/ed.js'));
 			},
@@ -233,7 +241,7 @@ function __init (initScope, done) {
 					}]
 				}, cb);
 			}],
-			modules: ['network', 'logger', 'bus', 'sequence', 'dbSequence', 'balancesSequence', 'db', 'logic', function (scope, cb) {
+			modules: ['network', 'logger', 'bus', 'sequence', 'dbSequence', 'balancesSequence', 'synchronousTasksSequence', 'db', 'logic', function (scope, cb) {
 				var tasks = {};
 				scope.rewiredModules = {};
 

From 82d83116e9ebc2bce87c220b6818f1dea0bf6340 Mon Sep 17 00:00:00 2001
From: MaciejBaj <macie.baj@gmail.com>
Date: Sun, 21 Jan 2018 16:37:58 +0100
Subject: [PATCH 03/17] Add synchronous tasks system tests skeleton

---
 test/system/synchronousTasks.js | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/test/system/synchronousTasks.js b/test/system/synchronousTasks.js
index e69de29bb2d..bb6c19efc57 100644
--- a/test/system/synchronousTasks.js
+++ b/test/system/synchronousTasks.js
@@ -0,0 +1,29 @@
+'use strict';
+
+var application = require('./../common/application');
+
+describe('synchronousTasks', function () {
+
+	var library;
+
+	before('init sandboxed application', function (done) {
+		application.init({sandbox: {name: 'lisk_test_synchronous_tasks'}}, function (scope) {
+			library = scope;
+			done();
+		});
+	});
+
+	after('cleanup sandboxed application', function (done) {
+		application.cleanup(done);
+	});
+
+	describe('when "attempt to forge" synchronous tasks runs every 100 ms and takes 200 ms', function () {
+
+		describe('when "blockchain synchronization" synchronous tasks runs every 100 ms and takes 200 ms', function () {
+
+			it('"attempt to forge" task should never start when "blockchain synchronization" task is running');
+
+			it('"blockchain synchronization" task should never start when "attempt to forge" task is running');
+		});
+	});
+});

From 419b5fe7a225f2b9bb6bbc19b9cbbcbcded82da7 Mon Sep 17 00:00:00 2001
From: Maciej Baj <macie.baj@gmail.com>
Date: Mon, 22 Jan 2018 14:10:53 +0100
Subject: [PATCH 04/17] Revert delegates file to the state from before #26
 changes

---
 modules/delegates.js | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/modules/delegates.js b/modules/delegates.js
index aa13c1d6f30..db7b0b1a890 100644
--- a/modules/delegates.js
+++ b/modules/delegates.js
@@ -25,7 +25,6 @@ __private.loaded = false;
 __private.blockReward = new BlockReward();
 __private.keypairs = {};
 __private.tmpKeypairs = {};
-__private.forgeAttemptInterval = 1000;
 
 /**
  * Initializes library with scope content and generates a Delegate instance.
@@ -47,7 +46,6 @@ function Delegates (cb, scope) {
 		network: scope.network,
 		schema: scope.schema,
 		balancesSequence: scope.balancesSequence,
-		synchronousTasksSequence: scope.synchronousTasksSequence,
 		logic: {
 			transaction: scope.logic.transaction,
 		},
@@ -63,7 +61,7 @@ function Delegates (cb, scope) {
 	self = this;
 
 	__private.assetTypes[transactionTypes.DELEGATE] = library.logic.transaction.attachAssetType(
-		transactionTypes.DELEGATE, 
+		transactionTypes.DELEGATE,
 		new Delegate(
 			scope.logger,
 			scope.schema
@@ -78,7 +76,7 @@ function Delegates (cb, scope) {
  * Gets delegate public keys sorted by vote descending.
  * @private
  * @param {function} cb - Callback function.
- * @returns {setImmediateCallback} 
+ * @returns {setImmediateCallback}
  */
 __private.getKeysSortByVote = function (cb) {
 	modules.accounts.getAccounts({
@@ -99,7 +97,7 @@ __private.getKeysSortByVote = function (cb) {
  * Gets delegate public keys from previous round, sorted by vote descending.
  * @private
  * @param {function} cb - Callback function.
- * @returns {setImmediateCallback} 
+ * @returns {setImmediateCallback}
  */
 __private.getDelegatesFromPreviousRound = function (cb) {
 	library.db.query(sql.getDelegatesSnapshot, {limit: slots.delegates}).then(function (rows) {
@@ -171,11 +169,11 @@ __private.getBlockSlotData = function (slot, height, cb) {
 };
 
 /**
- * Gets peers, checks consensus and generates new block, once delegates 
+ * Gets peers, checks consensus and generates new block, once delegates
  * are enabled, client is ready to forge and is the correct slot.
  * @private
  * @param {function} cb - Callback function.
- * @returns {setImmediateCallback} 
+ * @returns {setImmediateCallback}
  */
 __private.forge = function (cb) {
 	if (!Object.keys(__private.keypairs).length) {
@@ -340,7 +338,7 @@ __private.checkDelegates = function (publicKey, votes, state, cb) {
  * Loads delegates from config and stores in private `keypairs`.
  * @private
  * @param {function} cb - Callback function.
- * @returns {setImmediateCallback} 
+ * @returns {setImmediateCallback}
  */
 __private.loadDelegates = function (cb) {
 	var secrets;
@@ -600,15 +598,15 @@ Delegates.prototype.onBlockchainReady = function () {
 				library.logger.error('Failed to load delegates', err);
 			}
 
-			library.synchronousTasksSequence.add(function (sequenceCb) {
-				async.series([
-					__private.forge,
-					modules.transactions.fillPool
-				], sequenceCb);
-			}, cb);
+			async.series([
+				__private.forge,
+				modules.transactions.fillPool
+			], function () {
+				return setImmediate(cb);
+			});
 		}
 
-		jobsQueue.register('delegatesNextForge', nextForge, __private.forgeAttemptInterval);
+		jobsQueue.register('delegatesNextForge', nextForge, 1000);
 	});
 };
 

From 642ccf4aaf22f1e4879135a01c7faa0865792c74 Mon Sep 17 00:00:00 2001
From: Maciej Baj <macie.baj@gmail.com>
Date: Mon, 22 Jan 2018 14:11:31 +0100
Subject: [PATCH 05/17] Remove usages of synchronousTasksSequence

---
 app.js                     | 11 +--------
 modules/loader.js          | 49 ++++++++++++++++++--------------------
 test/common/application.js | 10 +-------
 3 files changed, 25 insertions(+), 45 deletions(-)

diff --git a/app.js b/app.js
index af0661ed49b..5df230699f3 100644
--- a/app.js
+++ b/app.js
@@ -332,15 +332,6 @@ d.run(function () {
 			cb(null, sequence);
 		}],
 
-		synchronousTasksSequence: ['logger', function (scope, cb) {
-			var sequence = new Sequence({
-				onWarning: function (current) {
-					scope.logger.warn('Synchronous tasks queue', current);
-				}
-			});
-			cb(null, sequence);
-		}],
-
 		/**
 		 * Once config, public, genesisblock, logger, build and network are completed,
 		 * adds configuration to `network.app`.
@@ -507,7 +498,7 @@ d.run(function () {
 		 * at leats will contain the required elements.
 		 * @param {nodeStyleCallback} cb - Callback function with resulted load.
 		 */
-		modules: ['network', 'connect', 'config', 'logger', 'bus', 'sequence', 'dbSequence', 'balancesSequence', 'synchronousTasksSequence', 'db', 'logic', 'cache', function (scope, cb) {
+		modules: ['network', 'connect', 'config', 'logger', 'bus', 'sequence', 'dbSequence', 'balancesSequence', 'db', 'logic', 'cache', function (scope, cb) {
 
 			var tasks = {};
 
diff --git a/modules/loader.js b/modules/loader.js
index 44d6d50de61..0bb9835f35f 100644
--- a/modules/loader.js
+++ b/modules/loader.js
@@ -44,7 +44,6 @@ function Loader (cb, scope) {
 		bus: scope.bus,
 		genesisblock: scope.genesisblock,
 		balancesSequence: scope.balancesSequence,
-		synchronousTasksSequence: scope.synchronousTasksSequence,
 		logic: {
 			transaction: scope.logic.transaction,
 			account: scope.logic.account,
@@ -610,32 +609,30 @@ __private.sync = function (cb) {
 	__private.isActive = true;
 	__private.syncTrigger(true);
 
-	library.synchronousTasksSequence.add(function (sequenceCb) {
-		async.series({
-			getPeersBefore: function (seriesCb) {
-				library.logger.debug('Establishing broadhash consensus before sync');
-				return modules.transport.getPeers({limit: constants.maxPeers}, seriesCb);
-			},
-			loadBlocksFromNetwork: function (seriesCb) {
-				return __private.loadBlocksFromNetwork(seriesCb);
-			},
-			updateSystem: function (seriesCb) {
-				return modules.system.update(seriesCb);
-			},
-			getPeersAfter: function (seriesCb) {
-				library.logger.debug('Establishing broadhash consensus after sync');
-				return modules.transport.getPeers({limit: constants.maxPeers}, seriesCb);
-			}
-		}, function (err) {
-			__private.isActive = false;
-			__private.syncTrigger(false);
-			__private.blocksToSync = 0;
+	async.series({
+		getPeersBefore: function (seriesCb) {
+			library.logger.debug('Establishing broadhash consensus before sync');
+			return modules.transport.getPeers({limit: constants.maxPeers}, seriesCb);
+		},
+		loadBlocksFromNetwork: function (seriesCb) {
+			return __private.loadBlocksFromNetwork(seriesCb);
+		},
+		updateSystem: function (seriesCb) {
+			return modules.system.update(seriesCb);
+		},
+		getPeersAfter: function (seriesCb) {
+			library.logger.debug('Establishing broadhash consensus after sync');
+			return modules.transport.getPeers({limit: constants.maxPeers}, seriesCb);
+		}
+	}, function (err) {
+		__private.isActive = false;
+		__private.syncTrigger(false);
+		__private.blocksToSync = 0;
 
-			library.logger.info('Finished sync');
-			library.bus.message('syncFinished');
-			return setImmediate(sequenceCb, err);
-		});
-	}, cb);
+		library.logger.info('Finished sync');
+		library.bus.message('syncFinished');
+		return setImmediate(cb, err);
+	});
 };
 
 /* 
diff --git a/test/common/application.js b/test/common/application.js
index d2849d90c50..401df446830 100644
--- a/test/common/application.js
+++ b/test/common/application.js
@@ -160,14 +160,6 @@ function __init (initScope, done) {
 				});
 				cb(null, sequence);
 			}],
-			synchronousTasksSequence: ['logger', function (scope, cb) {
-				var sequence = new Sequence({
-					onWarning: function (current) {
-						scope.logger.warn('Synchronous tasks queue', current);
-					}
-				});
-				cb(null, sequence);
-			}],
 			ed: function (cb) {
 				cb(null, require('../../helpers/ed.js'));
 			},
@@ -241,7 +233,7 @@ function __init (initScope, done) {
 					}]
 				}, cb);
 			}],
-			modules: ['network', 'logger', 'bus', 'sequence', 'dbSequence', 'balancesSequence', 'synchronousTasksSequence', 'db', 'logic', function (scope, cb) {
+			modules: ['network', 'logger', 'bus', 'sequence', 'dbSequence', 'balancesSequence', 'db', 'logic', function (scope, cb) {
 				var tasks = {};
 				scope.rewiredModules = {};
 

From f9cc957def75ea66213b623f8b0702c56813e3b6 Mon Sep 17 00:00:00 2001
From: Maciej Baj <macie.baj@gmail.com>
Date: Mon, 22 Jan 2018 14:13:18 +0100
Subject: [PATCH 06/17] Assign forge every 1000ms interval as variable

---
 modules/delegates.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/modules/delegates.js b/modules/delegates.js
index db7b0b1a890..12a7fb708cb 100644
--- a/modules/delegates.js
+++ b/modules/delegates.js
@@ -25,6 +25,7 @@ __private.loaded = false;
 __private.blockReward = new BlockReward();
 __private.keypairs = {};
 __private.tmpKeypairs = {};
+__private.forgeAttemptInterval = 1000;
 
 /**
  * Initializes library with scope content and generates a Delegate instance.
@@ -606,7 +607,7 @@ Delegates.prototype.onBlockchainReady = function () {
 			});
 		}
 
-		jobsQueue.register('delegatesNextForge', nextForge, 1000);
+		jobsQueue.register('delegatesNextForge', nextForge, __private.forgeAttemptInterval);
 	});
 };
 

From ab70f8f5cf6207d0393deda4a0cef870c2195eab Mon Sep 17 00:00:00 2001
From: Maciej Baj <macie.baj@gmail.com>
Date: Mon, 22 Jan 2018 14:49:45 +0100
Subject: [PATCH 07/17] Move delegates.onBlockchainReady logic into functions

---
 modules/delegates.js | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/modules/delegates.js b/modules/delegates.js
index 12a7fb708cb..4e63262bb38 100644
--- a/modules/delegates.js
+++ b/modules/delegates.js
@@ -585,29 +585,30 @@ Delegates.prototype.onBind = function (scope) {
 	);
 };
 
+__private.nextForge = function (cb) {
+	async.series([
+		__private.forge,
+		modules.transactions.fillPool
+	], function () {
+		return setImmediate(cb);
+	});
+};
+
+__private.logLoadDelegatesError = function (err) {
+	library.logger.error('Failed to load delegates', err);
+};
+
 /**
  * Loads delegates.
  * @implements module:transactions#Transactions~fillPool
  */
 Delegates.prototype.onBlockchainReady = function () {
 	__private.loaded = true;
-
 	__private.loadDelegates(function (err) {
-
-		function nextForge (cb) {
-			if (err) {
-				library.logger.error('Failed to load delegates', err);
-			}
-
-			async.series([
-				__private.forge,
-				modules.transactions.fillPool
-			], function () {
-				return setImmediate(cb);
-			});
+		if (err) {
+			jobsQueue.register('logLoadDelegatesError', __private.logLoadDelegatesError.bind(null, err), __private.forgeAttemptInterval);
 		}
-
-		jobsQueue.register('delegatesNextForge', nextForge, __private.forgeAttemptInterval);
+		jobsQueue.register('delegatesNextForge', __private.nextForge, __private.forgeAttemptInterval);
 	});
 };
 

From dda267ad23543934f4b90eecf0a3612f414db69c Mon Sep 17 00:00:00 2001
From: Maciej Baj <macie.baj@gmail.com>
Date: Mon, 22 Jan 2018 14:54:55 +0100
Subject: [PATCH 08/17] Add delegates.__private.nextForge to global sequence

---
 modules/delegates.js | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/modules/delegates.js b/modules/delegates.js
index 4e63262bb38..be85f01e685 100644
--- a/modules/delegates.js
+++ b/modules/delegates.js
@@ -585,13 +585,11 @@ Delegates.prototype.onBind = function (scope) {
 	);
 };
 
-__private.nextForge = function (cb) {
+__private.nextForge = function (sequenceCb) {
 	async.series([
 		__private.forge,
 		modules.transactions.fillPool
-	], function () {
-		return setImmediate(cb);
-	});
+	], sequenceCb);
 };
 
 __private.logLoadDelegatesError = function (err) {
@@ -608,7 +606,7 @@ Delegates.prototype.onBlockchainReady = function () {
 		if (err) {
 			jobsQueue.register('logLoadDelegatesError', __private.logLoadDelegatesError.bind(null, err), __private.forgeAttemptInterval);
 		}
-		jobsQueue.register('delegatesNextForge', __private.nextForge, __private.forgeAttemptInterval);
+		jobsQueue.register('delegatesNextForge', library.sequence.add.bind(null, __private.nextForge), __private.forgeAttemptInterval);
 	});
 };
 

From d6012a4ae1ecfa3844e442202c0db13a3f499513 Mon Sep 17 00:00:00 2001
From: Maciej Baj <macie.baj@gmail.com>
Date: Mon, 22 Jan 2018 15:36:12 +0100
Subject: [PATCH 09/17] Remove redundant sequence from
 delegates.__private.forge

---
 modules/delegates.js | 31 +++++++++++++------------------
 1 file changed, 13 insertions(+), 18 deletions(-)

diff --git a/modules/delegates.js b/modules/delegates.js
index be85f01e685..888eff00d9c 100644
--- a/modules/delegates.js
+++ b/modules/delegates.js
@@ -208,28 +208,23 @@ __private.forge = function (cb) {
 			return setImmediate(cb);
 		}
 
-		library.sequence.add(function (cb) {
-			async.series({
-				getPeers: function (seriesCb) {
-					return modules.transport.getPeers({limit: constants.maxPeers}, seriesCb);
-				},
-				checkBroadhash: function (seriesCb) {
-					if (modules.transport.poorConsensus()) {
-						return setImmediate(seriesCb, ['Inadequate broadhash consensus', modules.transport.consensus(), '%'].join(' '));
-					} else {
-						return setImmediate(seriesCb);
-					}
-				}
-			}, function (err) {
-				if (err) {
-					library.logger.warn(err);
-					return setImmediate(cb, err);
+		async.series({
+			getPeers: function (seriesCb) {
+				return modules.transport.getPeers({limit: constants.maxPeers}, seriesCb);
+			},
+			checkBroadhash: function (seriesCb) {
+				if (modules.transport.poorConsensus()) {
+					return setImmediate(seriesCb, ['Inadequate broadhash consensus', modules.transport.consensus(), '%'].join(' '));
 				} else {
-					return modules.blocks.process.generateBlock(currentBlockData.keypair, currentBlockData.time, cb);
+					return setImmediate(seriesCb);
 				}
-			});
+			},
+			generateBlock: function (seriesCb) {
+				return modules.blocks.process.generateBlock(currentBlockData.keypair, currentBlockData.time, seriesCb);
+			}
 		}, function (err) {
 			if (err) {
+				library.logger.warn(err);
 				library.logger.error('Failed to generate block within delegate slot', err);
 			} else {
 				var forgedBlock = modules.blocks.lastBlock.get();

From 77f9711497808cc86aa69368ec1049fba383ea21 Mon Sep 17 00:00:00 2001
From: Maciej Baj <macie.baj@gmail.com>
Date: Mon, 22 Jan 2018 15:50:46 +0100
Subject: [PATCH 10/17] Handle jobsQueue callbacks properly in
 delegates.onBlockchainReady

---
 modules/delegates.js | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/modules/delegates.js b/modules/delegates.js
index 888eff00d9c..09235a7b465 100644
--- a/modules/delegates.js
+++ b/modules/delegates.js
@@ -587,8 +587,9 @@ __private.nextForge = function (sequenceCb) {
 	], sequenceCb);
 };
 
-__private.logLoadDelegatesError = function (err) {
+__private.logLoadDelegatesError = function (err, cb) {
 	library.logger.error('Failed to load delegates', err);
+	return setImmediate(cb);
 };
 
 /**
@@ -599,9 +600,13 @@ Delegates.prototype.onBlockchainReady = function () {
 	__private.loaded = true;
 	__private.loadDelegates(function (err) {
 		if (err) {
-			jobsQueue.register('logLoadDelegatesError', __private.logLoadDelegatesError.bind(null, err), __private.forgeAttemptInterval);
+			jobsQueue.register('logLoadDelegatesError', function (jobsQueueCb) {
+				__private.logLoadDelegatesError(err, jobsQueueCb);
+			}, __private.forgeAttemptInterval);
 		}
-		jobsQueue.register('delegatesNextForge', library.sequence.add.bind(null, __private.nextForge), __private.forgeAttemptInterval);
+		jobsQueue.register('delegatesNextForge', function (jobsQueueCb) {
+			library.sequence.add(__private.nextForge, jobsQueueCb);
+		}, __private.forgeAttemptInterval);
 	});
 };
 

From 2eda4575111d183707e7d2aae27c4d2f531a1b48 Mon Sep 17 00:00:00 2001
From: Maciej Baj <macie.baj@gmail.com>
Date: Mon, 22 Jan 2018 17:25:35 +0100
Subject: [PATCH 11/17] Add tests to check forge and sync process exclusiveness

---
 test/system/synchronousTasks.js | 73 +++++++++++++++++++++++++++++++--
 1 file changed, 69 insertions(+), 4 deletions(-)

diff --git a/test/system/synchronousTasks.js b/test/system/synchronousTasks.js
index bb6c19efc57..e3ca4afe862 100644
--- a/test/system/synchronousTasks.js
+++ b/test/system/synchronousTasks.js
@@ -1,5 +1,7 @@
 'use strict';
 
+var expect = require('chai').expect;
+var Rx = require('rx');
 var application = require('./../common/application');
 
 describe('synchronousTasks', function () {
@@ -17,13 +19,76 @@ describe('synchronousTasks', function () {
 		application.cleanup(done);
 	});
 
-	describe('when "attempt to forge" synchronous tasks runs every 100 ms and takes 200 ms', function () {
+	describe('when events are emitted after any of synchronous task starts', function () {
 
-		describe('when "blockchain synchronization" synchronous tasks runs every 100 ms and takes 200 ms', function () {
+		var attemptToForgeRunningSubject = new Rx.BehaviorSubject();
+		var synchronizeBlockchainRunningSubject = new Rx.BehaviorSubject();
 
-			it('"attempt to forge" task should never start when "blockchain synchronization" task is running');
+		describe('when "attempt to forge" synchronous tasks runs every 100 ms and takes 101 ms', function () {
 
-			it('"blockchain synchronization" task should never start when "attempt to forge" task is running');
+			var intervalMs = 100;
+			var durationMs = intervalMs + 1;
+
+			before(function () {
+				library.modules.delegates.onBlockchainReady = library.rewiredModules.delegates.prototype.onBlockchainReady;
+				library.rewiredModules.delegates.__set__('__private.forgeAttemptInterval', intervalMs);
+				library.rewiredModules.delegates.__set__('__private.nextForge', function (nextForgeCb) {
+					attemptToForgeRunningSubject.onNext(true);
+					setTimeout(function () {
+						attemptToForgeRunningSubject.onNext(false);
+						nextForgeCb();
+					}, durationMs);
+				});
+				library.modules.delegates.onBlockchainReady();
+			});
+
+			describe('when "blockchain synchronization" synchronous tasks runs every 100 ms and takes 101 ms', function () {
+
+				before(function () {
+					library.rewiredModules.loader.__set__('__private.syncInterval', intervalMs);
+					library.rewiredModules.loader.__set__('__private.sync', function (nextForgeCb) {
+						synchronizeBlockchainRunningSubject.onNext(true);
+						setTimeout(function () {
+							synchronizeBlockchainRunningSubject.onNext(false);
+							nextForgeCb();
+						}, durationMs);
+					});
+					var jobsQueue = require('../../helpers/jobsQueue');
+					var originalLoaderSyncTimerJob = jobsQueue.jobs['loaderSyncTimer'];
+					clearTimeout(originalLoaderSyncTimerJob);  // Terminate original job
+					jobsQueue.jobs['loaderSyncTimer'] = null;  // Remove original job
+					library.modules.loader.onPeersReady();     // Execute the mocked blockchain synchronization process
+				});
+
+				describe('Within 5000 ms', function () {
+
+					beforeEach(function () {
+						setTimeout(function () {
+							attemptToForgeRunningSubject.onCompleted();
+							synchronizeBlockchainRunningSubject.onCompleted();
+							attemptToForgeRunningSubject = new Rx.BehaviorSubject();
+							synchronizeBlockchainRunningSubject = new Rx.BehaviorSubject();
+						}, 5000);
+					});
+
+					after(function () {
+						attemptToForgeRunningSubject.dispose();
+						synchronizeBlockchainRunningSubject.dispose();
+					});
+
+					it('"attempt to forge" task should never start when "blockchain synchronization" task is running', function (done) {
+						attemptToForgeRunningSubject
+							.filter(function (isStarting) {return isStarting;})
+							.subscribe(function () {expect(synchronizeBlockchainRunningSubject.getValue()).to.be.false;}, done, done);
+					});
+
+					it('"blockchain synchronization" task should never start when "attempt to forge" task is running', function (done) {
+						synchronizeBlockchainRunningSubject
+							.filter(function (isStarting) {return isStarting;})
+							.subscribe(function () {expect(attemptToForgeRunningSubject.getValue()).to.be.false;}, done, done);
+					});
+				});
+			});
 		});
 	});
 });

From 00de60118c017f54fbf4ae2581a0a31d2c85ba25 Mon Sep 17 00:00:00 2001
From: Maciej Baj <macie.baj@gmail.com>
Date: Mon, 22 Jan 2018 17:39:36 +0100
Subject: [PATCH 12/17] Remove redundant check if sync process runs in fillPool

---
 logic/transactionPool.js | 2 --
 1 file changed, 2 deletions(-)

diff --git a/logic/transactionPool.js b/logic/transactionPool.js
index dc3255e09a2..7cd9fbbbb91 100644
--- a/logic/transactionPool.js
+++ b/logic/transactionPool.js
@@ -583,8 +583,6 @@ TransactionPool.prototype.expireTransactions = function (cb) {
  * @returns {setImmediateCallback|applyUnconfirmedList}
  */
 TransactionPool.prototype.fillPool = function (cb) {
-	if (modules.loader.syncing()) { return setImmediate(cb); }
-
 	var unconfirmedCount = self.countUnconfirmed();
 	library.logger.debug('Transaction pool size: ' + unconfirmedCount);
 

From 5a675d61c65e86a8a2ea853b9ee3e67281ba4b73 Mon Sep 17 00:00:00 2001
From: Maciej Baj <macie.baj@gmail.com>
Date: Mon, 22 Jan 2018 17:42:34 +0100
Subject: [PATCH 13/17] Add rx-node as dev dependency

---
 package.json | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/package.json b/package.json
index 76911281c23..778317ac553 100644
--- a/package.json
+++ b/package.json
@@ -54,7 +54,6 @@
     "z-schema": "=3.18.2"
   },
   "devDependencies": {
-    "rewire": "=2.5.2",
     "bitcore-mnemonic": "=1.1.1",
     "bluebird": "=3.5.0",
     "browserify-bignum": "=1.3.0-2",
@@ -77,6 +76,8 @@
     "lisk-js": "=0.5.0",
     "mocha": "=3.2.0",
     "moment": "=2.17.1",
+    "rewire": "=2.5.2",
+    "rx-node": "=1.0.2",
     "sinon": "=1.17.7",
     "supertest": "=3.0.0"
   }

From d1fddaf0d965cd24fd0a7df83089058250c649fe Mon Sep 17 00:00:00 2001
From: Oliver Beddows <oliver@lightcurve.io>
Date: Tue, 23 Jan 2018 12:39:34 +0100
Subject: [PATCH 14/17] Apply standards

---
 test/system/synchronousTasks.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/system/synchronousTasks.js b/test/system/synchronousTasks.js
index e3ca4afe862..fb34a2aa69e 100644
--- a/test/system/synchronousTasks.js
+++ b/test/system/synchronousTasks.js
@@ -60,7 +60,7 @@ describe('synchronousTasks', function () {
 					library.modules.loader.onPeersReady();     // Execute the mocked blockchain synchronization process
 				});
 
-				describe('Within 5000 ms', function () {
+				describe('within 5000 ms', function () {
 
 					beforeEach(function () {
 						setTimeout(function () {

From 7051c568d3a77e37059d2c7a5302300cb87a375c Mon Sep 17 00:00:00 2001
From: Maciej Baj <macie.baj@gmail.com>
Date: Tue, 23 Jan 2018 12:40:41 +0100
Subject: [PATCH 15/17] Refactor synchronousTasks tests so it reuses the same
 task mock

---
 test/system/synchronousTasks.js | 53 +++++++++++++++++----------------
 1 file changed, 28 insertions(+), 25 deletions(-)

diff --git a/test/system/synchronousTasks.js b/test/system/synchronousTasks.js
index fb34a2aa69e..f872d03b890 100644
--- a/test/system/synchronousTasks.js
+++ b/test/system/synchronousTasks.js
@@ -21,38 +21,46 @@ describe('synchronousTasks', function () {
 
 	describe('when events are emitted after any of synchronous task starts', function () {
 
-		var attemptToForgeRunningSubject = new Rx.BehaviorSubject();
-		var synchronizeBlockchainRunningSubject = new Rx.BehaviorSubject();
+		var intervalMs;
+		var durationMs;
+		var attemptToForgeRunningSubject;
+		var synchronizeBlockchainRunningSubject;
+
+		var synchronousTaskMock = function (isTaskRunningSubject, nextCb) {
+			isTaskRunningSubject.onNext(true);
+			setTimeout(function () {
+				isTaskRunningSubject.onNext(false);
+				nextCb();
+			}, durationMs);
+		};
+
+		before(function () {
+			attemptToForgeRunningSubject = new Rx.BehaviorSubject();
+			synchronizeBlockchainRunningSubject = new Rx.BehaviorSubject();
+		});
+
+		after(function () {
+			attemptToForgeRunningSubject.dispose();
+			synchronizeBlockchainRunningSubject.dispose();
+		});
 
-		describe('when "attempt to forge" synchronous tasks runs every 100 ms and takes 101 ms', function () {
+		describe('when "attempt to forge" synchronous task runs every 100 ms and takes 101 ms', function () {
 
-			var intervalMs = 100;
-			var durationMs = intervalMs + 1;
+			intervalMs = 100;
+			durationMs = intervalMs + 1;
 
 			before(function () {
 				library.modules.delegates.onBlockchainReady = library.rewiredModules.delegates.prototype.onBlockchainReady;
 				library.rewiredModules.delegates.__set__('__private.forgeAttemptInterval', intervalMs);
-				library.rewiredModules.delegates.__set__('__private.nextForge', function (nextForgeCb) {
-					attemptToForgeRunningSubject.onNext(true);
-					setTimeout(function () {
-						attemptToForgeRunningSubject.onNext(false);
-						nextForgeCb();
-					}, durationMs);
-				});
+				library.rewiredModules.delegates.__set__('__private.nextForge', synchronousTaskMock.bind(null, attemptToForgeRunningSubject));
 				library.modules.delegates.onBlockchainReady();
 			});
 
-			describe('when "blockchain synchronization" synchronous tasks runs every 100 ms and takes 101 ms', function () {
+			describe('when "blockchain synchronization" synchronous task runs every 100 ms and takes 101 ms', function () {
 
 				before(function () {
 					library.rewiredModules.loader.__set__('__private.syncInterval', intervalMs);
-					library.rewiredModules.loader.__set__('__private.sync', function (nextForgeCb) {
-						synchronizeBlockchainRunningSubject.onNext(true);
-						setTimeout(function () {
-							synchronizeBlockchainRunningSubject.onNext(false);
-							nextForgeCb();
-						}, durationMs);
-					});
+					library.rewiredModules.loader.__set__('__private.sync', synchronousTaskMock.bind(null, synchronizeBlockchainRunningSubject));
 					var jobsQueue = require('../../helpers/jobsQueue');
 					var originalLoaderSyncTimerJob = jobsQueue.jobs['loaderSyncTimer'];
 					clearTimeout(originalLoaderSyncTimerJob);  // Terminate original job
@@ -71,11 +79,6 @@ describe('synchronousTasks', function () {
 						}, 5000);
 					});
 
-					after(function () {
-						attemptToForgeRunningSubject.dispose();
-						synchronizeBlockchainRunningSubject.dispose();
-					});
-
 					it('"attempt to forge" task should never start when "blockchain synchronization" task is running', function (done) {
 						attemptToForgeRunningSubject
 							.filter(function (isStarting) {return isStarting;})

From 830ff84af4ccd10aacb1413b4978358a522ad73c Mon Sep 17 00:00:00 2001
From: Oliver Beddows <oliver@lightcurve.io>
Date: Tue, 23 Jan 2018 12:42:27 +0100
Subject: [PATCH 16/17] Rename forgeAttemptInterval to forgeInterval

---
 modules/delegates.js            | 6 +++---
 test/system/synchronousTasks.js | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/modules/delegates.js b/modules/delegates.js
index 09235a7b465..6cd8241b9aa 100644
--- a/modules/delegates.js
+++ b/modules/delegates.js
@@ -25,7 +25,7 @@ __private.loaded = false;
 __private.blockReward = new BlockReward();
 __private.keypairs = {};
 __private.tmpKeypairs = {};
-__private.forgeAttemptInterval = 1000;
+__private.forgeInterval = 1000;
 
 /**
  * Initializes library with scope content and generates a Delegate instance.
@@ -602,11 +602,11 @@ Delegates.prototype.onBlockchainReady = function () {
 		if (err) {
 			jobsQueue.register('logLoadDelegatesError', function (jobsQueueCb) {
 				__private.logLoadDelegatesError(err, jobsQueueCb);
-			}, __private.forgeAttemptInterval);
+			}, __private.forgeInterval);
 		}
 		jobsQueue.register('delegatesNextForge', function (jobsQueueCb) {
 			library.sequence.add(__private.nextForge, jobsQueueCb);
-		}, __private.forgeAttemptInterval);
+		}, __private.forgeInterval);
 	});
 };
 
diff --git a/test/system/synchronousTasks.js b/test/system/synchronousTasks.js
index f872d03b890..bca434dcc72 100644
--- a/test/system/synchronousTasks.js
+++ b/test/system/synchronousTasks.js
@@ -51,7 +51,7 @@ describe('synchronousTasks', function () {
 
 			before(function () {
 				library.modules.delegates.onBlockchainReady = library.rewiredModules.delegates.prototype.onBlockchainReady;
-				library.rewiredModules.delegates.__set__('__private.forgeAttemptInterval', intervalMs);
+				library.rewiredModules.delegates.__set__('__private.forgeInterval', intervalMs);
 				library.rewiredModules.delegates.__set__('__private.nextForge', synchronousTaskMock.bind(null, attemptToForgeRunningSubject));
 				library.modules.delegates.onBlockchainReady();
 			});

From 957e514c75ded86fb0a3917dab8017f1c401b316 Mon Sep 17 00:00:00 2001
From: Oliver Beddows <oliver@lightcurve.io>
Date: Tue, 23 Jan 2018 12:57:29 +0100
Subject: [PATCH 17/17] Remove already logged error

---
 modules/delegates.js | 1 -
 1 file changed, 1 deletion(-)

diff --git a/modules/delegates.js b/modules/delegates.js
index 6cd8241b9aa..422ce07bdd8 100644
--- a/modules/delegates.js
+++ b/modules/delegates.js
@@ -224,7 +224,6 @@ __private.forge = function (cb) {
 			}
 		}, function (err) {
 			if (err) {
-				library.logger.warn(err);
 				library.logger.error('Failed to generate block within delegate slot', err);
 			} else {
 				var forgedBlock = modules.blocks.lastBlock.get();