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Code Issues Releases Wiki Activity

Fix syncer race condition (#7843)

Browse Source 
* Initial commit

* Log task choosing

* A tiny bit more logging

* Typo

* Restructure syncer to use a single state machine
This commit is contained in:
Jeremy Ruston 2023-11-24 13:02:09 +00:00 committed by GitHub
parent ca41a8db04
commit 1cb607249e
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 164 additions and 122 deletions
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286
core/modules/syncer.js
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@ -24,7 +24,7 @@ Syncer.prototype.titleSyncPollingInterval = "$:/config/SyncPollingInterval";
Syncer.prototype.titleSyncDisableLazyLoading = "$:/config/SyncDisableLazyLoading";
Syncer.prototype.titleSavedNotification = "$:/language/Notifications/Save/Done";
Syncer.prototype.titleSyncThrottleInterval = "$:/config/SyncThrottleInterval";
Syncer.prototype.taskTimerInterval = 1 * 1000; // Interval for sync timer
Syncer.prototype.taskTimerInterval = 0.25 * 1000; // Interval for sync timer
Syncer.prototype.throttleInterval = 1 * 1000; // Defer saving tiddlers if they've changed in the last 1s...
Syncer.prototype.errorRetryInterval = 5 * 1000; // Interval to retry after an error
Syncer.prototype.fallbackInterval = 10 * 1000; // Unless the task is older than 10s
@ -74,9 +74,11 @@ function Syncer(options) {
this.titlesHaveBeenLazyLoaded = {}; // Hashmap of titles of tiddlers that have already been lazily loaded from the server
// Timers
this.taskTimerId = null; // Timer for task dispatch
this.pollTimerId = null; // Timer for polling server
// Number of outstanding requests
this.numTasksInProgress = 0;
// True when we want to force an immediate sync from the server
this.forceSyncFromServer = false;
this.timestampLastSyncFromServer = new Date();
// Listen out for changes to tiddlers
this.wiki.addEventListener("change",function(changes) {
// Filter the changes to just include ones that are being synced
@ -187,6 +189,7 @@ Syncer.prototype.readTiddlerInfo = function() {
// Record information for known tiddlers
var self = this,
tiddlers = this.getSyncedTiddlers();
this.logger.log("Initialising tiddlerInfo for " + tiddlers.length + " tiddlers");
$tw.utils.each(tiddlers,function(title) {
var tiddler = self.wiki.getTiddler(title);
if(tiddler) {
@ -203,33 +206,38 @@ Syncer.prototype.readTiddlerInfo = function() {
Checks whether the wiki is dirty (ie the window shouldn't be closed)
*/
Syncer.prototype.isDirty = function() {
this.logger.log("Checking dirty status");
// Check tiddlers that are in the store and included in the filter function
var titles = this.getSyncedTiddlers();
for(var index=0; index<titles.length; index++) {
var title = titles[index],
tiddlerInfo = this.tiddlerInfo[title];
if(this.wiki.tiddlerExists(title)) {
if(tiddlerInfo) {
// If the tiddler is known on the server and has been modified locally then it needs to be saved to the server
if(this.wiki.getChangeCount(title) > tiddlerInfo.changeCount) {
var self = this;
function checkIsDirty() {
// Check tiddlers that are in the store and included in the filter function
var titles = self.getSyncedTiddlers();
for(var index=0; index<titles.length; index++) {
var title = titles[index],
tiddlerInfo = self.tiddlerInfo[title];
if(self.wiki.tiddlerExists(title)) {
if(tiddlerInfo) {
// If the tiddler is known on the server and has been modified locally then it needs to be saved to the server
if(self.wiki.getChangeCount(title) > tiddlerInfo.changeCount) {
return true;
}
} else {
// If the tiddler isn't known on the server then it needs to be saved to the server
return true;
}
} else {
// If the tiddler isn't known on the server then it needs to be saved to the server
}
}
// Check tiddlers that are known from the server but not currently in the store
titles = Object.keys(self.tiddlerInfo);
for(index=0; index<titles.length; index++) {
if(!self.wiki.tiddlerExists(titles[index])) {
// There must be a pending delete
return true;
}
}
return false;
}
// Check tiddlers that are known from the server but not currently in the store
titles = Object.keys(this.tiddlerInfo);
for(index=0; index<titles.length; index++) {
if(!this.wiki.tiddlerExists(titles[index])) {
// There must be a pending delete
return true;
}
}
return false;
var dirtyStatus = checkIsDirty();
this.logger.log("Dirty status was " + dirtyStatus);
return dirtyStatus;
};
/*
@ -258,6 +266,7 @@ Syncer.prototype.storeTiddler = function(tiddlerFields) {
adaptorInfo: this.syncadaptor.getTiddlerInfo(tiddler),
changeCount: this.wiki.getChangeCount(tiddlerFields.title)
};
this.logger.log("Updating tiddler info in syncer.storeTiddler for " + tiddlerFields.title + " " + JSON.stringify(this.tiddlerInfo[tiddlerFields.title]));
};
Syncer.prototype.getStatus = function(callback) {
@ -293,90 +302,8 @@ Syncer.prototype.getStatus = function(callback) {
Synchronise from the server by reading the skinny tiddler list and queuing up loads for any tiddlers that we don't already have up to date
*/
Syncer.prototype.syncFromServer = function() {
var self = this,
cancelNextSync = function() {
if(self.pollTimerId) {
clearTimeout(self.pollTimerId);
self.pollTimerId = null;
}
},
triggerNextSync = function() {
self.pollTimerId = setTimeout(function() {
self.pollTimerId = null;
self.syncFromServer.call(self);
},self.pollTimerInterval);
},
syncSystemFromServer = (self.wiki.getTiddlerText("$:/config/SyncSystemTiddlersFromServer") === "yes" ? true : false);
if(this.syncadaptor && this.syncadaptor.getUpdatedTiddlers) {
this.logger.log("Retrieving updated tiddler list");
cancelNextSync();
this.syncadaptor.getUpdatedTiddlers(self,function(err,updates) {
triggerNextSync();
if(err) {
self.displayError($tw.language.getString("Error/RetrievingSkinny"),err);
return;
}
if(updates) {
$tw.utils.each(updates.modifications,function(title) {
self.titlesToBeLoaded[title] = true;
});
$tw.utils.each(updates.deletions,function(title) {
if(syncSystemFromServer || !self.wiki.isSystemTiddler(title)) {
delete self.tiddlerInfo[title];
self.logger.log("Deleting tiddler missing from server:",title);
self.wiki.deleteTiddler(title);
}
});
if(updates.modifications.length > 0 || updates.deletions.length > 0) {
self.processTaskQueue();
}
}
});
} else if(this.syncadaptor && this.syncadaptor.getSkinnyTiddlers) {
this.logger.log("Retrieving skinny tiddler list");
cancelNextSync();
this.syncadaptor.getSkinnyTiddlers(function(err,tiddlers) {
triggerNextSync();
// Check for errors
if(err) {
self.displayError($tw.language.getString("Error/RetrievingSkinny"),err);
return;
}
// Keep track of which tiddlers we already know about have been reported this time
var previousTitles = Object.keys(self.tiddlerInfo);
// Process each incoming tiddler
for(var t=0; t<tiddlers.length; t++) {
// Get the incoming tiddler fields, and the existing tiddler
var tiddlerFields = tiddlers[t],
incomingRevision = tiddlerFields.revision + "",
tiddler = self.wiki.tiddlerExists(tiddlerFields.title) && self.wiki.getTiddler(tiddlerFields.title),
tiddlerInfo = self.tiddlerInfo[tiddlerFields.title],
currRevision = tiddlerInfo ? tiddlerInfo.revision : null,
indexInPreviousTitles = previousTitles.indexOf(tiddlerFields.title);
if(indexInPreviousTitles !== -1) {
previousTitles.splice(indexInPreviousTitles,1);
}
// Ignore the incoming tiddler if it's the same as the revision we've already got
if(currRevision !== incomingRevision) {
// Only load the skinny version if we don't already have a fat version of the tiddler
if(!tiddler || tiddler.fields.text === undefined) {
self.storeTiddler(tiddlerFields);
}
// Do a full load of this tiddler
self.titlesToBeLoaded[tiddlerFields.title] = true;
}
}
// Delete any tiddlers that were previously reported but missing this time
$tw.utils.each(previousTitles,function(title) {
if(syncSystemFromServer || !self.wiki.isSystemTiddler(title)) {
delete self.tiddlerInfo[title];
self.logger.log("Deleting tiddler missing from server:",title);
self.wiki.deleteTiddler(title);
}
});
self.processTaskQueue();
});
}
this.forceSyncFromServer = true;
this.processTaskQueue();
};
/*
@ -498,6 +425,7 @@ Syncer.prototype.processTaskQueue = function() {
if((!this.syncadaptor.isReady || this.syncadaptor.isReady()) && this.numTasksInProgress === 0) {
// Choose the next task to perform
var task = this.chooseNextTask();
self.logger.log("Chosen next task " + task);
// Perform the task if we had one
if(typeof task === "object" && task !== null) {
this.numTasksInProgress += 1;
@ -510,7 +438,7 @@ Syncer.prototype.processTaskQueue = function() {
} else {
self.updateDirtyStatus();
// Process the next task
self.processTaskQueue.call(self);
self.processTaskQueue.call(self);
}
});
} else {
@ -518,31 +446,39 @@ Syncer.prototype.processTaskQueue = function() {
this.updateDirtyStatus();
// And trigger a timeout if there is a pending task
if(task === true) {
this.triggerTimeout();
this.triggerTimeout(this.taskTimerInterval);
} else {
this.triggerTimeout(this.pollTimerInterval);
}
}
} else {
this.updateDirtyStatus();
this.updateDirtyStatus();
this.triggerTimeout(this.taskTimerInterval);
}
};
Syncer.prototype.triggerTimeout = function(interval) {
var self = this;
if(!this.taskTimerId) {
this.taskTimerId = setTimeout(function() {
self.taskTimerId = null;
self.processTaskQueue.call(self);
},interval || self.taskTimerInterval);
if(this.taskTimerId) {
clearTimeout(this.taskTimerId);
}
this.taskTimerId = setTimeout(function() {
self.taskTimerId = null;
self.processTaskQueue.call(self);
},interval || self.taskTimerInterval);
};
/*
Choose the next sync task. We prioritise saves, then deletes, then loads from the server
Choose the next sync task. We prioritise saves to the server, then getting updates from the server, then deletes to the server, then loads from the server
Returns either a task object, null if there's no upcoming tasks, or the boolean true if there are pending tasks that aren't yet due
Returns either:
* a task object
* the boolean true if there are pending sync tasks that aren't yet due
* null if there's no pending sync tasks (just the next poll)
*/
Syncer.prototype.chooseNextTask = function() {
var thresholdLastSaved = (new Date()) - this.throttleInterval,
var now = new Date(),
thresholdLastSaved = now - this.throttleInterval,
havePending = null;
// First we look for tiddlers that have been modified locally and need saving back to the server
var titles = this.getSyncedTiddlers();
@ -556,14 +492,18 @@ Syncer.prototype.chooseNextTask = function() {
isReadyToSave = !tiddlerInfo || !tiddlerInfo.timestampLastSaved || tiddlerInfo.timestampLastSaved < thresholdLastSaved;
if(hasChanged) {
if(isReadyToSave) {
return new SaveTiddlerTask(this,title);
return new SaveTiddlerTask(this,title);
} else {
havePending = true;
}
}
}
}
// Second, we check tiddlers that are known from the server but not currently in the store, and so need deleting on the server
// Second we check for an outstanding sync from server
if(this.forceSyncFromServer || (this.timestampLastSyncFromServer && (now.valueOf() >= (this.timestampLastSyncFromServer.valueOf() + this.pollTimerInterval)))) {
return new SyncFromServerTask(this);
}
// Third, we check tiddlers that are known from the server but not currently in the store, and so need deleting on the server
titles = Object.keys(this.tiddlerInfo);
for(index=0; index<titles.length; index++) {
title = titles[index];
@ -573,13 +513,13 @@ Syncer.prototype.chooseNextTask = function() {
return new DeleteTiddlerTask(this,title);
}
}
// Check for tiddlers that need loading
// Finally, check for tiddlers that need loading
title = Object.keys(this.titlesToBeLoaded)[0];
if(title) {
delete this.titlesToBeLoaded[title];
return new LoadTiddlerTask(this,title);
}
// No tasks are ready
// No tasks are ready now, but might be in the future
return havePending;
};
@ -589,6 +529,10 @@ function SaveTiddlerTask(syncer,title) {
this.type = "save";
}
SaveTiddlerTask.prototype.toString = function() {
return "SAVE " + this.title;
}
SaveTiddlerTask.prototype.run = function(callback) {
var self = this,
changeCount = this.syncer.wiki.getChangeCount(this.title),
@ -607,6 +551,7 @@ SaveTiddlerTask.prototype.run = function(callback) {
revision: revision,
timestampLastSaved: new Date()
};
self.syncer.logger.log("Updating tiddler info in SaveTiddlerTask.run for " + self.title + " " + JSON.stringify(self.syncer.tiddlerInfo[self.title]));
// Invoke the callback
callback(null);
},{
@ -624,6 +569,10 @@ function DeleteTiddlerTask(syncer,title) {
this.type = "delete";
}
DeleteTiddlerTask.prototype.toString = function() {
return "DELETE " + this.title;
}
DeleteTiddlerTask.prototype.run = function(callback) {
var self = this;
this.syncer.logger.log("Dispatching 'delete' task:",this.title);
@ -633,6 +582,7 @@ DeleteTiddlerTask.prototype.run = function(callback) {
return callback(err);
}
// Remove the info stored about this tiddler
self.syncer.logger.log("Deleting tiddler info in DeleteTiddlerTask.run for " + self.title);
delete self.syncer.tiddlerInfo[self.title];
// Invoke the callback
callback(null);
@ -647,6 +597,10 @@ function LoadTiddlerTask(syncer,title) {
this.type = "load";
}
LoadTiddlerTask.prototype.toString = function() {
return "LOAD " + this.title;
}
LoadTiddlerTask.prototype.run = function(callback) {
var self = this;
this.syncer.logger.log("Dispatching 'load' task:",this.title);
@ -664,6 +618,94 @@ LoadTiddlerTask.prototype.run = function(callback) {
});
};
function SyncFromServerTask(syncer) {
this.syncer = syncer;
this.type = "syncfromserver";
}
SyncFromServerTask.prototype.toString = function() {
return "SYNCFROMSERVER";
}
SyncFromServerTask.prototype.run = function(callback) {
var self = this;
var syncSystemFromServer = (self.syncer.wiki.getTiddlerText("$:/config/SyncSystemTiddlersFromServer") === "yes" ? true : false);
var successCallback = function() {
self.syncer.forceSyncFromServer = false;
self.syncer.timestampLastSyncFromServer = new Date();
callback(null);
};
if(this.syncer.syncadaptor.getUpdatedTiddlers) {
self.syncer.logger.log("Retrieving updated tiddler list");
this.syncer.syncadaptor.getUpdatedTiddlers(self,function(err,updates) {
if(err) {
self.syncer.displayError($tw.language.getString("Error/RetrievingSkinny"),err);
return callback(err);
}
if(updates) {
$tw.utils.each(updates.modifications,function(title) {
self.syncer.titlesToBeLoaded[title] = true;
});
$tw.utils.each(updates.deletions,function(title) {
if(syncSystemFromServer || !self.syncer.wiki.isSystemTiddler(title)) {
delete self.syncer.tiddlerInfo[title];
self.syncer.logger.log("Deleting tiddler missing from server:",title);
self.syncer.wiki.deleteTiddler(title);
}
});
}
return successCallback();
});
} else if(this.syncer.syncadaptor.getSkinnyTiddlers) {
this.syncer.logger.log("Retrieving skinny tiddler list");
this.syncer.syncadaptor.getSkinnyTiddlers(function(err,tiddlers) {
self.syncer.logger.log("Retrieved skinny tiddler list");
// Check for errors
if(err) {
self.syncer.displayError($tw.language.getString("Error/RetrievingSkinny"),err);
return callback(err);
}
// Keep track of which tiddlers we already know about have been reported this time
var previousTitles = Object.keys(self.syncer.tiddlerInfo);
// Process each incoming tiddler
for(var t=0; t<tiddlers.length; t++) {
// Get the incoming tiddler fields, and the existing tiddler
var tiddlerFields = tiddlers[t],
incomingRevision = tiddlerFields.revision + "",
tiddler = self.syncer.wiki.tiddlerExists(tiddlerFields.title) && self.syncer.wiki.getTiddler(tiddlerFields.title),
tiddlerInfo = self.syncer.tiddlerInfo[tiddlerFields.title],
currRevision = tiddlerInfo ? tiddlerInfo.revision : null,
indexInPreviousTitles = previousTitles.indexOf(tiddlerFields.title);
if(indexInPreviousTitles !== -1) {
previousTitles.splice(indexInPreviousTitles,1);
}
// Ignore the incoming tiddler if it's the same as the revision we've already got
if(currRevision !== incomingRevision) {
// Only load the skinny version if we don't already have a fat version of the tiddler
if(!tiddler || tiddler.fields.text === undefined) {
self.syncer.storeTiddler(tiddlerFields);
}
// Do a full load of this tiddler
self.syncer.titlesToBeLoaded[tiddlerFields.title] = true;
}
}
// Delete any tiddlers that were previously reported but missing this time
$tw.utils.each(previousTitles,function(title) {
if(syncSystemFromServer || !self.syncer.wiki.isSystemTiddler(title)) {
delete self.syncer.tiddlerInfo[title];
self.syncer.logger.log("Deleting tiddler missing from server:",title);
self.syncer.wiki.deleteTiddler(title);
}
});
self.syncer.forceSyncFromServer = false;
self.syncer.timestampLastSyncFromServer = new Date();
return successCallback();
});
} else {
return successCallback();
}
};
exports.Syncer = Syncer;
})();