mysql-libmysqlclient-transaction/lib/transaction.js

nodejs module node-mysql-libmysqlclient transaction

/* Wraps db.query and exposes function db.createQueue() */
module.exports = function(db, debug) {
    if(debug !== true)
        debug = false;
    if(debug)
        console.log("mysql-queues: debug mode enabled.");
    var options = {
        debug: debug,
        currentlyExecutingQueue: null,
        mainQueue: []
    };
    var dbQuery = db.query; //The old db.query function
    //Wrap db.query
    db.query = function(sql, cb) {
        //Run query if no Queue is running; otherwise, queue it in mainQueue
        if(options.currentlyExecutingQueue == null)
            return dbQuery.apply(db, arguments);
        else
            options.mainQueue.push(arguments);
    };
    //Create a new executable query Queue
    db.createQueue = function() {
        return new Queue(
            function() {
                return dbQuery.apply(db, arguments);
            },
            function () {
            //If the current Queue is a transaction that has not yet been committed, commit it
            var ceq = options.currentlyExecutingQueue;
            if(ceq != null && ceq.commit != null) {
                //Also, warn the user that relying on this behavior is a bad idea
                if(ceq._autoCommit !== true)
                    console.warn("WARNING: mysql-queues: Database transaction was " +
                        "implicitly committed.\nIt is HIGHLY recommended that you " +
                        "explicitly commit all transactions.\n" +
                        "The last query to run was:", ceq.lastExecuted.sql);
                ceq.commit(ceq._autoCommitCB);
                return;
            }
            options.currentlyExecutingQueue = null;
            //Called when a Queue has completed its processing and main queue should be executed
            while(options.mainQueue.length > 0) {
                var item = options.mainQueue.shift(); //Unsure of shift's performance
                if(item instanceof Queue) {
                    item.execute();
                    break; //After the Queue has been executed, the main queue will be resumed
                } else
                    dbQuery.apply(db, item);
            }
        }, options);
    };
    db.startTransaction = function() {
        return Queue.isNowTransaction(
            this.createQueue(),
            function() {
                return dbQuery.apply(db, arguments);
            }
        );
    };
}
function Queue(dbQuery, resumeMainQueue, options) {
    this.queue = [];
    this.paused = false;
    /* Add a query to the Queue */
    this.query = function(sql, cb) {
        this.queue.push({
            'sql': sql,
            'cb': cb
        });
        return this; //Chaining :)
    };
    /* Execute all queries on the Queue in order and prevent other queries from executing until
     all queries have been completed.
     */
    this.execute = function() {
        if(this.paused === true || this.executing)
            return;
        var that = this;
        //If another Queue is currently running, we put this on the mainQueue
        if(options.currentlyExecutingQueue != null && options.currentlyExecutingQueue != this)
            options.mainQueue.push(this);
        else if(that.queue.length > 0) {
            options.currentlyExecutingQueue = this;
            //console.log("Executing queue:", options.currentlyExecutingQueue);
            //Run everything in the queue
            that.executing = true;
            var done = 0, total = that.queue.length;
            for(var i = 0; i < total; i ++) {
                (function(item) {
                    //Execute the query
                    try {
                        if(item.sql == "COMMIT") delete that.rollback; //Keep 'em honest
                        that.lastExecuted = item; //For debugging and convenience
                        dbQuery(item.sql, function() {
                            if(options.debug && arguments[0] != null)
                                console.error("mysql-queues: An error occurred while executing the following " +
                                    "query:\n\t", item.sql);
                            //Execute the original callback first (which may add more queries to this Queue)
                            if(item.cb != null)
                                item.cb.apply(this, arguments);
                            //When the entire queue has completed...
                            if(++done == total) {
                                that.executing = false;
                                if(that.paused === true) return;
                                /* The query's callback may have queued more queries on this Queue.
                                 If so, execute this Queue again; otherwise, resumeMainQueue() */
                                if(that.queue.length == 0)
                                    resumeMainQueue();
                                else
                                    that.execute();
                            }
                        });
                    } catch(e) {
                        if(options.debug)
                            console.log("mysql-queues: An exception occurred for this query:\n\t",
                                item.sql);
                        throw e;
                    }
                })(that.queue[i]);
            }
            that.queue = [];
            //All queued queries are running, but we don't resume the main queue just yet
            //console.log("Queue Complete:", options.currentlyExecutingQueue);
        }
        else if(options.currentlyExecutingQueue == this)
            resumeMainQueue();
        return this; //Chaining :)
    };
    this.pause = function(maxWaitTime) {
        this.paused = true;
        if(maxWaitTime > 0) {
            var that = this;
            that.pauseTimer = setTimeout(function() {
                that.resume();
            }, maxWaitTime);
        }
        return this; //Chaining
    }
    this.resume = function() {
        if(this.pauseTimer)
            clearTimeout(this.pauseTimer);
        this.paused = false;
        this.execute();
        return this; //Chaining
    }
}
Queue.isNowTransaction = function(q, dbQuery) {
    q.query("START TRANSACTION");
    q.commit = function(cb) {
        if(this.queue.length > 0) {
            this._autoCommit = true;
            this._autoCommitCB = cb;
            this.resume();
        } else {
            delete this.commit;
            delete this._autoCommit;
            this.query("COMMIT", cb).resume();
        }
    }
    q.rollback = function(cb) {
        this.queue = [];
        delete this.commit;
        delete this.rollback;
        dbQuery("ROLLBACK", cb);
        this.resume();
    }
    return q;
}