Tips for performing a custom atomic update on a mongodb document

Question

Tips for performing a custom atomic update on a mongodb document

While MongoDB does offer the ability to perform atomic updates using findOneAndUpdate, it is limited to basic operations such as set or increment.

What I really need is a way to apply a custom function to transform my document:

const updateDoc = async (event) => {
  const oldState = await db.collection(collectionName).findOne({ name });
  const newState = customFunction(oldState, event);
  await db.collection(collectionName).replaceOne({ name }, newState);
}

This function will be invoked by a system that does not wait for promises to resolve before continuing operation, resulting in potentially multiple synchronous calls.

Is there a method to modify updateDoc to ensure atomicity so that when we execute:

updateDoc(event1); // without using await
updateDoc(event2);

We can guarantee that the stored document will reflect

customFunction(customFunction(initState, event1), event2)

?

Thank you

javascript mongodb transactions

Answer 1

Answer №1

One effective way to handle this scenario is by implementing a task scheduler that queues and executes updates sequentially:

class TaskScheduler {
  constructor(){
    this.isRunning = false;
    this.taskQueue = [];
  }

  add(task){
     this.taskQueue.push(task);
     if(!this.isRunning) this.executeTasks();
  }

  async executeTasks(){
    this.isRunning = true;
    while(this.taskQueue.length) await this.taskQueue.shift()();
    this.isRunning = false;
 }
}

You can use it as follows:

 const jobScheduler = new TaskScheduler();

 const updateDocument = async (event) => jobScheduler.add( _ => {
   const previousState = await db.collection(collectionName).findOne({ name });
   const newState = processNewState(previousState, event);
   await db.collection(collectionName).replaceOne({ name }, newState);
});

updateDocument(event1);
updateDocument(event2);

Answer 2

One effective way to handle this scenario is by implementing a task scheduler that queues and executes updates sequentially:

class TaskScheduler {
  constructor(){
    this.isRunning = false;
    this.taskQueue = [];
  }

  add(task){
     this.taskQueue.push(task);
     if(!this.isRunning) this.executeTasks();
  }

  async executeTasks(){
    this.isRunning = true;
    while(this.taskQueue.length) await this.taskQueue.shift()();
    this.isRunning = false;
 }
}

You can use it as follows:

 const jobScheduler = new TaskScheduler();

 const updateDocument = async (event) => jobScheduler.add( _ => {
   const previousState = await db.collection(collectionName).findOne({ name });
   const newState = processNewState(previousState, event);
   await db.collection(collectionName).replaceOne({ name }, newState);
});

updateDocument(event1);
updateDocument(event2);

Tips for performing a custom atomic update on a mongodb document

Answer №1

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