Resume tokens for reliability in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a change stream with a resume token.

MongoDB

const changeStream = collection.watch([], { resumeAfter: [1] });

Drag options to blanks, or click blank then click option'

AresumeToken

BbatchSize

CfullDocument

DstartAtOperationTime

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'startAtOperationTime' instead of 'resumeAfter' for resuming.

Passing the full document instead of the resume token.

Confusing batch size with resume token.

The resumeAfter option uses the resume token to continue watching changes from where it left off.

2fill in blank

medium

Complete the code to retrieve the resume token from a change stream event.

MongoDB

const resumeToken = changeEvent[1];

Drag options to blanks, or click blank then click option'

A_id

Btoken

CresumeToken

Did

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to access a non-existent 'resumeToken' field.

Using 'id' instead of '_id'.

Using 'token' which is not a valid field.

The resume token is stored in the _id field of the change event.

3fill in blank

hard

Fix the error in the code to resume a change stream after a disconnect.

MongoDB

const changeStream = collection.watch([], { [1]: lastResumeToken });

Drag options to blanks, or click blank then click option'

AstartAfter

BresumeAfter

CstartAtOperationTime

DfullDocument

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'startAfter' which is not a valid option.

Using 'startAtOperationTime' which resumes differently.

Confusing 'fullDocument' option with resume token.

To resume a change stream after a disconnect, use the resumeAfter option with the last resume token.

4fill in blank

hard

Fill both blanks to create a change stream that resumes after a token and returns full documents.

MongoDB

const changeStream = collection.watch([], { [1]: resumeToken, [2]: 'updateLookup' });

Drag options to blanks, or click blank then click option'

AresumeAfter

BstartAtOperationTime

CfullDocument

DbatchSize

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up 'startAtOperationTime' with 'resumeAfter'.

Using 'batchSize' instead of 'fullDocument'.

Not setting 'fullDocument' to 'updateLookup' when needed.

The resumeAfter option resumes the stream after the given token, and fullDocument: 'updateLookup' returns the full updated document on change.

5fill in blank

hard

Fill all three blanks to store the resume token from a change event and resume the stream correctly.

MongoDB

changeStream.on('change', (changeEvent) => {
  const [1] = changeEvent.[2];
  // Later resume with
  const resumedStream = collection.watch([], { [3]: [1] });
});

Drag options to blanks, or click blank then click option'

AlastResumeToken

B_id

CresumeAfter

DfullDocument

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variable names for the token.

Accessing a wrong field instead of '_id'.

Using 'fullDocument' instead of 'resumeAfter' to resume.

We store the resume token from changeEvent._id in lastResumeToken. Then we resume the stream using resumeAfter: lastResumeToken.