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Update change streams #12

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merged 2 commits into from
Feb 18, 2021
Merged

Update change streams #12

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a82e194
Update for 3.6 driver
ljhaywar Feb 12, 2021
b191b70
Update change stream pipe
ljhaywar Feb 18, 2021
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Update for 3.6 driver
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@ljhaywar
ljhaywar committed Feb 12, 2021
commit a82e19490e92039d7d42829fb2b35df7e55080cc
23 changes: 15 additions & 8 deletions changeStreams.js
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Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,7 @@ function closeChangeStream(timeInMs = 60000, changeStream) {
async function monitorListingsUsingEventEmitter(client, timeInMs = 60000, pipeline = []) {
const collection = client.db("sample_airbnb").collection("listingsAndReviews");

// See http://bit.ly/Node_watch for the watch() docs
// See https://mongodb.github.io/node-mongodb-native/3.6/api/Collection.html#watch for the watch() docs
const changeStream = collection.watch(pipeline);

// ChangeStream inherits from the Node Built-in Class EventEmitter (https://nodejs.org/dist/latest-v12.x/docs/api/events.html#events_class_eventemitter).
Expand All @@ -102,18 +102,25 @@ async function monitorListingsUsingEventEmitter(client, timeInMs = 60000, pipeli
async function monitorListingsUsingHasNext(client, timeInMs = 60000, pipeline = []) {
const collection = client.db("sample_airbnb").collection("listingsAndReviews");

// See http://bit.ly/Node_watch for the watch() docs
// See https://mongodb.github.io/node-mongodb-native/3.6/api/Collection.html#watch for the watch() docs
const changeStream = collection.watch(pipeline);

// Set a timer that will close the change stream after the given amount of time
// Function execution will continue because we are not using "await" here
closeChangeStream(timeInMs, changeStream);

// We can use ChangeStream's hasNext() function to wait for a new change in the change stream.
// If the change stream is closed, hasNext() will return false so the while loop will exit.
// See http://bit.ly/Node_ChangeStream for the ChangeStream docs.
while (await changeStream.hasNext()) {
console.log(await changeStream.next());
// See https://mongodb.github.io/node-mongodb-native/3.6/api/ChangeStream.html for the ChangeStream docs.
try {
while (await changeStream.hasNext()) {
console.log(await changeStream.next());
}
} catch (error) {
if (changeStream.isClosed()) {
console.log("The change stream is closed. Will not wait on any more changes.")
} else {
throw error;
}
}
}

Expand All @@ -127,10 +134,10 @@ async function monitorListingsUsingHasNext(client, timeInMs = 60000, pipeline =
async function monitorListingsUsingStreamAPI(client, timeInMs = 60000, pipeline = []) {
const collection = client.db('sample_airbnb').collection('listingsAndReviews');

// See http://bit.ly/Node_watch for the watch() docs
// See https://mongodb.github.io/node-mongodb-native/3.6/api/Collection.html#watch for the watch() docs
const changeStream = collection.watch(pipeline);

// See http://bit.ly/Node_pipe for the pipe() docs
// See https://mongodb.github.io/node-mongodb-native/3.6/api/ChangeStream.html#pipe for the pipe() docs
changeStream.pipe(
new stream.Writable({
objectMode: true,
Expand Down