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benjamingr/mongo.js

Created December 14, 2020 14:13
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  1. benjamingr created this gist Dec 14, 2020.
    17 changes: 17 additions & 0 deletions mongo.js
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,17 @@
    // Let's say I have transaction code that looks like:

    let state = 1;
    session.withTransaction(async () => {
    // this can retry, which means otherFn can run twice and possible insert the wrong value or in the wrong order
    state++;
    await Promise.all([
    coll1.insertOne({ abc: 1 }, { session });
    otherFn(state, session),
    ])
    });

    async function otherFn(state, session) {
    // get some data from redis or another DB
    await setTimeout(Math.random() * 100);
    await coll2.insertOne({abc: state});
    }