Transactions in feathers-mongodb - See https://github.com/feathersjs-ecosystem/feathers-mongodb/issues/127

feathers-mongodb+6.1.0.patch.js

# /node_modules/feathers-mongodb/lib/index.js
# Patched version of _get()

  _get (id, params = {}) {
    const { query } = this.filterQuery(params);

    query.$and = (query.$and || []).concat({ [this.id]: this._objectifyId(id) });
    let result = null;
    if (params.inTransaction)
      result = this.Model.findOneAndUpdate(query, {$set: { myLock: ObjectID() }});
    else
      result = this.Model.findOne(query);

    return result.then(data => {
      if (!data) {
        throw new errors.NotFound(`No record found for id '${id}'`);
      }

      return data;
    }).then(select(params, this.id)).catch(errorHandler);
  }

hooks.js

// eslint-disable-next-line no-unused-vars
function startTransaction(options = {}) {
  const transactionOptions = {
    readConcern: { level: "snapshot" },
    writeConcern: { w: "majority" },
    readPreference: "primary"
  };

  return async (context) => {
    const { app } = context;
    const client = await app.get("mongoClient");
    context.mongoSession = client.startSession();
    if (context.mongoSession.inTransaction())
      console.error("Already in transaction");
    await context.mongoSession.startTransaction(transactionOptions);
    context.params.inTransaction = true;
    return context;
  };
}

// eslint-disable-next-line no-unused-vars
function stopTransaction(options = {}) {
  return async (context) => {
    try {
      await commitWithRetry(context.mongoSession);
    } catch (error) {
      console.error("abortTransaction");
      await context.mongoSession.abortTransaction();
      throw error;
    }
    await context.mongoSession.endSession();
    delete context.params.inTransaction;
    return context;
  };
}

async function commitWithRetry(session) {
  try {
    await session.commitTransaction();
  } catch (error) {
    if (error.hasErrorLabel("UnknownTransactionCommitResult")) {
      console.error(
        "UnknownTransactionCommitResult, retrying commit operation ..."
      );
      await commitWithRetry(session);
    } else {
      console.error("Error during commit ...");
      throw error;
    }
  }
}

// eslint-disable-next-line no-unused-vars
function errorTransaction(options = {}) {
  return async (context) => {
    console.error("stopTransaction");
    if (context.mongoSession) {
      if (context.mongoSession.inTransaction())
        await context.mongoSession.abortTransaction();
      await context.mongoSession.endSession();
    }
    return context;
  };
}

module.exports = { startTransaction, stopTransaction, errorTransaction };