javascript - Mongodb v4.0 Transaction, MongoError: Transaction numbers are only allowed on a replica set member or mongos

Javascript - Mongodb v4.0 Transaction, MongoError: Transaction numbers are only allowed on a replica set member or mongos

The error "Transaction numbers are only allowed on a replica set member or mongos" typically occurs when trying to start a transaction on a standalone MongoDB server. MongoDB transactions require a replica set or a sharded cluster to work.

To resolve this issue, you need to ensure that your MongoDB deployment meets the requirements for transactions:

  1. Replica Set: If you are using a standalone MongoDB server, you need to convert it into a replica set. Even a single-node replica set allows you to use transactions.

    To convert your standalone server to a replica set:

    • Shut down your MongoDB server.
    • Edit the MongoDB configuration file (typically mongod.conf) to include the replSet option with a unique name.
    • Restart the MongoDB server with the modified configuration.
    • Connect to the MongoDB shell and run the rs.initiate() command to initiate the replica set.

    Example mongod.conf:

    replication: replSetName: "rs0"

  2. Mongos Router: If you are using sharding, ensure that you have a mongos router instance running. Transactions can only be used through a mongos instance in a sharded cluster.

Once you have a replica set or a sharded cluster set up, you can start transactions on MongoDB.

Example Usage:

const { MongoClient } = require('mongodb'); async function run() { const client = new MongoClient('mongodb://localhost:27017', { useNewUrlParser: true, useUnifiedTopology: true }); try { await client.connect(); const session = client.startSession(); try { await session.startTransaction(); const collection = client.db('mydb').collection('mycollection'); await collection.insertOne({ name: 'John' }, { session }); await session.commitTransaction(); } catch (error) { await session.abortTransaction(); throw error; } finally { session.endSession(); } } finally { await client.close(); } } run().catch(console.error);

Ensure that your MongoDB deployment is configured correctly with either a replica set or a sharded cluster, and you should be able to use transactions without encountering the "Transaction numbers are only allowed on a replica set member or mongos" error.

Examples

  1. JavaScript transaction in MongoDB example

    • Description: Learn how to implement transactions in MongoDB using JavaScript, ensuring proper handling of errors like "MongoError: Transaction numbers are only allowed on a replica set member or mongos".
    const session = client.startSession(); try { await session.startTransaction(); // Perform transactional operations await session.commitTransaction(); } catch (error) { await session.abortTransaction(); console.error("Transaction aborted:", error); } finally { session.endSession(); }

  2. MongoDB replica set setup tutorial

    • Description: Follow a step-by-step guide to set up a MongoDB replica set, resolving issues related to "MongoError: Transaction numbers are only allowed on a replica set member or mongos".
    # Initialize replica set mongod --port 27017 --dbpath /data/rs1 --replSet rs0 mongod --port 27018 --dbpath /data/rs2 --replSet rs0 mongod --port 27019 --dbpath /data/rs3 --replSet rs0 # Connect to primary node and initiate replica set mongo --port 27017 rs.initiate()

  3. MongoDB transactions in Node.js

    • Description: Explore how to use transactions in Node.js with MongoDB, tackling potential errors such as "MongoError: Transaction numbers are only allowed on a replica set member or mongos".
    const session = client.startSession(); try { await session.startTransaction(); // Transactional operations await session.commitTransaction(); } catch (error) { await session.abortTransaction(); console.error("Transaction aborted:", error); } finally { session.endSession(); }

  4. Handling MongoDB transaction errors

    • Description: Learn error handling techniques when implementing MongoDB transactions in JavaScript, including how to deal with "MongoError: Transaction numbers are only allowed on a replica set member or mongos".
    try { // Transactional operations } catch (error) { if (error instanceof MongoError && error.code === XXXXX) { // Handle specific transaction error } else { // Handle other errors } }

  5. MongoDB transactions with replica set

    • Description: Understand how to use MongoDB transactions within a replica set configuration, addressing issues like "MongoError: Transaction numbers are only allowed on a replica set member or mongos".
    const session = client.startSession(); try { await session.startTransaction({ readConcern: { level: 'snapshot' }, writeConcern: { w: 'majority' } }); // Transactional operations await session.commitTransaction(); } catch (error) { await session.abortTransaction(); console.error("Transaction aborted:", error); } finally { session.endSession(); }

  6. MongoDB replica set vs. standalone

    • Description: Understand the differences between running MongoDB in a replica set versus standalone mode, crucial for resolving errors like "MongoError: Transaction numbers are only allowed on a replica set member or mongos".
    In replica set mode, MongoDB allows transactions to be performed, whereas standalone mode doesn't support transactions.

  7. Handling MongoDB connection errors in Node.js

    • Description: Learn techniques to handle MongoDB connection errors in Node.js applications, including how to troubleshoot issues like "MongoError: Transaction numbers are only allowed on a replica set member or mongos".
    mongoose.connect(uri, options) .then(() => console.log("MongoDB connected")) .catch(error => console.error("MongoDB connection error:", error));

  8. Understanding MongoDB error codes

    • Description: Gain insight into MongoDB error codes and their meanings, aiding in troubleshooting issues such as "MongoError: Transaction numbers are only allowed on a replica set member or mongos".
    Error code XXXXX: Description of the error and potential resolutions.

  9. Configuring MongoDB for transactions

    • Description: Learn how to configure MongoDB for transaction support, ensuring proper setup to avoid errors like "MongoError: Transaction numbers are only allowed on a replica set member or mongos".
    // MongoDB configuration file (mongod.conf) replication: replSetName: "rs0"

  10. MongoDB transactional operations

    • Description: Explore various transactional operations supported by MongoDB, with guidance on avoiding errors such as "MongoError: Transaction numbers are only allowed on a replica set member or mongos".
    const session = client.startSession(); try { await session.startTransaction(); // Transactional operations await session.commitTransaction(); } catch (error) { await session.abortTransaction(); console.error("Transaction aborted:", error); } finally { session.endSession(); }

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