Write Operations Fail When Primary Replica is Down with Node.js

[Michael_Lynn]

It looks like your issue is caused by how the MongoDB driver handles elections. Even with retryWrites=true, writes that fail during an election are not retried automatically.

1. Increase serverSelectionTimeoutMS

   • Ensure the driver waits for a new primary instead of failing immediately:

const options = {   
  retryWrites: true,   
  retryReads: true,   
  serverSelectionTimeoutMS: 5000, // Wait 5 sec for primary   socketTimeoutMS: 30000,   
  connectTimeoutMS: 30000,   
  heartbeatFrequencyMS: 1000 
};

2. Implement a Retry Mechanism in Code

   • MongoDB doesn’t automatically retry writes during an election, so you need to handle retries manually:

async function safeWriteOperation() {
  let retries = 3;
  while (retries > 0) {
    try {
      await client.db("test").collection("data").insertOne({ name: "MongoDB" });
      console.log("Write successful");
      break;
    } catch (err) {
      if (err.message.includes("closed") || err.message.includes("NotPrimary")) {
        console.log("Write failed, retrying...", retries);
        retries--;
        await new Promise(res => setTimeout(res, 2000));
      } else {
        throw err;
      }
    }
  }
}

3. Ensure wtimeoutMS is Set for Write Concern

   • This ensures that writes wait for a new primary to be elected:

const url = 'mongodb://psmdb1:27017,psmdb2:27017,psmdb3:27017/?replicaSet=rs0&retryWrites=true&w=majority&wtimeoutMS=5000';

Some related docs…

• MongoDB Retryable Writes
• Handling Network Errors in Node.js
• Write Concern & wtimeoutMS