Common Issues
There are some common issues you may encounter with mongodb-memory-server (or also manually handling mongod instances), this guide will try to explain why they happen how to fix those issues.
MongoWriteConcernError: operation was interrupted
The Error MongoWriteConcernError: operation was interrupted happens when a operation which is not retryable fails, which includes for example db.dropDatabase.
This Error happens because mongodb firstly starts all instances, says they are okay and has a primary (which are all events mongodb-memory-server listens for before resolving .start), but the shortly after the .start is resolved, the instace that is primary decides to step-down due to whatever reason.
The fix is to manually re-try those operations, like:
// original:
async function setup(db) {
await db.dropDatabase();
}
// fix
async function setup(db) {
let retries = 5;
while (retries > 0) {
retries -= 1;
try {
await _setup(db);
} catch (err) {
if (err instanceof mongodb.MongoWriteConcernError && /operation was interrupted/.test(err.message)) {
continue;
}
throw err;
}
}
}
async function _setup(db) {
await db.dropDatabase();
}