docs(common-issues): add file

Author: hasezoey

docs/guides/common-issues.md

@@ -0,0 +1,43 @@
+---
+id: common-issues
+title: '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:
+
+```js
+// 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();
+}
+```
+
+See [Operations which are retry-able](https://www.mongodb.com/docs/manual/core/retryable-writes/#retryable-write-operations).

website/sidebars.js

@@ -38,6 +38,7 @@ module.exports = {
       'guides/known-issues',
       'guides/error-warning-details',
       'guides/mongodb-server-versions',
+      'guides/common-issues',
     ],
     Migration: ['guides/migration/migrate8', 'guides/migration/migrate7'],
   },