fix: remove readPreferenceTags for database&collection lookups if the cluster is sharded and readPreferenceTags was set COMPASS-9111 (#6818)

* set readPreference=secondaryPreferred for database&collection lookups if readPreferenceTags was set

* rather send a read preference with just the tags removed

* send everything as options

* Add a test plus a comment

Author: lerouxb

packages/data-service/src/connect.spec.ts

@@ -483,6 +483,63 @@ describe('connect', function () {
       });
     });
 
+    it('connects to sharded with readPreferenceTags', async function () {
+      const options = envs.getConnectionOptions('sharded');
+      /*
+      See ticket COMPASS-9111
+
+      This test is using readPreference=nearest because this cluster has node with the tag
+      ANALYTICS. readPreference=secondary would more closely mirror the
+      original ticket, but this cluster also has no secondaries so that would
+      fail regardless of readPreferenceTags.
+      
+      Ideally people would use readPreference=secondaryPreferred, but that works
+      regardless so isn't a good test and if it was the case that people used
+      that in the first place we'd never need this ticket.
+      
+      readPreference=nearest tries to find one that matches the criteria and
+      since the config server doesn't know about tags the following operations
+      would hang unless we remove the tags. You can confirm this manually by
+      hacking maybeOverrideReadPreference in data-service.ts.
+      */
+      const connectionString =
+        options.connectionString +
+        '&readPreference=nearest&readPreferenceTags=nodeType:ANALYTICS';
+      const connectionOptions = {
+        ...options,
+        connectionString,
+      };
+      await testConnection(connectionOptions, {
+        authenticatedUserRoles: [{ db: 'admin', role: 'root' }],
+        authenticatedUsers: [{ db: 'admin', user: 'root' }],
+      });
+
+      const dataService = await connect({
+        connectionOptions,
+      });
+
+      /*
+      Without us removing the read preference tags these operations would fail.
+
+      Normal database operations like find or aggregate will still fail
+      regardless because the cluster does not have a node with the ANALYTICS
+      tag, but this test never executes any of those
+      */
+      try {
+        const databases = await dataService.listDatabases();
+        const databaseNames = databases
+          .map((d) => d.name)
+          .filter((name) => !['local'].includes(name));
+        for (const databaseName of databaseNames) {
+          // don't really care what's in there, just that the calls succeed
+          await dataService.listCollections(databaseName);
+          await dataService.databaseStats(databaseName);
+        }
+      } finally {
+        await dataService.disconnect();
+      }
+    });
+
     describe('ssh', function () {
       it('connects with ssh (sshPassword)', async function () {
         await testConnection(envs.getConnectionOptions('sshPassword'), {

packages/data-service/src/data-service.ts

@@ -53,6 +53,7 @@ import type {
   SearchIndexDescription,
   ReadPreferenceMode,
 } from 'mongodb';
+import { ReadPreference } from 'mongodb';
 import ConnectionStringUrl from 'mongodb-connection-string-url';
 import parseNamespace from 'mongodb-ns';
 import type {
@@ -133,6 +134,25 @@ function isReadPreferenceSet(connectionString: string): boolean {
   );
 }
 
+function readPreferenceWithoutTags(readPreference: ReadPreference) {
+  return new ReadPreference(readPreference.mode, undefined, readPreference);
+}
+
+function maybeOverrideReadPreference(
+  isMongos: boolean,
+  readPreference?: ReadPreference
+): {
+  readPreference?: ReadPreference;
+} {
+  // see ticket COMPASS-9111 for why this is necessary
+  if (isMongos && readPreference?.tags) {
+    const newReadPreference = readPreferenceWithoutTags(readPreference);
+    return { readPreference: newReadPreference };
+  }
+
+  return {};
+}
+
 let id = 0;
 
 type ClientType = 'CRUD' | 'META';
@@ -1264,7 +1284,13 @@ class DataServiceImpl extends WithLogContext implements DataService {
     try {
       const cursor = this._database(databaseName, 'CRUD').listCollections(
         filter,
-        { nameOnly }
+        {
+          nameOnly,
+          ...maybeOverrideReadPreference(
+            this.isMongos(),
+            this._crudClient?.readPreference
+          ),
+        }
       );
       // Iterate instead of using .toArray() so we can emit
       // collection info update events as they come in.
@@ -1399,7 +1425,13 @@ class DataServiceImpl extends WithLogContext implements DataService {
           } as {
             listDatabases: 1;
           },
-          { enableUtf8Validation: false }
+          {
+            enableUtf8Validation: false,
+            ...maybeOverrideReadPreference(
+              this.isMongos(),
+              this._crudClient?.readPreference
+            ),
+          }
         );
         return databases.map((x) => ({
           ...x,
@@ -2542,7 +2574,13 @@ class DataServiceImpl extends WithLogContext implements DataService {
     const stats = await runCommand(
       db,
       { dbStats: 1 },
-      { enableUtf8Validation: false }
+      {
+        enableUtf8Validation: false,
+        ...maybeOverrideReadPreference(
+          this.isMongos(),
+          this._crudClient?.readPreference
+        ),
+      }
     );
     const normalized = adaptDatabaseInfo(stats);
     return { name, ...normalized };