SERVER-37333 applyOps builds background indexes in the foreground

2 files changed, 59 insertions, 0 deletions

diff --git a/jstests/core/apply_ops_invalid_index_spec.js b/jstests/core/apply_ops_invalid_index_spec.js
index d4d9b73ff05..2ca88081fa7 100644
--- a/jstests/core/apply_ops_invalid_index_spec.js
+++ b/jstests/core/apply_ops_invalid_index_spec.js
@@ -54,4 +54,54 @@
             o: {v: 1, key: {a: 1}, name: 'a_1_system_v1', ns: collNs, unknown: 1},
         }],
     }));
+
+    //
+    // Background indexes should be subject to the same level of validation as foreground indexes.
+    //
+
+    // Inserting a background index directly into system.indexes with a bad index key pattern should
+    // return an error.
+    assert.commandFailedWithCode(db.adminCommand({
+        applyOps: [{
+            op: 'i',
+            ns: systemIndexesNs,
+            o: {key: {b: 'sideways'}, name: 'b_1_bg_system_v2', ns: collNs, background: true},
+        }],
+    }),
+                                 ErrorCodes.CannotCreateIndex);
+
+    // Inserting a v:2 background index directly into system.indexes with an unknown field in the
+    // index spec should return an error.
+    assert.commandFailedWithCode(db.adminCommand({
+        applyOps: [{
+            op: 'i',
+            ns: systemIndexesNs,
+            o: {
+                v: 2,
+                key: {b: 1},
+                name: 'b_1_bg_system_v2',
+                ns: collNs,
+                background: true,
+                unknown: true,
+            },
+        }],
+    }),
+                                 ErrorCodes.InvalidIndexSpecificationOption);
+
+    // Inserting a background v:1 index directly into system.indexes with an unknown field in the
+    // index spec should work.
+    assert.commandWorked(db.adminCommand({
+        applyOps: [{
+            op: 'i',
+            ns: systemIndexesNs,
+            o: {
+                v: 1,
+                key: {b: 1},
+                name: 'b_1_bg_system_v1',
+                ns: collNs,
+                background: true,
+                unknown: true,
+            },
+        }],
+    }));
 })();
diff --git a/src/mongo/db/catalog/apply_ops.cpp b/src/mongo/db/catalog/apply_ops.cpp
index 770bc24b616..552376301cb 100644
--- a/src/mongo/db/catalog/apply_ops.cpp
+++ b/src/mongo/db/catalog/apply_ops.cpp
@@ -181,6 +181,15 @@ Status _applyOps(OperationContext* opCtx,
 
                         if (nss.isSystemDotIndexes()) {
                             invariant(opCtx->lockState()->isW());
+
+                            // Disable background index builds when inserting into system.indexes.
+                            // This causes the TempRelease to fail within applyOperation_inlock(),
+                            // leading to the background index being built in the foreground.
+                            // We do not want a background index build because we need to validate
+                            // the index spec and also to avoid issues resulting from any metadata
+                            // changes before the background thread starts.
+                            Lock::GlobalWrite nestedGlobalWriteLock(opCtx->lockState());
+
                             OldClientContext ctx(opCtx, nss.ns());
                             status =
                                 repl::applyOperation_inlock(opCtx, ctx.db(), opObj, alwaysUpsert);