SERVER-56062 CappedPositionLost during an index builds collection scan phase restarts

2 files changed, 56 insertions, 2 deletions

diff --git a/jstests/noPassthrough/index_build_capped_position_lost.js b/jstests/noPassthrough/index_build_capped_position_lost.js
new file mode 100644
index 00000000000..a1c7d454fb8
--- /dev/null
+++ b/jstests/noPassthrough/index_build_capped_position_lost.js
@@ -0,0 +1,51 @@
+/**
+ * Capped cursors return CappedPositionLost when the document they were positioned on gets deleted.
+ * When this occurs during the collection scan phase of an index build, it will get restarted.
+ */
+(function() {
+"use strict";
+
+load("jstests/libs/fail_point_util.js");
+load("jstests/noPassthrough/libs/index_build.js");
+
+const conn = MongoRunner.runMongod({});
+
+const dbName = "test";
+const collName = "index_build_capped_position_lost";
+
+const db = conn.getDB(dbName);
+assert.commandWorked(
+    db.createCollection(collName, {capped: true, size: 1024 * 1024 * 1024, max: 5}));
+
+const coll = db.getCollection(collName);
+
+for (let i = 0; i < 5; i++) {
+    assert.commandWorked(coll.insert({a: i}));
+}
+
+// Hang the collection scan phase of the index build when it's halfway finished.
+let fp = configureFailPoint(
+    conn, "hangIndexBuildDuringCollectionScanPhaseAfterInsertion", {fieldsToMatch: {a: 3}});
+
+const awaitCreateIndex = IndexBuildTest.startIndexBuild(conn, coll.getFullName(), {a: 1});
+fp.wait();
+
+// Rollover the capped collection.
+for (let i = 5; i < 10; i++) {
+    assert.commandWorked(coll.insert({a: i}));
+}
+
+fp.off();
+checkLog.containsJson(conn, 5470300, {
+    error: function(error) {
+        return error.code === ErrorCodes.CappedPositionLost;
+    }
+});                                                     // Collection scan restarted.
+checkLog.containsJson(conn, 20391, {totalRecords: 5});  // Collection scan complete.
+
+awaitCreateIndex();
+
+IndexBuildTest.assertIndexes(coll, 2, ["_id_", "a_1"]);
+
+MongoRunner.stopMongod(conn);
+}());
diff --git a/src/mongo/db/catalog/multi_index_block.cpp b/src/mongo/db/catalog/multi_index_block.cpp
index a4c39f1d56f..fb51a69d4e7 100644
--- a/src/mongo/db/catalog/multi_index_block.cpp
+++ b/src/mongo/db/catalog/multi_index_block.cpp
@@ -444,10 +444,13 @@ Status MultiIndexBlock::insertAllDocumentsInCollection(
                       RecoveryUnit::toString(opCtx->recoveryUnit()->getTimestampReadSource()),
                   "duration"_attr = duration_cast<Milliseconds>(Seconds(timer.seconds())));
         } catch (DBException& ex) {
-            if (ex.code() == ErrorCodes::ReadConcernMajorityNotAvailableYet) {
+            if (ex.code() == ErrorCodes::ReadConcernMajorityNotAvailableYet ||
+                ex.code() == ErrorCodes::CappedPositionLost) {
                 // Forced replica set re-configs will clear the majority committed snapshot,
                 // which may be used by the collection scan. The collection scan will restart
-                // from the beginning in this case.
+                // from the beginning in this case. Capped cursors are invalidated when the document
+                // they were positioned on gets deleted. The collection scan will restart in both
+                // cases.
                 restartCollectionScan = true;
                 logAndBackoff(
                     5470300,