From c1808dd194575ea7a49893e782df50fe29c00bd1 Mon Sep 17 00:00:00 2001
From: Gregory Noma <gregory.noma@gmail.com>
Date: Tue, 8 Sep 2020 13:22:22 -0400
Subject: SERVER-50711 Clear temp directory if no internal idents are parsed on
 startup

---
 jstests/noPassthrough/libs/index_build.js | 34 +++++++++++++++++++++++--------
 src/mongo/db/mongod_main.cpp              |  7 -------
 src/mongo/db/startup_recovery.cpp         | 14 +++++++++++++
 3 files changed, 40 insertions(+), 15 deletions(-)

diff --git a/jstests/noPassthrough/libs/index_build.js b/jstests/noPassthrough/libs/index_build.js
index 28f0b91fba0..09ca4b01b1c 100644
--- a/jstests/noPassthrough/libs/index_build.js
+++ b/jstests/noPassthrough/libs/index_build.js
@@ -617,18 +617,36 @@ const ResumableIndexBuildTest = class {
         ResumableIndexBuildTest.checkIndexes(
             rst, dbName, collName, indexName, postIndexBuildInserts);
 
-        if (!failWhileParsing) {
-            // Ensure that the persisted Sorter data was cleaned up after failing to resume. This
-            // cleanup does not occur if parsing failed.
-            const files = listFiles(primary.dbpath + "/_tmp");
+        const checkLogIdAfterRestart = function(primary, id) {
+            rst.stop(primary);
+            rst.start(primary, {noCleanData: true});
+            checkLog.containsJson(primary, id);
+        };
+
+        const checkTempDirectoryCleared = function(primary) {
+            const tempDir = primary.dbpath + "/_tmp";
+
+            // If the index build was interrupted for shutdown before anything was inserted into
+            // the Sorter, the temp directory may not exist.
+            if (!fileExists(tempDir))
+                return;
+
+            // Ensure that the persisted Sorter data was cleaned up after failing to resume.
+            const files = listFiles(tempDir);
             assert.eq(files.length, 0, files);
+        };
+
+        if (failWhileParsing) {
+            // If we fail while parsing, the persisted Sorter data will only be cleaned up after
+            // another restart.
+            checkLogIdAfterRestart(primary, 5071100);
+            checkTempDirectoryCleared(primary);
+        } else {
+            checkTempDirectoryCleared(primary);
 
             // If we fail after parsing, any remaining internal idents will only be cleaned up
             // after another restart.
-            clearRawMongoProgramOutput();
-            rst.stop(primary);
-            rst.start(primary, {noCleanData: true});
-            assert(RegExp("22257.*").test(rawMongoProgramOutput()));
+            checkLogIdAfterRestart(primary, 22257);
         }
     }
 };
diff --git a/src/mongo/db/mongod_main.cpp b/src/mongo/db/mongod_main.cpp
index c04117cfae3..d654bb7e881 100644
--- a/src/mongo/db/mongod_main.cpp
+++ b/src/mongo/db/mongod_main.cpp
@@ -445,13 +445,6 @@ ExitCode _initAndListen(ServiceContext* serviceContext, int listenPort) {
 
     startWatchdog(serviceContext);
 
-    // When starting up after an unclean shutdown, we do not attempt to use any of the temporary
-    // files left from the previous run. Thus, we remove them in this case.
-    if (!storageGlobalParams.readOnly &&
-        LastStorageEngineShutdownState::kUnclean == lastStorageEngineShutdownState) {
-        boost::filesystem::remove_all(storageGlobalParams.dbpath + "/_tmp/");
-    }
-
     if (mongodGlobalParams.scriptingEnabled) {
         ScriptEngine::setup();
     }
diff --git a/src/mongo/db/startup_recovery.cpp b/src/mongo/db/startup_recovery.cpp
index 309ffa96180..6beb7f8fa56 100644
--- a/src/mongo/db/startup_recovery.cpp
+++ b/src/mongo/db/startup_recovery.cpp
@@ -347,6 +347,20 @@ void reconcileCatalogAndRebuildUnfinishedIndexes(
     auto reconcileResult =
         fassert(40593, storageEngine->reconcileCatalogAndIdents(opCtx, reconcilePolicy));
 
+    // If we did not find any index builds to resume or we are starting up after an unclean
+    // shutdown, nothing in the temp directory will be used. Thus, we can clear it.
+    if (reconcileResult.indexBuildsToResume.empty() ||
+        lastStorageEngineShutdownState == LastStorageEngineShutdownState::kUnclean) {
+        LOGV2(5071100, "Clearing temp directory");
+
+        boost::system::error_code ec;
+        boost::filesystem::remove_all(storageGlobalParams.dbpath + "/_tmp/", ec);
+
+        if (ec) {
+            LOGV2(5071101, "Failed to clear temp directory", "error"_attr = ec.message());
+        }
+    }
+
     // Determine which indexes need to be rebuilt. rebuildIndexesOnCollection() requires that all
     // indexes on that collection are done at once, so we use a map to group them together.
     StringMap<IndexNameObjs> nsToIndexNameObjMap;
-- 
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