SERVER-21543 Lengthen delay before deleting old journal files

Conflicts:
	jstests/mmap_v1/dur_remove_old_journals.js

1 files changed, 5 insertions, 1 deletions

diff --git a/src/mongo/db/storage/mmap_v1/dur_journal.cpp b/src/mongo/db/storage/mmap_v1/dur_journal.cpp
index 0ab2ff648ca..2888cbdec63 100644
--- a/src/mongo/db/storage/mmap_v1/dur_journal.cpp
+++ b/src/mongo/db/storage/mmap_v1/dur_journal.cpp
@@ -674,7 +674,11 @@ void Journal::removeUnneededJournalFiles() {
     while (!_oldJournalFiles.empty()) {
         JFile f = _oldJournalFiles.front();
 
-        if (f.lastEventTimeMs < _lastFlushTime + ExtraKeepTimeMs) {
+        // 'f.lastEventTimeMs' is the timestamp of the last thing in the journal file.
+        // '_lastFlushTime' is the start time of the last successful flush of the data files to
+        // disk. We can't delete this journal file until the last successful flush time is at least
+        // 10 seconds after 'f.lastEventTimeMs'.
+        if (f.lastEventTimeMs + ExtraKeepTimeMs < _lastFlushTime) {
             // eligible for deletion
             boost::filesystem::path p(f.filename);
             log() << "old journal file will be removed: " << f.filename << endl;