fix journal recovery for case when lsn file is zero bytes long

2 files changed, 7 insertions, 0 deletions

diff --git a/db/dur_journal.cpp b/db/dur_journal.cpp
index 1738884006c..b8c259a6763 100644
--- a/db/dur_journal.cpp
+++ b/db/dur_journal.cpp
@@ -486,6 +486,11 @@ namespace mongo {
                 File f;
                 f.open(lsnPath().string().c_str());
                 assert(f.is_open());
+                if( f.len() == 0 ) { 
+                    // this could be 'normal' if we crashed at the right moment
+                    log() << "info lsn file is zero bytes long" << endl;
+                    return 0;
+                }
                 f.read(0,(char*)&L, sizeof(L));
                 unsigned long long lsn = L.get();
                 return lsn;
diff --git a/util/file.h b/util/file.h
index aed5d52fdaa..8ef58968ea6 100644
--- a/util/file.h
+++ b/util/file.h
@@ -38,6 +38,8 @@ namespace mongo {
     typedef boost::uint64_t fileofs;
 #endif
 
+    /* NOTE: not thread-safe. (at least the windows implementation isn't. */
+
     class FileInterface {
     public:
         void open(const char *fn) {}