handle empty logfiles on startup

UnitTests/Makefile.unittests

@@ -208,6 +208,7 @@ unittests-recovery:
 	@echo "================================================================================"
 	@echo
 
+	$(MAKE) execute-recovery-test PID=$(PID) RECOVERY_SCRIPT="empty-logfiles"
 	$(MAKE) execute-recovery-test PID=$(PID) RECOVERY_SCRIPT="many-logs"
 	$(MAKE) execute-recovery-test PID=$(PID) RECOVERY_SCRIPT="multiple-logs"
 	$(MAKE) execute-recovery-test PID=$(PID) RECOVERY_SCRIPT="collection-recreate"

arangod/Wal/Logfile.cpp

@@ -131,7 +131,14 @@ Logfile* Logfile::openExisting (std::string const& filename,
 ////////////////////////////////////////////////////////////////////////////////
 
 int Logfile::judge (std::string const& filename) {
-  if (basics::FileUtils::size(filename) < static_cast<off_t>(256 * sizeof(uint64_t))) {
+  off_t filesize = basics::FileUtils::size(filename);
+
+  if (filesize == 0) {
+    // empty logfile
+    return TRI_ERROR_ARANGO_DATAFILE_EMPTY;
+  }
+
+  if (filesize < static_cast<off_t>(256 * sizeof(uint64_t))) {
     // too small
     return TRI_ERROR_ARANGO_DATAFILE_UNREADABLE;
   }

js/server/tests/recovery/empty-logfiles.js

@@ -0,0 +1,64 @@
+
+var db = require("org/arangodb").db;
+var internal = require("internal");
+var jsunity = require("jsunity");
+var fs = require("fs");
+
+function runSetup () {
+  internal.debugClearFailAt();
+  
+  var i, num = 9999999999;
+  for (i = 0; i < 4; ++i) {
+    var filename = fs.join(db._path(), "../../journals/logfile-" + num + ".db");
+    num++;
+
+    // save an empty file 
+    fs.write(filename, "");
+  }
+  
+  db._drop("UnitTestsRecovery");
+  var c = db._create("UnitTestsRecovery"); 
+  c.save({ _key: "crashme" }, true); // wait for sync
+
+  internal.debugSegfault("crashing server");
+}
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief test suite
+////////////////////////////////////////////////////////////////////////////////
+
+function recoverySuite () {
+  jsunity.jsUnity.attachAssertions();
+
+  return {
+    setUp: function () {
+    },
+    tearDown: function () {
+    },
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief test whether we can start the server
+////////////////////////////////////////////////////////////////////////////////
+    
+    testEmptyLogfiles : function () {
+      // nothing to do - the server must start even in the face of empty logfiles
+    }
+        
+  };
+}
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief executes the test suite
+////////////////////////////////////////////////////////////////////////////////
+
+function main (argv) {
+  if (argv[1] === "setup") {
+    runSetup();
+    return 0;
+  }
+  else {
+    jsunity.run(recoverySuite);
+    return jsunity.done() ? 0 : 1;
+  }
+}
+