Roll instrumentation log files.

pkg/analysis_server/lib/src/server/driver.dart

Index: pkg/analysis_server/lib/src/server/driver.dart
diff --git a/pkg/analysis_server/lib/src/server/driver.dart b/pkg/analysis_server/lib/src/server/driver.dart
index 049037742b98d4a0a6709e0073ac8ce41a0268c5..845a2618dc90c2301a77b0ee6b4625b5c08af995 100644
--- a/pkg/analysis_server/lib/src/server/driver.dart
+++ b/pkg/analysis_server/lib/src/server/driver.dart
@@ -383,6 +383,7 @@ class Driver implements ServerStarter {
     //
     String logFilePath = results[INSTRUMENTATION_LOG_FILE];
     if (logFilePath != null) {
+      _rollLogFiles(logFilePath, 5);
       FileInstrumentationServer fileBasedServer =
           new FileInstrumentationServer(logFilePath);
       instrumentationServer = instrumentationServer != null
@@ -577,4 +578,20 @@ class Driver implements ServerStarter {
     }
     return uuid;
   }
+
+  /**
+   * Perform log files rolling.
+   *
+   * Rename existing files with names `[path].(x)` to `[path].(x+1)`.
+   * Keep at most [numOld] files.
+   * Rename the file with the given [path] to `[path].1`.
+   */
+  static void _rollLogFiles(String path, int numOld) {
+    for (int i = numOld - 1; i >= 0; i--) {
+      try {
+        String oldPath = i == 0 ? path : '$path.$i';
+        new File(oldPath).renameSync('$path.${i+1}');

[Brian Wilkerson, 2015/11/04 23:00:29]

Does rename work if there's already a file with that name? If not, don't we need
to explicitly delete "$path.$numOld"?

[scheglov, 2015/11/05 16:40:27]

Yes, it does.

   /**
   * Synchronously renames this file. Returns a [File]
   * instance for the renamed file.
   *
   * If [newPath] identifies an existing file, that file is
   * replaced. If [newPath] identifies an existing directory the
   * operation fails and an exception is thrown.
   */
  File renameSync(String newPath);

+      } catch (e) {}
+    }
+  }
 }