[JENKINS-43199] Reliably close build log file (#2954)

* [JENKINS-43199] Reliably close build log file.

* Try harder to ensure that the logger is closed at the end of the build.

core/src/main/java/hudson/model/Run.java

@@ -1698,6 +1698,7 @@ protected final void execute(@Nonnull RunExecution job) {
         if(result!=null)
             return;     // already built.
 
+        OutputStream logger = null;
         StreamBuildListener listener=null;
 
         runner = job;
@@ -1716,7 +1717,8 @@ protected final void execute(@Nonnull RunExecution job) {
                         charset = computer.getDefaultCharset();
                         this.charset = charset.name();
                     }
-                    listener = createBuildListener(job, listener, charset);
+                    logger = createLogger();
+                    listener = createBuildListener(job, logger, charset);
                     listener.started(getCauses());
 
                     Authentication auth = Jenkins.getAuthentication();
@@ -1798,23 +1800,32 @@ protected final void execute(@Nonnull RunExecution job) {
             try {
                 getParent().logRotate();
             } catch (Exception e) {
-		LOGGER.log(Level.SEVERE, "Failed to rotate log",e);
-	    }
+                LOGGER.log(Level.SEVERE, "Failed to rotate log",e);
+            }
         } finally {
             onEndBuilding();
+            if (logger != null) {
+                try {
+                    logger.close();
+                } catch (IOException x) {
+                    LOGGER.log(Level.WARNING, "failed to close log for " + Run.this, x);
+                }
+            }
         }
     }
 
-    private StreamBuildListener createBuildListener(@Nonnull RunExecution job, StreamBuildListener listener, Charset charset) throws IOException, InterruptedException {
+    private OutputStream createLogger() throws IOException {
         // don't do buffering so that what's written to the listener
         // gets reflected to the file immediately, which can then be
         // served to the browser immediately
-        OutputStream logger;
         try {
-            logger = Files.newOutputStream(getLogFile().toPath(), StandardOpenOption.CREATE, StandardOpenOption.APPEND);
+            return Files.newOutputStream(getLogFile().toPath(), StandardOpenOption.CREATE, StandardOpenOption.APPEND);
         } catch (InvalidPathException e) {
             throw new IOException(e);
         }
+    }
+
+    private StreamBuildListener createBuildListener(@Nonnull RunExecution job, OutputStream logger, Charset charset) throws IOException, InterruptedException {
         RunT build = job.getBuild();
 
         // Global log filters
@@ -1830,8 +1841,7 @@ private StreamBuildListener createBuildListener(@Nonnull RunExecution job, Strea
             }
         }
 
-        listener = new StreamBuildListener(logger,charset);
-        return listener;
+        return new StreamBuildListener(logger,charset);
     }
 
     /**