Ensure that context is destroyed on restart

scm-webapp/src/main/java/sonia/scm/lifecycle/BootstrapContextFilter.java

@@ -21,7 +21,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
-    
+
 package sonia.scm.lifecycle;
 
 //~--- non-JDK imports --------------------------------------------------------
@@ -103,7 +103,7 @@ public class BootstrapContextFilter extends GuiceFilter {
     }
   }
 
-  private class GuiceInjectionContext implements RestartStrategy.InjectionContext {
+  private class GuiceInjectionContext implements RestartStrategy.InternalInjectionContext {
 
     @Override
     public void initialize() {

scm-webapp/src/main/java/sonia/scm/lifecycle/ExitRestartStrategy.java

@@ -35,7 +35,7 @@ import java.util.function.IntConsumer;
  * <p>
  * This is useful if an external mechanism is able to restart the process after it has exited.
  */
-class ExitRestartStrategy implements RestartStrategy {
+class ExitRestartStrategy extends RestartStrategy {
 
   private static final Logger LOG = LoggerFactory.getLogger(ExitRestartStrategy.class);
 
@@ -45,6 +45,8 @@ class ExitRestartStrategy implements RestartStrategy {
 
   private IntConsumer exiter = System::exit;
 
+  private int exitCode;
+
   ExitRestartStrategy() {
   }
 
@@ -54,12 +56,12 @@ class ExitRestartStrategy implements RestartStrategy {
   }
 
   @Override
-  public void restart(InjectionContext context) {
-    int exitCode = determineExitCode();
-
-    LOG.warn("destroy injection context");
-    context.destroy();
+  public void prepareRestart(InjectionContext context) {
+    exitCode = determineExitCode();
+  }
 
+  @Override
+  protected void executeRestart(InjectionContext context) {
     LOG.warn("exit scm-manager with exit code {}", exitCode);
     exiter.accept(exitCode);
   }

scm-webapp/src/main/java/sonia/scm/lifecycle/PosixRestartStrategy.java

@@ -33,7 +33,7 @@ import static sonia.scm.lifecycle.CLibrary.*;
 /**
  * Restart strategy which uses execvp from libc. This strategy is only supported on posix base operating systems.
  */
-class PosixRestartStrategy implements RestartStrategy {
+class PosixRestartStrategy extends RestartStrategy {
 
   private static final Logger LOG = LoggerFactory.getLogger(PosixRestartStrategy.class);
 
@@ -41,10 +41,7 @@ class PosixRestartStrategy implements RestartStrategy {
   }
 
   @Override
-  public void restart(InjectionContext context) {
-    LOG.warn("destroy injection context");
-    context.destroy();
-
+  protected void executeRestart(InjectionContext context) {
     LOG.warn("restart scm-manager jvm process");
     try {
       restart();

scm-webapp/src/main/java/sonia/scm/lifecycle/RestartStrategy.java

@@ -24,23 +24,20 @@
 
 package sonia.scm.lifecycle;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.util.Optional;
 
 /**
  * Strategy for restarting SCM-Manager. Implementations must either have a default constructor or one taking the
  * class loader for the current context as a single argument.
  */
-public interface RestartStrategy {
+public abstract class RestartStrategy {
 
-  /**
-   * Context for Injection in SCM-Manager.
-   */
-  interface InjectionContext {
-    /**
-     * Initialize the injection context.
-     */
-    void initialize();
+  private static final Logger LOG = LoggerFactory.getLogger(RestartStrategy.class);
 
+  interface InternalInjectionContext extends InjectionContext {
     /**
      * Destroys the injection context.
      */
@@ -48,11 +45,43 @@ public interface RestartStrategy {
   }
 
   /**
-   * Restart SCM-Manager.
+   * Context for Injection in SCM-Manager.
+   */
+  public interface InjectionContext {
+    /**
+     * Initialize the injection context.
+     */
+    void initialize();
+  }
+
+  /**
+   * Restart SCM-Manager by first calling {@link #prepareRestart(InjectionContext)}, destroying the
+   * current context, and finally calling {@link #executeRestart(InjectionContext)}.
    *
    * @param context injection context
    */
-  void restart(InjectionContext context);
+  public final void restart(InternalInjectionContext context) {
+    prepareRestart(context);
+    LOG.warn("destroy injection context");
+    context.destroy();
+    executeRestart(context);
+  }
+
+  /**
+   * Prepare the restart of SCM-Manager. Here you can check whether restart is possible and,
+   * if necessary, throw a {@link RestartNotSupportedException} to abort the restart.
+   *
+   * @param context injection context
+   */
+  protected void prepareRestart(InjectionContext context) {
+  }
+
+  /**
+   * Actually restart SCM-Manager.
+   *
+   * @param context injection context
+   */
+  protected abstract void executeRestart(InjectionContext context);
 
   /**
    * Returns the configured strategy or empty if restart is not supported by the underlying platform.