SCM-Manager/scm-webapp/src/main/java/sonia/scm/boot/RestartServlet.java

package sonia.scm.boot;

import com.fasterxml.jackson.databind.ObjectMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import sonia.scm.Priority;
import sonia.scm.SCMContext;
import sonia.scm.Stage;
import sonia.scm.event.ScmEventBus;
import sonia.scm.filter.WebElement;

import javax.inject.Inject;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * This servlet sends a {@link RestartEvent} to the {@link ScmEventBus} which causes scm-manager to restart the context.
 * The {@link RestartServlet} can be used for reloading java code or for installing plugins without a complete restart.
 * At the moment the Servlet accepts only request, if scm-manager was started in the {@link Stage#DEVELOPMENT} stage.
 *
 * @since 2.0.0
 */
@Priority(0)
@WebElement("/restart")
public class RestartServlet extends HttpServlet {

  private static final Logger LOG = LoggerFactory.getLogger(RestartServlet.class);

  private final ObjectMapper objectMapper = new ObjectMapper();
  private final AtomicBoolean restarting = new AtomicBoolean();

  private final ScmEventBus eventBus;
  private final Stage stage;

  @Inject
  public RestartServlet() {
    this(ScmEventBus.getInstance(), SCMContext.getContext().getStage());
  }

  RestartServlet(ScmEventBus eventBus, Stage stage) {
    this.eventBus = eventBus;
    this.stage = stage;
  }

  @Override
  protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
    LOG.info("received sendRestartEvent request");

    if (isRestartAllowed()) {

      try (InputStream requestInput = req.getInputStream()) {
        Reason reason = objectMapper.readValue(requestInput, Reason.class);
        sendRestartEvent(resp, reason);
      } catch (IOException ex) {
        LOG.warn("failed to trigger sendRestartEvent event", ex);
        resp.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
      }

    } else {
      LOG.debug("received restart event in non development stage");
      resp.setStatus(HttpServletResponse.SC_NOT_ACCEPTABLE);
    }
  }

  private boolean isRestartAllowed() {
    return stage == Stage.DEVELOPMENT;
  }

  private void sendRestartEvent(HttpServletResponse response, Reason reason) {
    if ( restarting.compareAndSet(false, true) ) {
      LOG.info("trigger sendRestartEvent, because of {}", reason.getMessage());
      eventBus.post(new RestartEvent(RestartServlet.class, reason.getMessage()));

      response.setStatus(HttpServletResponse.SC_ACCEPTED);
    } else {
      LOG.warn("scm-manager restarts already");
      response.setStatus(HttpServletResponse.SC_CONFLICT);
    }
  }

  public static class Reason {

    private String message;

    public void setMessage(String message) {
      this.message = message;
    }

    public String getMessage() {
      return message;
    }
  }
}