/** {@inheritDoc} */
  @Override
  public void onKernalStart() throws GridException {
    discoLsnr =
        new GridLocalEventListener() {
          @Override
          public void onEvent(GridEvent evt) {
            assert evt instanceof GridDiscoveryEvent;

            assert evt.type() == EVT_NODE_LEFT || evt.type() == EVT_NODE_FAILED;

            GridDiscoveryEvent discoEvt = (GridDiscoveryEvent) evt;

            Collection<SharedDeployment> undeployed = new LinkedList<SharedDeployment>();

            if (log.isDebugEnabled()) log.debug("Processing node departure event: " + evt);

            synchronized (mux) {
              for (Iterator<List<SharedDeployment>> i1 = cache.values().iterator();
                  i1.hasNext(); ) {
                List<SharedDeployment> deps = i1.next();

                for (Iterator<SharedDeployment> i2 = deps.iterator(); i2.hasNext(); ) {
                  SharedDeployment dep = i2.next();

                  dep.removeParticipant(discoEvt.eventNodeId());

                  if (!dep.hasParticipants()) {
                    if (dep.deployMode() == SHARED) {
                      if (!dep.isUndeployed()) {
                        dep.undeploy();

                        // Undeploy.
                        i2.remove();

                        assert !dep.isRemoved();

                        dep.onRemoved();

                        undeployed.add(dep);

                        if (log.isDebugEnabled())
                          log.debug(
                              "Undeployed class loader as there are no participating "
                                  + "nodes: "
                                  + dep);
                      }
                    } else if (log.isDebugEnabled())
                      log.debug("Preserving deployment without node participants: " + dep);
                  } else if (log.isDebugEnabled())
                    log.debug("Keeping deployment as it still has participants: " + dep);
                }

                if (deps.isEmpty()) i1.remove();
              }
            }

            recordUndeployed(discoEvt.eventNodeId(), undeployed);
          }
        };

    ctx.event().addLocalEventListener(discoLsnr, EVT_NODE_FAILED, EVT_NODE_LEFT);

    Collection<SharedDeployment> undeployed = new LinkedList<SharedDeployment>();

    synchronized (mux) {
      for (Iterator<List<SharedDeployment>> i1 = cache.values().iterator(); i1.hasNext(); ) {
        List<SharedDeployment> deps = i1.next();

        for (Iterator<SharedDeployment> i2 = deps.iterator(); i2.hasNext(); ) {
          SharedDeployment dep = i2.next();

          for (UUID nodeId : dep.getParticipantNodeIds())
            if (ctx.discovery().node(nodeId) == null) dep.removeParticipant(nodeId);

          if (!dep.hasParticipants()) {
            if (dep.deployMode() == SHARED) {
              if (!dep.isUndeployed()) {
                dep.undeploy();

                // Undeploy.
                i2.remove();

                dep.onRemoved();

                undeployed.add(dep);

                if (log.isDebugEnabled())
                  log.debug("Undeployed class loader as there are no participating nodes: " + dep);
              }
            } else if (log.isDebugEnabled())
              log.debug("Preserving deployment without node participants: " + dep);
          } else if (log.isDebugEnabled())
            log.debug("Keeping deployment as it still has participants: " + dep);
        }

        if (deps.isEmpty()) i1.remove();
      }
    }

    recordUndeployed(null, undeployed);

    if (log.isDebugEnabled()) log.debug("Registered deployment discovery listener: " + discoLsnr);
  }
  /**
   * Removes obsolete deployments in case of redeploy.
   *
   * @param meta Request metadata.
   * @return List of shares deployment.
   */
  private GridTuple2<Boolean, SharedDeployment> checkRedeploy(GridDeploymentMetadata meta) {
    assert Thread.holdsLock(mux);

    SharedDeployment newDep = null;

    for (List<SharedDeployment> deps : cache.values()) {
      for (SharedDeployment dep : deps) {
        if (!dep.isUndeployed() && !dep.isPendingUndeploy()) {
          long undeployTimeout = ctx.config().getNetworkTimeout();

          SharedDeployment doomed = null;

          // Only check deployments with no participants.
          if (!dep.hasParticipants()) {
            // In case of SHARED deployment it is possible to get hear if
            // unmarshalling happens during undeploy. In this case, we
            // simply don't do anything.
            if (dep.deployMode() == CONTINUOUS) {
              if (dep.existingDeployedClass(meta.className()) != null) {
                // Change from shared deploy to shared undeploy or user version change.
                // Simply remove all deployments with no participating nodes.
                if (meta.deploymentMode() == SHARED
                    || !meta.userVersion().equals(dep.userVersion())) doomed = dep;
              }
            }
          }
          // If there are participants, we undeploy if class loader ID on some node changed.
          else if (dep.existingDeployedClass(meta.className()) != null) {
            GridTuple2<GridUuid, Long> ldr = dep.getClassLoaderId(meta.senderNodeId());

            if (ldr != null) {
              if (!ldr.get1().equals(meta.classLoaderId())) {
                // If deployed sequence number is less, then schedule for undeployment.
                if (ldr.get2() < meta.sequenceNumber()) {
                  if (log.isDebugEnabled())
                    log.debug(
                        "Received request for a class with newer sequence number "
                            + "(will schedule current class for undeployment) [newSeq="
                            + meta.sequenceNumber()
                            + ", oldSeq="
                            + ldr.get2()
                            + ", senderNodeId="
                            + meta.senderNodeId()
                            + ", newClsLdrId="
                            + meta.classLoaderId()
                            + ", oldClsLdrId="
                            + ldr.get1()
                            + ']');

                  doomed = dep;
                } else if (ldr.get2() > meta.sequenceNumber()) {
                  long time = System.currentTimeMillis() - dep.timestamp();

                  if (newDep == null && time < ctx.config().getNetworkTimeout()) {
                    // Set undeployTimeout, so the class will be scheduled
                    // for undeployment.
                    undeployTimeout = ctx.config().getNetworkTimeout() - time;

                    if (log.isDebugEnabled())
                      log.debug(
                          "Received execution request for a stale class (will deploy and "
                              + "schedule undeployment in "
                              + undeployTimeout
                              + "ms) "
                              + "[curSeq="
                              + ldr.get2()
                              + ", staleSeq="
                              + meta.sequenceNumber()
                              + ", cls="
                              + meta.className()
                              + ", senderNodeId="
                              + meta.senderNodeId()
                              + ", curLdrId="
                              + ldr.get1()
                              + ", staleLdrId="
                              + meta.classLoaderId()
                              + ']');

                    // We got the redeployed class before the old one.
                    // Simply create a temporary deployment for the sender node,
                    // and schedule undeploy for it.
                    newDep = createNewDeployment(meta, false);

                    doomed = newDep;
                  } else {
                    U.warn(
                        log,
                        "Received execution request for a class that has been redeployed "
                            + "(will ignore): "
                            + meta.alias());

                    if (log.isDebugEnabled())
                      log.debug(
                          "Received execution request for a class that has been redeployed "
                              + "(will ignore) [alias="
                              + meta.alias()
                              + ", dep="
                              + dep
                              + ']');

                    return F.t(false, null);
                  }
                } else {
                  U.error(
                      log,
                      "Sequence number does not correspond to class loader ID [seqNum="
                          + meta.sequenceNumber()
                          + ", dep="
                          + dep
                          + ']');

                  return F.t(false, null);
                }
              }
            }
          }

          if (doomed != null) {
            doomed.onUndeployScheduled();

            if (log.isDebugEnabled()) log.debug("Deployment was scheduled for undeploy: " + doomed);

            // Lifespan time.
            final long endTime = System.currentTimeMillis() + undeployTimeout;

            // Deployment to undeploy.
            final SharedDeployment undep = doomed;

            ctx.timeout()
                .addTimeoutObject(
                    new GridTimeoutObject() {
                      @Override
                      public GridUuid timeoutId() {
                        return undep.classLoaderId();
                      }

                      @Override
                      public long endTime() {
                        return endTime < 0 ? Long.MAX_VALUE : endTime;
                      }

                      @Override
                      public void onTimeout() {
                        boolean removed = false;

                        // Hot redeployment.
                        synchronized (mux) {
                          assert undep.isPendingUndeploy();

                          if (!undep.isUndeployed()) {
                            undep.undeploy();

                            undep.onRemoved();

                            removed = true;

                            Collection<SharedDeployment> deps = cache.get(undep.userVersion());

                            if (deps != null) {
                              for (Iterator<SharedDeployment> i = deps.iterator(); i.hasNext(); )
                                if (i.next() == undep) i.remove();

                              if (deps.isEmpty()) cache.remove(undep.userVersion());
                            }

                            if (log.isInfoEnabled())
                              log.info(
                                  "Undeployed class loader due to deployment mode change, "
                                      + "user version change, or hot redeployment: "
                                      + undep);
                          }
                        }

                        // Outside synchronization.
                        if (removed) undep.recordUndeployed(null);
                      }
                    });
          }
        }
      }
    }

    if (newDep != null) {
      List<SharedDeployment> list =
          F.addIfAbsent(cache, meta.userVersion(), F.<SharedDeployment>newList());

      assert list != null;

      list.add(newDep);
    }

    return F.t(true, newDep);
  }