/** {@inheritDoc} */
  @Override
  public void explicitUndeploy(UUID nodeId, String rsrcName) {
    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();

          if (dep.hasName(rsrcName)) {
            if (!dep.isUndeployed()) {
              dep.undeploy();

              dep.onRemoved();

              // Undeploy.
              i2.remove();

              undeployed.add(dep);

              if (log.isInfoEnabled()) log.info("Undeployed per-version class loader: " + dep);
            }

            break;
          }
        }

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

    recordUndeployed(null, undeployed);
  }
  /** {@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);
  }
  /** {@inheritDoc} */
  @Override
  public GridDeployment getDeployment(GridDeploymentMetadata meta) {
    assert meta != null;

    assert ctx.config().isPeerClassLoadingEnabled();

    // Validate metadata.
    assert meta.classLoaderId() != null;
    assert meta.senderNodeId() != null;
    assert meta.sequenceNumber() >= -1;
    assert meta.parentLoader() == null;

    if (log.isDebugEnabled())
      log.debug("Starting to peer-load class based on deployment metadata: " + meta);

    while (true) {
      List<SharedDeployment> depsToCheck = null;

      SharedDeployment dep = null;

      synchronized (mux) {
        // Check obsolete request.
        if (isDeadClassLoader(meta)) return null;

        List<SharedDeployment> deps = cache.get(meta.userVersion());

        if (deps != null) {
          assert !deps.isEmpty();

          for (SharedDeployment d : deps) {
            if (d.hasParticipant(meta.senderNodeId(), meta.classLoaderId())
                || meta.senderNodeId().equals(ctx.localNodeId())) {
              // Done.
              dep = d;

              break;
            }
          }

          if (dep == null) {
            GridTuple2<Boolean, SharedDeployment> redeployCheck = checkRedeploy(meta);

            if (!redeployCheck.get1()) {
              // Checking for redeployment encountered invalid state.
              if (log.isDebugEnabled())
                log.debug("Checking for redeployment encountered invalid state: " + meta);

              return null;
            }

            dep = redeployCheck.get2();

            if (dep == null) {
              // Find existing deployments that need to be checked
              // whether they should be reused for this request.
              for (SharedDeployment d : deps) {
                if (!d.isPendingUndeploy() && !d.isUndeployed()) {
                  if (depsToCheck == null) depsToCheck = new LinkedList<SharedDeployment>();

                  if (log.isDebugEnabled()) log.debug("Adding deployment to check: " + d);

                  depsToCheck.add(d);
                }
              }

              // If no deployment can be reused, create a new one.
              if (depsToCheck == null) {
                dep = createNewDeployment(meta, false);

                deps.add(dep);
              }
            }
          }
        } else {
          GridTuple2<Boolean, SharedDeployment> redeployCheck = checkRedeploy(meta);

          if (!redeployCheck.get1()) {
            // Checking for redeployment encountered invalid state.
            if (log.isDebugEnabled())
              log.debug("Checking for redeployment encountered invalid state: " + meta);

            return null;
          }

          dep = redeployCheck.get2();

          if (dep == null)
            // Create peer class loader.
            dep = createNewDeployment(meta, true);
        }
      }

      if (dep != null) {
        if (log.isDebugEnabled())
          log.debug("Found SHARED or CONTINUOUS deployment after first check: " + dep);

        // Cache the deployed class.
        Class<?> cls = dep.deployedClass(meta.className(), meta.alias());

        if (cls == null) {
          U.warn(
              log,
              "Failed to load peer class (ignore if class got undeployed during preloading) [alias="
                  + meta.alias()
                  + ", dep="
                  + dep
                  + ']');

          return null;
        }

        return dep;
      }

      assert meta.parentLoader() == null;
      assert depsToCheck != null;
      assert !depsToCheck.isEmpty();

      /*
       * Logic below must be performed outside of synchronization
       * because it involves network calls.
       */

      // Check if class can be loaded from existing nodes.
      // In most cases this loop will find something.
      for (SharedDeployment d : depsToCheck) {
        // Load class. Note, that remote node will not load this class.
        // The class will only be loaded on this node.
        Class<?> cls = d.deployedClass(meta.className(), meta.alias());

        if (cls != null) {
          synchronized (mux) {
            if (!d.isUndeployed() && !d.isPendingUndeploy()) {
              if (!addParticipant(d, meta)) return null;

              if (log.isDebugEnabled())
                log.debug(
                    "Acquired deployment after verifying it's availability on "
                        + "existing nodes [depCls="
                        + cls
                        + ", dep="
                        + d
                        + ", meta="
                        + meta
                        + ']');

              return d;
            }
          }
        } else if (log.isDebugEnabled()) {
          log.debug(
              "Deployment cannot be reused (class does not exist on participating nodes) [dep="
                  + d
                  + ", meta="
                  + meta
                  + ']');
        }
      }

      // We are here either because all participant nodes failed
      // or the class indeed should have a separate deployment.
      for (SharedDeployment d : depsToCheck) {
        // Temporary class loader.
        ClassLoader temp =
            new GridDeploymentClassLoader(
                GridUuid.randomUuid(),
                meta.userVersion(),
                meta.deploymentMode(),
                true,
                ctx,
                ctxLdr,
                meta.classLoaderId(),
                meta.senderNodeId(),
                meta.sequenceNumber(),
                comm,
                ctx.config().getNetworkTimeout(),
                log,
                ctx.config().getPeerClassLoadingClassPathExclude(),
                0,
                false);

        String path = U.classNameToResourceName(d.sampleClassName());

        // We check if any random class from existing deployment can be
        // loaded from sender node. If it can, then we reuse existing
        // deployment.
        InputStream rsrcIn = temp.getResourceAsStream(path);

        if (rsrcIn != null) {
          // We don't need the actual stream.
          U.closeQuiet(rsrcIn);

          synchronized (mux) {
            if (d.isUndeployed() || d.isPendingUndeploy()) continue;

            // Add new node prior to loading the class, so we attempt
            // to load the class from the latest node.
            if (!addParticipant(d, meta)) {
              if (log.isDebugEnabled())
                log.debug(
                    "Failed to add participant to deployment "
                        + "[meta="
                        + meta
                        + ", dep="
                        + dep
                        + ']');

              return null;
            }
          }

          Class<?> depCls = d.deployedClass(meta.className(), meta.alias());

          if (depCls == null) {
            U.error(
                log,
                "Failed to peer load class after loading it as a resource [alias="
                    + meta.alias()
                    + ", dep="
                    + dep
                    + ']');

            return null;
          }

          if (log.isDebugEnabled())
            log.debug(
                "Acquired deployment class after verifying other class "
                    + "availability on sender node [depCls="
                    + depCls
                    + ", rndCls="
                    + d.sampleClass()
                    + ", sampleClsName="
                    + d.sampleClassName()
                    + ", meta="
                    + meta
                    + ']');

          return d;
        } else if (log.isDebugEnabled())
          log.debug(
              "Deployment cannot be reused (random class could not be loaded from sender node) [dep="
                  + d
                  + ", meta="
                  + meta
                  + ']');
      }

      synchronized (mux) {
        if (log.isDebugEnabled())
          log.debug(
              "None of the existing class-loaders fit (will try to create a new one): " + meta);

        // Check obsolete request.
        if (isDeadClassLoader(meta)) return null;

        // Check that deployment picture has not changed.
        List<SharedDeployment> deps = cache.get(meta.userVersion());

        if (deps != null) {
          assert !deps.isEmpty();

          boolean retry = false;

          for (SharedDeployment d : deps) {
            // Double check if sender was already added.
            if (d.hasParticipant(meta.senderNodeId(), meta.classLoaderId())) {
              dep = d;

              retry = false;

              break;
            }

            // New deployment was added while outside of synchronization.
            // Need to recheck it again.
            if (!d.isPendingUndeploy() && !d.isUndeployed() && !depsToCheck.contains(d))
              retry = true;
          }

          if (retry) {
            if (log.isDebugEnabled()) log.debug("Retrying due to concurrency issues: " + meta);

            // Outer while loop.
            continue;
          }

          if (dep == null) {
            // No new deployments were added, so we can safely add ours.
            dep = createNewDeployment(meta, false);

            deps.add(dep);

            if (log.isDebugEnabled())
              log.debug(
                  "Adding new deployment within second check [dep=" + dep + ", meta=" + meta + ']');
          }
        } else {
          dep = createNewDeployment(meta, true);

          if (log.isDebugEnabled())
            log.debug(
                "Created new deployment within second check [dep=" + dep + ", meta=" + meta + ']');
        }
      }

      if (dep != null) {
        // Cache the deployed class.
        Class<?> cls = dep.deployedClass(meta.className(), meta.alias());

        if (cls == null) {
          U.warn(
              log,
              "Failed to load peer class (ignore if class got undeployed during preloading) [alias="
                  + meta.alias()
                  + ", dep="
                  + dep
                  + ']');

          return null;
        }
      }

      return dep;
    }
  }