BUG-5280: split out cds akka client substrate

[controller.git] / opendaylight / md-sal / cds-access-client / src / main / java / org / opendaylight / controller / cluster / access / client / BackendInfoResolver.java

diff --git a/opendaylight/md-sal/cds-access-client/src/main/java/org/opendaylight/controller/cluster/access/client/BackendInfoResolver.java b/opendaylight/md-sal/cds-access-client/src/main/java/org/opendaylight/controller/cluster/access/client/BackendInfoResolver.java
new file mode 100644 (file)
index 0000000..cb64809
--- /dev/null
+++ b/opendaylight/md-sal/cds-access-client/src/main/java/org/opendaylight/controller/cluster/access/client/BackendInfoResolver.java
@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2016 Cisco Systems, Inc. and others.  All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v10.html
+ */
+package org.opendaylight.controller.cluster.access.client;
+
+import akka.actor.ActorRef;
+import com.google.common.base.Preconditions;
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionStage;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Future;
+import javax.annotation.Nonnull;
+import javax.annotation.concurrent.ThreadSafe;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Caching resolver which resolves a cookie to a leader {@link ActorRef}. This class needs to be specialized by the
+ * client. It is used by {@link ClientActorBehavior} for request dispatch. Results are cached until they are invalidated
+ * by either the client actor (when a message timeout is detected) and by the specific frontend (on explicit
+ * invalidation or when updated information becomes available).
+ *
+ * @author Robert Varga
+ */
+@ThreadSafe
+public abstract class BackendInfoResolver<T extends BackendInfo> {
+    private static final Logger LOG = LoggerFactory.getLogger(BackendInfoResolver.class);
+    private final ConcurrentMap<Long, CompletableFuture<T>> backends = new ConcurrentHashMap<>();
+
+    /**
+     * Return the currently-resolved backend information, if available. This method is guaranteed not to block, but will
+     * initiate resolution of the information if there is none.
+     *
+     * @param cookie Backend cookie
+     * @return Backend information, if available
+     */
+    public final Optional<T> getFutureBackendInfo(final Long cookie) {
+        final Future<T> f = lookupBackend(cookie);
+        if (f.isDone()) {
+            try {
+                return Optional.of(f.get());
+            } catch (InterruptedException | ExecutionException e) {
+                LOG.debug("Resolution of {} failed", f, e);
+            }
+        }
+
+        return Optional.empty();
+    }
+
+    /**
+     * Invalidate a particular instance of {@link BackendInfo}, typically as a response to a request timing out. If
+     * the provided information is not the one currently cached this method does nothing.
+     *
+     * @param cookie Backend cookie
+     * @param info Previous information to be invalidated
+     */
+    public final void invalidateBackend(final long cookie, final @Nonnull CompletionStage<? extends BackendInfo> info) {
+        if (backends.remove(cookie, Preconditions.checkNotNull(info))) {
+            LOG.trace("Invalidated cache %s -> %s", Long.toUnsignedString(cookie), info);
+            invalidateBackendInfo(info);
+        }
+    }
+
+    /**
+     * Request new resolution of a particular backend identified by a cookie. This method is invoked when a client
+     * requests information which is not currently cached.
+     *
+     * @param cookie Backend cookie
+     * @return A {@link CompletableFuture} resulting in information about the backend
+     */
+    protected abstract @Nonnull CompletableFuture<T> resolveBackendInfo(final @Nonnull Long cookie);
+
+    /**
+     * Invalidate previously-resolved shard information. This method is invoked when a timeout is detected
+     * and the information may need to be refreshed.
+     *
+     * @param info Previous promise of backend information
+     */
+    protected abstract void invalidateBackendInfo(@Nonnull CompletionStage<? extends BackendInfo> info);
+
+    // This is what the client needs to start processing. For as long as we do not have this, we should not complete
+    // this stage until we have this information
+    final CompletionStage<? extends T> getBackendInfo(final Long cookie) {
+        return lookupBackend(cookie);
+    }
+
+    private CompletableFuture<T> lookupBackend(final Long cookie) {
+        return backends.computeIfAbsent(Preconditions.checkNotNull(cookie), this::resolveBackendInfo);
+    }
+}