GH-512: Add ping method to facilitate connection healthcheck between client and server

concourse-automation/src/main/java/com/cinchapi/concourse/automation/server/ManagedConcourseServer.java

@@ -2292,6 +2292,11 @@ public <T> Map<Long, Set<T>> navigate(String key, String ccl,
                     Timestamp.class).with(key, ccl, timestamp);
         }
 
+        @Override
+        public boolean ping() {
+            return invoke("ping").with();
+        }
+
         @Override
         public Map<Long, Boolean> ping(Collection<Long> records) {
             return invoke("ping", Collection.class).with(records);

concourse-driver-java/src/main/java/com/cinchapi/concourse/Concourse.java

@@ -5123,6 +5123,18 @@ public final <T> Map<Long, Set<T>> navigate(String key, Long record,
     public abstract <T> Map<Long, Set<T>> navigate(String key, String ccl,
             Timestamp timestamp);
 
+    /**
+     * Test the connection to the server.
+     * <p>
+     * Check if this client is still connected to the server by sending an echo
+     * request and awaiting a response. This can be used to ensure subsequent
+     * communication with the server is possible. If the connection is broken,
+     * it will be necessary to establish a new connection.
+     * 
+     * @return boolean - {@code true} if the connection is still alive
+     */
+    public abstract boolean ping();
+
     /**
      * Atomically check to see if each of the {@code records} currently contains
      * any data.

concourse-driver-java/src/main/java/com/cinchapi/concourse/ConcourseThriftDriver.java

@@ -15,6 +15,7 @@
  */
 package com.cinchapi.concourse;
 
+import java.net.SocketException;
 import java.nio.ByteBuffer;
 import java.util.Arrays;
 import java.util.Collection;
@@ -69,6 +70,7 @@
 import com.cinchapi.concourse.util.PrettyLinkedHashMap;
 import com.cinchapi.concourse.util.PrettyLinkedTableMap;
 import com.cinchapi.concourse.util.Transformers;
+import com.google.common.base.Throwables;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Sets;
@@ -98,6 +100,12 @@ class ConcourseThriftDriver extends Concourse {
         ENVIRONMENT = config.getEnvironment();
     }
 
+    /**
+     * Exceptions that indicate the connection to the server has failed.
+     */
+    private static final Set<Class<? extends Throwable>> FAILED_CONNECTION_EXCEPTION_TYPES = ImmutableSet
+            .of(TTransportException.class, SocketException.class);
+
     /**
      * The thrift client that actually handles aggregation RPC communication.
      */
@@ -2472,6 +2480,24 @@ public <T> Map<Long, Set<T>> navigate(final String key, final String ccl,
         });
     }
 
+    @Override
+    public boolean ping() {
+        try {
+            return execute(() -> core.ping(creds, transaction, environment));
+        }
+        catch (Exception e) {
+            Set<Class<?>> causes = Throwables.getCausalChain(e).stream()
+                    .map(Object::getClass).collect(Collectors.toSet());
+            if(!Sets.intersection(causes, FAILED_CONNECTION_EXCEPTION_TYPES)
+                    .isEmpty()) {
+                return false;
+            }
+            else {
+                throw e;
+            }
+        }
+    }
+
     @Override
     public Map<Long, Boolean> ping(Collection<Long> records) {
         return execute(() -> core.pingRecords(Collections.toLongList(records),

concourse-driver-java/src/main/java/com/cinchapi/concourse/ForwardingConcourse.java

@@ -1091,6 +1091,11 @@ public <T> Map<Long, Set<T>> navigate(String key, String ccl,
         return concourse.navigate(key, ccl, timestamp);
     }
 
+    @Override
+    public boolean ping() {
+        return concourse.ping();
+    }
+
     @Override
     public Map<Long, Boolean> ping(Collection<Long> records) {
         return concourse.ping(records);

concourse-driver-java/src/main/java/com/cinchapi/concourse/NoOpConcourse.java

@@ -1068,6 +1068,11 @@ public <T> Map<Long, Set<T>> navigate(String key, String ccl,
         throw new UnsupportedOperationException();
     }
 
+    @Override
+    public boolean ping() {
+        throw new UnsupportedOperationException();
+    }
+
     @Override
     public Map<Long, Boolean> ping(Collection<Long> records) {
         throw new UnsupportedOperationException();