Local Client for testing (without subscription yet)

Partial implementation of subscriptions.
Some bug fixes.

bulletin-board-client/src/main/java/meerkat/bulletinboard/SimpleBulletinBoardClient.java

@@ -1,13 +1,21 @@
 package meerkat.bulletinboard;
 
 import com.google.protobuf.ByteString;
+import com.google.protobuf.Timestamp;
 import meerkat.comm.CommunicationException;
+import meerkat.comm.MessageInputStream;
 import meerkat.crypto.Digest;
 import meerkat.crypto.concrete.SHA256Digest;
+import meerkat.protobuf.BulletinBoardAPI;
 import meerkat.protobuf.BulletinBoardAPI.*;
 import meerkat.protobuf.Voting.*;
 import meerkat.rest.*;
 
+import java.io.IOException;
+import java.io.InputStream;
+import java.lang.reflect.InvocationTargetException;
+import java.util.Collection;
+import java.util.Iterator;
 import java.util.List;
 
 import javax.ws.rs.client.Client;
@@ -129,6 +137,7 @@ public class SimpleBulletinBoardClient implements BulletinBoardClient{
      */
     @Override
     public List<BulletinBoardMessage> readMessages(MessageFilterList filterList) {
+
         WebTarget webTarget;
         Response response;
         BulletinBoardMessageList messageList;
@@ -139,6 +148,7 @@ public class SimpleBulletinBoardClient implements BulletinBoardClient{
         }
 
         for (String db : meerkatDBs) {
+
             try {
                 webTarget = client.target(db).path(BULLETIN_BOARD_SERVER_PATH).path(READ_MESSAGES_PATH);
 
@@ -151,9 +161,34 @@ public class SimpleBulletinBoardClient implements BulletinBoardClient{
                 }
 
             } catch (Exception e) {}
+
         }
 
         return null;
+
+    }
+
+    @Override
+    public SyncQuery generateSyncQuery(GenerateSyncQueryParams generateSyncQueryParams) throws CommunicationException {
+
+        WebTarget webTarget;
+        Response response;
+
+        for (String db : meerkatDBs) {
+
+            try {
+                webTarget = client.target(db).path(BULLETIN_BOARD_SERVER_PATH).path(GENERATE_SYNC_QUERY_PATH);
+
+                response = webTarget.request(Constants.MEDIATYPE_PROTOBUF).post(Entity.entity(generateSyncQueryParams, Constants.MEDIATYPE_PROTOBUF));
+
+                return response.readEntity(SyncQuery.class);
+
+            } catch (Exception e) {}
+
+        }
+
+        throw new CommunicationException("Could not contact any server");
+
     }
 
     public void close() {

bulletin-board-client/src/main/java/meerkat/bulletinboard/SingleServerBulletinBoardClient.java

@@ -7,6 +7,7 @@ import com.google.common.util.concurrent.MoreExecutors;
 import com.google.protobuf.ByteString;
 import meerkat.bulletinboard.workers.singleserver.*;
 import meerkat.comm.CommunicationException;
+import meerkat.protobuf.BulletinBoardAPI;
 import meerkat.protobuf.BulletinBoardAPI.*;
 import meerkat.protobuf.Voting.BulletinBoardClientParams;
 import meerkat.util.BulletinBoardUtils;
@@ -29,7 +30,7 @@ import java.util.concurrent.atomic.AtomicInteger;
  * If the list of servers contains more than one server: the server actually used is the first one
  * The class further implements a delayed access to the server after a communication error occurs
  */
-public class SingleServerBulletinBoardClient extends SimpleBulletinBoardClient implements AsyncBulletinBoardClient {
+public class SingleServerBulletinBoardClient extends SimpleBulletinBoardClient implements SubscriptionAsyncBulletinBoardClient {
 
     private final int MAX_RETRIES = 11;
 
@@ -275,13 +276,13 @@ public class SingleServerBulletinBoardClient extends SimpleBulletinBoardClient i
     class SubscriptionCallback implements FutureCallback<List<BulletinBoardMessage>> {
 
         private SingleServerReadMessagesWorker worker;
-        private final MessageHandler messageHandler;
+        private final FutureCallback<List<BulletinBoardMessage>> callback;
 
         private MessageFilterList.Builder filterBuilder;
 
-        public SubscriptionCallback(SingleServerReadMessagesWorker worker, MessageHandler messageHandler) {
+        public SubscriptionCallback(SingleServerReadMessagesWorker worker, FutureCallback<List<BulletinBoardMessage>> callback) {
             this.worker = worker;
-            this.messageHandler = messageHandler;
+            this.callback = callback;
             filterBuilder = worker.getPayload().toBuilder();
 
         }
@@ -290,7 +291,7 @@ public class SingleServerBulletinBoardClient extends SimpleBulletinBoardClient i
         public void onSuccess(List<BulletinBoardMessage> result) {
 
             // Report new messages to user
-            messageHandler.handleNewMessages(result);
+            callback.onSuccess(result);
 
             // Remove last filter from list (MIN_ENTRY one)
             filterBuilder.removeFilter(filterBuilder.getFilterCount() - 1);
@@ -315,14 +316,16 @@ public class SingleServerBulletinBoardClient extends SimpleBulletinBoardClient i
             // Notify client about failure
             fail();
 
-            // Reschedule exact same task
+            // Notify caller about failure and terminate subscription
-            scheduleWorker(worker, this);
+            callback.onFailure(t);
         }
     }
 
-    public SingleServerBulletinBoardClient(int threadPoolSize, long failDelayInMilliseconds, long subscriptionIntervalInMilliseconds) {
+    public SingleServerBulletinBoardClient(ListeningScheduledExecutorService executorService,
+                                           long failDelayInMilliseconds,
+                                           long subscriptionIntervalInMilliseconds) {
 
-        executorService = MoreExecutors.listeningDecorator(Executors.newScheduledThreadPool(threadPoolSize));
+        this.executorService = executorService;
 
         this.failDelayInMilliseconds = failDelayInMilliseconds;
         this.subscriptionIntervalInMilliseconds = subscriptionIntervalInMilliseconds;
@@ -332,6 +335,14 @@ public class SingleServerBulletinBoardClient extends SimpleBulletinBoardClient i
 
     }
 
+    public SingleServerBulletinBoardClient(int threadPoolSize, long failDelayInMilliseconds, long subscriptionIntervalInMilliseconds) {
+
+        this(MoreExecutors.listeningDecorator(Executors.newScheduledThreadPool(threadPoolSize)),
+                failDelayInMilliseconds,
+                subscriptionIntervalInMilliseconds);
+
+    }
+
     /**
      * Stores database location, initializes the web Client and
      * @param clientParams contains the data needed to access the DBs
@@ -567,8 +578,16 @@ public class SingleServerBulletinBoardClient extends SimpleBulletinBoardClient i
     }
 
     @Override
-    public void subscribe(MessageFilterList filterList, MessageHandler messageHandler) {
+    public void querySync(SyncQuery syncQuery, FutureCallback<SyncQueryResponse> callback) {
 
+        SingleServerQuerySyncWorker worker = new SingleServerQuerySyncWorker(meerkatDBs.get(0), syncQuery, MAX_RETRIES);
+
+        scheduleWorker(worker, new RetryCallback<>(worker, callback));
+
+    }
+
+    @Override
+    public void subscribe(MessageFilterList filterList, long startEntry, FutureCallback<List<BulletinBoardMessage>> callback) {
         // Remove all existing MIN_ENTRY filters and create new one that starts at 0
 
         MessageFilterList.Builder filterListBuilder = filterList.toBuilder();
@@ -583,15 +602,19 @@ public class SingleServerBulletinBoardClient extends SimpleBulletinBoardClient i
         }
         filterListBuilder.addFilter(MessageFilter.newBuilder()
                 .setType(FilterType.MIN_ENTRY)
-                .setEntry(0)
+                .setEntry(startEntry)
                 .build());
 
         // Create job with no retries
-        SingleServerReadMessagesWorker worker = new SingleServerReadMessagesWorker(meerkatDBs.get(0), filterListBuilder.build(), 1);
+        SingleServerReadMessagesWorker worker = new SingleServerReadMessagesWorker(meerkatDBs.get(0), filterListBuilder.build(), MAX_RETRIES);
 
-        // Submit job and create callback
+        // Submit job and create callback that retries on failure and handles repeated subscription
-        scheduleWorker(worker, new SubscriptionCallback(worker, messageHandler));
+        scheduleWorker(worker, new RetryCallback<>(worker, new SubscriptionCallback(worker, callback)));
+    }
 
+    @Override
+    public void subscribe(MessageFilterList filterList, FutureCallback<List<BulletinBoardMessage>> callback) {
+        subscribe(filterList, 0, callback);
     }
 
     @Override

bulletin-board-client/src/main/java/meerkat/bulletinboard/ThreadedBulletinBoardClient.java

@@ -5,6 +5,7 @@ import com.google.protobuf.ByteString;
 
 import meerkat.bulletinboard.workers.multiserver.*;
 import meerkat.comm.CommunicationException;
+import meerkat.protobuf.BulletinBoardAPI;
 import meerkat.protobuf.BulletinBoardAPI.*;
 import meerkat.protobuf.Voting.*;
 
@@ -55,7 +56,7 @@ public class ThreadedBulletinBoardClient extends SimpleBulletinBoardClient imple
 
         batchDigest = new GenericBatchDigest(digest);
 
-        minAbsoluteRedundancy = (int) (clientParams.getMinRedundancy() * clientParams.getBulletinBoardAddressCount());
+        minAbsoluteRedundancy = (int) (clientParams.getMinRedundancy() * (float) clientParams.getBulletinBoardAddressCount());
 
         executorService = Executors.newFixedThreadPool(JOBS_THREAD_NUM);
 
@@ -223,9 +224,13 @@ public class ThreadedBulletinBoardClient extends SimpleBulletinBoardClient imple
 
     }
 
+    /**
+     * This method is not supported by this class!
+     * This is because it has no meaning when considering more than one server without knowing which server will be contacted
+     */
     @Override
-    public void subscribe(MessageFilterList filterList, MessageHandler messageHandler) {
+    public void querySync(SyncQuery syncQuery, FutureCallback<SyncQueryResponse> callback) {
-        // TODO: Implement
+        callback.onFailure(new IllegalAccessError("querySync is not supported by this class"));
     }
 
     @Override

bulletin-board-client/src/main/java/meerkat/bulletinboard/workers/singleserver/SingleServerGetRedundancyWorker.java

@@ -2,6 +2,7 @@ package meerkat.bulletinboard.workers.singleserver;
 
 import meerkat.bulletinboard.SingleServerWorker;
 import meerkat.comm.CommunicationException;
+import meerkat.comm.MessageInputStream;
 import meerkat.protobuf.BulletinBoardAPI.*;
 import meerkat.rest.Constants;
 
@@ -11,6 +12,10 @@ import javax.ws.rs.client.Entity;
 import javax.ws.rs.client.WebTarget;
 import javax.ws.rs.core.Response;
 
+import java.io.IOException;
+import java.io.InputStream;
+import java.lang.reflect.InvocationTargetException;
+
 import static meerkat.bulletinboard.BulletinBoardConstants.BULLETIN_BOARD_SERVER_PATH;
 import static meerkat.bulletinboard.BulletinBoardConstants.READ_MESSAGES_PATH;
 
@@ -45,17 +50,19 @@ public class SingleServerGetRedundancyWorker extends SingleServerWorker<MessageI
 
         // Send request to Server
 
+        // Send request to Server
         webTarget = client.target(serverAddress).path(BULLETIN_BOARD_SERVER_PATH).path(READ_MESSAGES_PATH);
-        response = webTarget.request(Constants.MEDIATYPE_PROTOBUF).post(Entity.entity(msgFilterList, Constants.MEDIATYPE_PROTOBUF));
+        InputStream in = webTarget.request(Constants.MEDIATYPE_PROTOBUF).post(Entity.entity(msgFilterList, Constants.MEDIATYPE_PROTOBUF), InputStream.class);
+
+        MessageInputStream<BulletinBoardMessage> inputStream = null;
 
         // Retrieve answer
 
         try {
 
-            // If a BulletinBoardMessageList is returned: the read was successful
+            inputStream = MessageInputStream.MessageInputStreamFactory.createMessageInputStream(in, BulletinBoardMessage.class);
-            BulletinBoardMessageList msgList = response.readEntity(BulletinBoardMessageList.class);
 
-            if (msgList.getMessageList().size() > 0){
+            if (inputStream.asList().size() > 0){
                 // Message exists in the server
                 return 1.0f;
             }
@@ -64,14 +71,15 @@ public class SingleServerGetRedundancyWorker extends SingleServerWorker<MessageI
                 return 0.0f;
             }
 
-        } catch (ProcessingException | IllegalStateException e) {
+        } catch (Exception e) {
 
             // Read failed
             throw new CommunicationException("Server access failed");
 
-        }
+        } finally {
-        finally {
+            try {
-            response.close();
+                inputStream.close();
+            } catch (IOException ignored) {}
         }
 
     }

bulletin-board-client/src/test/java/ThreadedBulletinBoardClientIntegrationTest.java

@@ -1,556 +0,0 @@
-import com.google.common.util.concurrent.FutureCallback;
-import com.google.protobuf.*;
-import com.google.protobuf.Timestamp;
-import meerkat.bulletinboard.AsyncBulletinBoardClient;
-import meerkat.bulletinboard.CompleteBatch;
-import meerkat.bulletinboard.GenericBatchDigitalSignature;
-import meerkat.bulletinboard.ThreadedBulletinBoardClient;
-import meerkat.comm.CommunicationException;
-import meerkat.crypto.concrete.ECDSASignature;
-import meerkat.protobuf.BulletinBoardAPI.*;
-import meerkat.protobuf.Crypto;
-
-import meerkat.protobuf.Voting.*;
-import meerkat.util.BulletinBoardMessageComparator;
-
-import org.junit.After;
-import org.junit.Before;
-import org.junit.Test;
-
-import static org.junit.Assert.*;
-import static org.hamcrest.CoreMatchers.*;
-import static org.hamcrest.number.OrderingComparison.*;
-
-import java.io.IOException;
-import java.io.InputStream;
-import java.security.*;
-import java.security.cert.CertificateException;
-import java.util.*;
-import java.util.concurrent.Semaphore;
-
-/**
- * Created by Arbel Deutsch Peled on 05-Dec-15.
- */
-public class ThreadedBulletinBoardClientIntegrationTest {
-
-    // Signature resources
-
-    private GenericBatchDigitalSignature signers[];
-    private ByteString[] signerIDs;
-
-    private static String KEYFILE_EXAMPLE = "/certs/enduser-certs/user1-key-with-password-secret.p12";
-    private static String KEYFILE_EXAMPLE3 = "/certs/enduser-certs/user3-key-with-password-shh.p12";
-
-    private static String KEYFILE_PASSWORD1 = "secret";
-    private static String KEYFILE_PASSWORD3 = "shh";
-
-    private static String CERT1_PEM_EXAMPLE = "/certs/enduser-certs/user1.crt";
-    private static String CERT3_PEM_EXAMPLE = "/certs/enduser-certs/user3.crt";
-
-    // Server data
-
-    private static String PROP_GETTY_URL = "gretty.httpBaseURI";
-    private static String DEFAULT_BASE_URL = "http://localhost:8081";
-    private static String BASE_URL =  System.getProperty(PROP_GETTY_URL, DEFAULT_BASE_URL);
-
-    // Client and callbacks
-
-    private AsyncBulletinBoardClient bulletinBoardClient;
-
-    private PostCallback postCallback;
-    private PostCallback failPostCallback = new PostCallback(true,false);
-
-    private RedundancyCallback redundancyCallback;
-    private ReadCallback readCallback;
-    private ReadBatchCallback readBatchCallback;
-
-    // Sync and misc
-
-    private Semaphore jobSemaphore;
-    private Vector<Throwable> thrown;
-    private Random random;
-
-    // Constructor
-
-    public ThreadedBulletinBoardClientIntegrationTest(){
-
-        signers = new GenericBatchDigitalSignature[2];
-        signerIDs = new ByteString[signers.length];
-        signers[0] = new GenericBatchDigitalSignature(new ECDSASignature());
-        signers[1] = new GenericBatchDigitalSignature(new ECDSASignature());
-
-        InputStream keyStream = getClass().getResourceAsStream(KEYFILE_EXAMPLE);
-        char[] password = KEYFILE_PASSWORD1.toCharArray();
-
-        KeyStore.Builder keyStoreBuilder;
-        try {
-            keyStoreBuilder = signers[0].getPKCS12KeyStoreBuilder(keyStream, password);
-
-            signers[0].loadSigningCertificate(keyStoreBuilder);
-
-            signers[0].loadVerificationCertificates(getClass().getResourceAsStream(CERT1_PEM_EXAMPLE));
-
-            keyStream = getClass().getResourceAsStream(KEYFILE_EXAMPLE3);
-            password = KEYFILE_PASSWORD3.toCharArray();
-
-            keyStoreBuilder = signers[1].getPKCS12KeyStoreBuilder(keyStream, password);
-            signers[1].loadSigningCertificate(keyStoreBuilder);
-
-            signers[1].loadVerificationCertificates(getClass().getResourceAsStream(CERT3_PEM_EXAMPLE));
-
-            for (int i = 0 ; i < signers.length ; i++) {
-                signerIDs[i] = signers[i].getSignerID();
-            }
-
-        } catch (IOException e) {
-            System.err.println("Failed reading from signature file " + e.getMessage());
-            fail("Failed reading from signature file " + e.getMessage());
-        } catch (CertificateException e) {
-            System.err.println("Failed reading certificate " + e.getMessage());
-            fail("Failed reading certificate " + e.getMessage());
-        } catch (KeyStoreException e) {
-            System.err.println("Failed reading keystore " + e.getMessage());
-            fail("Failed reading keystore " + e.getMessage());
-        } catch (NoSuchAlgorithmException e) {
-            System.err.println("Couldn't find signing algorithm " + e.getMessage());
-            fail("Couldn't find signing algorithm " + e.getMessage());
-        } catch (UnrecoverableKeyException e) {
-            System.err.println("Couldn't find signing key " + e.getMessage());
-            fail("Couldn't find signing key " + e.getMessage());
-        }
-
-    }
-
-    // Callback definitions
-
-    protected void genericHandleFailure(Throwable t){
-        System.err.println(t.getCause() + " " + t.getMessage());
-        thrown.add(t);
-        jobSemaphore.release();
-    }
-
-    private class PostCallback implements FutureCallback<Boolean>{
-
-        private boolean isAssert;
-        private boolean assertValue;
-
-        public PostCallback() {
-            this(false);
-        }
-
-        public PostCallback(boolean isAssert) {
-            this(isAssert,true);
-        }
-
-        public PostCallback(boolean isAssert, boolean assertValue) {
-            this.isAssert = isAssert;
-            this.assertValue = assertValue;
-        }
-
-        @Override
-        public void onSuccess(Boolean msg) {
-            System.err.println("Post operation completed");
-            jobSemaphore.release();
-            //TODO: Change Assert mechanism to exception one
-            if (isAssert) {
-                if (assertValue) {
-                    assertThat("Post operation failed", msg, is(Boolean.TRUE));
-                } else {
-                    assertThat("Post operation succeeded unexpectedly", msg, is(Boolean.FALSE));
-                }
-            }
-        }
-
-        @Override
-        public void onFailure(Throwable t) {
-            genericHandleFailure(t);
-        }
-    }
-
-    private class RedundancyCallback implements FutureCallback<Float>{
-
-        private float minRedundancy;
-
-        public RedundancyCallback(float minRedundancy) {
-            this.minRedundancy = minRedundancy;
-        }
-
-        @Override
-        public void onSuccess(Float redundancy) {
-            System.err.println("Redundancy found is: " + redundancy);
-            jobSemaphore.release();
-            assertThat(redundancy, greaterThanOrEqualTo(minRedundancy));
-        }
-
-        @Override
-        public void onFailure(Throwable t) {
-            genericHandleFailure(t);
-        }
-    }
-
-    private class ReadCallback implements FutureCallback<List<BulletinBoardMessage>>{
-
-        private List<BulletinBoardMessage> expectedMsgList;
-
-        public ReadCallback(List<BulletinBoardMessage> expectedMsgList) {
-            this.expectedMsgList = expectedMsgList;
-        }
-
-        @Override
-        public void onSuccess(List<BulletinBoardMessage> messages) {
-
-            System.err.println(messages);
-            jobSemaphore.release();
-
-            BulletinBoardMessageComparator msgComparator = new BulletinBoardMessageComparator();
-
-            assertThat(messages.size(), is(expectedMsgList.size()));
-
-            Iterator<BulletinBoardMessage> expectedMessageIterator = expectedMsgList.iterator();
-            Iterator<BulletinBoardMessage> receivedMessageIterator = messages.iterator();
-
-            while (expectedMessageIterator.hasNext()) {
-                assertThat(msgComparator.compare(expectedMessageIterator.next(), receivedMessageIterator.next()), is(0));
-            }
-
-        }
-
-        @Override
-        public void onFailure(Throwable t) {
-            genericHandleFailure(t);
-        }
-    }
-
-    private class ReadBatchCallback implements FutureCallback<CompleteBatch> {
-
-        private CompleteBatch expectedBatch;
-
-        public ReadBatchCallback(CompleteBatch expectedBatch) {
-            this.expectedBatch = expectedBatch;
-        }
-
-        @Override
-        public void onSuccess(CompleteBatch batch) {
-
-            System.err.println(batch);
-            jobSemaphore.release();
-
-            assertThat("Batch returned is incorrect", batch, is(equalTo(expectedBatch)));
-
-        }
-
-        @Override
-        public void onFailure(Throwable t) {
-            genericHandleFailure(t);
-        }
-    }
-
-    // Randomness generators
-
-    private byte randomByte(){
-        return (byte) random.nextInt();
-    }
-
-    private byte[] randomByteArray(int length) {
-
-        byte[] randomBytes = new byte[length];
-
-        for (int i = 0; i < length ; i++){
-            randomBytes[i] = randomByte();
-        }
-
-        return randomBytes;
-
-    }
-
-    private CompleteBatch createRandomBatch(int signer, int batchId, int length) throws SignatureException {
-
-        CompleteBatch completeBatch = new CompleteBatch();
-
-        // Create data
-
-        completeBatch.setBeginBatchMessage(BeginBatchMessage.newBuilder()
-                .setSignerId(signerIDs[signer])
-                .setBatchId(batchId)
-                .addTag("Test")
-                .build());
-
-        for (int i = 0 ; i < length ; i++){
-
-            BatchData batchData = BatchData.newBuilder()
-                    .setData(ByteString.copyFrom(randomByteArray(i)))
-                    .build();
-
-            completeBatch.appendBatchData(batchData);
-
-        }
-
-        completeBatch.setTimestamp(Timestamp.newBuilder()
-                .setSeconds(Math.abs(90))
-                .setNanos(50)
-                .build());
-
-        signers[signer].updateContent(completeBatch);
-
-        completeBatch.setSignature(signers[signer].sign());
-
-        return completeBatch;
-
-    }
-
-    // Test methods
-
-    /**
-     * Takes care of initializing the client and the test resources
-     */
-    @Before
-    public void init(){
-
-        bulletinBoardClient = new ThreadedBulletinBoardClient();
-
-        random = new Random(0); // We use insecure randomness in tests for repeatability
-
-        List<String> testDB = new LinkedList<>();
-        testDB.add(BASE_URL);
-
-        bulletinBoardClient.init(BulletinBoardClientParams.newBuilder()
-            .addAllBulletinBoardAddress(testDB)
-            .setMinRedundancy((float) 1.0)
-            .build());
-
-        postCallback = new PostCallback();
-        redundancyCallback = new RedundancyCallback((float) 1.0);
-
-        thrown = new Vector<>();
-        jobSemaphore = new Semaphore(0);
-
-    }
-
-    /**
-     * Closes the client and makes sure the test fails when an exception occurred in a separate thread
-     */
-
-    @After
-    public void close() {
-
-        bulletinBoardClient.close();
-
-        if (thrown.size() > 0) {
-            assert false;
-        }
-
-    }
-
-    /**
-     * Tests the standard post, redundancy and read methods
-     */
-    @Test
-    public void postTest() {
-
-        byte[] b1 = {(byte) 1, (byte) 2, (byte) 3, (byte) 4};
-        byte[] b2 = {(byte) 11, (byte) 12, (byte) 13, (byte) 14};
-        byte[] b3 = {(byte) 21, (byte) 22, (byte) 23, (byte) 24};
-
-        BulletinBoardMessage msg;
-
-        MessageFilterList filterList;
-        List<BulletinBoardMessage> msgList;
-
-        MessageID messageID;
-
-        msg = BulletinBoardMessage.newBuilder()
-                .setMsg(UnsignedBulletinBoardMessage.newBuilder()
-                        .addTag("Signature")
-                        .addTag("Trustee")
-                        .setData(ByteString.copyFrom(b1))
-                        .setTimestamp(Timestamp.newBuilder()
-                                .setSeconds(20)
-                                .setNanos(30)
-                                .build())
-                        .build())
-                .addSig(Crypto.Signature.newBuilder()
-                        .setType(Crypto.SignatureType.DSA)
-                        .setData(ByteString.copyFrom(b2))
-                        .setSignerId(ByteString.copyFrom(b3))
-                        .build())
-                .addSig(Crypto.Signature.newBuilder()
-                        .setType(Crypto.SignatureType.ECDSA)
-                        .setData(ByteString.copyFrom(b3))
-                        .setSignerId(ByteString.copyFrom(b2))
-                        .build())
-                .build();
-
-        messageID = bulletinBoardClient.postMessage(msg,postCallback);
-
-        try {
-            jobSemaphore.acquire();
-        } catch (InterruptedException e) {
-            System.err.println(e.getCause() + " " + e.getMessage());
-        }
-
-        bulletinBoardClient.getRedundancy(messageID,redundancyCallback);
-
-        filterList = MessageFilterList.newBuilder()
-                .addFilter(
-                        MessageFilter.newBuilder()
-                                .setType(FilterType.TAG)
-                                .setTag("Signature")
-                                .build()
-                )
-                .addFilter(
-                        MessageFilter.newBuilder()
-                                .setType(FilterType.TAG)
-                                .setTag("Trustee")
-                                .build()
-                )
-                .build();
-
-        msgList = new LinkedList<>();
-        msgList.add(msg);
-
-        readCallback = new ReadCallback(msgList);
-
-        bulletinBoardClient.readMessages(filterList, readCallback);
-        try {
-            jobSemaphore.acquire(2);
-        } catch (InterruptedException e) {
-            System.err.println(e.getCause() + " " + e.getMessage());
-        }
-
-    }
-
-    /**
-     * Tests posting a batch by parts
-     * Also tests not being able to post to a closed batch
-     * @throws CommunicationException, SignatureException, InterruptedException
-     */
-    @Test
-    public void testBatchPost() throws CommunicationException, SignatureException, InterruptedException {
-
-        final int SIGNER = 1;
-        final int BATCH_ID = 100;
-        final int BATCH_LENGTH = 100;
-
-        CompleteBatch completeBatch = createRandomBatch(SIGNER, BATCH_ID, BATCH_LENGTH);
-
-        // Begin batch
-
-        bulletinBoardClient.beginBatch(completeBatch.getBeginBatchMessage(), postCallback);
-
-        jobSemaphore.acquire();
-
-        // Post data
-
-        bulletinBoardClient.postBatchData(signerIDs[SIGNER], BATCH_ID, completeBatch.getBatchDataList(), postCallback);
-
-        jobSemaphore.acquire();
-
-        // Close batch
-
-        CloseBatchMessage closeBatchMessage = CloseBatchMessage.newBuilder()
-                .setBatchId(BATCH_ID)
-                .setBatchLength(BATCH_LENGTH)
-                .setTimestamp(Timestamp.newBuilder()
-                        .setSeconds(50)
-                        .setNanos(80)
-                        .build())
-                .setSig(completeBatch.getSignature())
-                .build();
-
-        bulletinBoardClient.closeBatch(closeBatchMessage, postCallback);
-
-        jobSemaphore.acquire();
-
-        // Attempt to open batch again
-
-        bulletinBoardClient.beginBatch(completeBatch.getBeginBatchMessage(), failPostCallback);
-
-        // Attempt to add batch data
-
-        bulletinBoardClient.postBatchData(signerIDs[SIGNER], BATCH_ID, completeBatch.getBatchDataList(), failPostCallback);
-
-        jobSemaphore.acquire(2);
-
-        // Read batch data
-
-        BatchSpecificationMessage batchSpecificationMessage =
-                BatchSpecificationMessage.newBuilder()
-                        .setSignerId(signerIDs[SIGNER])
-                        .setBatchId(BATCH_ID)
-                        .setStartPosition(0)
-                        .build();
-
-        readBatchCallback = new ReadBatchCallback(completeBatch);
-
-        bulletinBoardClient.readBatch(batchSpecificationMessage, readBatchCallback);
-
-        jobSemaphore.acquire();
-
-    }
-
-    /**
-     * Posts a complete batch message
-     * Checks reading od the message
-     * @throws CommunicationException, SignatureException, InterruptedException
-     */
-    @Test
-    public void testCompleteBatchPost() throws CommunicationException, SignatureException, InterruptedException {
-
-        final int SIGNER = 0;
-        final int BATCH_ID = 101;
-        final int BATCH_LENGTH = 50;
-
-        // Post batch
-
-        CompleteBatch completeBatch = createRandomBatch(SIGNER, BATCH_ID, BATCH_LENGTH);
-
-        bulletinBoardClient.postBatch(completeBatch,postCallback);
-
-        jobSemaphore.acquire();
-
-        // Read batch
-
-        BatchSpecificationMessage batchSpecificationMessage =
-                BatchSpecificationMessage.newBuilder()
-                        .setSignerId(signerIDs[SIGNER])
-                        .setBatchId(BATCH_ID)
-                        .setStartPosition(0)
-                        .build();
-
-        readBatchCallback = new ReadBatchCallback(completeBatch);
-
-        bulletinBoardClient.readBatch(batchSpecificationMessage, readBatchCallback);
-
-        jobSemaphore.acquire();
-
-    }
-
-    /**
-     * Tests that an unopened batch cannot be closed
-     * @throws CommunicationException, InterruptedException
-     */
-    @Test
-    public void testInvalidBatchClose() throws CommunicationException, InterruptedException {
-
-        final int NON_EXISTENT_BATCH_ID = 999;
-
-        CloseBatchMessage closeBatchMessage =
-                CloseBatchMessage.newBuilder()
-                        .setBatchId(NON_EXISTENT_BATCH_ID)
-                        .setBatchLength(1)
-                        .setSig(Crypto.Signature.getDefaultInstance())
-                        .setTimestamp(Timestamp.newBuilder()
-                                .setSeconds(9)
-                                .setNanos(12)
-                                .build())
-                        .build();
-
-        // Try to close the (unopened) batch;
-
-        bulletinBoardClient.closeBatch(closeBatchMessage, failPostCallback);
-
-        jobSemaphore.acquire();
-
-    }
-
-}

bulletin-board-client/src/test/java/meerkat/bulletinboard/LocalBulletinBoardClientTest.java

@@ -0,0 +1,107 @@
+package meerkat.bulletinboard;
+
+import meerkat.bulletinboard.sqlserver.*;
+import meerkat.comm.CommunicationException;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.security.SignatureException;
+import java.sql.Connection;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.List;
+
+import static org.junit.Assert.fail;
+
+/**
+ * Created by Arbel Deutsch Peled on 05-Dec-15.
+ */
+public class LocalBulletinBoardClientTest {
+
+    private static final int THREAD_NUM = 3;
+    private static final String DB_NAME = "TestDB";
+
+    // Tester
+    private GenericBulletinBoardClientTester clientTest;
+
+    public LocalBulletinBoardClientTest() throws CommunicationException {
+
+        H2QueryProvider queryProvider = new H2QueryProvider(DB_NAME) ;
+
+        try {
+
+            Connection conn = queryProvider.getDataSource().getConnection();
+            Statement stmt = conn.createStatement();
+
+            List<String> deletionQueries = queryProvider.getSchemaDeletionCommands();
+
+            for (String deletionQuery : deletionQueries) {
+                stmt.execute(deletionQuery);
+            }
+
+        } catch (SQLException e) {
+            System.err.println(e.getMessage());
+            throw new CommunicationException(e.getCause() + " " + e.getMessage());
+        }
+
+        BulletinBoardServer server = new BulletinBoardSQLServer(queryProvider);
+        server.init(DB_NAME);
+
+        LocalBulletinBoardClient client = new LocalBulletinBoardClient(server, THREAD_NUM);
+
+        clientTest = new GenericBulletinBoardClientTester(client);
+
+    }
+
+    // Test methods
+
+    /**
+     * Takes care of initializing the client and the test resources
+     */
+    @Before
+    public void init(){
+
+        clientTest.init();
+
+    }
+
+    /**
+     * Closes the client and makes sure the test fails when an exception occurred in a separate thread
+     */
+
+    @After
+    public void close() {
+
+        clientTest.close();
+
+    }
+
+    @Test
+    public void postTest() {
+
+        clientTest.postTest();
+
+    }
+
+    @Test
+    public void testBatchPost() throws CommunicationException, SignatureException, InterruptedException {
+
+        clientTest.testBatchPost();
+    }
+
+    @Test
+    public void testCompleteBatchPost() throws CommunicationException, SignatureException, InterruptedException {
+
+        clientTest.testCompleteBatchPost();
+
+    }
+
+    @Test
+    public void testInvalidBatchClose() throws CommunicationException, InterruptedException {
+
+        clientTest.testInvalidBatchClose();
+
+    }
+
+}

bulletin-board-server/src/main/java/meerkat/bulletinboard/sqlserver/BulletinBoardSQLServer.java

@@ -5,6 +5,7 @@ import java.util.*;
 
 import com.google.protobuf.*;
 
+import com.google.protobuf.Timestamp;
 import meerkat.bulletinboard.*;
 import meerkat.bulletinboard.sqlserver.mappers.*;
 import static meerkat.bulletinboard.BulletinBoardConstants.*;
@@ -26,6 +27,7 @@ import javax.sql.DataSource;
 
 import meerkat.util.BulletinBoardUtils;
 import meerkat.util.TimestampComparator;
+import org.springframework.jdbc.core.RowMapper;
 import org.springframework.jdbc.core.namedparam.MapSqlParameterSource;
 import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
 import org.springframework.jdbc.support.GeneratedKeyHolder;
@@ -586,14 +588,12 @@ public class BulletinBoardSQLServer implements BulletinBoardServer{
 
 	}
 
-
 	/**
-	 * Used to retrieve just basic information about messages to allow calculation of checksum
+	 * Private implementation of the message stub reader for returning result as a list
 	 * @param filterList is a filter list that defines which messages the client is interested in
-	 * @return a list of Bulletin Board Messages that contain just the entry number, timestamp and message ID for each message
+	 * @return the requested list of message stubs
-	 * 			The message ID is returned inside the message data field
      */
-	protected List<BulletinBoardMessage> readMessageStubs(MessageFilterList filterList) {
+	private List<BulletinBoardMessage> readMessageStubs(MessageFilterList filterList) {
 
 		StringBuilder sqlBuilder = new StringBuilder(50 * (filterList.getFilterCount() + 1));
 
@@ -635,6 +635,7 @@ public class BulletinBoardSQLServer implements BulletinBoardServer{
 
 	}
 
+
 	/**
 	 * This method returns a string representation of the tag associated with a batch ID
 	 * @param batchId is the given batch ID
@@ -644,6 +645,7 @@ public class BulletinBoardSQLServer implements BulletinBoardServer{
 		return BATCH_ID_TAG_PREFIX + Integer.toString(batchId);
 	}
 
+
 	/**
 	 * This method checks if a specified batch exists and is already closed
 	 * @param signerId is the ID of the publisher of the batch
@@ -687,6 +689,7 @@ public class BulletinBoardSQLServer implements BulletinBoardServer{
 
 	}
 
+
 	@Override
 	public BoolMsg beginBatch(BeginBatchMessage message) throws CommunicationException {
 
@@ -719,8 +722,10 @@ public class BulletinBoardSQLServer implements BulletinBoardServer{
 		jdbcTemplate.batchUpdate(sql,namedParameters);
 
 		return BoolMsg.newBuilder().setValue(true).build();
+
 	}
 
+
 	@Override
 	public BoolMsg postBatchMessage(BatchMessage batchMessage) throws CommunicationException{
 
@@ -744,6 +749,7 @@ public class BulletinBoardSQLServer implements BulletinBoardServer{
 
 	}
 
+
 	@Override
 	public BoolMsg closeBatchMessage(CloseBatchMessage message) throws CommunicationException {
 
@@ -767,13 +773,12 @@ public class BulletinBoardSQLServer implements BulletinBoardServer{
 			return BoolMsg.newBuilder().setValue(false).build();
 		}
 
-
 		// Get Tags and add them to CompleteBatch
 
 		sql = sqlQueryProvider.getSQLString(QueryType.GET_BATCH_TAGS);
 		namedParameters = new MapSqlParameterSource();
 
-		namedParameters.addValue(QueryType.GET_BATCH_TAGS.getParamName(0),signerId);
+		namedParameters.addValue(QueryType.GET_BATCH_TAGS.getParamName(0),signerId.toByteArray());
 		namedParameters.addValue(QueryType.GET_BATCH_TAGS.getParamName(1),batchId);
 
 		List<String> tags = jdbcTemplate.query(sql, namedParameters, new StringMapper());
@@ -847,6 +852,7 @@ public class BulletinBoardSQLServer implements BulletinBoardServer{
 		return BoolMsg.newBuilder().setValue(true).build();
 	}
 
+
 	@Override
 	public void readBatch(BatchSpecificationMessage message, MessageOutputStream<BatchData> out) throws CommunicationException, IllegalArgumentException{
 
@@ -866,6 +872,7 @@ public class BulletinBoardSQLServer implements BulletinBoardServer{
 
 	}
 
+
 	/**
 	 * Finds the entry number of the last entry in the database
 	 * @return the entry number, or -1 if no entries are found
@@ -884,10 +891,80 @@ public class BulletinBoardSQLServer implements BulletinBoardServer{
 
 	}
 
+	@Override
+	public SyncQuery generateSyncQuery(GenerateSyncQueryParams generateSyncQueryParams) {
+
+		if (generateSyncQueryParams == null
+				|| !generateSyncQueryParams.hasFilterList()
+				|| generateSyncQueryParams.getFilterList().getFilterCount() <= 0
+				|| generateSyncQueryParams.getBreakpointListCount() <= 0){
+
+			return SyncQuery.getDefaultInstance();
+
+		}
+
+		List<BulletinBoardMessage> messages = readMessageStubs(generateSyncQueryParams.getFilterList());
+
+		if (messages.size() <= 0){
+			return SyncQuery.newBuilder().build();
+		}
+
+		SyncQuery.Builder resultBuilder = SyncQuery.newBuilder();
+
+		Iterator<BulletinBoardMessage> messageIterator = messages.iterator();
+		Iterator<Float> breakpointIterator = generateSyncQueryParams.getBreakpointListList().iterator();
+
+		Checksum checksum = new SimpleChecksum();
+		checksum.setDigest(new SHA256Digest());
+
+		Timestamp lastTimestamp = Timestamp.getDefaultInstance();
+		BulletinBoardMessage message = messageIterator.next();
+		long currentMessageNum = 1;
+
+		boolean checksumChanged = true;
+
+		while (breakpointIterator.hasNext()){
+
+			Float breakpoint = breakpointIterator.next();
+
+			// Continue while breakpoint not reached, or it has been reached but no new timestamp has been encountered since
+			while ( messageIterator.hasNext()
+					&& ((float) currentMessageNum / (float) messages.size() <= breakpoint)
+					|| ((float) currentMessageNum / (float) messages.size() > breakpoint
+					&& lastTimestamp.equals(message.getMsg().getTimestamp()))){
+
+				checksumChanged = true;
+
+				checksum.update(message.getMsg().getData());
+
+				lastTimestamp = message.getMsg().getTimestamp();
+				message = messageIterator.next();
+
+			}
+
+			if (checksumChanged) {
+
+				checksum.update(message.getMsg().getData());
+				resultBuilder.addQuery(SingleSyncQuery.newBuilder()
+						.setTimeOfSync(message.getMsg().getTimestamp())
+						.setChecksum(checksum.getChecksum())
+						.build());
+
+			}
+
+			checksumChanged = false;
+
+		}
+
+		return resultBuilder.build();
+
+	}
+
+
 	/**
 	 * Searches for the latest time of sync of the DB relative to a given query and returns the metadata needed to complete the sync
-	 * The checksum up to (and including) each given timestamp is calculated using bitwise XOR on 8-byte sized blocks of the message IDs
+	 * The checksum up to (and including) each given timestamp is calculated using an instance of SimpleChecksum
-	 * @param syncQuery contains a succinct representation of states to compare to
+	 * @param syncQuery contains a succinct representation of states to compare against
 	 * @return the current last entry num and latest time of sync if there is one; -1 as last entry and empty timestamp otherwise
 	 * @throws CommunicationException
      */
@@ -960,6 +1037,7 @@ public class BulletinBoardSQLServer implements BulletinBoardServer{
 
 	}
 
+
 	@Override
 	public void close() {}
 

bulletin-board-server/src/main/java/meerkat/bulletinboard/sqlserver/mappers/MessageCallbackHandler.java

@@ -20,9 +20,9 @@ import java.util.List;
  */
 public class MessageCallbackHandler implements RowCallbackHandler {
 
-    NamedParameterJdbcTemplate jdbcTemplate;
+    private final NamedParameterJdbcTemplate jdbcTemplate;
-    SQLQueryProvider sqlQueryProvider;
+    private final SQLQueryProvider sqlQueryProvider;
-    MessageOutputStream<BulletinBoardMessage> out;
+    private final MessageOutputStream<BulletinBoardMessage> out;
 
     public MessageCallbackHandler(NamedParameterJdbcTemplate jdbcTemplate, SQLQueryProvider sqlQueryProvider, MessageOutputStream<BulletinBoardMessage> out) {
 

bulletin-board-server/src/main/java/meerkat/bulletinboard/sqlserver/mappers/MessageStubCallbackHandler.java

@@ -0,0 +1,59 @@
+package meerkat.bulletinboard.sqlserver.mappers;
+
+import com.google.protobuf.ByteString;
+import com.google.protobuf.InvalidProtocolBufferException;
+import meerkat.bulletinboard.sqlserver.BulletinBoardSQLServer.SQLQueryProvider.QueryType;
+import meerkat.comm.MessageOutputStream;
+import meerkat.protobuf.BulletinBoardAPI.BulletinBoardMessage;
+import meerkat.protobuf.BulletinBoardAPI.UnsignedBulletinBoardMessage;
+import meerkat.protobuf.Crypto;
+import meerkat.util.BulletinBoardUtils;
+import org.springframework.jdbc.core.RowCallbackHandler;
+import org.springframework.jdbc.core.namedparam.MapSqlParameterSource;
+import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
+
+import java.io.IOException;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.List;
+
+/**
+ * Created by Arbel Deutsch Peled on 21-Feb-16.
+ */
+public class MessageStubCallbackHandler implements RowCallbackHandler {
+
+    private final MessageOutputStream<BulletinBoardMessage> out;
+
+    public MessageStubCallbackHandler(MessageOutputStream<BulletinBoardMessage> out) {
+
+        this.out = out;
+
+    }
+
+    @Override
+    public void processRow(ResultSet rs) throws SQLException {
+
+        BulletinBoardMessage result;
+
+        result = BulletinBoardMessage.newBuilder()
+                .setEntryNum(rs.getLong(1))
+                .setMsg(UnsignedBulletinBoardMessage.newBuilder()
+                        .setData(ByteString.copyFrom(rs.getBytes(2)))
+                        .setTimestamp(BulletinBoardUtils.toTimestampProto(rs.getTimestamp(3)))
+                        .build())
+                .build();
+
+        try {
+
+            out.writeMessage(result);
+
+        } catch (IOException e) {
+
+            //TODO: log
+            e.printStackTrace();
+
+        }
+
+    }
+
+}

bulletin-board-server/src/main/java/meerkat/bulletinboard/webapp/BulletinBoardWebApp.java

@@ -22,7 +22,7 @@ import static meerkat.rest.Constants.*;
 
 import java.io.IOException;
 import java.io.OutputStream;
-import java.util.List;
+import java.util.Collection;
 
 /**
  * An implementation of the BulletinBoardServer which functions as a WebApp
@@ -183,6 +183,21 @@ public class BulletinBoardWebApp implements BulletinBoardServer, ServletContextL
 		}
 	}
 
+	@Path(GENERATE_SYNC_QUERY_PATH)
+	@POST
+	@Consumes(MEDIATYPE_PROTOBUF)
+	@Produces(MEDIATYPE_PROTOBUF)
+	@Override
+	public SyncQuery generateSyncQuery(GenerateSyncQueryParams generateSyncQueryParams) throws CommunicationException {
+		try {
+			init();
+			return bulletinBoard.generateSyncQuery(generateSyncQueryParams);
+		} catch (CommunicationException | IllegalArgumentException e) {
+			System.err.println(e.getMessage());
+			return null;
+		}
+	}
+
 	@Path(READ_BATCH_PATH)
 	@POST
 	@Consumes(MEDIATYPE_PROTOBUF)

meerkat-common/src/main/java/meerkat/bulletinboard/AsyncBulletinBoardClient.java

@@ -11,10 +11,6 @@ import java.util.List;
  */
 public interface AsyncBulletinBoardClient extends BulletinBoardClient {
 
-    public interface MessageHandler {
-        void handleNewMessages(List<BulletinBoardMessage> messageList);
-    }
-
     /**
      * Post a message to the bulletin board in an asynchronous manner
      * @param msg is the message to be posted
@@ -100,11 +96,12 @@ public interface AsyncBulletinBoardClient extends BulletinBoardClient {
      */
     public void readBatch(BatchSpecificationMessage batchSpecificationMessage, FutureCallback<CompleteBatch> callback);
 
+
     /**
-     * Subscribes to a notifier that will return any new messages on the server that match the given filters
+     * Perform a Sync Query on the bulletin board
-     * @param filterList defines the set of filters for message retrieval
+     * @param syncQuery defines the query
-     * @param messageHandler defines the handler for new messages received
+     * @param callback is a callback for handling the result of the query
      */
-    public void subscribe(MessageFilterList filterList, MessageHandler messageHandler);
+    public void querySync(SyncQuery syncQuery, FutureCallback<SyncQueryResponse> callback);
 
 }

meerkat-common/src/main/java/meerkat/bulletinboard/BulletinBoardClient.java

@@ -5,6 +5,7 @@ import meerkat.protobuf.Voting.*;
 
 import static meerkat.protobuf.BulletinBoardAPI.*;
 
+import java.util.Collection;
 import java.util.List;
 
 /**
@@ -26,8 +27,6 @@ public interface BulletinBoardClient {
      */
     MessageID postMessage(BulletinBoardMessage msg) throws CommunicationException;
 
-
-
     /**
      * Check how "safe" a given message is in a synchronous manner
      * @param id is the unique message identifier for retrieval
@@ -40,11 +39,21 @@ public interface BulletinBoardClient {
      * Note that if messages haven't been "fully posted", this might return a different
      * set of messages in different calls. However, messages that are fully posted
      * are guaranteed to be included.
-     * @param filterList return only messages that match the filters (null means no filtering).
+     * @param filterList return only messages that match the filters (null means no filtering)
      * @return the list of messages
      */
     List<BulletinBoardMessage> readMessages(MessageFilterList filterList);
 
+    /**
+     * Create a SyncQuery to test against that corresponds with the current server state for a specific filter list
+     * Should only be called on instances for which the actual server contacted is known (i.e. there is only one server)
+     * @param GenerateSyncQueryParams defines the required information needed to generate the query
+     *                    These are represented as fractions of the total number of relevant messages
+     * @return The generated SyncQuery
+     * @throws CommunicationException when no DB can be contacted
+     */
+    SyncQuery generateSyncQuery(GenerateSyncQueryParams GenerateSyncQueryParams) throws CommunicationException;
+
     /**
      * Closes all connections, if any.
      * This is done in a synchronous (blocking) way.

meerkat-common/src/main/java/meerkat/bulletinboard/BulletinBoardConstants.java

@@ -8,6 +8,7 @@ public interface BulletinBoardConstants {
     // Relative addresses for Bulletin Board operations
 
     public static final String BULLETIN_BOARD_SERVER_PATH = "/bbserver";
+    public static final String GENERATE_SYNC_QUERY_PATH = "/generatesyncquery";
     public static final String READ_MESSAGES_PATH = "/readmessages";
     public static final String READ_BATCH_PATH = "/readbatch";
     public static final String POST_MESSAGE_PATH = "/postmessage";

meerkat-common/src/main/java/meerkat/bulletinboard/BulletinBoardServer.java

@@ -4,6 +4,8 @@ import meerkat.comm.CommunicationException;
 import meerkat.comm.MessageOutputStream;
 import meerkat.protobuf.BulletinBoardAPI.*;
 
+import java.util.Collection;
+
 
 /**
  * Created by Arbel on 07/11/15.
@@ -28,7 +30,7 @@ public interface BulletinBoardServer{
 	 * @throws CommunicationException on DB connection error
      */
 	public BoolMsg postMessage(BulletinBoardMessage msg) throws CommunicationException;
-	 
+
 	 /**
 	  * Read all messages posted matching the given filter
 	  * @param filterList return only messages that match the filters (empty list or null means no filtering)
@@ -77,6 +79,13 @@ public interface BulletinBoardServer{
      */
 	public void readBatch(BatchSpecificationMessage message, MessageOutputStream<BatchData> out) throws CommunicationException, IllegalArgumentException;
 
+	/**
+	 * Create a SyncQuery to test against that corresponds with the current server state for a specific filter list
+	 * @param generateSyncQueryParams defines the information needed to generate the query
+	 * @return The generated SyncQuery
+	 * @throws CommunicationException on DB connection error
+	 */
+	SyncQuery generateSyncQuery(GenerateSyncQueryParams generateSyncQueryParams) throws CommunicationException;
 
 	/**
 	 * Queries the database for sync status with respect to a given sync query

meerkat-common/src/main/java/meerkat/bulletinboard/BulletinBoardSubscriber.java

@@ -0,0 +1,32 @@
+package meerkat.bulletinboard;
+
+import com.google.common.util.concurrent.FutureCallback;
+import meerkat.protobuf.BulletinBoardAPI.BulletinBoardMessage;
+import meerkat.protobuf.BulletinBoardAPI.MessageFilterList;
+
+import java.util.List;
+
+/**
+ * Created by Arbel Deutsch Peled on 03-Mar-16.
+ * This interface defines the behaviour required from a subscription service to Bulletin Board messages
+ */
+public interface BulletinBoardSubscriber {
+
+    /**
+     * Subscribes to a notifier that will return any new messages on the server that match the given filters
+     * In case of communication error: the subscription is terminated
+     * @param filterList defines the set of filters for message retrieval
+     * @param callback defines how to handle new messages received and/or a failures in communication
+     */
+    public void subscribe(MessageFilterList filterList, FutureCallback<List<BulletinBoardMessage>> callback);
+
+    /**
+     * Subscribes to a notifier that will return any new messages on the server that match the given filters
+     * In case of communication error: the subscription is terminated
+     * @param filterList defines the set of filters for message retrieval
+     * @param startEntry defines the first entry number to consider
+     * @param callback defines how to handle new messages received and/or a failures in communication
+     */
+    public void subscribe(MessageFilterList filterList, long startEntry, FutureCallback<List<BulletinBoardMessage>> callback);
+
+}

meerkat-common/src/main/java/meerkat/bulletinboard/BulletinBoardSynchronizer.java

@@ -0,0 +1,22 @@
+package meerkat.bulletinboard;
+
+/**
+ * Created by Arbel Deutsch Peled on 08-Mar-16.
+ * This interface defines the behaviour of a bulletin board synchronizer
+ * This is used to make sure that data in a specific instance of a bulletin board server is duplicated to a sufficient percentage of the other servers
+ */
+public interface BulletinBoardSynchronizer extends Runnable{
+
+    /**
+     *
+     * @param localClient is a client for the local DB instance
+     * @param remoteClient is a client for the remote DBs
+     * @param minRedundancy
+     */
+    public void init(BulletinBoardClient localClient, AsyncBulletinBoardClient remoteClient, float minRedundancy);
+
+    @Override
+    public void run();
+
+
+}

meerkat-common/src/main/java/meerkat/bulletinboard/CompleteBatch.java

@@ -139,7 +139,12 @@ public class CompleteBatch {
 
     @Override
     public String toString() {
+
+        if (beginBatchMessage == null || beginBatchMessage.getSignerId() == null)
+            return "Unspecified batch " + super.toString();
+
         return "Batch " + beginBatchMessage.getSignerId().toString() + ":" + beginBatchMessage.getBatchId();
+
     }
 
 }

meerkat-common/src/main/java/meerkat/bulletinboard/SubscriptionAsyncBulletinBoardClient.java

@@ -0,0 +1,7 @@
+package meerkat.bulletinboard;
+
+/**
+ * Created by Arbel Deutsch Peled on 03-Mar-16.
+ */
+public interface SubscriptionAsyncBulletinBoardClient extends AsyncBulletinBoardClient, BulletinBoardSubscriber {
+}

meerkat-common/src/main/proto/meerkat/BulletinBoardAPI.proto

@@ -146,6 +146,18 @@ message SyncQuery {
 
 }
 
+// This message defines the required information for generation of a SyncQuery instance by the server
+message GenerateSyncQueryParams {
+
+    // Defines the set of messages required
+    MessageFilterList filterList = 1;
+
+    // Defines the locations in the list of messages to calculate single sync queries for
+    // The values should be between 0.0 and 1.0 and define the location in fractions of the size of the message set
+    repeated float breakpointList = 2;
+
+}
+
 // This message defines the server's response format to a sync query
 message SyncQueryResponse {