Exposing an interface that allows the fine tuning of the alpha parameter used to calculate the exponential moving average of measured latencies

graphenej/src/main/java/cy/agorise/graphenej/api/android/NetworkService.java

@@ -58,6 +58,7 @@ import cy.agorise.graphenej.network.NodeProvider;
 import cy.agorise.graphenej.operations.CustomOperation;
 import cy.agorise.graphenej.operations.LimitOrderCreateOperation;
 import cy.agorise.graphenej.operations.TransferOperation;
+import cy.agorise.graphenej.stats.ExponentialMovingAverage;
 import io.reactivex.Observer;
 import io.reactivex.android.schedulers.AndroidSchedulers;
 import io.reactivex.annotations.Nullable;
@@ -79,29 +80,69 @@ public class NetworkService extends Service {
     public static final int NORMAL_CLOSURE_STATUS = 1000;
 
     // Time to wait before retrying a connection attempt
-    private final int DEFAULT_RETRY_DELAY = 5000;
+    private final int DEFAULT_RETRY_DELAY = 500;
 
+    /**
+     * Constant to be used as a key in order to pass the user name information, in case the
+     * provided API nodes might require this information.
+     */
     public static final String KEY_USERNAME = "key_username";
 
+    /**
+     * Constant to be used as a key in order to pass the password information, in case the
+     * provided API nodes might require this information.
+     * <p>
+     * This information should be passed as an intent extra when calling the bindService
+     * or startService methods.
+     */
     public static final String KEY_PASSWORD = "key_password";
 
+    /**
+     * Constant used as a key in order to specify which APIs the application will be requiring.
+     * <p>
+     * This information should be passed as an intent extra when calling the bindService
+     * or startService methods.
+     */
     public static final String KEY_REQUESTED_APIS = "key_requested_apis";
 
+    /**
+     * Constant used as a key in order to let the NetworkService know whether or not it should
+     * start a recurring node latency verification task.
+     * <p>
+     * This information should be passed as an intent extra when calling the bindService
+     * or startService methods.
+     */
     public static final String KEY_ENABLE_LATENCY_VERIFIER = "key_enable_latency_verifier";
 
+    /**
+     * Constant used as a key in order to specify the alpha (or smoothing) factor to be used in
+     * the exponential moving average calculated from the different latency samples. This only
+     * makes sense if the latency verification feature is enabled of course.
+     * <p>
+     * This information should be passed as an intent extra when calling the bindService
+     * or startService methods.
+     */
+    public static final String KEY_NODE_LATENCY_SMOOTHING_FACTOR = "key_node_latency_smoothing_factor";
+
     /**
      * Key used to pass via intent a boolean extra to specify whether the connection should
      * be automatically established.
+     * <p>
+     * This information should be passed as an intent extra when calling the bindService
+     * or startService methods.
      */
     public static final String KEY_AUTO_CONNECT = "key_auto_connect";
 
     /**
      * Key used to pass via intent a list of node URLs. The value passed should be a String
      * containing a simple comma separated list of URLs.
-     *
+     * <p>
      * For example:
      *
      *      wss://domain1.com/ws,wss://domain2.com/ws,wss://domain3.com/ws
+     * <p>
+     * This information should be passed as an intent extra when calling the bindService
+     * or startService methods.
      */
     public static final String KEY_NODE_URLS = "key_node_urls";
 
@@ -264,9 +305,10 @@ public class NetworkService extends Service {
             // a first round of measurements in order to be sure to select the
             // best node.
             if(verifyNodeLatency){
+                double alpha = extras.getDouble(KEY_NODE_LATENCY_SMOOTHING_FACTOR, ExponentialMovingAverage.DEFAULT_ALPHA);
                 ArrayList<FullNode> fullNodes = new ArrayList<>();
                 for(String url : urls){
-                    fullNodes.add(new FullNode(url));
+                    fullNodes.add(new FullNode(url, alpha));
                 }
                 nodeLatencyVerifier = new NodeLatencyVerifier(fullNodes);
                 fullNodePublishSubject = nodeLatencyVerifier.start();

graphenej/src/main/java/cy/agorise/graphenej/api/android/NetworkServiceManager.java

@@ -15,6 +15,8 @@ import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
 
+import cy.agorise.graphenej.stats.ExponentialMovingAverage;
+
 /**
  * This class should be instantiated at the application level of the android app.
  *
@@ -52,6 +54,7 @@ public class NetworkServiceManager implements Application.ActivityLifecycleCallb
     private List<String> mCustomNodeUrls = new ArrayList<>();
     private boolean mAutoConnect;
     private boolean mVerifyLatency;
+    private double alpha;
 
     /**
      * Runnable used to schedule a service disconnection once the app is not visible to the user for
@@ -194,6 +197,7 @@ public class NetworkServiceManager implements Application.ActivityLifecycleCallb
         private List<String> customNodeUrls;
         private boolean autoconnect = true;
         private boolean verifyNodeLatency;
+        private double alpha = ExponentialMovingAverage.DEFAULT_ALPHA;
 
         /**
          * Sets the user name, if required to connect to a node.
@@ -269,6 +273,17 @@ public class NetworkServiceManager implements Application.ActivityLifecycleCallb
             return this;
         }
 
+        /**
+         * Sets the node latency verification's exponential moving average alpha parameter.
+         * @param alpha The alpha parameter to use when computing the exponential moving average of the
+         *              measured latencies.
+         * @return              The Builder instance.
+         */
+        public Builder setLatencyAverageAlpha(double alpha){
+            this.alpha = alpha;
+            return this;
+        }
+
         /**
          * Method used to build a {@link NetworkServiceManager} instance with all of the characteristics
          * passed as parameters.

graphenej/src/main/java/cy/agorise/graphenej/network/FullNode.java

@@ -8,14 +8,35 @@ import cy.agorise.graphenej.stats.ExponentialMovingAverage;
 public class FullNode implements Comparable {
 
     private String mUrl;
-    private ExponentialMovingAverage latency;
+    private ExponentialMovingAverage mLatency;
     private boolean isConnected;
 
     private FullNode(){}
 
+    /**
+     * Constructor used to specify both the node URL and the alpha parameter that one wishes to set the
+     * exponential moving average with.
+     * <p>
+     * The alpha parameter represents the degree of weighting decrease, and can be specified as any value
+     * between 0 and 1. A higher alpha discounts older observations faster.
+     *
+     * @param url       The node URL.
+     * @param alpha     The alpha parameter used to compute the exponential moving average.
+     */
+    public FullNode(String url, double alpha){
+        mLatency = new ExponentialMovingAverage(alpha);
+        mUrl = url;
+    }
+
+    /**
+     * Constructor used to specify only the node URL.
+     * <p>
+     * The alpha parameter is set to the value specified at {@link ExponentialMovingAverage#DEFAULT_ALPHA}
+     *
+     * @param url   The node URL.
+     */
     public FullNode(String url){
-        latency = new ExponentialMovingAverage(ExponentialMovingAverage.DEFAULT_ALPHA);
+        this(url, ExponentialMovingAverage.DEFAULT_ALPHA);
-        this.mUrl = url;
     }
 
     /**
@@ -39,7 +60,7 @@ public class FullNode implements Comparable {
      * @return  The exponential moving average object instance
      */
     public ExponentialMovingAverage getLatencyAverage(){
-        return latency;
+        return mLatency;
     }
 
     /**
@@ -47,7 +68,7 @@ public class FullNode implements Comparable {
      * @return  The latest latency average value
      */
     public double getLatencyValue() {
-        return latency.getAverage();
+        return mLatency.getAverage();
     }
 
     public boolean isConnected() {
@@ -59,17 +80,17 @@ public class FullNode implements Comparable {
     }
 
     /**
-     * Method that updates the latency average with a new value.
+     * Method that updates the mLatency average with a new value.
-     * @param latency   Most recent latency sample to be added to the exponential average
+     * @param latency   Most recent mLatency sample to be added to the exponential average
      */
     public void addLatencyValue(double latency) {
-        this.latency.updateValue(latency);
+        this.mLatency.updateValue(latency);
     }
 
     @Override
     public int compareTo(Object o) {
         FullNode node = (FullNode) o;
-        return (int) Math.ceil(latency.getAverage() - node.getLatencyValue());
+        return (int) Math.ceil(mLatency.getAverage() - node.getLatencyValue());
     }
 
     @Override

graphenej/src/main/java/cy/agorise/graphenej/network/NodeLatencyVerifier.java

@@ -154,7 +154,6 @@ public class NodeLatencyVerifier {
                     long before = timestamps.get(fullNode);
                     delay = after - before;
                 }
-
                 fullNode.addLatencyValue(delay);
                 subject.onNext(fullNode);
             }else{

sample/src/main/java/cy/agorise/labs/sample/SampleApplication.java

@@ -38,6 +38,7 @@ public class SampleApplication extends Application {
                 .setCustomNodeUrls(nodes)
                 .setAutoConnect(true)
                 .setNodeLatencyVerification(true)
+                .setLatencyAverageAlpha(0.1f)
                 .build(this);
 
         // Registering this class as a listener to all activity's callback cycle events, in order to