[#52317] android-client: Add exponential backoff to management WS rec…

…onnections

devices/android-client/app/src/main/java/com/antmicro/update/rdfm/mgmt/ManagementClient.java

@@ -7,6 +7,7 @@
 import com.antmicro.update.rdfm.Utils;
 import com.antmicro.update.rdfm.exceptions.DeviceUnauthorizedException;
 import com.antmicro.update.rdfm.exceptions.ServerConnectionException;
+import com.antmicro.update.rdfm.utilities.BackoffCounter;
 import com.antmicro.update.rdfm.utilities.HttpUtils;
 
 import java.util.HashMap;
@@ -22,6 +23,8 @@
 
 public final class ManagementClient extends WebSocketListener {
     private static final String TAG = "ManagementWS";
+    private static final long MIN_RECONNECT_INTERVAL_MILLIS = 1_000;
+    private static final long MAX_RECONNECT_INTERVAL_MILLIS = 120_000;
     private final String mServerAddress;
     private final int mMaxShellCount;
     private final IDeviceTokenProvider mTokenProvider;
@@ -122,11 +125,15 @@ public void onFailure(WebSocket webSocket, Throwable t, Response response) {
     }
 
     private void reconnectThread() {
+        BackoffCounter counter = new BackoffCounter(MIN_RECONNECT_INTERVAL_MILLIS, MAX_RECONNECT_INTERVAL_MILLIS);
         while (true) {
+            long sleepDurationMillis = counter.next();
+            Log.i(TAG, "Reconnecting in " + sleepDurationMillis + "ms..");
+
             // Delay until reconnection
             while (true) {
                 try {
-                    Thread.sleep(5000);
+                    Thread.sleep(sleepDurationMillis);
                     break;
                 } catch (InterruptedException e) {
                     // empty

devices/android-client/app/src/main/java/com/antmicro/update/rdfm/utilities/BackoffCounter.java

@@ -0,0 +1,38 @@
+package com.antmicro.update.rdfm.utilities;
+
+public class BackoffCounter {
+    private long mCurrent;
+    private final long mInitialValue;
+    private final long mMaxValue;
+
+    public BackoffCounter(long initialValue, long maxValue) {
+        if (initialValue > maxValue) {
+            throw new IllegalArgumentException("initialValue is larger than maxValue");
+        }
+        mCurrent = initialValue;
+        mInitialValue = initialValue;
+        mMaxValue = maxValue;
+    }
+
+    /**
+     * Advance the backoff counter and return the new value.
+     *
+     * @return new backoff value
+     */
+    public long next() {
+        mCurrent = Math.multiplyExact(mCurrent, 2L);
+        if (mCurrent > mMaxValue) {
+            mCurrent = mMaxValue;
+        }
+        return mCurrent;
+    }
+
+    /**
+     * Reset the counter to its initial value
+     */
+    public void reset() {
+        mCurrent = mInitialValue;
+    }
+
+
+}