Adjust update period based on lifetime and COAP_EXCHANGE_LIFETIME.

leshan-client-cf/src/main/java/org/eclipse/leshan/client/californium/CaliforniumEndpointsManager.java

@@ -189,6 +189,28 @@ public synchronized Collection<Server> createEndpoints(Collection<? extends Serv
         }
     }
 
+    @Override
+    public long getMaxCommunicationPeriodFor(Server server, long lifetimeInMs) {
+        // See https://github.com/OpenMobileAlliance/OMA_LwM2M_for_Developers/issues/283 to better understand.
+        // TODO For DTLS, worst Handshake scenario should be taking into account too.
+
+        int floor = 30000; // value from which we stop to adjust communication period using COAP EXCHANGE LIFETIME.
+
+        // To be sure registration doesn't expired, update request should be send considering all CoAP retransmissions
+        // and registration lifetime.
+        // See https://tools.ietf.org/html/rfc7252#section-4.8.2
+        long exchange_lifetime = coapConfig.getLong(NetworkConfig.Keys.EXCHANGE_LIFETIME, 247);
+        if (lifetimeInMs - exchange_lifetime >= floor) {
+            return lifetimeInMs - exchange_lifetime;
+        } else {
+            LOG.warn("Too small lifetime : we advice to not use a lifetime < (COAP EXCHANGE LIFETIME + 30s)");
+            // lifetime value is too short, so we do a compromise and we don't remove COAP EXCHANGE LIFETIME completely
+            // We distribute the remaining lifetime range [0, exchange_lifetime + floor] on the remaining range
+            // [1,floor]s.
+            return lifetimeInMs * (floor - 1000) / (exchange_lifetime + floor) + 1000;
+        }
+    }
+
     @Override
     public synchronized void forceReconnection(Server server) {
         // TODO support multi server

leshan-client-core/src/main/java/org/eclipse/leshan/client/EndpointsManager.java

@@ -26,6 +26,8 @@ public interface EndpointsManager {
 
     Collection<Server> createEndpoints(Collection<? extends ServerInfo> serverInfo);
 
+    long getMaxCommunicationPeriodFor(Server server, long lifetimeInSeconds);
+
     void forceReconnection(Server server);
 
     void start();

leshan-client-core/src/main/java/org/eclipse/leshan/client/engine/DefaultRegistrationEngine.java

@@ -70,16 +70,15 @@ public class DefaultRegistrationEngine implements RegistrationEngine {
 
     private static final long NOW = 0;
 
-    // We choose a default timeout a bit higher to the MAX_TRANSMIT_WAIT(62-93s) which is the time from starting to
-    // send a Confirmable message to the time when an acknowledgement is no longer expected.
+    // Timeout for bootstrap/register/update request
     private final long requestTimeoutInMs;
     // de-registration is only used on stop/destroy for now.
     private final long deregistrationTimeoutInMs;
-    // bootstrap timeout
+    // Bootstrap session timeout
     private final int bootstrapSessionTimeoutInSec;
-    // time between bootstrap retry should be configurable and incremental
+    // Time between bootstrap retry should incremental
     private final int retryWaitingTimeInMs;
-    // time between 2 update requests (used only if it is smaller than the lifetime)
+    // Time between 2 update requests (used only if it is smaller than the lifetime)
     private Integer communicationPeriodInMs;
 
     private static enum Status {
@@ -278,7 +277,7 @@ private Status register(Server server) throws InterruptedException {
                 LOG.info("Registered with location '{}'.", registrationID);
 
                 // Update every lifetime period
-                long delay = calculateNextUpdate(dmInfo.lifetime);
+                long delay = calculateNextUpdate(server, dmInfo.lifetime);
                 scheduleUpdate(server, registrationID, new RegistrationUpdate(), delay);
 
                 if (observer != null) {
@@ -385,7 +384,7 @@ private Status update(Server server, String registrationID, RegistrationUpdate r
             } else if (response.getCode() == ResponseCode.CHANGED) {
                 // Update successful, so we reschedule new update
                 LOG.info("Registration update succeed.");
-                long delay = calculateNextUpdate(dmInfo.lifetime);
+                long delay = calculateNextUpdate(server, dmInfo.lifetime);
                 scheduleUpdate(server, registrationID, new RegistrationUpdate(), delay);
                 if (observer != null) {
                     observer.onUpdateSuccess(server, registrationID);
@@ -405,13 +404,12 @@ private Status update(Server server, String registrationID, RegistrationUpdate r
         }
     }
 
-    private long calculateNextUpdate(long lifetimeInSeconds) {
-        // lifetime - 10%
-        // life time is in seconds and we return the delay in milliseconds
+    private long calculateNextUpdate(Server server, long lifetimeInSeconds) {
+        long maxComminucationPeriod = endpointsManager.getMaxCommunicationPeriodFor(server, lifetimeInSeconds * 1000);
         if (communicationPeriodInMs != null) {
-            return Math.min(communicationPeriodInMs, lifetimeInSeconds * 900l);
+            return Math.min(communicationPeriodInMs, maxComminucationPeriod);
         } else {
-            return lifetimeInSeconds * 900l;
+            return maxComminucationPeriod;
         }
     }