Refactor SNMP devices' sessions establishing

common/transport/snmp/src/main/java/org/thingsboard/server/transport/snmp/SnmpTransportContext.java

@@ -55,7 +55,6 @@ import java.util.Optional;
 import java.util.UUID;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentLinkedDeque;
-import java.util.stream.Collectors;
 
 @TbSnmpTransportComponent
 @Component
@@ -72,25 +71,30 @@ public class SnmpTransportContext extends TransportContext {
     private final SnmpAuthService snmpAuthService;
 
     private final Map<DeviceId, DeviceSessionContext> sessions = new ConcurrentHashMap<>();
-    private Collection<DeviceId> allSnmpDevicesIds = new ConcurrentLinkedDeque<>();
+    private final Collection<DeviceId> allSnmpDevicesIds = new ConcurrentLinkedDeque<>();
 
     @AfterStartUp(order = 2)
-    public void initDevicesSessions() {
+    public void fetchDevicesAndEstablishSessions() {
         log.info("Initializing SNMP devices sessions");
-        allSnmpDevicesIds = protoEntityService.getAllSnmpDevicesIds().stream()
-                .map(DeviceId::new)
-                .collect(Collectors.toList());
-        log.trace("Found all SNMP devices ids: {}", allSnmpDevicesIds);
 
-        List<DeviceId> managedDevicesIds = allSnmpDevicesIds.stream()
-                .filter(deviceId -> balancingService.isManagedByCurrentTransport(deviceId.getId()))
-                .collect(Collectors.toList());
-        log.info("SNMP devices managed by current SNMP transport: {}", managedDevicesIds);
+        int batchIndex = 0;
+        int batchSize = 512;
+        boolean nextBatchExists = true;
 
-        managedDevicesIds.stream()
-                .map(protoEntityService::getDeviceById)
-                .collect(Collectors.toList())
-                .forEach(this::establishDeviceSession);
+        while (nextBatchExists) {
+            TransportProtos.GetSnmpDevicesResponseMsg snmpDevicesResponse = protoEntityService.getSnmpDevicesIds(batchIndex, batchSize);
+            snmpDevicesResponse.getIdsList().stream()
+                    .map(id -> new DeviceId(UUID.fromString(id)))
+                    .peek(allSnmpDevicesIds::add)
+                    .filter(deviceId -> balancingService.isManagedByCurrentTransport(deviceId.getId()))
+                    .map(protoEntityService::getDeviceById)
+                    .forEach(device -> getExecutor().execute(() -> establishDeviceSession(device)));
+
+            nextBatchExists = snmpDevicesResponse.getHasNextPage();
+            batchIndex++;
+        }
+
+        log.debug("Found all SNMP devices ids: {}", allSnmpDevicesIds);
     }
 
     private void establishDeviceSession(Device device) {

common/transport/snmp/src/main/java/org/thingsboard/server/transport/snmp/service/ProtoTransportEntityService.java

@@ -81,26 +81,7 @@ public class ProtoTransportEntityService {
                 .orElseThrow(() -> new IllegalArgumentException("Device credentials not found"));
     }
 
-    public List<UUID> getAllSnmpDevicesIds() {
-        List<UUID> result = new ArrayList<>();
-
-        int page = 0;
-        int pageSize = 512;
-        boolean hasNextPage = true;
-
-        while (hasNextPage) {
-            TransportProtos.GetSnmpDevicesResponseMsg responseMsg = requestSnmpDevicesIds(page, pageSize);
-            result.addAll(responseMsg.getIdsList().stream()
-                    .map(UUID::fromString)
-                    .collect(Collectors.toList()));
-            hasNextPage = responseMsg.getHasNextPage();
-            page++;
-        }
-
-        return result;
-    }
-
-    private TransportProtos.GetSnmpDevicesResponseMsg requestSnmpDevicesIds(int page, int pageSize) {
+    public TransportProtos.GetSnmpDevicesResponseMsg getSnmpDevicesIds(int page, int pageSize) {
         TransportProtos.GetSnmpDevicesRequestMsg requestMsg = TransportProtos.GetSnmpDevicesRequestMsg.newBuilder()
                 .setPage(page)
                 .setPageSize(pageSize)