Methods for active-active stateful network service cluster

A non-transitory machine readable medium storing a program for execution by a set of processing units of a first service node to provide a service, the program comprising sets of instructions for:

• at the first service node of a service node cluster that provides the service for a plurality of data message flows addressed to destination compute nodes:
• receiving, from a forwarding element that selects the first service node as a primary service node for a particular data message flow, a data message in the particular data message flow and providing the service to the data message;
• identifying, based on a first membership state of the service node cluster, a second service node as a secondary service node for the particular data message flow in case the first service node is unavailable and sending service state information to the second service node to use in case the second service node has to provide the service to the particular data message flow;
• detecting a modified, second membership state of the service node cluster;
• and
• identifying, based on the second membership state of the service node cluster, a third service node as a secondary service node for the particular data message flow and sending service state information for the particular data message flow to the third service node to use in case the third service node has to provide the service to the particular data message flow.