public int getPingInterval() {
    if (pingInterval < 0) {
      throw new IllegalStateException(
          "ping interval is only known for a subscription feed connection");
    }
    return pingInterval;
  }
returns the time between server-to-client ping messages on idle subscription connections
geode-core/src/main/java/org/apache/geode/internal/cache/tier/sockets/ServerQueueStatus.java