gossip: Implement GossipDigestSynVerbHandler

gms/gossiper.cc

@@ -13,6 +13,45 @@ gossiper::gossiper()
     init_messaging_service_handler();
 }
 
+/*
+ * First construct a map whose key is the endpoint in the GossipDigest and the value is the
+ * GossipDigest itself. Then build a list of version differences i.e difference between the
+ * version in the GossipDigest and the version in the local state for a given InetAddress.
+ * Sort this list. Now loop through the sorted list and retrieve the GossipDigest corresponding
+ * to the endpoint from the map that was initially constructed.
+*/
+void gossiper::do_sort(std::vector<gossip_digest>& g_digest_list) {
+    /* Construct a map of endpoint to GossipDigest. */
+    std::map<inet_address, gossip_digest> ep_to_digest_map;
+    for (auto g_digest : g_digest_list) {
+        ep_to_digest_map.emplace(g_digest.get_endpoint(), g_digest);
+    }
+
+    /*
+     * These digests have their maxVersion set to the difference of the version
+     * of the local EndpointState and the version found in the GossipDigest.
+    */
+    std::vector<gossip_digest> diff_digests;
+    for (auto g_digest : g_digest_list) {
+        auto ep = g_digest.get_endpoint();
+        auto ep_state = this->get_endpoint_state_for_endpoint(ep);
+        int version = ep_state ? this->get_max_endpoint_state_version(*ep_state) : 0;
+        int diff_version = ::abs(version - g_digest.get_max_version());
+        diff_digests.emplace_back(gossip_digest(ep, g_digest.get_generation(), diff_version));
+    }
+
+    g_digest_list.clear();
+    std::sort(diff_digests.begin(), diff_digests.end());
+    int size = diff_digests.size();
+    /*
+     * Report the digests in descending order. This takes care of the endpoints
+     * that are far behind w.r.t this local endpoint
+    */
+    for (int i = size - 1; i >= 0; --i) {
+        g_digest_list.emplace_back(ep_to_digest_map[diff_digests[i].get_endpoint()]);
+    }
+}
+
 void gossiper::init_messaging_service_handler() {
     ms().register_handler(messaging_verb::ECHO, [] (empty_msg msg) {
         return make_ready_future<empty_msg>();
@@ -22,20 +61,34 @@ void gossiper::init_messaging_service_handler() {
         get_local_failure_detector().force_conviction(from);
         return messaging_service::no_wait();
     });
-    ms().register_handler(messaging_verb::GOSSIP_DIGEST_SYN, [] (gossip_digest_syn msg) {
+    ms().register_handler(messaging_verb::GOSSIP_DIGEST_SYN, [this] (gossip_digest_syn syn_msg) {
         // TODO: Implement processing of incoming ACK2 message
-        print("gossiper: Server got syn msg = %s\n", msg);
-        auto ep = inet_address("2.2.2.2");
-        int32_t gen = 800;
-        int32_t ver = 900;
-        std::vector<gms::gossip_digest> digests{
-            {ep, gen++, ver++},
-        };
-        std::map<inet_address, endpoint_state> eps{
-            {ep, endpoint_state()},
-        };
-        gms::gossip_digest_ack ack(std::move(digests), std::move(eps));
-        return make_ready_future<gossip_digest_ack>(ack);
+        print("gossiper: Server got syn msg = %s\n", syn_msg);
+        inet_address from;
+        if (!this->is_enabled()) {
+            return make_ready_future<gossip_digest_ack>(gossip_digest_ack());
+        }
+
+        /* If the message is from a different cluster throw it away. */
+        // FIXME: DatabaseDescriptor.getClusterName and DatabaseDescriptor.getPartitionerName()
+#if 0
+        if (!syn_msg.cluster_id().equals(DatabaseDescriptor.getClusterName())) {
+            //logger.warn("ClusterName mismatch from {} {}!={}", from, syn_msg.clusterId, DatabaseDescriptor.getClusterName());
+            return;
+        }
+
+        if (syn_msg.partioner() != "" && !syn_msg.partioner.equals(DatabaseDescriptor.getPartitionerName())) {
+            logger.warn("Partitioner mismatch from {} {}!={}", from, syn_msg.partioner, DatabaseDescriptor.getPartitionerName());
+            return;
+        }
+#endif
+        auto g_digest_list = syn_msg.get_gossip_digests();
+        do_sort(g_digest_list);
+        std::vector<gossip_digest> delta_gossip_digest_list;
+        std::map<inet_address, endpoint_state> delta_ep_state_map;
+        this->examine_gossiper(g_digest_list, delta_gossip_digest_list, delta_ep_state_map);
+        gms::gossip_digest_ack ack_msg(std::move(delta_gossip_digest_list), std::move(delta_ep_state_map));
+        return make_ready_future<gossip_digest_ack>(std::move(ack_msg));
     });
     ms().register_handler_oneway(messaging_verb::GOSSIP_DIGEST_ACK2, [this] (gossip_digest_ack2 msg) {
         print("gossiper: Server got ack2 msg = %s\n", msg);

gms/gossiper.hh

@@ -85,6 +85,7 @@ private:
     shard_id get_shard_id(inet_address to) {
         return shard_id{to, _default_cpuid};
     }
+    void do_sort(std::vector<gossip_digest>& g_digest_list);
     timer<lowres_clock> _scheduled_gossip_task;
 private:
     inet_address get_broadcast_address() {