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My experience is that DNS discovery fails when 1 node out of 3 is down, and discovery spends all of maxDiscoverAttempts trying to get gossip from the node that is down, instead of also considering the other 2 nodes' IPs registered with a multi-address DNS name.
I was able to implement the behaviour I expect like this
# ClusterDiscovery.java:
void discover(ConnectionState state) {
- List<InetSocketAddress> candidates = new ArrayList<>(this.seeds);
+ List<InetSocketAddress> candidates = new ArrayList<>();
+
+ if (state.getSettings().isDnsDiscover()) {
+ try {
+ InetSocketAddress dnsSeed = this.seeds.get(0);
+
+ // Resolve cluster DNS name
+ candidates = Arrays.stream(InetAddress.getAllByName(dnsSeed.getHostName()))
+ .map(addr -> new InetSocketAddress(addr, dnsSeed.getPort()))
+ .collect(Collectors.toList());
+
+ } catch (UnknownHostException e) {
+ throw new UncheckedIOException(e);
+ }
+ } else {
+ candidates = new ArrayList<>(this.seeds);
+ }
if (candidates.size() > 1) {I'm not sure, however, if you'd prefer to delegate somehow this behaviour to the gRPC client, since it's the gRPC client that currently does the lookup.
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