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https://issues.apache.org/jira/browse/CASSANDRA-19580?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17840241#comment-17840241
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Cameron Zemek commented on CASSANDRA-19580:
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Yeah so what breaks if use same state as when replacing with different address?
I looked through CASSANDRA-8523 and didn't understand what different about
replacing when reusing the same IP address. Why isn't the node in UJ state when
doing replacements, that is receiving writes but not reads.
What do you think would be the correct fix here? Is sending an empty SYN like
shadow round okay? Why does examineGossiper not send back states for missing
digests (it only compares for the digests in the SYN)?
Considering that SYN messages are sent randomly, it seems like could also end
up with this 'Unable to contact any seeds!' path if none of the nodes randomly
pick the replacement node to send a SYN to.
> Unable to contact any seeds with node in hibernate status
> ---------------------------------------------------------
>
> Key: CASSANDRA-19580
> URL: https://issues.apache.org/jira/browse/CASSANDRA-19580
> Project: Cassandra
> Issue Type: Bug
> Reporter: Cameron Zemek
> Priority: Normal
>
> We have customer running into the error 'Unable to contact any seeds!' . I
> have been able to reproduce this issue if I kill Cassandra as its joining
> which will put the node into hibernate status. Once a node is in hibernate it
> will no longer receive any SYN messages from other nodes during startup and
> as it sends only itself as digest in outbound SYN messages it never receives
> any states in any of the ACK replies. So once it gets to the check
> `seenAnySeed` in it fails as the endpointStateMap is empty.
>
> A workaround is copying the system.peers table from other node but this is
> less than ideal. I tested modifying maybeGossipToSeed as follows:
> {code:java}
> /* Possibly gossip to a seed for facilitating partition healing */
> private void maybeGossipToSeed(MessageOut<GossipDigestSyn> prod)
> {
> int size = seeds.size();
> if (size > 0)
> {
> if (size == 1 &&
> seeds.contains(FBUtilities.getBroadcastAddress()))
> {
> return;
> }
> if (liveEndpoints.size() == 0)
> {
> List<GossipDigest> gDigests = prod.payload.gDigests;
> if (gDigests.size() == 1 &&
> gDigests.get(0).endpoint.equals(FBUtilities.getBroadcastAddress()))
> {
> gDigests = new ArrayList<GossipDigest>();
> GossipDigestSyn digestSynMessage = new
> GossipDigestSyn(DatabaseDescriptor.getClusterName(),
>
> DatabaseDescriptor.getPartitionerName(),
>
> gDigests);
> MessageOut<GossipDigestSyn> message = new
> MessageOut<GossipDigestSyn>(MessagingService.Verb.GOSSIP_DIGEST_SYN,
>
> digestSynMessage,
>
> GossipDigestSyn.serializer);
> sendGossip(message, seeds);
> }
> else
> {
> sendGossip(prod, seeds);
> }
> }
> else
> {
> /* Gossip with the seed with some probability. */
> double probability = seeds.size() / (double)
> (liveEndpoints.size() + unreachableEndpoints.size());
> double randDbl = random.nextDouble();
> if (randDbl <= probability)
> sendGossip(prod, seeds);
> }
> }
> }
> {code}
> Only problem is this is the same as SYN from shadow round. It does resolve
> the issue however as then receive an ACK with all the states.
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