krummas commented on code in PR #4613:
URL: https://github.com/apache/cassandra/pull/4613#discussion_r2896103534
##########
src/java/org/apache/cassandra/tcm/Startup.java:
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@@ -184,6 +239,128 @@ public static void
initializeAsNonCmsNode(Function<Processor, Processor> wrapPro
}
}
+
+ /**
+ * If the broadcast address of this node has changed, we must verify the
endpoints it knows for
+ * the members of the CMS are still reachable and valid. This is necessary
for the node to submit
+ * a STARTUP transformation which updates its broadcast address in
ClusterMetadata.
+ *
+ * If the node is itself a CMS member, it is also a requirement to be able
to contact a
+ * majority of the other CMS members in order to perform the serial reads
and writes which
+ * constitute committing to and fetching from the distributed metadata log.
+ *
+ * To do this, we use a simple protocol:
+ * 1. For each CMS member in our replayed ClusterMetadata, ping the
associated broadcast address
+ * to query for id of the node at that address. This determines whether
the endpoint still
+ * belongs to that same node (which is/was a CMS member).
+ * 2. While we don't have confirmed current addresses for a majority of
CMS nodes:
+ * 2a. Run discovery to locate as many peer addresses as possible.
+ * 2b. Query every discovered endpoint and ask for its node id.
+ * If we still don't have confirmed addresses for a majority of CMS
members, go to 2a and
+ * repeat as peers may themselves still be starting up and so may have
become discoverable.
+ *
+ * This process builds up a mapping of id -> current address for CMS
members which can then be
+ * used to construct a set of temporary redirects between addresses
according to ClusterMetadata
+ * and the newly discovered ones.
+ *
+ * As each CMS node with a changed address goes through the startup
process, it will commit its
+ * STARTUP transformation and the new broadcast address will be found in
ClusterMetadata. A log
+ * listener is used to react to these transformations by removing
redundant address overrides
+ * as they are enacted.
+ *
+ * @param nodeId derived from the persisted id of this node from the
system.peers table
+ * @param replayed current ClusterMetadata after replaying the metadata
log for startup
+ */
+ private static ClusterMetadata initializeCMSLookup(NodeId nodeId,
ClusterMetadata replayed)
+ {
+ InetAddressAndPort oldAddress = replayed.directory.endpoint(nodeId);
+ InetAddressAndPort newAddress =
FBUtilities.getBroadcastAddressAndPort();
+ if (newAddress.equals(oldAddress))
+ return replayed;
+
+ Map<NodeId, InetAddressAndPort> previousCMS = new HashMap<>();
+ replayed.fullCMSMemberIds().forEach(id -> previousCMS.put(id,
replayed.directory.endpoint(id)));
+ Map<NodeId, InetAddressAndPort> confirmedCMS = new HashMap<>();
+
+ Set<InetAddressAndPort> candidates = new
HashSet<>(previousCMS.values());
+ candidates.add(newAddress);
+
+ int maxRounds = 5;
+ int currentRound = 0;
+ long roundTimeNanos = Math.min(TimeUnit.SECONDS.toNanos(4),
+
DatabaseDescriptor.getDiscoveryTimeout(TimeUnit.NANOSECONDS) / maxRounds);
+ // TODO a non-CMS node only needs to be able to contact a single CMS
member to commit its STARTUP
Review Comment:
right, I think I just wanted to remove the todo
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