dsmiley commented on code in PR #3510:
URL: https://github.com/apache/solr/pull/3510#discussion_r2323518552
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solr/solrj-zookeeper/src/java/org/apache/solr/common/cloud/ZkStateReader.java:
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@@ -872,38 +873,40 @@ public void removeLiveNodesListener(LiveNodesListener
listener) {
}
/**
- * Returns the lowest Solr version among all live nodes in the cluster. It's
not greater than
- * {@link SolrVersion#LATEST_STRING}. Will not return null. If older Solr
nodes have joined that
- * don't declare their version, the result won't be accurate, but it's at
least an upper bound on
- * the possible version it might be.
+ * Returns the lowest Solr version among all live nodes in the cluster. If
older Solr nodes have
+ * joined that don't declare their version, the result won't be accurate,
but it's at least an
+ * upper bound on the possible version it might be.
*
- * @return the lowest Solr version of the cluster; not null
+ * @return an Optional containing the lowest Solr version of nodes in the
cluster, or empty if no
+ * live nodes exist or all nodes return 9.9.0 for unspecified versions
*/
- public SolrVersion fetchLowestSolrVersion() throws KeeperException,
InterruptedException {
+ public Optional<SolrVersion> fetchLowestSolrVersion()
+ throws KeeperException, InterruptedException {
List<String> liveNodeNames = zkClient.getChildren(LIVE_NODES_ZKNODE, null,
true);
- SolrVersion lowest = SolrVersion.LATEST; // current software
+ SolrVersion lowest = null;
// the last version to not specify its version in live nodes
final SolrVersion UNSPECIFIED_VERSION = SolrVersion.valueOf("9.9.0");
+
for (String nodeName : liveNodeNames) {
String path = LIVE_NODES_ZKNODE + "/" + nodeName;
byte[] data = zkClient.getData(path, null, null, true);
if (data == null || data.length == 0) {
- return UNSPECIFIED_VERSION;
+ return Optional.of(UNSPECIFIED_VERSION);
Review Comment:
I was very deliberate about what to do here, and the javadocs should spell
this out. If there's no data for a particular node, then we know an older
version of Solr is a member of this cluster. An empty return from the method
here conveys something different -- that there are no members of the cluster
yet.
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