janhoy commented on a change in pull request #1528:
URL: https://github.com/apache/lucene-solr/pull/1528#discussion_r429829357
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File path: solr/core/src/java/org/apache/solr/cloud/ZkController.java
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@@ -491,6 +494,41 @@ public boolean isClosed() {
assert ObjectReleaseTracker.track(this);
}
+ /**
+ * <p>Verifies if /clusterstate.json exists in Zookeepeer, and if it does
and is not empty, refuses to start and outputs
+ * a helpful message regarding collection migration.</p>
+ *
+ * <p>If /clusterstate.json exists and is empty, it is removed.</p>
+ */
+ private void checkNoOldClusterstate(final SolrZkClient zkClient) throws
InterruptedException {
+ try {
+ if (!zkClient.exists(ZkStateReader.UNSUPPORTED_CLUSTER_STATE, true)) {
+ return;
+ }
+
+ final byte[] data =
zkClient.getData(ZkStateReader.UNSUPPORTED_CLUSTER_STATE, null, null, true);
+
+ if (Arrays.equals("{}".getBytes(StandardCharsets.UTF_8), data)) {
+ // Empty json. This log will only occur once.
+ log.warn("{} no longer supported starting with Solr 9. Found empty
file on Zookeeper, deleting it.", ZkStateReader.UNSUPPORTED_CLUSTER_STATE);
+ zkClient.delete(ZkStateReader.UNSUPPORTED_CLUSTER_STATE, -1, true);
Review comment:
Running 8.x nodes might get a callback since they have a watch. Have not
checked the callback handling code, but if the code don't handle DELETE
operation then either nothing happens or an exception is thrown...
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