pkuwm commented on a change in pull request #642: Fix handleNewSession creating
ephemeral node with expired session
URL: https://github.com/apache/helix/pull/642#discussion_r361219969
##########
File path:
helix-core/src/main/java/org/apache/helix/manager/zk/zookeeper/ZkClient.java
##########
@@ -556,15 +634,55 @@ public String create(final String path, Object datat,
final List<ACL> acl, final
}
long startT = System.currentTimeMillis();
try {
- final byte[] data = datat == null ? null : serialize(datat, path);
- checkDataSizeLimit(data);
- String actualPath = retryUntilConnected(new Callable<String>() {
- @Override
- public String call() throws Exception {
- return getConnection().create(path, data, acl, mode);
+ final byte[] dataBytes = dataObject == null ? null :
serialize(dataObject, path);
+ checkDataSizeLimit(dataBytes);
+
+ /*
+ * We pass different implementation of callable.
+ * 1. If the session id is null, it means the operation is NOT session
aware.
+ * In this case, we will implement a regular callable to create a node.
+ * 2. Otherwise, the operation is session aware. We will use a to
+ * create a node which is guaranteed to be created in the expected
session.
+ */
+ final String actualPath = retryUntilConnected(() -> {
+ ZooKeeper zooKeeper = ((ZkConnection) getConnection()).getZookeeper();
+
+ /*
+ * 1. If the session id is NOT null and create mode is EPHEMERAL or
EPHEMERAL_SEQUENTIAL,
+ * the operation is session aware. We have to check the whether or not
the
+ * passed-in(expected) session id matches actual session's id.
+ * If not, ephemeral node creation is failed. This validation is
+ * critical to guarantee the ephemeral node created by the expected ZK
session.
+ *
+ * 2. Otherwise, the operation is NOT session aware.
+ * In this case, we will use the actual zookeeper session to create
the node.
+ */
+ if (expectedSessionId != null && !expectedSessionId.isEmpty()
+ && (mode == CreateMode.EPHEMERAL || mode ==
CreateMode.EPHEMERAL_SEQUENTIAL)) {
+ acquireEventLock();
Review comment:
Comments added.
Regarding the optimization you mentioned, I don't think we can make it.
Because in retryUntilConnect, we don't know if the operation is session aware
or not. If it is NOT session aware, we still have to retry even the session is
expired. So we can only check session is matched or not after retry and
connected in callable.call()
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