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new 4d50a44555 Enable ZooKeeper client to establish connection in
read-only mode (#4244)
4d50a44555 is described below
commit 4d50a445553a3a5d4af3aed973ac64bcd4132789
Author: Masahiro Sakamoto <[email protected]>
AuthorDate: Wed Jul 10 15:07:29 2024 +0900
Enable ZooKeeper client to establish connection in read-only mode (#4244)
### Motivation
If the system property `readonlymode.enabled` is set to true on a ZooKeeper
server, read-only mode is enabled. Data can be read from the server in
read-only mode even if that server is split from the quorum.
https://zookeeper.apache.org/doc/current/zookeeperAdmin.html#Experimental+Options%2FFeatures
To connect to the server in read-only mode, the client must also allow
read-only mode. The `ZooKeeperClient` class in the bookkeeper repository also
has an option called `allowReadOnlyMode`.
https://github.com/apache/bookkeeper/blob/15171e1904f7196d8e9f4116ab2aecdf582e0032/bookkeeper-server/src/main/java/org/apache/bookkeeper/zookeeper/ZooKeeperClient.java#L219-L222
However, even if this option is set to true, the connection to the server
in read-only mode will actually fail. The cause is in the
`ZooKeeperWatcherBase` class. When the `ZooKeeperWatcherBase` class receives
the `SyncConnected` event, it releases `clientConnectLatch` and assumes that
the connection is complete.
https://github.com/apache/bookkeeper/blob/15171e1904f7196d8e9f4116ab2aecdf582e0032/bookkeeper-server/src/main/java/org/apache/bookkeeper/zookeeper/ZooKeeperWatcherBase.java#L128-L144
However, if the server is in read-only mode, it will receive
`ConnectedReadOnly` instead of `SyncConnected`. This causes the connection to
time out without being completed.
### Changes
Modified the switch statement in the `ZooKeeperWatcherBase` class to
release `clientConnectLatch` when `ConnectedReadOnly` is received if the
`allowReadOnlyMode` option is true.
By the way, `allowReadOnlyMode` is never set to true in BookKeeper. So this
change would be useless for BookKeeper. However, it is useful for Pulsar.
Because Pulsar also uses `ZooKeeperWatcherBase` and needs to be able to connect
to ZooKeeper in read-only mode.
https://github.com/apache/pulsar/blob/cba1600d0f6a82f1ea194f3214a80f283fe8dc27/pulsar-metadata/src/main/java/org/apache/pulsar/metadata/impl/PulsarZooKeeperClient.java#L242-L244
---
.../bookkeeper/zookeeper/ZooKeeperClient.java | 6 ++---
.../bookkeeper/zookeeper/ZooKeeperWatcherBase.java | 19 +++++++++++---
.../client/BookKeeperClientZKSessionExpiry.java | 2 +-
.../apache/bookkeeper/client/BookKeeperTest.java | 2 +-
.../replication/TestReplicationWorker.java | 2 +-
.../apache/bookkeeper/test/ZooKeeperCluster.java | 2 +-
.../bookkeeper/test/ZooKeeperClusterUtil.java | 8 ++++++
.../bookkeeper/zookeeper/TestZooKeeperClient.java | 30 +++++++++++++++++++++-
8 files changed, 59 insertions(+), 12 deletions(-)
diff --git
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/zookeeper/ZooKeeperClient.java
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/zookeeper/ZooKeeperClient.java
index c742f829e0..3bddcb2f2b 100644
---
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/zookeeper/ZooKeeperClient.java
+++
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/zookeeper/ZooKeeperClient.java
@@ -241,9 +241,9 @@ public class ZooKeeperClient extends ZooKeeper implements
Watcher, AutoCloseable
// Create a watcher manager
StatsLogger watcherStatsLogger = statsLogger.scope("watcher");
- ZooKeeperWatcherBase watcherManager =
- null == watchers ? new
ZooKeeperWatcherBase(sessionTimeoutMs, watcherStatsLogger) :
- new ZooKeeperWatcherBase(sessionTimeoutMs,
watchers, watcherStatsLogger);
+ ZooKeeperWatcherBase watcherManager = (null == watchers)
+ ? new ZooKeeperWatcherBase(sessionTimeoutMs,
allowReadOnlyMode, watcherStatsLogger)
+ : new ZooKeeperWatcherBase(sessionTimeoutMs,
allowReadOnlyMode, watchers, watcherStatsLogger);
ZooKeeperClient client = new ZooKeeperClient(
connectString,
sessionTimeoutMs,
diff --git
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/zookeeper/ZooKeeperWatcherBase.java
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/zookeeper/ZooKeeperWatcherBase.java
index 758f079d0d..e44a5f364c 100644
---
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/zookeeper/ZooKeeperWatcherBase.java
+++
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/zookeeper/ZooKeeperWatcherBase.java
@@ -44,6 +44,7 @@ public class ZooKeeperWatcherBase implements Watcher {
.getLogger(ZooKeeperWatcherBase.class);
private final int zkSessionTimeOut;
+ private final boolean allowReadOnlyMode;
private volatile CountDownLatch clientConnectLatch = new CountDownLatch(1);
private final CopyOnWriteArraySet<Watcher> childWatchers =
new CopyOnWriteArraySet<Watcher>();
@@ -53,18 +54,20 @@ public class ZooKeeperWatcherBase implements Watcher {
private final ConcurrentHashMap<EventType, Counter> eventCounters =
new ConcurrentHashMap<EventType, Counter>();
- public ZooKeeperWatcherBase(int zkSessionTimeOut) {
- this(zkSessionTimeOut, NullStatsLogger.INSTANCE);
+ public ZooKeeperWatcherBase(int zkSessionTimeOut, boolean
allowReadOnlyMode) {
+ this(zkSessionTimeOut, allowReadOnlyMode, NullStatsLogger.INSTANCE);
}
- public ZooKeeperWatcherBase(int zkSessionTimeOut, StatsLogger statsLogger)
{
- this(zkSessionTimeOut, new HashSet<Watcher>(), statsLogger);
+ public ZooKeeperWatcherBase(int zkSessionTimeOut, boolean
allowReadOnlyMode, StatsLogger statsLogger) {
+ this(zkSessionTimeOut, allowReadOnlyMode, new HashSet<Watcher>(),
statsLogger);
}
public ZooKeeperWatcherBase(int zkSessionTimeOut,
+ boolean allowReadOnlyMode,
Set<Watcher> childWatchers,
StatsLogger statsLogger) {
this.zkSessionTimeOut = zkSessionTimeOut;
+ this.allowReadOnlyMode = allowReadOnlyMode;
this.childWatchers.addAll(childWatchers);
this.statsLogger = statsLogger;
}
@@ -130,6 +133,14 @@ public class ZooKeeperWatcherBase implements Watcher {
LOG.info("ZooKeeper client is connected now.");
clientConnectLatch.countDown();
break;
+ case ConnectedReadOnly:
+ if (allowReadOnlyMode) {
+ LOG.info("ZooKeeper client is connected in read-only mode
now.");
+ clientConnectLatch.countDown();
+ } else {
+ LOG.warn("ZooKeeper client is connected in read-only mode,
which is not allowed.");
+ }
+ break;
case Disconnected:
LOG.info("ZooKeeper client is disconnected from zookeeper now,"
+ " but it is OK unless we received EXPIRED event.");
diff --git
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/BookKeeperClientZKSessionExpiry.java
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/BookKeeperClientZKSessionExpiry.java
index b1a8bb66dd..c72834397e 100644
---
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/BookKeeperClientZKSessionExpiry.java
+++
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/BookKeeperClientZKSessionExpiry.java
@@ -51,7 +51,7 @@ public class BookKeeperClientZKSessionExpiry extends
BookKeeperClusterTestCase {
byte[] sessionPasswd =
bkc.getZkHandle().getSessionPasswd();
try {
- ZooKeeperWatcherBase watcher = new
ZooKeeperWatcherBase(10000);
+ ZooKeeperWatcherBase watcher = new
ZooKeeperWatcherBase(10000, false);
ZooKeeper zk = new
ZooKeeper(zkUtil.getZooKeeperConnectString(), 10000,
watcher,
sessionId, sessionPasswd);
zk.close();
diff --git
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/BookKeeperTest.java
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/BookKeeperTest.java
index 45647079d8..14b71a163d 100644
---
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/BookKeeperTest.java
+++
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/BookKeeperTest.java
@@ -1072,7 +1072,7 @@ public class BookKeeperTest extends
BookKeeperClusterTestCase {
public void testZKConnectionLossForLedgerCreation() throws Exception {
int zkSessionTimeOut = 10000;
AtomicLong ledgerIdToInjectFailure = new AtomicLong(INVALID_LEDGERID);
- ZooKeeperWatcherBase zooKeeperWatcherBase = new
ZooKeeperWatcherBase(zkSessionTimeOut,
+ ZooKeeperWatcherBase zooKeeperWatcherBase = new
ZooKeeperWatcherBase(zkSessionTimeOut, false,
NullStatsLogger.INSTANCE);
MockZooKeeperClient zkFaultInjectionWrapper = new
MockZooKeeperClient(zkUtil.getZooKeeperConnectString(),
zkSessionTimeOut, zooKeeperWatcherBase,
ledgerIdToInjectFailure);
diff --git
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/replication/TestReplicationWorker.java
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/replication/TestReplicationWorker.java
index f4a9245c76..507f143d5c 100644
---
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/replication/TestReplicationWorker.java
+++
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/replication/TestReplicationWorker.java
@@ -1103,7 +1103,7 @@ public class TestReplicationWorker extends
BookKeeperClusterTestCase {
* create MockZooKeeperClient instance and wait for it to be connected.
*/
int zkSessionTimeOut = 10000;
- ZooKeeperWatcherBase zooKeeperWatcherBase = new
ZooKeeperWatcherBase(zkSessionTimeOut,
+ ZooKeeperWatcherBase zooKeeperWatcherBase = new
ZooKeeperWatcherBase(zkSessionTimeOut, false,
NullStatsLogger.INSTANCE);
MockZooKeeperClient zkFaultInjectionWrapper = new
MockZooKeeperClient(zkUtil.getZooKeeperConnectString(),
zkSessionTimeOut, zooKeeperWatcherBase);
diff --git
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/test/ZooKeeperCluster.java
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/test/ZooKeeperCluster.java
index 08ecbd7cc1..b0e828bd5c 100644
---
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/test/ZooKeeperCluster.java
+++
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/test/ZooKeeperCluster.java
@@ -64,7 +64,7 @@ public interface ZooKeeperCluster {
default void expireSession(ZooKeeper zk) throws Exception {
long id = zk.getSessionId();
byte[] password = zk.getSessionPasswd();
- ZooKeeperWatcherBase w = new ZooKeeperWatcherBase(10000);
+ ZooKeeperWatcherBase w = new ZooKeeperWatcherBase(10000, false);
ZooKeeper zk2 = new ZooKeeper(getZooKeeperConnectString(),
zk.getSessionTimeout(), w, id, password);
w.waitForConnection();
zk2.close();
diff --git
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/test/ZooKeeperClusterUtil.java
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/test/ZooKeeperClusterUtil.java
index 3eace4a62c..6dbf182110 100644
---
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/test/ZooKeeperClusterUtil.java
+++
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/test/ZooKeeperClusterUtil.java
@@ -139,4 +139,12 @@ public class ZooKeeperClusterUtil implements
ZooKeeperCluster {
public void sleepCluster(int time, TimeUnit timeUnit, CountDownLatch l)
throws InterruptedException, IOException {
throw new UnsupportedOperationException("sleepServer operation is not
supported for ZooKeeperClusterUtil");
}
+
+ public void stopPeer(int id) throws Exception {
+ quorumUtil.shutdown(id);
+ }
+
+ public void enableLocalSession(boolean localSessionEnabled) {
+ quorumUtil.enableLocalSession(localSessionEnabled);
+ }
}
diff --git
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/zookeeper/TestZooKeeperClient.java
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/zookeeper/TestZooKeeperClient.java
index e62e5c08b2..d06892b27d 100644
---
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/zookeeper/TestZooKeeperClient.java
+++
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/zookeeper/TestZooKeeperClient.java
@@ -171,7 +171,7 @@ public abstract class TestZooKeeperClient extends TestCase {
};
final int timeout = 2000;
ZooKeeperWatcherBase watcherManager =
- new ZooKeeperWatcherBase(timeout).addChildWatcher(testWatcher);
+ new ZooKeeperWatcherBase(timeout,
false).addChildWatcher(testWatcher);
List<Watcher> watchers = new ArrayList<Watcher>(1);
watchers.add(testWatcher);
ZooKeeperClient client = new ShutdownZkServerClient(
@@ -895,4 +895,32 @@ public abstract class TestZooKeeperClient extends TestCase
{
logger.info("Delete children from znode " + path);
}
+ @Test
+ public void testAllowReadOnlyMode() throws Exception {
+ if (zkUtil instanceof ZooKeeperClusterUtil) {
+ System.setProperty("readonlymode.enabled", "true");
+ ((ZooKeeperClusterUtil) zkUtil).enableLocalSession(true);
+ zkUtil.restartCluster();
+ Thread.sleep(2000);
+ ((ZooKeeperClusterUtil) zkUtil).stopPeer(2);
+ ((ZooKeeperClusterUtil) zkUtil).stopPeer(3);
+ }
+
+ try (ZooKeeperClient client = ZooKeeperClient.newBuilder()
+ .connectString(zkUtil.getZooKeeperConnectString())
+ .sessionTimeoutMs(30000)
+ .watchers(new HashSet<Watcher>())
+ .operationRetryPolicy(retryPolicy)
+ .allowReadOnlyMode(true)
+ .build()) {
+ Assert.assertTrue("Client failed to connect a ZooKeeper in
read-only mode.",
+ client.getState().isConnected());
+ } finally {
+ if (zkUtil instanceof ZooKeeperClusterUtil) {
+ System.setProperty("readonlymode.enabled", "false");
+ ((ZooKeeperClusterUtil) zkUtil).enableLocalSession(false);
+ }
+ }
+ }
+
}
