pvary commented on code in PR #10484:
URL: https://github.com/apache/iceberg/pull/10484#discussion_r1701369847


##########
flink/v1.19/flink/src/main/java/org/apache/iceberg/flink/maintenance/operator/TagBasedLockFactory.java:
##########
@@ -0,0 +1,179 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.iceberg.flink.maintenance.operator;
+
+import java.io.IOException;
+import java.util.Optional;
+import java.util.UUID;
+import org.apache.flink.annotation.Internal;
+import org.apache.iceberg.ManageSnapshots;
+import org.apache.iceberg.Table;
+import org.apache.iceberg.flink.TableLoader;
+import 
org.apache.iceberg.relocated.com.google.common.annotations.VisibleForTesting;
+import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
+import org.apache.iceberg.util.Tasks;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Iceberg table {@link ManageSnapshots#createTag(String, long)}/{@link
+ * ManageSnapshots#removeTag(String)} based lock implementation for {@link 
TriggerLockFactory}.
+ */
+@Internal
+public class TagBasedLockFactory implements TriggerLockFactory {
+  private static final Logger LOG = 
LoggerFactory.getLogger(TagBasedLockFactory.class);
+  @VisibleForTesting static final String RUNNING_TAG_PREFIX = 
"__flink_maintenance_running_";
+  @VisibleForTesting static final String RECOVERING_TAG_PREFIX = 
"__flink_maintenance_recovering_";
+  private static final int CHANGE_ATTEMPTS = 3;
+
+  private final TableLoader tableLoader;
+  private transient Table table;
+
+  public TagBasedLockFactory(TableLoader tableLoader) {
+    this.tableLoader = tableLoader;
+  }
+
+  @Override
+  public void open() {
+    tableLoader.open();
+    this.table = tableLoader.loadTable();
+  }
+
+  @Override
+  public TriggerLockFactory.Lock createLock() {
+    return new Lock(table, RUNNING_TAG_PREFIX);
+  }
+
+  @Override
+  public TriggerLockFactory.Lock createRecoveryLock() {
+    return new Lock(table, RECOVERING_TAG_PREFIX);
+  }
+
+  @Override
+  public void close() throws IOException {
+    tableLoader.close();
+  }
+
+  public static class Lock implements TriggerLockFactory.Lock {
+    private final Table table;
+    private final String lockPrefix;
+
+    public Lock(Table table, String lockPrefix) {
+      Preconditions.checkNotNull(table, "Table should not be null");
+      Preconditions.checkNotNull(lockPrefix, "Lock key should not be null");
+      this.table = table;
+      this.lockPrefix = lockPrefix;
+    }
+
+    /**
+     * The lock will be acquired by jobs with creating a new tag. A new empty 
commit is added for a
+     * table without snapshots.
+     *
+     * @return <code>true</code> if the lock is acquired by this operator
+     */
+    @Override
+    public boolean tryLock() {
+      if (isHeld()) {
+        LOG.info("Lock is already held. The relevant tag: {}", findLock());
+        return false;
+      }
+
+      if (table.currentSnapshot() == null) {
+        // Create an empty commit
+        table.newFastAppend().commit();
+        LOG.info("Empty table, new empty commit added for using tags");
+      }
+
+      String lockKey = lockPrefix + UUID.randomUUID();
+      try {
+        Tasks.foreach(1)
+            .retry(CHANGE_ATTEMPTS)
+            .stopOnFailure()
+            .throwFailureWhenFinished()
+            .run(
+                unused -> {
+                  try {
+                    table.refresh();
+                    ManageSnapshots manage = table.manageSnapshots();
+                    manage.createTag(lockKey, 
table.currentSnapshot().snapshotId());
+                    manage.commit();
+                    LOG.debug("Lock created");
+                  } catch (Exception e) {
+                    if (!isHeld()) {
+                      LOG.warn("Retrying lock after exception", e);
+                      throw e;
+                    } else {
+                      LOG.debug("Lock created, hiding exception", e);
+                    }
+                  }
+                });
+      } catch (Exception e) {
+        LOG.info("Concurrent lock created. Is there a concurrent maintenance 
job running?", e);
+        return false;
+      }
+
+      return true;
+    }
+
+    @Override
+    public void unlock() {
+      table.refresh();
+
+      Optional<String> lockKey = findLock();
+      if (lockKey.isPresent()) {
+        Tasks.foreach(lockKey.get())
+            .retry(CHANGE_ATTEMPTS)
+            .stopOnFailure()
+            .throwFailureWhenFinished()
+            .run(
+                key -> {
+                  try {
+                    table.refresh();
+                    ManageSnapshots manage = table.manageSnapshots();
+                    manage.removeTag(key);
+                    manage.commit();
+                  } catch (Exception e) {
+                    table.refresh();
+                    if (table.refs().containsKey(key)) {
+                      LOG.warn("Retrying lock removal after exception", e);
+                      throw e;
+                    } else {
+                      LOG.debug("Lock removed, hiding exception", e);
+                    }
+                  }
+                });
+        LOG.debug("Lock removed");
+      } else {
+        LOG.warn(
+            "Missing lock, can not remove. Found only the following tags: {}.",
+            table.refs().keySet());
+      }
+    }
+
+    @Override
+    public boolean isHeld() {
+      table.refresh();
+      return findLock().isPresent();
+    }
+
+    private Optional<String> findLock() {
+      return table.refs().keySet().stream().filter(tag -> 
tag.startsWith(lockPrefix)).findAny();

Review Comment:
   Done



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