From 75cec6d9816c123bd644d9b85d86a9a35dca0ba4 Mon Sep 17 00:00:00 2001
From: congbo <39078850+congbobo184@users.noreply.github.com>
Date: Fri, 12 Nov 2021 13:11:42 +0800
Subject: [PATCH] [Transaction] Fix topicTransactionBuffer handle null snapshot
 (#12758)

fix https://github.com/apache/pulsar/issues/12754
Now when delete topic, we will write a null value to Transaction buffer snapshot topic, other topic recover by this transaction buffer snapshot system topic, will produce NPE

judge NPE logic

(cherry picked from commit c90c89b07ce544b92becedfaa7a0090b4b73edd2)
---
 .../buffer/impl/TopicTransactionBuffer.java     | 14 ++++++++------
 .../client/impl/TransactionEndToEndTest.java    | 17 +++++++++++++++++
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/pulsar-broker/src/main/java/org/apache/pulsar/broker/transaction/buffer/impl/TopicTransactionBuffer.java b/pulsar-broker/src/main/java/org/apache/pulsar/broker/transaction/buffer/impl/TopicTransactionBuffer.java
index 220b4327cceac..12d5ee42cc7c8 100644
--- a/pulsar-broker/src/main/java/org/apache/pulsar/broker/transaction/buffer/impl/TopicTransactionBuffer.java
+++ b/pulsar-broker/src/main/java/org/apache/pulsar/broker/transaction/buffer/impl/TopicTransactionBuffer.java
@@ -472,12 +472,14 @@ public void run() {
                 try {
                     while (reader.hasMoreEvents()) {
                         Message<TransactionBufferSnapshot> message = reader.readNext();
-                        TransactionBufferSnapshot transactionBufferSnapshot = message.getValue();
-                        if (topic.getName().equals(transactionBufferSnapshot.getTopicName())) {
-                            callBack.handleSnapshot(transactionBufferSnapshot);
-                            this.startReadCursorPosition = PositionImpl.get(
-                                    transactionBufferSnapshot.getMaxReadPositionLedgerId(),
-                                    transactionBufferSnapshot.getMaxReadPositionEntryId());
+                        if (topic.getName().equals(message.getKey())) {
+                            TransactionBufferSnapshot transactionBufferSnapshot = message.getValue();
+                            if (transactionBufferSnapshot != null) {
+                                callBack.handleSnapshot(transactionBufferSnapshot);
+                                this.startReadCursorPosition = PositionImpl.get(
+                                        transactionBufferSnapshot.getMaxReadPositionLedgerId(),
+                                        transactionBufferSnapshot.getMaxReadPositionEntryId());
+                            }
                         }
                     }
                 } catch (PulsarClientException pulsarClientException) {
diff --git a/pulsar-broker/src/test/java/org/apache/pulsar/client/impl/TransactionEndToEndTest.java b/pulsar-broker/src/test/java/org/apache/pulsar/client/impl/TransactionEndToEndTest.java
index f971b5a770cca..d5ae61c012e50 100644
--- a/pulsar-broker/src/test/java/org/apache/pulsar/client/impl/TransactionEndToEndTest.java
+++ b/pulsar-broker/src/test/java/org/apache/pulsar/client/impl/TransactionEndToEndTest.java
@@ -377,6 +377,23 @@ private void txnAckTest(boolean batchEnable, int maxBatchSize,
         }
     }
 
+    @Test
+    public void testAfterDeleteTopicOtherTopicCanRecover() throws Exception {
+        String topicOne = "persistent://" + NAMESPACE1 + "/topic-one";
+        String topicTwo = "persistent://" + NAMESPACE1 + "/topic-two";
+        String sub = "test";
+        admin.topics().createNonPartitionedTopic(topicOne);
+        admin.topics().createSubscription(topicOne, "test", MessageId.earliest);
+        admin.topics().delete(topicOne);
+
+        Producer<String> producer = pulsarClient.newProducer(Schema.STRING).topic(topicTwo).create();
+        Consumer<String> consumer = pulsarClient.newConsumer(Schema.STRING)
+                .topic(topicTwo).subscriptionName(sub).subscribe();
+        String content = "test";
+        producer.send(content);
+        assertEquals(consumer.receive().getValue(), content);
+    }
+
     @Test
     public void txnMessageAckTest() throws Exception {
         String topic = TOPIC_MESSAGE_ACK_TEST;