[ratis] branch master updated: RATIS-1707. Fix corner case when getPrevious in LogAppenderBase (#745)

[szetszwo]

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szetszwo pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/ratis.git


The following commit(s) were added to refs/heads/master by this push:
     new 89853ea72 RATIS-1707. Fix corner case when getPrevious in 
LogAppenderBase (#745)
89853ea72 is described below

commit 89853ea72bf8357d1a6983b8b52419d0ec6ccf1e
Author: Nibiru <axcsd3...@qq.com>
AuthorDate: Thu Sep 22 17:14:06 2022 +0800

    RATIS-1707. Fix corner case when getPrevious in LogAppenderBase (#745)
---
 .../apache/ratis/server/impl/RaftServerImpl.java    | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git 
a/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java 
b/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java
index 8555d3b30..8c37e6273 100644
--- 
a/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java
+++ 
b/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java
@@ -1329,15 +1329,18 @@ class RaftServerImpl implements RaftServer.Division,
       List<LogEntryProto> entries) {
     if (entries != null && !entries.isEmpty()) {
       final long index0 = entries.get(0).getIndex();
-
-      if (previous == null || previous.getTerm() == 0) {
-        Preconditions.assertTrue(index0 == 0,
-            "Unexpected Index: previous is null but entries[%s].getIndex()=%s",
-            0, index0);
-      } else {
-        Preconditions.assertTrue(previous.getIndex() == index0 - 1,
-            "Unexpected Index: previous is %s but entries[%s].getIndex()=%s",
-            previous, 0, index0);
+      // Check if next entry's index is 1 greater than the snapshotIndex. If 
yes, then
+      // we do not have to check for the existence of previous.
+      if (index0 != state.getSnapshotIndex() + 1) {
+        if (previous == null || previous.getTerm() == 0) {
+          Preconditions.assertTrue(index0 == 0,
+              "Unexpected Index: previous is null but 
entries[%s].getIndex()=%s",
+              0, index0);
+        } else {
+          Preconditions.assertTrue(previous.getIndex() == index0 - 1,
+              "Unexpected Index: previous is %s but entries[%s].getIndex()=%s",
+              previous, 0, index0);
+        }
       }
 
       for (int i = 0; i < entries.size(); i++) {