BewareMyPower commented on a change in pull request #11621:
URL: https://github.com/apache/pulsar/pull/11621#discussion_r686102144
##########
File path:
managed-ledger/src/main/java/org/apache/bookkeeper/mledger/impl/ManagedLedgerImpl.java
##########
@@ -3202,8 +3203,9 @@ public PositionImpl getPreviousPosition(PositionImpl
position) {
return PositionImpl.get(position.getLedgerId(),
position.getEntryId() - 1);
}
+ final NavigableMap<Long, LedgerInfo> ledgersCopied = new
TreeMap<>(ledgers);
// The previous position will be the last position of an earlier
ledgers
- NavigableMap<Long, LedgerInfo> headMap =
ledgers.headMap(position.getLedgerId(), false);
+ NavigableMap<Long, LedgerInfo> headMap =
ledgersCopied.headMap(position.getLedgerId(), false);
Review comment:
The point here is even if we catch the NPE, there's still a chance that
`ledgers` might be modified during the iteration.
A better way to avoid coping the whole map might be adding all null checks
for each access, here's my suggested change:
```diff
diff --git
a/managed-ledger/src/main/java/org/apache/bookkeeper/mledger/impl/ManagedLedgerImpl.java
b/managed-ledger/src/main/java/org/apache/bookkeeper/mledger/impl/ManagedLedgerImpl.java
index 5ea1346ca89..77b3984f614 100644
---
a/managed-ledger/src/main/java/org/apache/bookkeeper/mledger/impl/ManagedLedgerImpl.java
+++
b/managed-ledger/src/main/java/org/apache/bookkeeper/mledger/impl/ManagedLedgerImpl.java
@@ -3205,7 +3205,8 @@ public class ManagedLedgerImpl implements
ManagedLedger, CreateCallback {
// The previous position will be the last position of an earlier
ledgers
NavigableMap<Long, LedgerInfo> headMap =
ledgers.headMap(position.getLedgerId(), false);
- if (headMap.isEmpty()) {
+ final Map.Entry<Long, LedgerInfo> firstEntry = headMap.firstEntry();
+ if (firstEntry == null) {
// There is no previous ledger, return an invalid position in
the current ledger
return PositionImpl.get(position.getLedgerId(), -1);
}
@@ -3213,13 +3214,13 @@ public class ManagedLedgerImpl implements
ManagedLedger, CreateCallback {
// We need to find the most recent non-empty ledger
for (long ledgerId : headMap.descendingKeySet()) {
LedgerInfo li = headMap.get(ledgerId);
- if (li.getEntries() > 0) {
+ if (li != null && li.getEntries() > 0) {
return PositionImpl.get(li.getLedgerId(), li.getEntries() -
1);
}
}
// in case there are only empty ledgers, we return a position in
the first one
- return PositionImpl.get(headMap.firstEntry().getKey(), -1);
+ return PositionImpl.get(firstEntry.getKey(), -1);
}
/**
```
What do you think? @codelipenghui @hangc0276 @gaozhangmin
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