daguimu opened a new pull request, #16172:
URL: https://github.com/apache/dubbo/pull/16172
## Problem
`SchemaDescriptorRegistry` has three thread-safety issues. This class is
called during gRPC service registration, which can happen from multiple threads
concurrently.
### Issue 1: `SERVICES` uses plain `HashSet`
```java
private static final Set<String> SERVICES = new HashSet<>(); // NOT
thread-safe
public static void addSchemaDescriptor(String serviceName, FileDescriptor
fd) {
SERVICES.add(serviceName); // concurrent write — can corrupt internal
state
```
### Issue 2: Check-then-act race in `addExtension()`
```java
if (!EXTENSIONS.containsKey(name)) { // Thread A: false
EXTENSIONS.put(name, new HashMap<>()); // Thread A: puts HashMap-1
} // Thread B: also false (race!)
// Thread B: puts HashMap-2,
overwriting HashMap-1!
Map<Integer, FileDescriptor> fdMap = EXTENSIONS.get(name);
fdMap.put(number, fd); // Thread A writes to HashMap-2 (Thread B's),
HashMap-1 entries lost
```
### Issue 3: Inner `HashMap` accessed concurrently
The inner `Map<Integer, FileDescriptor>` created in `addExtension()` is a
plain `HashMap`, but `fdMap.put()` can be called concurrently from different
threads registering different extensions for the same containing type.
## Fix
Three minimal changes (net -6 lines):
1. `SERVICES`: `new HashSet<>()` → `ConcurrentHashMap.newKeySet()`
2. `addExtension`: check-then-act → `EXTENSIONS.computeIfAbsent(name, k ->
new ConcurrentHashMap<>()).put(number, fd)`
3. Inner map: `new HashMap<>()` → `new ConcurrentHashMap<>()` (via the
`computeIfAbsent` lambda)
All changes are API-compatible drop-in replacements with zero behavioral
change.
## Tests
No new tests added — this is a pure collection type replacement. The class
has no existing tests and creating `FileDescriptor` instances requires protobuf
compilation infrastructure. The fix is self-evidently correct: replacing
non-thread-safe collections with their concurrent equivalents.
## Impact
- 1 file changed, 2 insertions, 8 deletions
- Eliminates risk of data corruption in gRPC reflection service registration
- Zero behavioral change for callers
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