ZOOKEEPER-4377: KeeperException.create NPE for unknown error codes (backport)

zookeeper-docs/src/main/resources/markdown/zookeeperQuotas.md

@@ -31,7 +31,7 @@ limitations under the License.
 
 ZooKeeper has both namespace and bytes quotas. You can use the ZooKeeperMain class to set up quotas.
 This fork backports the native quota enforcement released in Apache ZooKeeper 3.8.7
-(ZOOKEEPER-3301 and ZOOKEEPER-4219). Per-namespace quota metrics
+(ZOOKEEPER-3301, ZOOKEEPER-4219, and ZOOKEEPER-4377). Per-namespace quota metrics
 (ZOOKEEPER-4211) are not included.
 Soft limits produce warnings; hard limits reject writes with `QuotaExceededException`.
 Both checks require the startup JVM property `-Dzookeeper.enforceQuota=true`, which defaults to

zookeeper-server/src/main/java/org/apache/zookeeper/KeeperException.java

@@ -154,7 +154,7 @@ public static KeeperException create(Code code) {
             return new TotalEphemeralLimitExceeded();
         case OK:
         default:
-            throw new IllegalArgumentException("Invalid exception code");
+            throw new IllegalArgumentException("Invalid exception code:" + code.code);
         }
     }
 
@@ -439,10 +439,15 @@ public int intValue() {
         /**
          * Get the Code value for a particular integer error code
          * @param code int error code
-         * @return Code value corresponding to specified int code, or null
+         * @return Code value corresponding to specified int code
+         * @throws IllegalArgumentException if the client does not recognize the code
          */
         public static Code get(int code) {
-            return lookup.get(code);
+            Code codeVal = lookup.get(code);
+            if (codeVal == null) {
+                throw new IllegalArgumentException("The current client version cannot lookup this code:" + code);
+            }
+            return codeVal;
         }
     }
 

zookeeper-server/src/test/java/org/apache/zookeeper/KeeperExceptionQuotaTest.java

@@ -20,6 +20,7 @@
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 import org.apache.zookeeper.cli.CliWrapperException;
 import org.junit.Test;
 
@@ -39,4 +40,14 @@ public void testEphemeralErrorDecoding() {
         assertTrue(error instanceof KeeperException.TotalEphemeralLimitExceeded);
         assertEquals("/session", error.getPath());
     }
+
+    @Test
+    public void testUnknownWireErrorIsExplicit() {
+        try {
+            KeeperException.create(KeeperException.Code.get(Integer.MIN_VALUE), "/unknown");
+            fail("An unknown wire error must be reported explicitly");
+        } catch (IllegalArgumentException expected) {
+            assertTrue(expected.getMessage().contains(Integer.toString(Integer.MIN_VALUE)));
+        }
+    }
 }