fixes #2308 resolve a memory leak issue in the rate-limit handler

rate-limit/src/main/java/com/networknt/limit/LimitHandler.java

@@ -47,7 +47,7 @@ public class LimitHandler implements MiddlewareHandler {
 
     public LimitHandler() throws Exception{
         config = LimitConfig.load();
-        logger.info("RateLimit started with key type:" + config.getKey().name());
+        logger.info("RateLimit started with key type {}", config.getKey().name());
         rateLimiter = new RateLimiter(config);
     }
 
@@ -61,7 +61,7 @@ public LimitHandler() throws Exception{
     @Deprecated
     public LimitHandler(LimitConfig cfg) throws Exception{
         config = cfg;
-        logger.info("RateLimit started with key type:" + config.getKey().name());
+        logger.info("RateLimit started with key type {}", config.getKey().name());
         rateLimiter = new RateLimiter(cfg);
     }
 

rate-limit/src/main/java/com/networknt/limit/RateLimiter.java

@@ -17,18 +17,19 @@
 /**
  *  Rate limit logic for light-4j framework. The config will define in the limit.yml config file.
  *
- * By default Rate limit will handle on the server(service) level. But framework support client and address level limitation
+ * By default, Rate limit will handle on the server(service) level. But framework support client and address level limitation
  *
  * @author Gavin Chen
  */
 public class RateLimiter {
     private static final String LIMIT_KEY_NOT_FOUND = "ERR10073";
     protected LimitConfig config;
 
-    private Map<String, Map<Long, AtomicLong>> serverTimeMap = new ConcurrentHashMap<>();
+    private final Map<String, Map<Long, AtomicLong>> serverTimeMap = new ConcurrentHashMap<>();
 
-    private Map<String, Map<TimeUnit, Map<Long, AtomicLong>>> directTimeMap = new ConcurrentHashMap<>();
+    private final Map<String, Map<TimeUnit, Map<Long, AtomicLong>>> directTimeMap = new ConcurrentHashMap<>();
     private static final Logger logger = LoggerFactory.getLogger(RateLimiter.class);
+    static final String UNKNOWN_PREFIX = "/unknown/prefix"; // this is the bucket for all other request path that is not defined in the config
     static final String ADDRESS_TYPE = "address";
     static final String CLIENT_TYPE = "client";
     static final String USER_TYPE = "user";
@@ -224,13 +225,7 @@ protected RateLimitResponse isAllowDirect(String directKey, String path, String
      */
     public RateLimitResponse isAllowByServer(String path) {
         long currentTimeWindow = Instant.now().getEpochSecond();
-        Map<Long, AtomicLong> timeMap = lookupServerTimeMap(path);
-        if(timeMap == null) {
-            timeMap = new ConcurrentHashMap<>();
-            synchronized(this) {
-                serverTimeMap.put(path, timeMap);
-            }
-        }
+        Map<Long, AtomicLong> timeMap = lookupServerTimeMap(path);  // defined and unknown one if not defined.
         LimitQuota limitQuota = config.getServer() != null ? lookupLimitQuota(path) : null;
         if(limitQuota == null) {
             limitQuota = this.config.getRateLimit().get(0);
@@ -264,7 +259,16 @@ private Map<Long, AtomicLong> lookupServerTimeMap(String path) {
             }
         }
         if(prefix == null) {
-            return null;
+            // the request path is not in the defined path prefix. Use the default path prefix UNKNOWN_PREFIX.
+            if(!serverTimeMap.containsKey(UNKNOWN_PREFIX)) {
+                Map<Long, AtomicLong> timeMap = new ConcurrentHashMap<>();
+                synchronized(this) {
+                    serverTimeMap.put(UNKNOWN_PREFIX, timeMap);
+                }
+                return timeMap;
+            } else {
+                return serverTimeMap.get(UNKNOWN_PREFIX);
+            }
         } else {
             return serverTimeMap.get(prefix);
         }

rate-limit/src/test/java/com/networknt/limit/RateLimiterTest.java

@@ -7,6 +7,7 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Random;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
@@ -135,4 +136,45 @@ public RateLimitResponse callByAddressAsync() throws Exception {
         return rateLimiterAddress.isAllowDirect(address, "/v1/address", RateLimiter.ADDRESS_TYPE);
     }
 
+    @Test
+    public void testByServerMemoryLeak() throws Exception {
+        List<RateLimitResponse> responseList = new ArrayList<>();
+        Callable<RateLimitResponse> task =this::callByServerAsyncRandom;
+        List<Callable<RateLimitResponse>> tasks = Collections.nCopies(12, task);
+
+        //change the thread number here to test multi-threads
+        ExecutorService executorService = Executors.newFixedThreadPool(1);
+        List<Future<RateLimitResponse>> futures = executorService.invokeAll(tasks);
+        for (Future<RateLimitResponse> future : futures) {
+            responseList.add(future.get());
+        }
+
+        // Assert.assertEquals(responseList.size(), 12);
+        List<RateLimitResponse> rejects = responseList.stream().filter(r->!r.isAllow()).collect(Collectors.toList());
+        Assert.assertEquals(rejects.size(), 2);
+        executorService.shutdown();
+    }
+
+    // Method to generate a random string of a given length
+    public static String generateRandomString(int length) {
+        // Characters to choose from
+        String characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
+        Random random = new Random();
+        StringBuilder sb = new StringBuilder(length);
+
+        // Loop to append random characters to the StringBuilder
+        for (int i = 0; i < length; i++) {
+            int randomIndex = random.nextInt(characters.length());
+            sb.append(characters.charAt(randomIndex));
+        }
+
+        return sb.toString();
+    }
+
+    public RateLimitResponse callByServerAsyncRandom() throws Exception {
+        LimitQuota limitQuota = limitConfig.getServer().get("/v1/" + generateRandomString(10));
+        return rateLimiter.isAllowByServer( "/v1/" + generateRandomString(10));
+    }
+
+
 }