perf: Backport allocation reduction optimizations from 2.x

eureka-client/src/main/java/com/netflix/discovery/AbstractAzToRegionMapper.java

@@ -40,6 +40,7 @@ public List<String> get() {
             });
 
     private final Map<String, String> availabilityZoneVsRegion = new ConcurrentHashMap<String, String>();
+    private final Map<String, String> parsedAzCache = new ConcurrentHashMap<String, String>();
     private String[] regionsToFetch;
 
     protected AbstractAzToRegionMapper(EurekaClientConfig clientConfig) {
@@ -53,6 +54,7 @@ public synchronized void setRegionsToFetch(String[] regionsToFetch) {
             this.regionsToFetch = regionsToFetch;
             logger.info("Fetching availability zone to region mapping for regions {}", (Object) regionsToFetch);
             availabilityZoneVsRegion.clear();
+            parsedAzCache.clear();
             for (String remoteRegion : regionsToFetch) {
                 Set<String> availabilityZones = getZonesForARegion(remoteRegion);
                 if (null == availabilityZones
@@ -83,6 +85,7 @@ public synchronized void setRegionsToFetch(String[] regionsToFetch) {
         } else {
             logger.info("Regions to fetch is null. Erasing older mapping if any.");
             availabilityZoneVsRegion.clear();
+            parsedAzCache.clear();
             this.regionsToFetch = EMPTY_STR_ARRAY;
         }
     }
@@ -96,9 +99,15 @@ public synchronized void setRegionsToFetch(String[] regionsToFetch) {
 
     @Override
     public String getRegionForAvailabilityZone(String availabilityZone) {
-        String region = availabilityZoneVsRegion.get(availabilityZone);
+        String region = parsedAzCache.get(availabilityZone);
         if (null == region) {
-            return parseAzToGetRegion(availabilityZone);
+            region = availabilityZoneVsRegion.get(availabilityZone);
+            if (null == region) {
+                region = parseAzToGetRegion(availabilityZone);
+            }
+            if (region != null) {
+                parsedAzCache.put(availabilityZone, region);
+            }
         }
         return region;
     }

eureka-client/src/main/java/com/netflix/discovery/DiscoveryClient.java

@@ -1001,15 +1001,15 @@ private boolean fetchRegistry(boolean forceFullRegistryFetch) {
                     || (!Strings.isNullOrEmpty(clientConfig.getRegistryRefreshSingleVipAddress()))
                     || forceFullRegistryFetch
                     || (applications == null)
-                    || (applications.getRegisteredApplications().size() == 0)
+                    || applications.isRegisteredApplicationsEmpty()
                     || (applications.getVersion() == -1)) //Client application does not have latest library supporting delta
             {
                 logger.info("Disable delta property : {}", clientConfig.shouldDisableDelta());
                 logger.info("Single vip registry refresh property : {}", clientConfig.getRegistryRefreshSingleVipAddress());
                 logger.info("Force full registry fetch : {}", forceFullRegistryFetch);
                 logger.info("Application is null : {}", (applications == null));
                 logger.info("Registered Applications size is zero : {}",
-                        (applications.getRegisteredApplications().size() == 0));
+                        applications.isRegisteredApplicationsEmpty());
                 logger.info("Application version is -1: {}", (applications.getVersion() == -1));
                 getAndStoreFullRegistry();
             } else {

eureka-client/src/main/java/com/netflix/discovery/converters/EurekaJacksonCodec.java

@@ -424,6 +424,15 @@ protected void autoMarshalEligible(Object o, JsonGenerator jgen) {
     public static class InstanceInfoDeserializer extends JsonDeserializer<InstanceInfo> {
         private static char[] BUF_AT_CLASS = "@class".toCharArray();
 
+        /** Extract uppercase from current JsonParser cursor. Avoids lambda capture. */
+        private static String toUpperCase(JsonParser jp) {
+            try {
+                return jp.getText().toUpperCase();
+            } catch (IOException e) {
+                throw new RuntimeJsonMappingException(e.getMessage());
+            }
+        }
+
         enum InstanceInfoField {
             HOSTNAME(ELEM_HOST),
             INSTANCE_ID(ELEM_INSTANCE_ID),
@@ -515,14 +524,7 @@ public InstanceInfo deserialize(JsonParser jp, DeserializationContext context) t
                         break;
                     case APP:
                         builder.setAppNameForDeser(
-                                intern.apply(jp, CacheScope.APPLICATION_SCOPE,
-                                ()->{
-                                    try {
-                                        return jp.getText().toUpperCase();
-                                    } catch (IOException e) {
-                                        throw new RuntimeJsonMappingException(e.getMessage());
-                                    }
-                              }));
+                                intern.apply(jp, CacheScope.APPLICATION_SCOPE, InstanceInfoDeserializer::toUpperCase));
                         break;
                     case IP:
                         builder.setIPAddr(intern.apply(jp));
@@ -590,14 +592,8 @@ public InstanceInfo deserialize(JsonParser jp, DeserializationContext context) t
                         builder.setHealthCheckUrlsForDeser(null, intern.apply(jp.getText()));
                         break;
                     case APPGROUPNAME:
-                        builder.setAppGroupNameForDeser(intern.apply(jp, CacheScope.GLOBAL_SCOPE, 
-                                ()->{
-                                    try {
-                                        return jp.getText().toUpperCase();
-                                    } catch (IOException e) {
-                                        throw new RuntimeJsonMappingException(e.getMessage());
-                                    }
-                              }));
+                        builder.setAppGroupNameForDeser(
+                                intern.apply(jp, CacheScope.GLOBAL_SCOPE, InstanceInfoDeserializer::toUpperCase));
                         break;
                     case HOMEPAGEURL:
                         builder.setHomePageUrlForDeser(intern.apply(jp.getText()));
@@ -638,7 +634,9 @@ public InstanceInfo deserialize(JsonParser jp, DeserializationContext context) t
                                 String key = intern.apply(jp, CacheScope.GLOBAL_SCOPE);
                                 jsonToken = jp.nextToken();
                                 String value = intern.apply(jp, CacheScope.APPLICATION_SCOPE );
-                                metadataMap = Optional.ofNullable(metadataMap).orElseGet(METADATA_MAP_SUPPLIER);
+                                if (metadataMap == null) {
+                                    metadataMap = METADATA_MAP_SUPPLIER.get();
+                                }
                                 metadataMap.put(key, value);
                             }
                         };   

eureka-client/src/main/java/com/netflix/discovery/shared/Application.java

@@ -28,6 +28,7 @@
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Consumer;
 
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonIgnore;
@@ -135,7 +136,11 @@ public void removeInstance(InstanceInfo i) {
      */
     @JsonProperty("instance")
     public List<InstanceInfo> getInstances() {
-        return Optional.ofNullable(shuffledInstances.get()).orElseGet(this::getInstancesAsIsFromEureka);
+        List<InstanceInfo> instances = shuffledInstances.get();
+        if (instances == null) {
+            instances = this.getInstancesAsIsFromEureka();
+        }
+        return instances;
     }
 
     /**
@@ -152,6 +157,18 @@ public List<InstanceInfo> getInstancesAsIsFromEureka() {
         }
     }
 
+    /**
+     * Iterate over instances without creating a defensive copy.
+     * Package-private to avoid exposing unsynchronized iteration to external callers.
+     * Callers should be sure that this is a quick iteration.
+     */
+    void forEachInstance(Consumer<InstanceInfo> consumer) {
+        synchronized (instances) {
+            for (InstanceInfo info : instances) {
+                consumer.accept(info);
+            }
+        }
+    }
 
     /**
      * Get the instance info that matches the given id.