diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/AgentHandshakePropertyType.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/AgentHandshakePropertyType.java
index db01ee44f..5968d0225 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/AgentHandshakePropertyType.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/AgentHandshakePropertyType.java
@@ -21,14 +21,13 @@ import java.util.Map;
 import com.navercorp.pinpoint.rpc.util.ClassUtils;
 
 /**
+ * You must modify {@link com.navercorp.pinpoint.collector.receiver.tcp.AgentHandshakePropertyType} when you modify this enum type.
+ * But There is no compatibility issue if you only add some properties.   
+ * 
  * @author koo.taejin
  */
 public enum AgentHandshakePropertyType {
 
-	// 해당 객체는 profiler, collector 양쪽에 함꼐 있음 
-	// 변경시 함께 변경 필요
-	// map으로 처리하기 때문에 이전 파라미터 제거 대신 추가할 경우 확장성에는 문제가 없음
-
 	SUPPORT_SERVER("supportServer", Boolean.class),
 	
 	HOSTNAME("hostName", String.class),
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/AgentInfoSenderListener.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/AgentInfoSenderListener.java
index b0644bc1d..8d791ab92 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/AgentInfoSenderListener.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/AgentInfoSenderListener.java
@@ -64,8 +64,8 @@ public class AgentInfoSenderListener implements FutureListener<ResponseMessage>
 	private TBase<?, ?> deserialize(Future<ResponseMessage> future) {
         final ResponseMessage responseMessage = future.getResult();
 
-        // TODO theradlocalcache로 변경해야 되는지 검토 자주 생성이 될수 있는 객체라서 life cycle이 상이함.
-        // caching해야 될려나?
+        // TODO Should we change this to thread local cache? This object's life cycle is different because it could be created many times.
+        // Should we cache this?
         byte[] message = responseMessage.getMessage();
         return SerializationUtils.deserialize(message, HeaderTBaseDeserializerFactory.DEFAULT_FACTORY, null);
         
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/AgentInformationFactory.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/AgentInformationFactory.java
index e6ab71a33..2fff74874 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/AgentInformationFactory.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/AgentInformationFactory.java
@@ -41,8 +41,8 @@ public class AgentInformationFactory {
         if (serverType == null) {
             throw new NullPointerException("serverType must not be null");
         }
-        // TODO 일단 임시로 호환성을 위해 agentid에 machinename을 넣도록 하자
-        // TODO 박스 하나에 서버 인스턴스를 여러개 실행할 때에 문제가 될 수 있음.
+        // For compatibility issue, use machineName as agentId when agengId is not provided.
+        // This could be a problem if more than one server instances run on a box.
         final String machineName = NetworkUtils.getHostName();
         final String hostIp = NetworkUtils.getHostIp();
         final String agentId = getId("pinpoint.agentId", machineName, PinpointConstants.AGENT_NAME_MAX_LEN);
@@ -62,8 +62,9 @@ public class AgentInformationFactory {
 		if (id == null) {
 			throw new NullPointerException("id must not be null");
 		}
-        // 에러 체크 로직을 bootclass 앞단으로 이동시켜야 함.
-        // 아니면 여기서 체크해서 실패시 agent동작을 하지 않도록 하던가 하는 추가 동작을 해야함.
+		
+		// TODO AgengId should be validated before bootclass.
+		// or agent should stop when validataion is failed here. 
         final byte[] bytes = BytesUtils.toBytes(id);
 		if (bytes.length > maxlen) {
             logger.warn("{} is too long(1~24). value={}", idName, id);
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/ClassFileTransformerDispatcher.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/ClassFileTransformerDispatcher.java
index ba19f185d..ba878ef6d 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/ClassFileTransformerDispatcher.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/ClassFileTransformerDispatcher.java
@@ -98,10 +98,10 @@ public class ClassFileTransformerDispatcher implements ClassFileTransformer {
             if (className.equals("net/spy/memcached/CacheManager")) {
                 logger.debug("no modifier for CacheManager");
             }
-            // TODO : 디버그 용도로 추가함
-            // TODO : modifier가 중복 적용되면 어떻게 되지???
+            // TODO For debug
+            // TODO What if a modifier is duplicated?
             if (this.profilerConfig.getProfilableClassFilter().filter(className)) {
-                  // 테스트 장비에서 callstack view가 잘 보이는지 확인하려고 추가함.
+                // Added to see if call stack view is OK on a test machine.
                 findModifier = this.modifierRegistry.findModifier("*");
             } else {
                 return null;
@@ -120,8 +120,7 @@ public class ClassFileTransformerDispatcher implements ClassFileTransformer {
             try {
                 return findModifier.modify(classLoader, javassistClassName, protectionDomain, classFileBuffer);
             } finally {
-                // null일 경우도 다시 원복하는게 맞음.
-                // getContextClass 호출시 에러가 발생하였을 경우 여기서 호출당하지 않으므로 이부분에서 원복하는게 맞음.
+                // The context class loader have to be recovered even if it was null.
                 thread.setContextClassLoader(before);
             }
         }
@@ -189,7 +188,7 @@ public class ClassFileTransformerDispatcher implements ClassFileTransformer {
     }
 
     /*
-     * for plugins. This method is not used now because plugin feature is not completed yet.
+     * for plugins. This method is not used yet because plugin feature is not completed.
      */
     private void loadPlugins(DefaultModifierRegistry modifierRepository) {
         String pluginPath = agent.getAgentPath() + File.separatorChar + "plugin";
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/DefaultAgent.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/DefaultAgent.java
index eaa1e52a6..63f025a21 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/DefaultAgent.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/DefaultAgent.java
@@ -93,11 +93,10 @@ public class DefaultAgent implements Agent {
     private final AgentInformation agentInformation;
     private final ServerMetaDataHolder serverMetaDataHolder;
 
-    // agent의 상태,
     private volatile AgentStatus agentStatus;
 
     static {
-        // rpc쪽 preload
+        // Preload classes related to pinpoint-rpc module.
         ClassPreLoader.preload();
     }
 
@@ -158,7 +157,6 @@ public class DefaultAgent implements Agent {
 
         this.agentInfoSender = new AgentInfoSender(tcpDataSender, profilerConfig.getAgentInfoSendRetryInterval(), this.agentInformation, this.serverMetaDataHolder);
 
-        // JVM 통계 등을 주기적으로 수집하여 collector에 전송하는 monitor를 초기화한다.
         this.agentStatMonitor = new AgentStatMonitor(this.statDataSender, this.agentInformation.getAgentId(), this.agentInformation.getStartTime());
         
         
@@ -171,8 +169,9 @@ public class DefaultAgent implements Agent {
         preLoadClass();
 
         /**
-         * FIXME tomcat의 경우에는 com.navercorp.pinpoint.profiler.modifier.tomcat.interceptor.CatalinaAwaitInterceptor가 org/apache/catalina/startup/Catalina/await함수가 실행되기
-         * 전에 실행해주나. stand alone application은 그렇지 않으므로..
+         * FIXME
+         * In case of Tomcat, com.navercorp.pinpoint.profiler.modifier.tomcat.interceptor.CatalinaAwaitInterceptor invokes start() method 
+         * before entering await() method of org.apache.catalina.startup.Catalina. But for other applications, it must be invoked directly. 
          */
         if (typeResolver.isManuallyStartupRequired()) {
             start();
@@ -223,9 +222,9 @@ public class DefaultAgent implements Agent {
         final String binderClassName = binder.getClass().getName();
         PLogger pLogger = binder.getLogger(binder.getClass().getName());
         pLogger.info("PLoggerFactory.initialize() bind:{} cl:{}", binderClassName, binder.getClass().getClassLoader());
-        // static LoggerFactory에 binder를 붙임.
+        // Set binder to static LoggerFactory
+        // Should we unset binder at shutdonw hook or stop()?
         PLoggerFactory.initialize(binder);
-        // shutdown hook이나 stop에 LoggerBinder의 연결을 풀어야 되는가?
     }
 
     private TraceContext createTraceContext(short serverType) {
@@ -290,10 +289,6 @@ public class DefaultAgent implements Agent {
     }
 
     protected PinpointSocket createPinpointSocket(String host, int port, PinpointSocketFactory factory) {
-        // 1.2 버전이 Tcp Data Command 허용하는 버전이 아니기 떄문에 true이던 false이던 무조건 SimpleLoggingMessageListener를 이용하게 함
-        // SimpleLoggingMessageListener.LISTENER 는 서로 통신을 하지 않게 설정되어 있음 (테스트코드는 pinpoint-rpc에 존재)
-        // 1.3 버전으로 할 경우 아래 분기에서 MessageListener 변경 필요
-
         PinpointSocket socket = null;
         for (int i = 0; i < 3; i++) {
             try {
@@ -376,7 +371,7 @@ public class DefaultAgent implements Agent {
         this.agentInfoSender.stop();
         this.agentStatMonitor.stop();
 
-        // 종료 처리 필요.
+        // Need to process stop
         this.spanDataSender.stop();
         this.statDataSender.stop();
         this.tcpDataSender.stop();
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/DefaultClassFileFilter.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/DefaultClassFileFilter.java
index eddb980a2..b7f9466f4 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/DefaultClassFileFilter.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/DefaultClassFileFilter.java
@@ -34,7 +34,7 @@ public class DefaultClassFileFilter implements ClassFileFilter {
 
 	@Override
 	public boolean doFilter(ClassLoader classLoader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classFileBuffer) {
-		// fast java class skip
+		// fast skip java classes
 		if (className.startsWith("java")) {
 			if (className.startsWith("/", 4) || className.startsWith("x/", 4)) {
 				return SKIP;
@@ -42,11 +42,11 @@ public class DefaultClassFileFilter implements ClassFileFilter {
 		}
 
 		if (classLoader == agentLoader) {
-			// agent의 clssLoader에 로드된 클래스는 스킵한다.
+			// skip classes loaded by agent class loader.
 			return SKIP;
 		}
-		// 자기 자신의 패키지도 제외
-		// 향후 패키지명 변경에 의해 코드 변경이 필요함.
+		
+		// Skip pinpoint packages too.
 		if (className.startsWith("com/navercorp/pinpoint/")) {
 			return SKIP;
 		}
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/CallStack.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/CallStack.java
index 0e2aaa8a0..9f8992d62 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/CallStack.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/CallStack.java
@@ -30,14 +30,13 @@ import java.util.Arrays;
 public class CallStack {
 
     private static final Logger logger = LoggerFactory.getLogger(CallStack.class);
-    // 추적 depth크기 제한을 위해서 필요. 해당 사이즈를 넘어갈경우 부드럽게 트레이스를 무시하는 로직이 필요함.
-    private static final int TRACE_STACK_MAX_SIZE = 64;
 
     private static final int STACK_SIZE = 8;
     private static final int STACK_INCREASE_SIZE = 8;
 
     private final Span span;
-    // CallStack을 동시성 환경에서 복사해서 볼수 있는 방법이 필요함.
+    
+    // We have to find some way to copy call stack in concurrent situation. 
     private StackFrame[] stack = new StackFrame[STACK_SIZE];
 
 
@@ -54,14 +53,15 @@ public class CallStack {
         return span;
     }
 
+    // without synchronization for the present.
 //    public synchronized int getIndex() {
     public int getIndex() {
-        // 일단 락 안잡는 코드로 함.
        return index;
     }
 
-    // copy시의 락 생각할 경우 좀더 정교하게 잡을수 있을듯.
-    // push, pop, copy만 락을 잡아도 될거 같은 생각이 듬.
+    
+    // We could handle synchronization more precisely.
+    // Maybe synchonizing push, pop, copy would be enough.
     public synchronized StackFrame getCurrentStackFrame() {
         return stack[index];
     }
@@ -133,7 +133,7 @@ public class CallStack {
     private PinpointException createStackException(String stackApiPoint, final int index) {
         final PinpointException ex = new PinpointException("Profiler CallStack check. index:" + index + " stackApiPoint:" + stackApiPoint);
         if (logger.isWarnEnabled()) {
-            // 자체 stack dump 필요.
+            // need to dump stack.
             logger.warn("invalid callStack found stack dump:{}", this, ex);
         }
         return ex;
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DefaultAsyncTrace.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DefaultAsyncTrace.java
index a37abf334..fc240f96f 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DefaultAsyncTrace.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DefaultAsyncTrace.java
@@ -40,11 +40,6 @@ public class DefaultAsyncTrace implements AsyncTrace {
 
 
     public static final int NON_REGIST = -1;
-    // private int id;
-    // 비동기일 경우 traceenable의 경우 애매함. span을 보내는것으로 데이터를 생성하므로 약간 이상.
-    // private boolean tracingEnabled;
-
-
 
     private final AtomicInteger state = new AtomicInteger(STATE_INIT);
 
@@ -136,12 +131,6 @@ public class DefaultAsyncTrace implements AsyncTrace {
             String drop = StringUtils.drop(th.getMessage());
 
             recordAttribute(AnnotationKey.EXCEPTION, drop);
-
-//            TODO 비동기 api일 경우, span에 exception을 마크하기가 까다로움
-//            AnnotationKey span = getCallStack().getSpan();
-//            if (span.getErrCode() == 0) {
-//                span.setErrCode(1);
-//            }
         }
     }
 
@@ -178,7 +167,6 @@ public class DefaultAsyncTrace implements AsyncTrace {
         this.spanEvent.setDestinationId(destinationId);
     }
 
-    // TODO: endPoint로 받으면 합치는데 비용이 들어가 그냥 한번에 받는게 나을것 같음.
     @Override
     public void recordEndPoint(final String endPoint) {
         this.spanEvent.setEndPoint(endPoint);
@@ -202,15 +190,13 @@ public class DefaultAsyncTrace implements AsyncTrace {
 
     public void timeout() {
         if (state.compareAndSet(STATE_INIT, STATE_TIMEOUT)) {
-            // TODO timeout spanEvent log 던지기.
-            // 뭘 어떤 내용을 던져야 되는지 아직 모르겠음????
+            // TODO 
         }
     }
 
     public boolean fire() {
         if (state.compareAndSet(STATE_INIT, STATE_FIRE)) {
             if (timeoutTask != null) {
-                // timeout이 걸려 있는 asynctrace일 경우 호출해 준다.
                 this.timeoutTask.cancel();
             }
             return true;
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DefaultTrace.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DefaultTrace.java
index 32cf801fd..4526792b9 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DefaultTrace.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DefaultTrace.java
@@ -124,8 +124,8 @@ public final class DefaultTrace implements Trace {
 
     private StackFrame createSpanEventStackFrame(int stackId) {
         SpanEvent spanEvent = new SpanEvent(callStack.getSpan());
-        // Span내부의 SpanEvent로 들어가지 않을 경우 사용하기 위해 set한다.
 
+        // Set properties for the case when stackFrame is not used as part of Span.
         SpanEventStackFrame stackFrame = new SpanEventStackFrame(spanEvent);
         stackFrame.setStackFrameId(stackId);
         stackFrame.setSequence(nextSequence());
@@ -185,7 +185,8 @@ public final class DefaultTrace implements Trace {
 //        metricResponseTime();
         pop(ROOT_STACKID);
         callStack.popRoot();
-        // 잘못된 stack 조작시 다음부터 그냥 nullPointerException이 발생할건데 괜찮은가?
+        
+        // If the stack is not handled properly, NullPointerException will be thrown after this. Is it OK?
         this.currentStackFrame = null;
     }
 
@@ -227,7 +228,7 @@ public final class DefaultTrace implements Trace {
     public void traceBlockEnd(int stackId) {
         pop(stackId);
         StackFrame popStackFrame = callStack.pop();
-        // pop 할때 frame위치를 원복해야 한다.
+        // When pop, current frame have to be recovered.
         this.currentStackFrame = popStackFrame;
     }
 
@@ -235,7 +236,7 @@ public final class DefaultTrace implements Trace {
         final StackFrame currentStackFrame = this.currentStackFrame;
         int stackFrameId = currentStackFrame.getStackFrameId();
         if (stackFrameId != stackId) {
-            // 자체 stack dump를 하면 오류발견이 쉬울것으로 생각됨
+            // stack dump will make debugging easy.
             if (logger.isWarnEnabled()) {
                 PinpointException exception = new PinpointException("Corrupted CallStack found");
                 logger.warn("Corrupted CallStack found. StackId not matched. expected:{} current:{}", stackId, stackFrameId, exception);
@@ -296,7 +297,7 @@ public final class DefaultTrace implements Trace {
             return;
         }
         final String drop = StringUtils.drop(th.getMessage(), 256);
-        // exception class가 proxy라서 class Name이 불규칙하면 문제가 발생할수 있다.
+        // An exception that is an instance of a proxy class could make something wrong becuase the class name will vary.  
         final int exceptionId = traceContext.cacheString(th.getClass().getName());
         this.currentStackFrame.setExceptionInfo(exceptionId, drop);
 
@@ -320,7 +321,7 @@ public final class DefaultTrace implements Trace {
 
     @Override
     public void recordApi(MethodDescriptor methodDescriptor, Object[] args) {
-        // API 저장 방법의 개선 필요.                                                                                        
+        // Need to improve the way of storing APIs.                                                                                        
         recordApi(methodDescriptor);
         recordArgs(args);
     }
@@ -350,7 +351,7 @@ public final class DefaultTrace implements Trace {
             for (int i = start; i < max; i++) {
                 recordAttribute(AnnotationKey.getArgs(i), args[i]);
             }
-            // TODO MAX 사이즈를 넘는건 마크만 해줘야 하나?
+            // TODO How to handle if args length is greater than MAX_ARGS_SIZE?
         }
     }
 
@@ -373,7 +374,7 @@ public final class DefaultTrace implements Trace {
             for (int i = 0; i < max; i++) {
                 recordAttribute(AnnotationKey.getArgs(i), args[i]);
             }
-            // TODO MAX 사이즈를 넘는건 마크만 해줘야 하나?                                                                  
+         // TODO How to handle if args length is greater than MAX_ARGS_SIZE?                                                                  
         }
     }
 
@@ -468,14 +469,14 @@ public final class DefaultTrace implements Trace {
 
     @Override
     public void recordEndPoint(final String endPoint) {
-        // TODO API 단일화 필요.                                                                                             
+        // TODO Need to unify API                                                                                           
         StackFrame currentStackFrame = this.currentStackFrame;
         currentStackFrame.setEndPoint(endPoint);
     }
 
     @Override
     public void recordRemoteAddress(final String remoteAddress) {
-        // TODO API 단일화 필요.
+        // TODO Need to unify API
         StackFrame currentStackFrame = this.currentStackFrame;
         if (currentStackFrame instanceof RootStackFrame) {
             ((RootStackFrame) currentStackFrame).setRemoteAddress(remoteAddress);
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DefaultTraceContext.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DefaultTraceContext.java
index d6d5e794f..a98a9f768 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DefaultTraceContext.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DefaultTraceContext.java
@@ -107,7 +107,7 @@ public class DefaultTraceContext implements TraceContext {
     }
 
     /**
-     * sampling 여부까지 체크하여 유효성을 검증한 후 Trace를 리턴한다.
+     * Return trace only if current transaction can be sampled.
      * @return
      */
     public Trace currentTraceObject() {
@@ -119,7 +119,7 @@ public class DefaultTraceContext implements TraceContext {
     }
 
     /**
-     * 유효성을 검증하지 않고 Trace를 리턴한다.
+     * Return trace without sampling check.
      * @return
      */
     @Override
@@ -145,7 +145,7 @@ public class DefaultTraceContext implements TraceContext {
         return profilerConfig;
     }
 
-    // remote 에서 샘플링 대상으로 선정된 경우.
+    // Will be invoked when current transaction is picked as sampling target at remote.
     public Trace continueTraceObject(final TraceId traceID) {
         return traceFactory.continueTraceObject(traceID);
     }
@@ -239,7 +239,7 @@ public class DefaultTraceContext implements TraceContext {
         if (transactionId == null) {
             throw new NullPointerException("transactionId must not be null");
         }
-        // TODO parse error 때 예외 처리 필요.
+        // TODO Should handle exception when parsing failed.
         return DefaultTraceId.parse(transactionId, parentSpanID, spanID, flags);
     }
 
@@ -254,13 +254,12 @@ public class DefaultTraceContext implements TraceContext {
         final Result cachingResult = this.sqlCache.put(normalizedSql);
         if (cachingResult.isNewValue()) {
             if (isDebug) {
-                // TODO hit% 로그를 남겨야 문제 발생시 도움이 될듯 하다.
+                // TODO logging hit ratio could help debugging
                 logger.debug("NewSQLParsingResult:{}", parsingResult);
             }
-            // newValue란 의미는 cache에 인입됬다는 의미이고 이는 신규 sql문일 가능성이 있다는 의미임.
-            // 그러므로 메타데이터를 서버로 전송해야 한다.
-
-
+            
+            // isNewValue means that the value is newly cached.  
+            // So the sql could be new one. We have to send sql metadata to collector.
             final TSqlMetaData sqlMetaData = new TSqlMetaData();
             sqlMetaData.setAgentId(getAgentId());
             sqlMetaData.setAgentStartTime(getAgentStartTime());
@@ -268,7 +267,7 @@ public class DefaultTraceContext implements TraceContext {
             sqlMetaData.setSqlId(cachingResult.getId());
             sqlMetaData.setSql(normalizedSql);
 
-            // 좀더 신뢰성이 있는 tcp connection이 필요함.
+            // Need more reliable tcp connection
             this.priorityDataSender.request(sqlMetaData);
         }
         parsingResult.setId(cachingResult.getId());
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DisableTrace.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DisableTrace.java
index 5cafa9bf2..5c454ca88 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DisableTrace.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DisableTrace.java
@@ -30,7 +30,7 @@ import com.navercorp.pinpoint.common.util.ParsingResult;
 public class DisableTrace  implements Trace {
 
     public static final DisableTrace INSTANCE = new DisableTrace();
-    // 구지 객체를 생성하여 사용할 필요가 없을듯.
+
     private DisableTrace() {
     }
 
@@ -86,7 +86,7 @@ public class DisableTrace  implements Trace {
 
     @Override
     public boolean canSampled() {
-        // sampling false를 항상 false를 리턴한다.
+        // always return false
         return false;
     }
 
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/GlobalCallTrace.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/GlobalCallTrace.java
index db103cf8f..c3c46fb9c 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/GlobalCallTrace.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/GlobalCallTrace.java
@@ -25,8 +25,6 @@ import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.atomic.AtomicInteger;
 
 /**
- * 뭔가 복잡한 비동기 call trace시 객체 등록용으로 쓰자.
- * 근데 손좀봐야 될듯.뭔가 좀 구림.
  * @author emeroad
  */
 @Deprecated
@@ -38,12 +36,9 @@ public class GlobalCallTrace {
 
     private ConcurrentMap<Integer, AsyncTrace> trace = new ConcurrentHashMap<Integer, AsyncTrace>(32);
     private AtomicInteger idGenerator = new AtomicInteger(0);
-    // stop을 해줘야 할듯.
     private Timer timer = new Timer("Pinpoint-GlobalCallTrace-Timer-" + timerId.getAndIncrement(), true);
 
     public int registerTraceObject(AsyncTrace asyncTrace) {
-        // TODO 연관관계가 전달부분이 영 별로임.
-
         TimeoutTask timeoutTask = new TimeoutTask(trace, asyncTrace.getAsyncId());
         asyncTrace.setTimeoutTask(timeoutTask);
 
@@ -68,7 +63,6 @@ public class GlobalCallTrace {
         if (asyncTrace != null) {
             boolean result = ((DefaultAsyncTrace)asyncTrace).fire();
             if (!result) {
-                // 이미 timeout된 asyncTrace임.
                 return null;
             }
         }
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/MetricTrace.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/MetricTrace.java
index 3525f0acb..f7ac74430 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/MetricTrace.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/MetricTrace.java
@@ -107,8 +107,8 @@ public class MetricTrace implements Trace {
 
     private StackFrame createSpanEventStackFrame(int stackId) {
         SpanEvent spanEvent = new SpanEvent(callStack.getSpan());
-        // Span내부의 SpanEvent로 들어가지 않을 경우 사용하기 위해 set한다.
-
+        
+        // Set properties for the case when stackFrame is not used as part of Span.
         SpanEventStackFrame stackFrame = new SpanEventStackFrame(spanEvent);
         stackFrame.setStackFrameId(stackId);
 
@@ -167,7 +167,8 @@ public class MetricTrace implements Trace {
         metricResponseTime();
         checkStackId(ROOT_STACKID);
         callStack.popRoot();
-        // 잘못된 stack 조작시 다음부터 그냥 nullPointerException이 발생할건데 괜찮은가?
+
+        // If the stack is not handled properly, NullPointerException will be thrown after this. Is it OK?
         this.currentStackFrame = null;
     }
 
@@ -193,7 +194,7 @@ public class MetricTrace implements Trace {
     public void traceBlockEnd(int stackId) {
         checkStackId(stackId);
         StackFrame popStackFrame = callStack.pop();
-        // pop 할때 frame위치를 원복해야 한다.
+        // When pop, current frame have to be recovered.
         this.currentStackFrame = popStackFrame;
     }
 
@@ -201,7 +202,7 @@ public class MetricTrace implements Trace {
         final StackFrame currentStackFrame = this.currentStackFrame;
         int stackFrameId = currentStackFrame.getStackFrameId();
         if (stackFrameId != stackId) {
-            // 자체 stack dump를 하면 오류발견이 쉬울것으로 생각됨
+            // stack dump will make debugging easy.
             if (logger.isWarnEnabled()) {
                 PinpointException exception = new PinpointException("Corrupted CallStack found");
                 logger.warn("Corrupted CallStack found. StackId not matched. expected:{} current:{}", stackId, stackFrameId, exception);
@@ -239,7 +240,7 @@ public class MetricTrace implements Trace {
         if (th == null) {
             return;
         }
-        // TODO 추가적인 객체를 생성하지 않도록 MARK Exception이 있으면 좋을것 같음.
+        // TODO We'd better having MARK Exception to prevent more objects being created.
         this.currentStackFrame.setExceptionInfo(EXCEPTION_MARK, "");
 
         final Span span = getCallStack().getSpan();
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/SpanChunkFactory.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/SpanChunkFactory.java
index 8cae8d450..da0d74c59 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/SpanChunkFactory.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/SpanChunkFactory.java
@@ -38,7 +38,7 @@ public class SpanChunkFactory {
         if (flushData == null) {
             throw new NullPointerException("flushData must not be null");
         }
-        // TODO 반드시 1개 이상이라는 조건을 충족해야 된다.
+        // TODO must be equals to or greater than 1
         final int size = flushData.size();
         if (size < 1) {
             throw new IllegalArgumentException("flushData.size() < 1 size:" + size);
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/SpanEvent.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/SpanEvent.java
index f7a8740d4..a35ec6f55 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/SpanEvent.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/SpanEvent.java
@@ -56,8 +56,9 @@ public class SpanEvent extends TSpanEvent {
     public void markStartTime() {
 //        spanEvent.setStartElapsed((int) (startTime - parentSpanStartTime));
         final int startElapsed = (int)(System.currentTimeMillis() - span.getStartTime());
-        // startElapsed이 0이면 마크를 안하는 로직은 거의 쓸모가 없다. 하지 말것.
-        // Span에서 최초 SpanEvent나 0이 나올 가능성이 있고, 이후 SpanEvent의 경우는 거의 그렇지 않음.
+        
+        // If startElapsed is 0, logic without mark is useless. Don't do that.
+        // The first SpaneEvent of a Sapn could result in 0. Not likely afterwards.
         this.setStartElapsed(startElapsed);
     }
 
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/SpanId.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/SpanId.java
index 53b2bc119..15705f60e 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/SpanId.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/SpanId.java
@@ -30,13 +30,13 @@ public class SpanId {
 //    private static final Random seed = new Random();
 
     public static long newSpanId() {
-        // thread 마다 가능한 겹치지 않는 값이 생성되면 문제 없으므로 ThreadLocalRandom으로 변경함.
         final Random random = getRandom();
 
         return createSpanId(random);
     }
 
-    // 이거 구현 바꾸면 다른 random 사용이 가능함.
+    // Changed to ThreadLocalRandom because unique value per thread will be enough.
+    // If you need to change Random implementation, modify this method.
     private static Random getRandom() {
         return ThreadLocalRandom.current();
     }
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/TraceFactory.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/TraceFactory.java
index 4443efe39..138ca2f87 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/TraceFactory.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/TraceFactory.java
@@ -31,7 +31,7 @@ public interface TraceFactory {
 
     Trace disableSampling();
 
-    // remote 에서 샘플링 대상으로 선정된 경우.
+    // picked as sampling target at remote
     Trace continueTraceObject(TraceId traceID);
 
     Trace newTraceObject();
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/storage/BufferedStorage.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/storage/BufferedStorage.java
index c909b00a6..1f763d912 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/storage/BufferedStorage.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/storage/BufferedStorage.java
@@ -85,8 +85,8 @@ public class BufferedStorage implements Storage {
             if (logger.isErrorEnabled()) {
                 logger.error("storage is null. discard spanEvent:{}", spanEvent);
             }
-            // 이미 span이 와서 flush된 상황임.
-            // 비동기를 이쪽에 포함시키면 이렇게 될수 있으나. 현재 구조를 변경할 계획임.
+            
+            // Already flushed. This could happen with async processing.
             return;
         }
         storage.add(spanEvent);
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/storage/LogStorageFactory.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/storage/LogStorageFactory.java
index 3b3020412..b4d1d85f1 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/storage/LogStorageFactory.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/storage/LogStorageFactory.java
@@ -31,7 +31,7 @@ public class LogStorageFactory implements StorageFactory {
 
     @Override
     public Storage createStorage() {
-        // 상태 없음 그냥 재활용하면 됨.
+         // reuse because it has no states.
         return DEFAULT_STORAGE;
     }
 
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/interceptor/bci/AspectWeaverClass.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/interceptor/bci/AspectWeaverClass.java
index 35b55cb41..63312812e 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/interceptor/bci/AspectWeaverClass.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/interceptor/bci/AspectWeaverClass.java
@@ -192,7 +192,7 @@ public class AspectWeaverClass {
 
 	private CtMethod copyMethod(CtClass sourceClass, CtMethod sourceMethod) throws CannotCompileException {
 
-		// id라도 더 줘야 될려나?
+		// need id?
 
 		String copyMethodName = methodNameReplacer.replaceMethodName(sourceMethod.getName());
 
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/interceptor/bci/ClassLoadChecker.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/interceptor/bci/ClassLoadChecker.java
index 25263047b..8a2dcfea9 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/interceptor/bci/ClassLoadChecker.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/interceptor/bci/ClassLoadChecker.java
@@ -56,7 +56,7 @@ public class ClassLoadChecker {
             if (className == null) {
                 throw new NullPointerException("className must not be null");
             }
-            // classLoader는 null일수도 있을거 같음. 몇몇 java reference의 최상위 로더의 경우 null 이 나옴.
+            // classLoader could be null (some jdk classes)
             this.classLoader = classLoader;
             this.className = className;
         }
diff --git a/profiler/src/main/java/com/navercorp/pinpoint/profiler/interceptor/bci/JavaAssistByteCodeInstrumentor.java b/profiler/src/main/java/com/navercorp/pinpoint/profiler/interceptor/bci/JavaAssistByteCodeInstrumentor.java
index 4df7945a4..2cbb43c01 100644
--- a/profiler/src/main/java/com/navercorp/pinpoint/profiler/interceptor/bci/JavaAssistByteCodeInstrumentor.java
+++ b/profiler/src/main/java/com/navercorp/pinpoint/profiler/interceptor/bci/JavaAssistByteCodeInstrumentor.java
@@ -50,7 +50,8 @@ public class JavaAssistByteCodeInstrumentor implements ByteCodeInstrumentor {
     private final boolean isDebug = logger.isDebugEnabled();
 
     private final NamedClassPool rootClassPool;
-    // classPool의 수평적 확장이 필요할수 있음. was에 여러개의 webapp가 있을 경우 충돌방지.
+    
+    // TODO Need to separate childClassPool per class space to prevent collision(ex: multiple web applications on a Tomcat server)
     private final NamedClassPool childClassPool;
 
     private Agent agent;
@@ -68,7 +69,7 @@ public class JavaAssistByteCodeInstrumentor implements ByteCodeInstrumentor {
         this.rootClassPool = createClassPool(pathNames, "rootClassPool");
         this.childClassPool = createChildClassPool(rootClassPool, "childClassPool");
         this.agent = agent;
-        // agent의 class는 rootClassPool에 넣는다.
+        // Add Pinpoint classes to rootClassPool
         checkLibrary(this.getClass().getClassLoader(), this.rootClassPool, this.getClass().getName());
     }
 
@@ -116,11 +117,12 @@ public class JavaAssistByteCodeInstrumentor implements ByteCodeInstrumentor {
     }
 
     public void checkLibrary(ClassLoader classLoader, NamedClassPool classPool, String javassistClassName) {
-        // 최상위 classLoader일 경우 null이라 찾을필요가 없음.
+        // if it's loaded by boot class loader, classLoader is null.
         if (classLoader == null) {
             return;
         }
-        // TODO Util로 뽑을까?
+        
+        // TODO extract to Util?
         final boolean findClass = findClass(javassistClassName, classPool);
         if (findClass) {
             if (isDebug) {
@@ -160,16 +162,15 @@ public class JavaAssistByteCodeInstrumentor implements ByteCodeInstrumentor {
         }
         try {
             final NamedClassPool classPool = findClassPool(classLoader);
-            // classLoader로 락을 잡는게 안전함.
-            // 어차피 classLoader에서 락을 잡고 들어오는점도 있고. 예외 사항이 발생할수 있기 때문에.
-            // classLoader의 재진입 락을 잡고 들어오는게 무난함.
+            
+            // It's safe to synchronize on classLoader because current thread already hold lock on classLoader.
+            // Without lock, maybe something could go wrong.
             synchronized (classLoader)  {
                 if (this.classLoadChecker.exist(classLoader, defineClass)) {
                     return classLoader.loadClass(defineClass);
                 } else {
                     final CtClass clazz = classPool.get(defineClass);
 
-                    // 로그 레벨을 debug로 하니 개발때 제대로 체크 안하는 사람이 있어서 수정함.
                     checkTargetClassInterface(clazz);
 
                     defineAbstractSuperClass(clazz, classLoader, protectedDomain);
@@ -200,20 +201,22 @@ public class JavaAssistByteCodeInstrumentor implements ByteCodeInstrumentor {
     private void defineAbstractSuperClass(CtClass clazz, ClassLoader classLoader, ProtectionDomain protectedDomain) throws NotFoundException, CannotCompileException {
         final CtClass superClass = clazz.getSuperclass();
         if (superClass == null) {
-            // java.lang.Object가 아닌 경우 null은 안나올듯.
+            // maybe java.lang.Object
             return;
         }
         final int modifiers = superClass.getModifiers();
         if (Modifier.isAbstract(modifiers)) {
             if (this.classLoadChecker.exist(classLoader, superClass.getName())) {
-                // nestedClass는 자기 자신에게만 속해 있으므로 로드 여부 체크가 필요 없으나 abstractClass는 같이 사용할수 있으므로 체크해야 된다.
+                // We have to check if abstract super classes is already loaded because it could be used by other classes unlike nested classes.
                 return;
             }
+            
             if (isInfo) {
                 logger.info("defineAbstractSuperClass class:{} cl:{}", superClass.getName(), classLoader);
             }
-            // 좀더 정확하게 java 스펙처럼 하려면 제귀를 돌면서 추가로 super를 확인해야 되나. 구지 그래야 되나 싶다. 패스.
-            // 스펙상 1차원 abstractClass만 지원하는 것으로..
+            
+            // If it was more strict we had to make a recursive call to check super class of super class.
+            // But it seems like too much. We'll check direct super class only.
             superClass.toClass(classLoader, protectedDomain);
         }
     }
@@ -224,7 +227,7 @@ public class JavaAssistByteCodeInstrumentor implements ByteCodeInstrumentor {
             return;
         }
         for (CtClass nested : nestedClasses) {
-            // 재귀하면서 최하위부터 로드
+            // load from inner-most to outer.
             defineNestedClass(nested, classLoader, protectedDomain);
             if (isInfo) {
                 logger.info("defineNestedClass class:{} cl:{}", nested.getName(), classLoader);
@@ -274,14 +277,14 @@ public class JavaAssistByteCodeInstrumentor implements ByteCodeInstrumentor {
     private void loadClassLoaderLibraries(ClassLoader classLoader, NamedClassPool classPool) {
         if (classLoader instanceof URLClassLoader) {
             URLClassLoader urlClassLoader = (URLClassLoader) classLoader;
-            // classLoader가 가지고 있는 전체 리소스를 가능한 패스로 다 걸어야 됨
-            // 임의의 class가 없을 경우 class의 byte code를 classpool에 적재 할 수 없음.
+            // We have to add every class path URLs to classPool.
+            // To load bytecode of a class, ClassPool requires every classes referenced by the class. 
             URL[] urlList = urlClassLoader.getURLs();
             for (URL tempURL : urlList) {
                 String filePath = tempURL.getFile();
                 try {
                     classPool.appendClassPath(filePath);
-                    // 만약 한개만 로딩해도 된다면. return true 할것
+
                     if (isInfo) {
                         logger.info("Loaded cl:{} classPool:{} {} ", classLoader.getClass().getName(), classPool.getName(), filePath);
                     }