provider啟動之前之Filter擴充。
filter的概念在很多架構架構都有涉及，實作的手法也是大同小異，鍊式調用，一環勾着一環，有點類似棧的思想，先進後出。
dubbo filter原生的filter挺多，足夠正常使用，自實作後面再講。現在由于在說provider的啟動，是以先講源碼，把啟動流程捋順。
dubbo filter的初始化在于ProtocolFilterWrapper這個包裝類裡面的buildInvokerChain方法，這裡依然使用SPI加載擷取适合的filter，在filter的注解類似@Activate(group = Constants.PROVIDER, order = -110000)，group表明是provider還是consumer，order為鍊式順序，越小越先過濾。說回來，buildInvokerChain循環周遊filter并放入相應的invoker，形成單連結清單，層層調用。調用順序：EchoFilter->ClassLoaderFilter->GenericFilter->ContextFilter->TraceFilter->TimeoutFilter->MonitorFilter->ExceptionFilter。
簡介：
EchoFilter： 回聲測試用于檢測服務是否可用，回聲測試按照正常請求流程執行，能夠測試整個調用是否通暢，可用于監控。
ClassLoaderFilter：切換線程上下文使用的classloader，用于SPI。
GenericFilter： 泛接口實作方式主要用于伺服器端沒有API接口及模型類元的情況，參數及傳回值中的所有POJO均用Map表示，通常用于架構內建。
ContextFilter：處理請求的上下文資訊。
TraceFilter：QOS服務中telnet相關調用。
TimeoutFilter：逾時過濾器。
MonitorFilter： dubbo monitor監控相關。
ExceptionFilter：異常捕捉。
private static <T> Invoker<T> buildInvokerChain(final Invoker<T> invoker, String key, String group) {
Invoker<T> last = invoker;
List<Filter> filters = ExtensionLoader.getExtensionLoader(Filter.class).getActivateExtension(invoker.getUrl(), key, group);
if (!filters.isEmpty()) {
for (int i = filters.size() - 1; i >= 0; i--) {
final Filter filter = filters.get(i);
final Invoker<T> next = last;
last = new Invoker<T>() {
@Override
public Class<T> getInterface() {
return invoker.getInterface();
}
@Override
public URL getUrl() {
return invoker.getUrl();
}
@Override
public boolean isAvailable() {
return invoker.isAvailable();
}
@Override
public Result invoke(Invocation invocation) throws RpcException {
Result result = filter.invoke(next, invocation);
if (result instanceof AsyncRpcResult) {
AsyncRpcResult asyncResult = (AsyncRpcResult) result;
asyncResult.thenApplyWithContext(r -> filter.onResponse(r, invoker, invocation));
return asyncResult;
} else {
return filter.onResponse(result, invoker, invocation);
}
}
@Override
public void destroy() {
invoker.destroy();
}
@Override
public String toString() {
return invoker.toString();
}
};
}
}
return last;
}
EchoFilter：回聲測試使用，發送任意字元串，傳回該字元串，測試某個伺服器是否開啟。發什麼傳回什麼。
@Override
public Result invoke(Invoker<?> invoker, Invocation inv) throws RpcException {
if (inv.getMethodName().equals(Constants.$ECHO) && inv.getArguments() != null && inv.getArguments().length == 1) {
return new RpcResult(inv.getArguments()[0]);
}
return invoker.invoke(inv);
}
classloaderFilter：類加載器切換
@Override
public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
ClassLoader ocl = Thread.currentThread().getContextClassLoader();
Thread.currentThread().setContextClassLoader(invoker.getInterface().getClassLoader());
try {
return invoker.invoke(invocation);
} finally {
Thread.currentThread().setContextClassLoader(ocl);
}
}
GenericFilter：傳遞方法名方法名直接調用，下例：
Object result = genericService.$invoke("sayHello", new String[] {"java.lang.String"}, new Object[] {"world"});
@Override
public Result invoke(Invoker<?> invoker, Invocation inv) throws RpcException {
if (inv.getMethodName().equals(Constants.$INVOKE)
&& inv.getArguments() != null
&& inv.getArguments().length == 3
&& !GenericService.class.isAssignableFrom(invoker.getInterface())) {
String name = ((String) inv.getArguments()[0]).trim();
String[] types = (String[]) inv.getArguments()[1];
Object[] args = (Object[]) inv.getArguments()[2];
try {
Method method = ReflectUtils.findMethodByMethodSignature(invoker.getInterface(), name, types);
Class<?>[] params = method.getParameterTypes();
if (args == null) {
args = new Object[params.length];
}
String generic = inv.getAttachment(Constants.GENERIC_KEY);
if (StringUtils.isBlank(generic)) {
generic = RpcContext.getContext().getAttachment(Constants.GENERIC_KEY);
}
if (StringUtils.isEmpty(generic)
|| ProtocolUtils.isDefaultGenericSerialization(generic)) {
args = PojoUtils.realize(args, params, method.getGenericParameterTypes());
} else if (ProtocolUtils.isJavaGenericSerialization(generic)) {
for (int i = 0; i < args.length; i++) {
if (byte[].class == args[i].getClass()) {
try(UnsafeByteArrayInputStream is = new UnsafeByteArrayInputStream((byte[]) args[i])) {
args[i] = ExtensionLoader.getExtensionLoader(Serialization.class)
.getExtension(Constants.GENERIC_SERIALIZATION_NATIVE_JAVA)
.deserialize(null, is).readObject();
} catch (Exception e) {
throw new RpcException("Deserialize argument [" + (i + 1) + "] failed.", e);
}
} else {
throw new RpcException(
"Generic serialization [" +
Constants.GENERIC_SERIALIZATION_NATIVE_JAVA +
"] only support message type " +
byte[].class +
" and your message type is " +
args[i].getClass());
}
}
} else if (ProtocolUtils.isBeanGenericSerialization(generic)) {
for (int i = 0; i < args.length; i++) {
if (args[i] instanceof JavaBeanDescriptor) {
args[i] = JavaBeanSerializeUtil.deserialize((JavaBeanDescriptor) args[i]);
} else {
throw new RpcException(
"Generic serialization [" +
Constants.GENERIC_SERIALIZATION_BEAN +
"] only support message type " +
JavaBeanDescriptor.class.getName() +
" and your message type is " +
args[i].getClass().getName());
}
}
}
Result result = invoker.invoke(new RpcInvocation(method, args, inv.getAttachments()));
if (result.hasException()
&& !(result.getException() instanceof GenericException)) {
return new RpcResult(new GenericException(result.getException()));
}
if (ProtocolUtils.isJavaGenericSerialization(generic)) {
try {
UnsafeByteArrayOutputStream os = new UnsafeByteArrayOutputStream(512);
ExtensionLoader.getExtensionLoader(Serialization.class)
.getExtension(Constants.GENERIC_SERIALIZATION_NATIVE_JAVA)
.serialize(null, os).writeObject(result.getValue());
return new RpcResult(os.toByteArray());
} catch (IOException e) {
throw new RpcException("Serialize result failed.", e);
}
} else if (ProtocolUtils.isBeanGenericSerialization(generic)) {
return new RpcResult(JavaBeanSerializeUtil.serialize(result.getValue(), JavaBeanAccessor.METHOD));
} else {
return new RpcResult(PojoUtils.generalize(result.getValue()));
}
} catch (NoSuchMethodException e) {
throw new RpcException(e.getMessage(), e);
} catch (ClassNotFoundException e) {
throw new RpcException(e.getMessage(), e);
}
}
return invoker.invoke(inv);
}
ContextFilter：處理請求的上下文環境
@Override
public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
Map<String, String> attachments = invocation.getAttachments();
if (attachments != null) {
attachments = new HashMap<>(attachments);
attachments.remove(Constants.PATH_KEY);
attachments.remove(Constants.INTERFACE_KEY);
attachments.remove(Constants.GROUP_KEY);
attachments.remove(Constants.VERSION_KEY);
attachments.remove(Constants.DUBBO_VERSION_KEY);
attachments.remove(Constants.TOKEN_KEY);
attachments.remove(Constants.TIMEOUT_KEY);
// Remove async property to avoid being passed to the following invoke chain.
attachments.remove(Constants.ASYNC_KEY);
attachments.remove(Constants.TAG_KEY);
attachments.remove(Constants.FORCE_USE_TAG);
}
RpcContext.getContext()
.setInvoker(invoker)
.setInvocation(invocation)
// .setAttachments(attachments) // merged from dubbox
.setLocalAddress(invoker.getUrl().getHost(),
invoker.getUrl().getPort());
// merged from dubbox
// we may already added some attachments into RpcContext before this filter (e.g. in rest protocol)
if (attachments != null) {
if (RpcContext.getContext().getAttachments() != null) {
RpcContext.getContext().getAttachments().putAll(attachments);
} else {
RpcContext.getContext().setAttachments(attachments);
}
}
if (invocation instanceof RpcInvocation) {
((RpcInvocation) invocation).setInvoker(invoker);
}
try {
return invoker.invoke(invocation);
} finally {
// IMPORTANT! For async scenario, we must remove context from current thread, so we always create a new RpcContext for the next invoke for the same thread.
RpcContext.removeContext();
RpcContext.removeServerContext();
}
}
TraceFilter：QOS服務中telnet相關調用
1. trace XxxService: 跟蹤 1 次服務任意方法的調用情況
2. trace XxxService 10: 跟蹤 10 次服務任意方法的調用情況
3. trace XxxService xxxMethod: 跟蹤 1 次服務方法的調用情況
4. trace XxxService xxxMethod 10: 跟蹤 10 次服務方法的調用情況
@Override
public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
long start = System.currentTimeMillis();
Result result = invoker.invoke(invocation);
long end = System.currentTimeMillis();
if (tracers.size() > 0) {
String key = invoker.getInterface().getName() + "." + invocation.getMethodName();
Set<Channel> channels = tracers.get(key);
if (channels == null || channels.isEmpty()) {
key = invoker.getInterface().getName();
channels = tracers.get(key);
}
if (CollectionUtils.isNotEmpty(channels)) {
for (Channel channel : new ArrayList<>(channels)) {
if (channel.isConnected()) {
try {
int max = 1;
Integer m = (Integer) channel.getAttribute(TRACE_MAX);
if (m != null) {
max = m;
}
int count = 0;
AtomicInteger c = (AtomicInteger) channel.getAttribute(TRACE_COUNT);
if (c == null) {
c = new AtomicInteger();
channel.setAttribute(TRACE_COUNT, c);
}
count = c.getAndIncrement();
if (count < max) {
String prompt = channel.getUrl().getParameter(Constants.PROMPT_KEY, Constants.DEFAULT_PROMPT);
channel.send("\r\n" + RpcContext.getContext().getRemoteAddress() + " -> "
+ invoker.getInterface().getName()
+ "." + invocation.getMethodName()
+ "(" + JSON.toJSONString(invocation.getArguments()) + ")" + " -> " + JSON.toJSONString(result.getValue())
+ "\r\nelapsed: " + (end - start) + " ms."
+ "\r\n\r\n" + prompt);
}
if (count >= max - 1) {
channels.remove(channel);
}
} catch (Throwable e) {
channels.remove(channel);
logger.warn(e.getMessage(), e);
}
} else {
channels.remove(channel);
}
}
}
}
return result;
}
TimeoutFilter：逾時過濾器，逾時後輸出警告日志
@Override
public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
if (invocation.getAttachments() != null) {
long start = System.currentTimeMillis();
invocation.getAttachments().put(TIMEOUT_FILTER_START_TIME, String.valueOf(start));
} else {
if (invocation instanceof RpcInvocation) {
RpcInvocation invc = (RpcInvocation) invocation;
long start = System.currentTimeMillis();
invc.setAttachment(TIMEOUT_FILTER_START_TIME, String.valueOf(start));
}
}
return invoker.invoke(invocation);
}
MonitorFilter：MonitorFilter向DubboMonitor發送資料
@Override
public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
if (invoker.getUrl().hasParameter(Constants.MONITOR_KEY)) {
RpcContext context = RpcContext.getContext(); // provider must fetch context before invoke() gets called
String remoteHost = context.getRemoteHost();
long start = System.currentTimeMillis(); // record start timestamp
getConcurrent(invoker, invocation).incrementAndGet(); // count up
try {
Result result = invoker.invoke(invocation); // proceed invocation chain
collect(invoker, invocation, result, remoteHost, start, false);
return result;
} catch (RpcException e) {
collect(invoker, invocation, null, remoteHost, start, true);
throw e;
} finally {
getConcurrent(invoker, invocation).decrementAndGet(); // count down
}
} else {
return invoker.invoke(invocation);
}
}
ExceptionFilter：異常捕捉
@Override
public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
try {
return invoker.invoke(invocation);
} catch (RuntimeException e) {
logger.error("Got unchecked and undeclared exception which called by " + RpcContext.getContext().getRemoteHost()
+ ". service: " + invoker.getInterface().getName() + ", method: " + invocation.getMethodName()
+ ", exception: " + e.getClass().getName() + ": " + e.getMessage(), e);
throw e;
}
}
filter是dubbo很重要的一環，對于攔截請求驗證，處理入參，傳回參數統一處理有很大的作用。
![Dubbo-go 源碼筆記（二）用戶端調用過程配置檔案和用戶端源代碼實作遠端過程調用從 client 到 server 的 invoker 嵌套鍊- 小結[圖]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)