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本文主要研究一下sentinel的SentinelGatewayFilter
SentinelGatewayFilter
Sentinel-1.6.2/sentinel-adapter/sentinel-spring-cloud-gateway-adapter/src/main/java/com/alibaba/csp/sentinel/adapter/gateway/sc/SentinelGatewayFilter.java
public class SentinelGatewayFilter implements GatewayFilter, GlobalFilter {
private final GatewayParamParser paramParser = new GatewayParamParser<>(
new ServerWebExchangeItemParser());
@Override
public Mono filter(ServerWebExchange exchange, GatewayFilterChain chain) {
Route route = exchange.getAttribute(ServerWebExchangeUtils.GATEWAY_ROUTE_ATTR);
Mono asyncResult = chain.filter(exchange);
if (route != null) {
String routeId = route.getId();
Object[] params = paramParser.parseParameterFor(routeId, exchange,
r -> r.getResourceMode() == SentinelGatewayConstants.RESOURCE_MODE_ROUTE_ID);
String origin = Optional.ofNullable(GatewayCallbackManager.getRequestOriginParser())
.map(f -> f.apply(exchange))
.orElse("");
asyncResult = asyncResult.transform(
new SentinelReactorTransformer<>(new EntryConfig(routeId, EntryType.IN,
1, params, new ContextConfig(contextName(routeId), origin)))
);
}
Set matchingApis = pickMatchingApiDefinitions(exchange);
for (String apiName : matchingApis) {
Object[] params = paramParser.parseParameterFor(apiName, exchange,
r -> r.getResourceMode() == SentinelGatewayConstants.RESOURCE_MODE_CUSTOM_API_NAME);
asyncResult = asyncResult.transform(
new SentinelReactorTransformer<>(new EntryConfig(apiName, EntryType.IN, 1, params))
);
}
return asyncResult;
}
private String contextName(String route) {
return SentinelGatewayConstants.GATEWAY_CONTEXT_ROUTE_PREFIX + route;
}
Set pickMatchingApiDefinitions(ServerWebExchange exchange) {
return GatewayApiMatcherManager.getApiMatcherMap().values()
.stream()
.filter(m -> m.test(exchange))
.map(WebExchangeApiMatcher::getApiName)
.collect(Collectors.toSet());
}
} - SentinelGatewayFilter实现了GatewayFilter、GlobalFilter接口；其filter方法主要是获取route信息，然后对asyncResult进行transform，这里使用的是SentinelReactorTransformer
SentinelReactorTransformer
Sentinel-1.6.2/sentinel-adapter/sentinel-reactor-adapter/src/main/java/com/alibaba/csp/sentinel/adapter/reactor/SentinelReactorTransformer.java
public class SentinelReactorTransformer implements Function, Publisher> {
private final EntryConfig entryConfig;
public SentinelReactorTransformer(String resourceName) {
this(new EntryConfig(resourceName));
}
public SentinelReactorTransformer(EntryConfig entryConfig) {
AssertUtil.notNull(entryConfig, "entryConfig cannot be null");
this.entryConfig = entryConfig;
}
@Override
public Publisher apply(Publisher publisher) {
if (publisher instanceof Mono) {
return new MonoSentinelOperator<>((Mono) publisher, entryConfig);
}
if (publisher instanceof Flux) {
return new FluxSentinelOperator<>((Flux) publisher, entryConfig);
}
throw new IllegalStateException("Publisher type is not supported: " + publisher.getClass().getCanonicalName());
}
} - SentinelReactorTransformer使用entryConfig创建了MonoSentinelOperator或者MonoSentinelOperator
MonoSentinelOperator
Sentinel-1.6.2/sentinel-adapter/sentinel-reactor-adapter/src/main/java/com/alibaba/csp/sentinel/adapter/reactor/MonoSentinelOperator.java
public class MonoSentinelOperator extends MonoOperator {
private final EntryConfig entryConfig;
public MonoSentinelOperator(Mono source, EntryConfig entryConfig) {
super(source);
AssertUtil.notNull(entryConfig, "entryConfig cannot be null");
this.entryConfig = entryConfig;
}
@Override
public void subscribe(CoreSubscriber actual) {
source.subscribe(new SentinelReactorSubscriber<>(entryConfig, actual, true));
}
} - MonoSentinelOperator在subscribe的时候，使用的是SentinelReactorSubscriber
FluxSentinelOperator
Sentinel-1.6.2/sentinel-adapter/sentinel-reactor-adapter/src/main/java/com/alibaba/csp/sentinel/adapter/reactor/FluxSentinelOperator.java
public class FluxSentinelOperator extends FluxOperator {
private final EntryConfig entryConfig;
public FluxSentinelOperator(Flux source, EntryConfig entryConfig) {
super(source);
AssertUtil.notNull(entryConfig, "entryConfig cannot be null");
this.entryConfig = entryConfig;
}
@Override
public void subscribe(CoreSubscriber actual) {
source.subscribe(new SentinelReactorSubscriber<>(entryConfig, actual, false));
}
} - FluxSentinelOperator在subscribe的时候，使用的是SentinelReactorSubscriber
SentinelReactorSubscriber
Sentinel-1.6.2/sentinel-adapter/sentinel-reactor-adapter/src/main/java/com/alibaba/csp/sentinel/adapter/reactor/SentinelReactorSubscriber.java
public class SentinelReactorSubscriber extends InheritableBaseSubscriber {
private final EntryConfig entryConfig;
private final CoreSubscriber actual;
private final boolean unary;
private volatile AsyncEntry currentEntry;
private final AtomicBoolean entryExited = new AtomicBoolean(false);
public SentinelReactorSubscriber(EntryConfig entryConfig,
CoreSubscriber actual,
boolean unary) {
checkEntryConfig(entryConfig);
this.entryConfig = entryConfig;
this.actual = actual;
this.unary = unary;
}
private void checkEntryConfig(EntryConfig config) {
AssertUtil.notNull(config, "entryConfig cannot be null");
}
@Override
public Context currentContext() {
if (currentEntry == null || entryExited.get()) {
return actual.currentContext();
}
com.alibaba.csp.sentinel.context.Context sentinelContext = currentEntry.getAsyncContext();
if (sentinelContext == null) {
return actual.currentContext();
}
return actual.currentContext()
.put(SentinelReactorConstants.SENTINEL_CONTEXT_KEY, currentEntry.getAsyncContext());
}
private void doWithContextOrCurrent(Supplier> contextSupplier,
Runnable f) {
Optional contextOpt = contextSupplier.get();
if (!contextOpt.isPresent()) {
// Provided context is absent, use current context.
f.run();
} else {
// Run on provided context.
ContextUtil.runOnContext(contextOpt.get(), f);
}
}
private void entryWhenSubscribed() {
ContextConfig sentinelContextConfig = entryConfig.getContextConfig();
if (sentinelContextConfig != null) {
// If current we're already in a context, the context config won't work.
ContextUtil.enter(sentinelContextConfig.getContextName(), sentinelContextConfig.getOrigin());
}
try {
AsyncEntry entry = SphU.asyncEntry(entryConfig.getResourceName(), entryConfig.getEntryType(),
entryConfig.getAcquireCount(), entryConfig.getArgs());
this.currentEntry = entry;
actual.onSubscribe(this);
} catch (BlockException ex) {
// Mark as completed (exited) explicitly.
entryExited.set(true);
// Signal cancel and propagate the {@code BlockException}.
cancel();
actual.onSubscribe(this);
actual.onError(ex);
} finally {
if (sentinelContextConfig != null) {
ContextUtil.exit();
}
}
}
@Override
protected void hookOnSubscribe(Subscription subscription) {
doWithContextOrCurrent(() -> currentContext().getOrEmpty(SentinelReactorConstants.SENTINEL_CONTEXT_KEY),
this::entryWhenSubscribed);
}
@Override
protected void hookOnNext(T value) {
if (isDisposed()) {
tryCompleteEntry();
return;
}
doWithContextOrCurrent(() -> Optional.ofNullable(currentEntry).map(AsyncEntry::getAsyncContext),
() -> actual.onNext(value));
if (unary) {
// For some cases of unary operator (Mono), we have to do this during onNext hook.
// e.g. this kind of order: onSubscribe() -> onNext() -> cancel() -> onComplete()
// the onComplete hook will not be executed so we'll need to complete the entry in advance.
tryCompleteEntry();
}
}
@Override
protected void hookOnComplete() {
tryCompleteEntry();
actual.onComplete();
}
@Override
protected boolean shouldCallErrorDropHook() {
// When flow control triggered or stream terminated, the incoming
// deprecated exceptions should be dropped implicitly, so we'll not call the `onErrorDropped` hook.
return !entryExited.get();
}
@Override
protected void hookOnError(Throwable t) {
if (currentEntry != null && currentEntry.getAsyncContext() != null) {
// Normal requests with non-BlockException will go through here.
Tracer.traceContext(t, 1, currentEntry.getAsyncContext());
}
tryCompleteEntry();
actual.onError(t);
}
@Override
protected void hookOnCancel() {
}
private boolean tryCompleteEntry() {
if (currentEntry != null && entryExited.compareAndSet(false, true)) {
currentEntry.exit(1, entryConfig.getArgs());
return true;
}
return false;
}
} - SentinelReactorSubscriber继承了InheritableBaseSubscriber(
拷贝自reactor.core.publisher.BaseSubscriber，允许子类覆盖onSubscribe、onNext、onError、onComplete方法) - 这里hookOnSubscribe调用了entryWhenSubscribed，它在sentinelContextConfig不为null的时候会先执行ContextUtil.enter，然后使用SphU.asyncEntry创建了AsyncEntry，最后在finally里头在sentinelContextConfig不为null的时候执行ContextUtil.exit();
- 这里hookOnNext、hookOnComplete、hookOnError都调用了tryCompleteEntry方法，它主要是尝试退出AsyncEntry
小结
- SentinelGatewayFilter实现了GatewayFilter、GlobalFilter接口；其filter方法主要是获取route信息，然后对asyncResult进行transform，这里使用的是SentinelReactorTransformer
- SentinelReactorTransformer使用entryConfig创建了MonoSentinelOperator或者MonoSentinelOperator；它们在subscribe的时候，使用的是SentinelReactorSubscriber
- SentinelReactorSubscriber主要是在hookOnSubscribe的时候调用了entryWhenSubscribed方法创建AsyncEntry，在hookOnNext、hookOnComplete、hookOnError的时候调用了tryCompleteEntry方法，尝试退出AsyncEntry
doc
- SentinelGatewayFilter