聊聊skywalking的httpclient-plugin

序

本文主要研究一下skywalking的httpclient-plugin

skywalking-plugin.def

skywalking-6.6.0/apm-sniffer/apm-sdk-plugin/httpClient-4.x-plugin/src/main/resources/skywalking-plugin.def

httpclient-4.x=org.apache.skywalking.apm.plugin.httpClient.v4.define.AbstractHttpClientInstrumentation
httpclient-4.x=org.apache.skywalking.apm.plugin.httpClient.v4.define.InternalHttpClientInstrumentation
httpclient-4.x=org.apache.skywalking.apm.plugin.httpClient.v4.define.MinimalHttpClientInstrumentation
httpclient-4.x=org.apache.skywalking.apm.plugin.httpClient.v4.define.DefaultRequestDirectorInstrumentation
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httpClient-4.x-plugin定义了四个增强，分别是AbstractHttpClientInstrumentation、InternalHttpClientInstrumentation、MinimalHttpClientInstrumentation、DefaultRequestDirectorInstrumentation；它们都继承了HttpClientInstrumentation

HttpClientInstrumentation

skywalking-6.6.0/apm-sniffer/apm-sdk-plugin/httpClient-4.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/httpClient/v4/define/HttpClientInstrumentation.java

public abstract class HttpClientInstrumentation extends ClassInstanceMethodsEnhancePluginDefine {

    private static final String INTERCEPT_CLASS = "org.apache.skywalking.apm.plugin.httpClient.v4.HttpClientExecuteInterceptor";

    @Override
    public ConstructorInterceptPoint[] getConstructorsInterceptPoints() {
        return null;
    }

    protected String getInstanceMethodsInterceptor() {
        return INTERCEPT_CLASS;
    }
}
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HttpClientInstrumentation继承了ClassInstanceMethodsEnhancePluginDefine，其使用的interceptor为org.apache.skywalking.apm.plugin.httpClient.v4.HttpClientExecuteInterceptor

AbstractHttpClientInstrumentation

skywalking-6.6.0/apm-sniffer/apm-sdk-plugin/httpClient-4.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/httpClient/v4/define/AbstractHttpClientInstrumentation.java

public class AbstractHttpClientInstrumentation extends HttpClientInstrumentation {

    private static final String ENHANCE_CLASS = "org.apache.http.impl.client.AbstractHttpClient";

    @Override
    public ClassMatch enhanceClass() {
        return byName(ENHANCE_CLASS);
    }

    /**
     * version 4.2, intercept method: execute, intercept
     * public final HttpResponse execute(HttpHost target, HttpRequest request, HttpContext context)
     */
    @Override
    public InstanceMethodsInterceptPoint[] getInstanceMethodsInterceptPoints() {
        return new InstanceMethodsInterceptPoint[] {
            new InstanceMethodsInterceptPoint() {
                @Override
                public ElementMatcher<MethodDescription> getMethodsMatcher() {
                    return named("doExecute");
                }

                @Override
                public String getMethodsInterceptor() {
                    return getInstanceMethodsInterceptor();
                }

                @Override
                public boolean isOverrideArgs() {
                    return false;
                }
            }
        };
    }
}
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AbstractHttpClientInstrumentation继承了HttpClientInstrumentation，其增强的是org.apache.http.impl.client.DefaultRequestDirector的doExecute方法

InternalHttpClientInstrumentation

skywalking-6.6.0/apm-sniffer/apm-sdk-plugin/httpClient-4.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/httpClient/v4/define/InternalHttpClientInstrumentation.java

public class InternalHttpClientInstrumentation extends HttpClientInstrumentation {

    private static final String ENHANCE_CLASS = "org.apache.http.impl.client.InternalHttpClient";

    @Override
    public ClassMatch enhanceClass() {
        return NameMatch.byName(ENHANCE_CLASS);
    }

    @Override
    public InstanceMethodsInterceptPoint[] getInstanceMethodsInterceptPoints() {
        return new InstanceMethodsInterceptPoint[] {
            new InstanceMethodsInterceptPoint() {
                @Override
                public ElementMatcher<MethodDescription> getMethodsMatcher() {
                    return named("doExecute");
                }

                @Override
                public String getMethodsInterceptor() {
                    return getInstanceMethodsInterceptor();
                }

                @Override
                public boolean isOverrideArgs() {
                    return false;
                }
            }
        };
    }
}
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InternalHttpClientInstrumentation继承了HttpClientInstrumentation，其增强的是org.apache.http.impl.client.InternalHttpClient的doExecute方法

MinimalHttpClientInstrumentation

skywalking-6.6.0/apm-sniffer/apm-sdk-plugin/httpClient-4.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/httpClient/v4/define/MinimalHttpClientInstrumentation.java

public class MinimalHttpClientInstrumentation extends HttpClientInstrumentation {

    private static final String ENHANCE_CLASS = "org.apache.http.impl.client.MinimalHttpClient";

    @Override
    public ClassMatch enhanceClass() {
        return NameMatch.byName(ENHANCE_CLASS);
    }

    @Override
    public InstanceMethodsInterceptPoint[] getInstanceMethodsInterceptPoints() {
        return new InstanceMethodsInterceptPoint[] {
            new InstanceMethodsInterceptPoint() {
                @Override
                public ElementMatcher<MethodDescription> getMethodsMatcher() {
                    return named("doExecute");
                }

                @Override
                public String getMethodsInterceptor() {
                    return getInstanceMethodsInterceptor();
                }

                @Override
                public boolean isOverrideArgs() {
                    return false;
                }
            }
        };
    }
}
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MinimalHttpClientInstrumentation继承了HttpClientInstrumentation，其增强的是org.apache.http.impl.client.MinimalHttpClient的doExecute方法

DefaultRequestDirectorInstrumentation

skywalking-6.6.0/apm-sniffer/apm-sdk-plugin/httpClient-4.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/httpClient/v4/define/DefaultRequestDirectorInstrumentation.java

public class DefaultRequestDirectorInstrumentation extends HttpClientInstrumentation {

    /**
     * Enhance class.
     */
    private static final String ENHANCE_CLASS = "org.apache.http.impl.client.DefaultRequestDirector";

    /**
     * DefaultRequestDirector is default implement.
     * usually use in version 4.0-4.2
     * since 4.3, this class is Deprecated.
     */
    @Override
    public ClassMatch enhanceClass() {
        return NameMatch.byName(ENHANCE_CLASS);
    }

    @Override
    public InstanceMethodsInterceptPoint[] getInstanceMethodsInterceptPoints() {
        return new InstanceMethodsInterceptPoint[] {
            new InstanceMethodsInterceptPoint() {
                @Override
                public ElementMatcher<MethodDescription> getMethodsMatcher() {
                    return named("execute");
                }

                @Override
                public String getMethodsInterceptor() {
                    return getInstanceMethodsInterceptor();
                }

                @Override
                public boolean isOverrideArgs() {
                    return false;
                }
            }
        };
    }
}
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DefaultRequestDirectorInstrumentation继承了HttpClientInstrumentation，其增强的是org.apache.http.impl.client.DefaultRequestDirector的execute方法

HttpClientExecuteInterceptor

skywalking-6.6.0/apm-sniffer/apm-sdk-plugin/httpClient-4.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/httpClient/v4/HttpClientExecuteInterceptor.java

public class HttpClientExecuteInterceptor implements InstanceMethodsAroundInterceptor {

    @Override public void beforeMethod(EnhancedInstance objInst, Method method, Object[] allArguments,
                                       Class<?>[] argumentsTypes, MethodInterceptResult result) throws Throwable {
        if (allArguments[0] == null || allArguments[1] == null) {
            // illegal args, can't trace. ignore.
            return;
        }
        final HttpHost httpHost = (HttpHost)allArguments[0];
        HttpRequest httpRequest = (HttpRequest)allArguments[1];
        final ContextCarrier contextCarrier = new ContextCarrier();

        String remotePeer = httpHost.getHostName() + ":" + port(httpHost);

        String uri = httpRequest.getRequestLine().getUri();
        String requestURI = getRequestURI(uri);
        String operationName = requestURI;
        AbstractSpan span = ContextManager.createExitSpan(operationName, contextCarrier, remotePeer);

        span.setComponent(ComponentsDefine.HTTPCLIENT);
        Tags.URL.set(span, buildSpanValue(httpHost,uri));
        Tags.HTTP.METHOD.set(span, httpRequest.getRequestLine().getMethod());
        SpanLayer.asHttp(span);

        CarrierItem next = contextCarrier.items();
        while (next.hasNext()) {
            next = next.next();
            httpRequest.setHeader(next.getHeadKey(), next.getHeadValue());
        }
    }

    @Override public Object afterMethod(EnhancedInstance objInst, Method method, Object[] allArguments,
                                        Class<?>[] argumentsTypes, Object ret) throws Throwable {
        if (allArguments[0] == null || allArguments[1] == null) {
            return ret;
        }

        if (ret != null) {
            HttpResponse response = (HttpResponse)ret;
            StatusLine responseStatusLine = response.getStatusLine();
            if (responseStatusLine != null) {
                int statusCode = responseStatusLine.getStatusCode();
                AbstractSpan span = ContextManager.activeSpan();
                if (statusCode >= 400) {
                    span.errorOccurred();
                    Tags.STATUS_CODE.set(span, Integer.toString(statusCode));
                }
            }
        }

        ContextManager.stopSpan();
        return ret;
    }

    @Override public void handleMethodException(EnhancedInstance objInst, Method method, Object[] allArguments,
                                                Class<?>[] argumentsTypes, Throwable t) {
        AbstractSpan activeSpan = ContextManager.activeSpan();
        activeSpan.errorOccurred();
        activeSpan.log(t);
    }

    private String getRequestURI(String uri) throws MalformedURLException {
        if (isUrl(uri)) {
            String requestPath = new URL(uri).getPath();
            return requestPath != null && requestPath.length() > 0 ? requestPath : "/";
        } else {
            return uri;
        }
    }

    private boolean isUrl(String uri) {
        String lowerUrl = uri.toLowerCase();
        return lowerUrl.startsWith("http") || lowerUrl.startsWith("https");
    }

    private String buildSpanValue(HttpHost httpHost, String uri) {
        if (isUrl(uri)) {
            return uri;
        } else {
            StringBuilder buff = new StringBuilder();
            buff.append(httpHost.getSchemeName().toLowerCase());
            buff.append("://");
            buff.append(httpHost.getHostName());
            buff.append(":");
            buff.append(port(httpHost));
            buff.append(uri);
            return buff.toString();
        }
    }

    private int port(HttpHost httpHost) {
        int port = httpHost.getPort();
        return port > 0 ? port : "https".equals(httpHost.getSchemeName().toLowerCase()) ? 443 : 80;
    }
}
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HttpClientExecuteInterceptor实现了InstanceMethodsAroundInterceptor接口，其beforeMethod方法根据httpHost及httpRequest参数来构造requestURI、operationName等信息，并通过httpRequest的header透传contextCarrier.items()；其afterMethod方法解析statusCode，对于statusCode大于等于400的标记span.errorOccurred()并设置tag，最后ContextManager.stopSpan()；其handleMethodException方法主要是执行activeSpan.errorOccurred()及activeSpan.log(t)

小结

httpClient-4.x-plugin定义了四个增强，分别是AbstractHttpClientInstrumentation、InternalHttpClientInstrumentation、MinimalHttpClientInstrumentation、DefaultRequestDirectorInstrumentation；它们都继承了HttpClientInstrumentation；使用HttpClientExecuteInterceptor去增强org.apache.http.impl.client.DefaultRequestDirector的doExecute方法、org.apache.http.impl.client.InternalHttpClient的doExecute方法、org.apache.http.impl.client.MinimalHttpClient的doExecute方法、org.apache.http.impl.client.DefaultRequestDirector的execute方法

doc

skywalking-plugin