Opentracing基本模型

image.png

如图，在跟踪链中有以下几个比较重要的数据结构和概念：

span：标识一次分布式调用，其自身包含了id，parentId(指向上级Span的id)， traceIds，服务名称等重要属性，其应尽量保持精简；

trace：标识整个请求链，即一些列Span的组合。其自身的ID将贯穿整个调用链，其中的每个Span都必须携带这个traceId，因此traceId将在整个调用链中传递；

cs：客户端发起请求，标志Span的开始；

sr：服务端接收到请求，并开始处理内部事务，其中sr - cs则为网络延迟和时钟抖动；

ss：服务端处理完请求，返回响应内容，其中ss - sr则为服务端处理请求耗时；

cr：客户端接收到服务端响应内容，标志着Span的结束，其中cr - ss则为网络延迟和时钟抖动。

客户端调用时间=cr-cs

服务端处理时间=sr-ss

分布式系统调用跟踪的基本架构要求

低侵入性，高性能，高可用容错，低丢失率等。

基于GRPC的分布式系统调用跟踪实践

创建TraceContext

TraceContext通过Threadlocal对span进行保存，并且将traceid和spanid向底层服务传递，zebra对线程上下文传递进行了封装，具体参照GRPC如何实现公共参数与业务参数分离传递下面是TraceContext具体代码

public class TraceContext{

private static final String SPAN_LIST_KEY = "spanList";

public static final String TRACE_ID_KEY = "traceId";

public static final String SPAN_ID_KEY = "spanId";

public static final String ANNO_CS = "cs";

public static final String ANNO_CR = "cr";

public static final String ANNO_SR = "sr";

public static final String ANNO_SS = "ss";

private TraceContext(){}

public static void setTraceId(String traceId) {

RpcContext.getContext().set(TRACE_ID_KEY, traceId);

}

public static String getTraceId() {

return (String) RpcContext.getContext().get(TRACE_ID_KEY);

}

public static String getSpanId() {

return (String) RpcContext.getContext().get(SPAN_ID_KEY);

}

public static void setSpanId(String spanId) {

RpcContext.getContext().set(SPAN_ID_KEY, spanId);

}

@SuppressWarnings("unchecked")

public static void addSpan(Span span){

((List)RpcContext.getContext().get(SPAN_LIST_KEY)).add(span);

}

@SuppressWarnings("unchecked")

public static List getSpans(){

return (List) RpcContext.getContext().get(SPAN_LIST_KEY);

}

public static void clear(){

RpcContext.getContext().remove(TRACE_ID_KEY);

RpcContext.getContext().remove(SPAN_ID_KEY);

RpcContext.getContext().remove(SPAN_LIST_KEY);

}

public static void start(){

clear();

RpcContext.getContext().set(SPAN_LIST_KEY, new ArrayList());

}

}

创建TraceAgent

TraceAgent将span信息上传至kafka，代码如下：

public class TraceAgent {

private GrpcProperties grpcProperties;

private KafkaSender sender;

private AsyncReporter report;

public TraceAgent() {

grpcProperties = SpringContextUtils.getBean(GrpcProperties.class);

sender = KafkaSender.newBuilder().bootstrapServers(grpcProperties.getCallChainUpdAddr()).topic("zipkin").encoding(Encoding.JSON).build();

report = AsyncReporter.builder(sender).build();

}

public void send(final List spans){

spans.forEach(item ->{

report.report(item);

});

}

}

创建ZebraClientTracing

ZebraClientTracing用于记录调用端的span信息，具体代码如下：

@Component

public class ZebraClientTracing {

public Span startTrace(String method) {

String id = IdUtils.get() + "";

String traceId = null;

if (null == TraceContext.getTraceId()) {

TraceContext.start();

traceId = id;

} else {

traceId = TraceContext.getTraceId();

}

long timestamp = System.currentTimeMillis() * 1000;

// 注册本地信息

Endpoint endpoint = Endpoint.newBuilder().ip(NetUtils.getLocalHost()).serviceName(EtcdRegistry.serviceName)

.port(50003).build();

// 初始化span

Span consumerSpan = Span.newBuilder().localEndpoint(endpoint).id(id).traceId(traceId)

.parentId(TraceContext.getSpanId() + "").name(EtcdRegistry.serviceName).timestamp(timestamp)

.addAnnotation(timestamp, TraceContext.ANNO_CS).putTag("method", method)

.putTag("pkgId", RpcContext.getContext().getAttachment("pkg")).build();

// 将tracing id和spanid放到上下文

RpcContext.getContext().get().put(TraceContext.TRACE_ID_KEY, consumerSpan.traceId());

RpcContext.getContext().get().put(TraceContext.SPAN_ID_KEY, String.valueOf(consumerSpan.id()));

return consumerSpan;

}

public void endTrace(Span span, Stopwatch watch,int code) {

span = span.toBuilder().addAnnotation(System.currentTimeMillis() * 1000, TraceContext.ANNO_CR)

.duration(watch.stop().elapsed(TimeUnit.MICROSECONDS)).putTag("code", code+"").build();

TraceAgent traceAgent = new TraceAgent();

traceAgent.send(TraceContext.getSpans());

}

}

创建ZebraServerTracing

ZebraServerTracing用于记录服务端的span信息，具体代码如下：

@Component

public class ZebraServerTracing {

public Span startTrace(String method) {

String traceId = (String) RpcContext.getContext().get(TraceContext.TRACE_ID_KEY);

String parentSpanId = (String) RpcContext.getContext().get(TraceContext.SPAN_ID_KEY);

String id = IdUtils.get() + "";

TraceContext.start();

TraceContext.setTraceId(traceId);

TraceContext.setSpanId(parentSpanId);

long timestamp = System.currentTimeMillis() * 1000;

Endpoint endpoint = Endpoint.newBuilder().ip(NetUtils.getLocalHost()).serviceName(EtcdRegistry.serviceName)

.port(50003).build();

Span providerSpan = Span.newBuilder().id(id).parentId(parentSpanId).traceId(traceId)

.name(EtcdRegistry.serviceName).timestamp(timestamp).localEndpoint(endpoint)

.addAnnotation(timestamp, TraceContext.ANNO_SR).putTag("method", method)

.putTag("pkgId", RpcContext.getContext().getAttachment("pkg"))

.build();

TraceContext.addSpan(providerSpan);

return providerSpan;

}

public void endTrace(Span span, Stopwatch watch,int code) {

span = span.toBuilder().addAnnotation(System.currentTimeMillis() * 1000, TraceContext.ANNO_SS)

.duration(watch.stop().elapsed(TimeUnit.MICROSECONDS)).putTag("code", code+"").build();

TraceAgent traceAgent = new TraceAgent();

traceAgent.send(TraceContext.getSpans());

}

}

创建grpc client拦截器

public class HeaderClientInterceptor implements ClientInterceptor {

private static final Logger log = LogManager.getLogger(HeaderClientInterceptor.class);

private final ZebraClientTracing clientTracing;

public static ClientInterceptor instance() {

return new HeaderClientInterceptor();

}

private HeaderClientInterceptor() {

clientTracing = SpringContextUtils.getBean(ZebraClientTracing.class);

}

@Override

public ClientCall interceptCall(MethodDescriptor method,

CallOptions callOptions, Channel next) {

return new SimpleForwardingClientCall(next.newCall(method, callOptions)) {

//判断API网关是否要打开调用链

boolean isGatewayTracing = "1".equals(RpcContext.getContext().getAttachment(ZebraConstants.ZEBRA_OPEN_TRACING))?true:false;

boolean isSubTracing = RpcContext.getContext().get(TraceContext.TRACE_ID_KEY)!=null?true:false;

Stopwatch watch =null;

Span span =null;

@Override

public void start(Listener responseListener, Metadata headers) {

if(isSubTracing||isGatewayTracing){

span =clientTracing.startTrace(method.getFullMethodName());

watch = Stopwatch.createStarted();

}

copyThreadLocalToMetadata(headers);

super.start(new SimpleForwardingClientCallListener(responseListener) {

@Override

public void onHeaders(Metadata headers) {

super.onHeaders(headers);

}

@Override

public void onClose(Status status, Metadata trailers) {

super.onClose(status, trailers);

if(isSubTracing||isGatewayTracing)

clientTracing.endTrace(span, watch,status.getCode().value());

}

}, headers);

}

};

}

private void copyThreadLocalToMetadata(Metadata headers) {

Map attachments = RpcContext.getContext().getAttachments();

Map values = RpcContext.getContext().get();

try {

if (!attachments.isEmpty()) {

headers.put(GrpcUtil.GRPC_CONTEXT_ATTACHMENTS, SerializerUtil.toJson(attachments));

}

if (!values.isEmpty()) {

headers.put(GrpcUtil.GRPC_CONTEXT_VALUES, SerializerUtil.toJson(values));

}

} catch (Throwable e) {

log.error(e.getMessage(), e);

}

}

}

创建grpc server拦截器

public class HeaderServerInterceptor implements ServerInterceptor {

private static final Logger log = LogManager.getLogger(HeaderServerInterceptor.class);

private final ZebraServerTracing serverTracing;

public static ServerInterceptor instance() {

return new HeaderServerInterceptor();

}

private HeaderServerInterceptor() {

serverTracing = SpringContextUtils.getBean(ZebraServerTracing.class);

}

@Override

public Listener interceptCall(ServerCall call, final Metadata headers,

ServerCallHandler next) {

return next.startCall(new SimpleForwardingServerCall(call) {

boolean isSubTracing = RpcContext.getContext().get(TraceContext.TRACE_ID_KEY) != null ? true : false;

Stopwatch watch = null;

Span span = null;

@Override

public void request(int numMessages) {

if (isSubTracing) {

span = serverTracing.startTrace(call.getMethodDescriptor().getFullMethodName());

watch = Stopwatch.createStarted();

}

InetSocketAddress remoteAddress = (InetSocketAddress) call.getAttributes()

.get(Grpc.TRANSPORT_ATTR_REMOTE_ADDR);

RpcContext.getContext().setAttachment(ZebraConstants.REMOTE_ADDRESS, remoteAddress.getHostString());

copyMetadataToThreadLocal(headers);

log.debug("FullMethodName:{},RemoteAddress={},attachments={},context={}",

call.getMethodDescriptor().getFullMethodName(), remoteAddress.getHostString(),

headers.get(GrpcUtil.GRPC_CONTEXT_ATTACHMENTS), headers.get(GrpcUtil.GRPC_CONTEXT_VALUES));

super.request(numMessages);

}

@Override

public void close(Status status, Metadata trailers) {

delegate().close(status, trailers);

if(isSubTracing)

serverTracing.endTrace(span, watch,status.getCode().value());

}

}, headers);

}

private void copyMetadataToThreadLocal(Metadata headers) {

String attachments = headers.get(GrpcUtil.GRPC_CONTEXT_ATTACHMENTS);

String values = headers.get(GrpcUtil.GRPC_CONTEXT_VALUES);

try {

if (attachments != null) {

Map attachmentsMap = SerializerUtil.fromJson(attachments,

new TypeToken>() {

}.getType());

RpcContext.getContext().setAttachments(attachmentsMap);

}

if (values != null) {

Map valuesMap = SerializerUtil.fromJson(values, new TypeToken>() {

}.getType());

for (Map.Entry entry : valuesMap.entrySet()) {

RpcContext.getContext().set(entry.getKey(), entry.getValue());

}

}

} catch (Throwable e) {

log.error(e.getMessage(), e);

}

}

}