This is Jaeger's client side instrumentation library for Node.js that implements Javascript OpenTracing API 1.0.
Please see CONTRIBUTING.md.
npm install --save jaeger-client
var initTracer = require('jaeger-client').initTracer;
// See schema https://github.com/jaegertracing/jaeger-client-node/blob/master/src/configuration.js#L37
var config = {
serviceName: 'my-awesome-service',
};
var options = {
tags: {
'my-awesome-service.version': '1.1.2',
},
metrics: metrics,
logger: logger,
};
var tracer = initTracer(config, options);The metrics and logger objects shown in the above example must satisfy the MetricsFactory and Logger APIs respectively.
The Tracer instance created by initTracer is OpenTracing-1.0 compliant. See opentracing-javascript for usage examples.
Because tchannel-node does not have instrumentation for OpenTracing, Jaeger-Client exposes methods wrapping tchannel handlers, and encoded channels. An encoded channel is a channel wrapped in either a thrift encoder TChannelAsThrift, or json encoder TChannelAsJson. To wrap a server handler for thrift one can initialize a tchannel bridge, and wrap the encoded handler function with a tracedHandler decorator. The tchannel bridge takes an OpenTracing tracer, and a context factory. The context factory must be a function that returns a context with the methods 'getSpan', and 'setSpan' which retrieve and assign the span to the context respectively.
import { TChannelBridge } from 'jaeger-client';
import Context from 'some-conformant-context';
function contextFactory() {
return new Context();
}
let bridge = new TChannelBridge(tracer, { contextFactory: contextFactory });
let server = new TChannel({ serviceName: 'server' });
server.listen(4040, '127.0.0.1');
let serverThriftChannel = TChannelAsThrift({
channel: server,
entryPoint: path.join(__dirname, 'thrift', 'echo.thrift'), // file path to a thrift file
});
let perProcessOptions = {};
serverThriftChannel.register(
server,
'Echo::echo',
perProcessOptions,
bridge.tracedHandler((perProcessOptions, req, head, body, callback) => {
/* Your handler code goes here. */
})
);Outbound calls can be made in two ways, shown below.
import { TChannelBridge } from 'jaeger-client';
let bridge = new TChannelBridge(tracer);
// Create the toplevel client channel.
let client = new TChannel();
// Create the client subchannel that makes requests.
let clientSubChannel = client.makeSubChannel({
serviceName: 'server',
peers: ['127.0.0.1:4040'],
});
let encodedThriftChannel = TChannelAsThrift({
channel: clientSubChannel,
entryPoint: path.join(__dirname, 'thrift', 'echo.thrift'), // file path to a thrift file
});
// wrap encodedThriftChannel in a tracing decorator
let tracedChannel = bridge.tracedChannel(encodedThriftChannel);
// The encodedThriftChannel's (also true for json encoded channels) request object can call 'send' directly.
let req = tracedChannel.request({
serviceName: 'server',
context: context, // must be passed through from the service handler shown above
headers: { cn: 'echo' },
});
// headers should contain your outgoing tchannel headers if any.
// In this instance 'send' is being called on the request object, and not the channel.
req.send('Echo::echo', headers, { value: 'some-string' });let tracedChannel = bridge.tracedChannel(encodedThriftChannel);
// tracedChannel.channel refers to encodedThriftChannel's inner channel which
// is clientSubChannel in this instance.
let req = tracedChannel.channel.request({
serviceName: 'server',
headers: { cn: 'echo' },
context: context, // must be passed through from the service handler shown above
timeout: someTimeout,
});
// send() can be called directly on the tracing decorator
tracedChannel.send(req, 'Echo::echo', o.headers, { value: 'some-string' }, clientCallback);The OpenTracing API defines a sampling.priority standard tag that can be used to affect the sampling of a span and its children:
span.setTag(opentracing_tags.SAMPLING_PRIORITY, 1);Jaeger Tracer also understands a special HTTP Header jaeger-debug-id, which can be set in the incoming request, e.g.
curl -H "jaeger-debug-id: some-correlation-id" http://myhost.comWhen Jaeger sees this header in the request that otherwise has no tracing context, it ensures that the new trace started for this request will be sampled in the "debug" mode (meaning it should survive all downsampling that might happen in the collection pipeline), and the root span will have a tag as if this statement was executed:
span.setTag('jaeger-debug-id', 'some-correlation-id');This allows using Jaeger UI to find the trace by this tag.
Support for Zipkin's B3 Propagation HTTP headers is provided by the ZipkinB3TextMapCodec, which can be configured instead of the default TextMapCodec.
The new codec can be used by registering it with a tracer instance as both an injector and an extractor:
let codec = new ZipkinB3TextMapCodec({ urlEncoding: true });
tracer.registerInjector(opentracing.FORMAT_HTTP_HEADERS, codec);
tracer.registerExtractor(opentracing.FORMAT_HTTP_HEADERS, codec);
This can prove useful when compatibility with existing Zipkin tracing/instrumentation is desired.
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