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feat(instrumentation-express): propagate context and measure full handler spans #2638

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feat(instrumentation-express): propagate context and measure full handler spans #2638

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8d6662f
feat(instrumentation-express): propagate context and measure full han…
raphael-theriault-swi Jan 10, 2025
5c016d9
Merge branch 'main' into express-context
pichlermarc Jan 29, 2025
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16 changes: 11 additions & 5 deletions plugins/node/opentelemetry-instrumentation-express/src/instrumentation.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -215,6 +215,9 @@ export class ExpressInstrumentation extends InstrumentationBase<ExpressInstrumen
attributes: Object.assign(attributes, metadata.attributes),
});

const parentContext = context.active();
let currentContext = trace.setSpan(parentContext, span);

const { requestHook } = instrumentation.getConfig();
if (requestHook) {
safeExecuteInTheMiddle(
Expand All @@ -234,12 +237,15 @@ export class ExpressInstrumentation extends InstrumentationBase<ExpressInstrumen
}

let spanHasEnded = false;
// TODO: Fix router spans (getRouterPath does not work properly) to
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Can you expand on what you mean by not working properly or create an issue so this doesn't get lost?

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You can see in the nested routers test that the created router spans never include the /posts section of the route. If I were to propagate context and nest them we'd end up with /api/user/:id -> /:postId -> /api/user/posts/:postId which is really confusing.

// have useful names before removing this branch
if (
metadata.attributes[AttributeNames.EXPRESS_TYPE] !==
ExpressLayerType.MIDDLEWARE
metadata.attributes[AttributeNames.EXPRESS_TYPE] ===
ExpressLayerType.ROUTER
) {
span.end();
spanHasEnded = true;
currentContext = parentContext;
}
// listener for response.on('finish')
const onResponseFinish = () => {
Expand Down Expand Up @@ -278,12 +284,12 @@ export class ExpressInstrumentation extends InstrumentationBase<ExpressInstrumen
(req[_LAYERS_STORE_PROPERTY] as string[]).pop();
}
const callback = args[callbackIdx] as Function;
return callback.apply(this, arguments);
return context.bind(parentContext, callback).apply(this, arguments);
};
}

try {
return original.apply(this, arguments);
return context.bind(currentContext, original).apply(this, arguments);
} catch (anyError) {
const [error, message] = asErrorAndMessage(anyError);
span.recordException(error);
Expand All @@ -296,7 +302,7 @@ export class ExpressInstrumentation extends InstrumentationBase<ExpressInstrumen
/**
* At this point if the callback wasn't called, that means either the
* layer is asynchronous (so it will call the callback later on) or that
* the layer directly end the http response, so we'll hook into the "finish"
* the layer directly ends the http response, so we'll hook into the "finish"
* event to handle the later case.
*/
if (!spanHasEnded) {
Expand Down
4 changes: 2 additions & 2 deletions plugins/node/opentelemetry-instrumentation-express/test/express.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -97,7 +97,7 @@ describe('ExpressInstrumentation', () => {
);
assert.strictEqual(response, 'tata');
rootSpan.end();
assert.strictEqual(finishListenerCount, 2);
assert.strictEqual(finishListenerCount, 3);
assert.notStrictEqual(
memoryExporter
.getFinishedSpans()
Expand Down Expand Up @@ -202,7 +202,7 @@ describe('ExpressInstrumentation', () => {
);
assert.strictEqual(response, 'tata');
rootSpan.end();
assert.strictEqual(finishListenerCount, 2);
assert.strictEqual(finishListenerCount, 3);
assert.notStrictEqual(
memoryExporter
.getFinishedSpans()
Expand Down