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chore: address PR comments
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@vmarchaud
vmarchaud committed Jan 19, 2020
1 parent 9d0a4e0 commit 95dfd78
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215 changes: 96 additions & 119 deletions packages/opentelemetry-plugin-express/src/express.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -14,27 +14,36 @@
* limitations under the License.
*/

// mongodb.Server type is deprecated so every use trigger a lint error
/* tslint:disable:deprecation */

import { BasePlugin } from '@opentelemetry/core';
import { CanonicalCode, Span, Attributes } from '@opentelemetry/types';
import { Attributes } from '@opentelemetry/types';
import * as express from 'express';
import * as core from "express-serve-static-core";
import * as shimmer from 'shimmer';
import {
ExpressLayer,
ExpressRouter,
AttributeNames,
PatchedRequest,
Parameters,
PathParams,
_MIDDLEWARES_STORE_PROPERTY
} from './types';
import {
getLayerMetadata,
storeLayerPath,
patchEnd,
} from './utils'
import { VERSION } from './version';

export const kPatched: unique symbol = Symbol('express-layer-patched');
/**
* This symbol is used to mark express layer as being already instrumented
* since its possible to use a given layer multiple times (ex: middlewares)
*/
export const kLayerPatched: unique symbol = Symbol('express-layer-patched');

/** Express instrumentation plugin for OpenTelemetry */
export class ExpressPlugin extends BasePlugin<typeof express> {
private readonly _COMPONENT = 'express';

readonly _COMPONENT = 'express';
readonly supportedVersions = ['^4.0.0'];

constructor(readonly moduleName: string) {
Expand All @@ -47,87 +56,91 @@ export class ExpressPlugin extends BasePlugin<typeof express> {
protected patch() {
this._logger.debug('Patching Express');

if (this._moduleExports) {
const routerProto = (this._moduleExports
.Router as unknown) as express.Router;
const plugin = this;

this._logger.debug('patching express.Router.prototype.route');
shimmer.wrap(routerProto, 'route', (original: Function) => {
return function route_trace(
this: ExpressRouter,
arg: string | Function
) {
const route = original.apply(this, arguments);
const layer = this.stack[this.stack.length - 1] as ExpressLayer;
plugin._applyPatch(layer, typeof arg === 'string' ? arg : undefined);
return route;
// tslint:disable-next-line:no-any
} as any;
});
this._logger.debug('patching express.Router.prototype.use');
shimmer.wrap(routerProto, 'use', (original: Function) => {
return function use(this: express.Application, arg: string | Function) {
const route = original.apply(this, arguments);
const layer = this.stack[this.stack.length - 1] as ExpressLayer;
plugin._applyPatch(layer, typeof arg === 'string' ? arg : undefined);
return route;
// tslint:disable-next-line:no-any
} as any;
});
this._logger.debug('patching express.Application.use');
shimmer.wrap(
this._moduleExports.application,
'use',
(original: Function) => {
return function use(
this: { _router: ExpressRouter },
arg: string | Function
) {
const route = original.apply(this, arguments);
const layer = this._router.stack[this._router.stack.length - 1];
plugin._applyPatch(
layer,
typeof arg === 'string' ? arg : undefined
);
return route;
// tslint:disable-next-line:no-any
} as any;
}
);
if (this._moduleExports === undefined || this._moduleExports === null) {
return this._moduleExports;
}
const routerProto = (this._moduleExports.Router as unknown) as express.Router;

this._logger.debug('patching express.Router.prototype.route');
shimmer.wrap(routerProto, 'route', this._getRoutePatch.bind(this));

this._logger.debug('patching express.Router.prototype.use');
shimmer.wrap(routerProto, 'use', this._getRouterUsePatch.bind(this));

this._logger.debug('patching express.Application.use');
shimmer.wrap(this._moduleExports.application, 'use', this._getAppUsePatch.bind(this));

return this._moduleExports;
}

/** Unpatches all MongoDB patched functions. */
unpatch(): void {
shimmer.unwrap(this._moduleExports.Router.prototype, 'use');
shimmer.unwrap(this._moduleExports.Router.prototype, 'route');
shimmer.unwrap(this._moduleExports.application, 'use');
/**
* Get the patch for Router.route function
* @param original
*/
private _getRoutePatch (original: (path: PathParams) => express.IRoute) {
const plugin = this
return function route_trace(
this: ExpressRouter,
...args: Parameters<typeof original>
) {
const route = original.apply(this, args);
const layer = this.stack[this.stack.length - 1] as ExpressLayer;
plugin._applyPatch(layer, typeof args[0] === 'string' ? args[0] : undefined);
return route;
};
}

/**
* Store layers path in the request to be able to construct route later
* @param request The request where
* @param value the value to push into the array
* Get the patch for Router.use function
* @param original
*/
private _storeLayerPath(request: PatchedRequest, value?: string) {
if (Array.isArray(request.__ot_middlewares) === false) {
Object.defineProperty(request, '__ot_middlewares', {
enumerable: false,
value: [],
});
}
if (value === undefined) return;
(request.__ot_middlewares as string[]).push(value);
private _getRouterUsePatch (original: express.IRouterHandler<express.Router> & express.IRouterMatcher<express.Router>) {
const plugin = this
return function use(
this: express.Application,
...args: Parameters<typeof original>
) {
const route = original.apply(this, args);
const layer = this.stack[this.stack.length - 1] as ExpressLayer;
plugin._applyPatch(layer, typeof args[0] === 'string' ? args[0] : undefined);
return route;
// tslint:disable-next-line:no-any
} as any
}

/**
* Get the patch for Application.use function
* @param original
*/
private _getAppUsePatch (original: core.ApplicationRequestHandler<express.Application>) {
const plugin = this
return function use(
this: { _router: ExpressRouter },
...args: Parameters<typeof original>
) {
const route = original.apply(this, args);
const layer = this._router.stack[this._router.stack.length - 1];
plugin._applyPatch(
layer,
typeof args[0] === 'string' ? args[0] : undefined
);
return route;
// tslint:disable-next-line:no-any
} as any;
}

/** Unpatches all Express patched functions. */
unpatch(): void {
shimmer.unwrap(this._moduleExports.Router.prototype, 'use');
shimmer.unwrap(this._moduleExports.Router.prototype, 'route');
shimmer.unwrap(this._moduleExports.application, 'use');
}

/** Creates spans for Cursor operations */
/** Patch each express layer to create span and propagate scope */
private _applyPatch(layer: ExpressLayer, layerPath?: string) {
const plugin = this;
if (layer[kPatched] === true) return;
layer[kPatched] = true;
if (layer[kLayerPatched] === true) return;
layer[kLayerPatched] = true;
this._logger.debug('patching express.Router.Layer.handle');
shimmer.wrap(layer, 'handle', function(original: Function) {
if (original.length === 4) return original;
Expand All @@ -138,31 +151,18 @@ export class ExpressPlugin extends BasePlugin<typeof express> {
res: express.Response,
next: express.NextFunction
) {
plugin._storeLayerPath(req, layerPath);
const route = (req.__ot_middlewares as string[]).join('');
storeLayerPath(req, layerPath);
const route = (req[_MIDDLEWARES_STORE_PROPERTY] as string[]).join('');
const attributes: Attributes = {
[AttributeNames.COMPONENT]: plugin._COMPONENT,
[AttributeNames.HTTP_ROUTE]: route.length > 0 ? route : undefined,
};
let spanName = '';
if (layer.name === 'router') {
spanName = `express router - ${layerPath}`;
attributes[AttributeNames.EXPRESS_NAME] = layerPath;
attributes[AttributeNames.EXPRESS_TYPE] = 'router';
} else if (layer.name === 'bound dispatch') {
spanName = `express request handler`;
attributes[AttributeNames.EXPRESS_TYPE] = 'request_handler';
} else {
spanName = `express middleware - ${layer.name}`;
attributes[AttributeNames.EXPRESS_NAME] = layer.name;
attributes[AttributeNames.EXPRESS_TYPE] = 'middleware';
}
const span = plugin._tracer.startSpan(spanName, {
const metadata = getLayerMetadata(layer, layerPath)

const span = plugin._tracer.startSpan(metadata.name, {
parent: plugin._tracer.getCurrentSpan(),
attributes,
attributes: Object.assign(attributes, metadata.attributes),
});
// if we cant create a span, abort
if (span === null) return original.apply(this, arguments);
// verify we have a callback
let callbackIdx = Array.from(arguments).findIndex(
arg => typeof arg === 'function'
Expand All @@ -172,9 +172,9 @@ export class ExpressPlugin extends BasePlugin<typeof express> {
arguments[callbackIdx] = function() {
callbackHasBeenCalled = true;
if (!(req.route && arguments[0] instanceof Error)) {
(req.__ot_middlewares as string[]).pop();
(req[_MIDDLEWARES_STORE_PROPERTY] as string[]).pop();
}
return plugin._patchEnd(span, plugin._tracer.bind(next))();
return patchEnd(span, plugin._tracer.bind(next))();
};
}
const result = original.apply(this, arguments);
Expand All @@ -187,29 +187,6 @@ export class ExpressPlugin extends BasePlugin<typeof express> {
};
});
}

/**
* Ends a created span.
* @param span The created span to end.
* @param resultHandler A callback function.
*/
private _patchEnd(span: Span, resultHandler: Function): Function {
return function patchedEnd(this: {}, ...args: unknown[]) {
const error = args[0];
if (error instanceof Error) {
span.setStatus({
code: CanonicalCode.INTERNAL,
message: error.message,
});
} else {
span.setStatus({
code: CanonicalCode.OK,
});
}
span.end();
return resultHandler.apply(this, args);
};
}
}

export const plugin = new ExpressPlugin('express');
16 changes: 13 additions & 3 deletions packages/opentelemetry-plugin-express/src/types.ts
View file
Original file line number Diff line number Diff line change
Expand Up @@ -14,10 +14,14 @@
* limitations under the License.
*/

import { kPatched } from './express';
import { kLayerPatched } from './express';
import { Request } from 'express';

export type PatchedRequest = { ['__ot_middlewares']?: string[] } & Request;
export const _MIDDLEWARES_STORE_PROPERTY = '__ot_middlewares'

export type Parameters<T> = T extends (...args: infer T) => any ? T : unknown[];
export type PatchedRequest = { [_MIDDLEWARES_STORE_PROPERTY]?: string[] } & Request;
export type PathParams = string | RegExp | Array<string | RegExp>;

// https://github.com/expressjs/express/blob/master/lib/router/index.js#L53
export type ExpressRouter = {
Expand All @@ -32,7 +36,7 @@ export type ExpressRouter = {
// https://github.com/expressjs/express/blob/master/lib/router/layer.js#L33
export type ExpressLayer = {
handle: Function;
[kPatched]?: boolean;
[kLayerPatched]?: boolean;
name: string;
params: { [key: string]: string };
path: string;
Expand All @@ -46,3 +50,9 @@ export enum AttributeNames {
EXPRESS_TYPE = 'express.type',
EXPRESS_NAME = 'express.name',
}

export enum ExpressLayerType {
ROUTER = 'router',
MIDDLEWARE = 'middleware',
REQUEST_HANDLER = 'request_handler'
}
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