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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 | 17x 17x 17x 17x 17x 5x 5x 1x 4x 4x 4x 4x 4x 4x 2x 2x 2x | import {
CallHandler,
ExecutionContext,
HttpException,
Inject,
Injectable,
NestInterceptor,
} from '@nestjs/common';
import { Observable, throwError } from 'rxjs';
import { catchError, tap } from 'rxjs/operators';
import type { Histogram } from 'prom-client';
import { HTTP_DURATION_HISTOGRAM } from './metrics.tokens';
interface RequestLike {
method: string;
route?: { path?: string };
}
@Injectable()
export class HttpMetricsInterceptor implements NestInterceptor {
constructor(
@Inject(HTTP_DURATION_HISTOGRAM)
private readonly histogram: Histogram<'method' | 'route' | 'status_code'>,
) {}
intercept(context: ExecutionContext, next: CallHandler): Observable<unknown> {
if (context.getType() !== 'http') {
return next.handle();
}
const startedAt = process.hrtime.bigint();
const request = context.switchToHttp().getRequest<RequestLike>();
const record = (statusCode: number): void => {
const seconds = Number(process.hrtime.bigint() - startedAt) / 1e9;
this.histogram.observe(
{
method: request.method,
// The route TEMPLATE (/work-orders/:id), never the raw URL: one
// label value per endpoint keeps metric cardinality bounded.
route: request.route?.path ?? 'unmatched',
status_code: String(statusCode),
},
seconds,
);
};
return next.handle().pipe(
tap(() =>
record(
context.switchToHttp().getResponse<{ statusCode: number }>()
.statusCode,
),
),
catchError((error: unknown) => {
record(error instanceof HttpException ? error.getStatus() : 500);
return throwError(() => error);
}),
);
}
}
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