Feature Req: Otel middleware

[kevbook]

Since Otel Telemetry is becoming the standard, it would be good to have a middleware that also plays well with Hono logger

[DawnImpulse]

any updates on this @yusukebe ?

[EdamAme-x]

resemble?
#3025

[yusukebe]

Hi @DawnImpulse

There is no update. We (at least I) don't plan to create it right now, so I hope someone works on it.

[smhmayboudi]

Here is a simple solution. It needs a test as well. Do you have any suggestion about coding?

@kevbook @DawnImpulse @yusukebe

import otelapi, { type Tracer } from "@opentelemetry/api";
import {
  context,
  propagation,
  SpanKind,
  SpanStatusCode,
  trace,
} from "@opentelemetry/api";
import type { MiddlewareHandler } from "hono";

import type { Env } from "../../env.ts";
import type { PortLogger } from "../logger/logger.ts";

let otel: typeof otelapi | undefined;
let rawTracer: Tracer | undefined;

export const opentelemetryMiddleware =
  (logger: PortLogger): MiddlewareHandler<Env> =>
  async (ctx, next) => {
    if (!otel) {
      try {
        await next();
        if (ctx.error) {
          logger.error({ error: ctx.error.message });
        }
      } catch (error) {
        logger.error({
          error: error instanceof Error ? error.message : "unknown error",
        });
        throw error;
      }
      return;
    }

    if (!rawTracer) {
      rawTracer = otel.trace.getTracer("hono-poc", "0.0.0");
    }

    const span = rawTracer.startSpan(
      "opentelemetry.infrastructure.middleware",
      {
        attributes: {
          "http.method": ctx.req.method,
          "http.url": ctx.req.url,
        },
        kind: SpanKind.SERVER,
      },
      propagation.extract(context.active(), ctx.req.raw.headers),
    );

    try {
      await context.with(trace.setSpan(context.active(), span), async () => {
        await next();
      });
      if (ctx.error) {
        logger.error({ error: ctx.error.message });
        span.recordException(ctx.error);
        span.setStatus({
          code: SpanStatusCode.ERROR,
          message: ctx.error.message,
        });
      } else {
        span.setStatus({ code: SpanStatusCode.OK });
      }
    } catch (error) {
      logger.error({
        error: error instanceof Error ? error.message : "unknown error",
      });
      span.recordException(error as Error);
      span.setStatus({
        code: SpanStatusCode.ERROR,
        message: error instanceof Error ? error.message : "unknown error",
      });
      throw error;
    }
    span.end();
  };