How to get the response body in custom middleware?

[tdwells90]

Hi,

Quick question. I'm making a small custom middleware (very similar to the logger middleware in the source files) that sends all API requests to Axiom for logging and monitoring.

I want to send the response body to Axiom, too, but can't seem to find a way to do it. Anyone know? Here is my current code (some stuff changed) for an example.

import type { Context, MiddlewareHandler } from "hono"
import { time } from "./time"

const axiomDataset = 'dataset-name'
const axiomEndpoint = 'https://api.axiom.co'
const axiomUrl = `${axiomEndpoint}/v1/datasets/${axiomDataset}/ingest`

export const logApiRequest = (): MiddlewareHandler => {
  return async (c: Context, next) => {
    if (c.env.ENV === 'local') return await next() // Don't log local requests

    const axiomToken = c.env.AXIOM_API_KEY

    if (!axiomToken) {
      console.error('AXIOM_API_KEY is not set')
      return
    }

    const { method, url, path, raw } = c.req
    const start = time(new Date())

    await next()

    const axiomBody = {
      environment: c.env.ENV,
      path,
      url,
      duration: time(new Date()) - start,
      method: method,
      headers: raw?.headers,
      body: raw?.body,
      statusCode: c.res?.status,
      response: c.res?.body,
    }

    return fetch(axiomUrl, {
      method: 'POST',
      body: JSON.stringify(axiomBody),
      headers: {
        'Content-Type': 'application/x-ndjson',
        Authorization: `Bearer ${axiomToken}`,
      },
    })
  }
}

Thanks!

Tom.

[nicougou]

Here is what should work :

await next()

// clone the response
const originalResponse = c.res.clone()
// get the body
const body: any = await originalResponse.json()

[Andrew-Chen-Wang]

In case anyone's looking for a full solution including the request and response body, this is based on the Hono logger middleware:

/**
 * Logger middleware for development; based on Hono's default logger middleware
 */
export const devLoggerMiddleware = createMiddleware(async (c, next) => {
  const { method, url, raw } = c.req
  const path = url.slice(url.indexOf("/", 8))
  console.debug("<--" /* Incoming */, method, path)
  if (method === "POST" || method === "PUT" || method === "PATCH") {
    try {
      const requestBody = await raw.clone().json()
      console.log("Request Body:", JSON.stringify(requestBody, null, 2))
    } catch (e) {
      console.log("Request Body (not JSON or empty):", await c.req.text())
    }
  }
  const start = Date.now()

  await next()

  const time = (start: number) => {
    const delta = Date.now() - start
    return delta < 1e3 ? delta + "ms" : Math.round(delta / 1e3) + "s"
  }

  const originalResponse = c.res.clone()
  const responseBody: any = await originalResponse.json()
  console.debug("-->" /* Outgoing */, method, path, c.res.status, time(start))
  console.debug(JSON.stringify(responseBody, null, 2))
})