Log errors to Sentry from a Cloudflare Worker

index.js

// Get the key from the "DSN" at: https://sentry.io/settings/<org>/projects/<project>/keys/
// The "DSN" will be in the form: https://<SENTRY_KEY>@sentry.io/<SENTRY_PROJECT_ID>
// eg, https://[email protected]/123456
const SENTRY_PROJECT_ID = '123456'
const SENTRY_KEY = '0000aaaa1111bbbb2222cccc3333dddd'

// Useful if you have multiple apps within a project – not necessary, only used in TAGS and SERVER_NAME below
const APP = 'my-app'

// https://docs.sentry.io/error-reporting/configuration/?platform=javascript#environment
const ENV = 'development'

// https://docs.sentry.io/error-reporting/configuration/?platform=javascript#release
// A string describing the version of the release – we just use: git rev-parse --verify HEAD
// You can use this to associate files/source-maps: https://docs.sentry.io/cli/releases/#upload-files
const RELEASE = '0000aaaa1111bbbb2222cccc3333dddd'

// https://docs.sentry.io/enriching-error-data/context/?platform=javascript#tagging-events
const TAGS = { app: APP }

// https://docs.sentry.io/error-reporting/configuration/?platform=javascript#server-name
const SERVER_NAME = `${APP}-${ENV}`

// Indicates the name of the SDK client
const CLIENT_NAME = 'mhart-cloudflare-worker'
const CLIENT_VERSION = '1.0.0'
const RETRIES = 5

// The log() function takes an Error object and the current request
//
// Eg, from a worker:
//
// addEventListener('fetch', event => {
//   event.respondWith(async () => {
//     try {
//       throw new Error('Oh no!')
//     } catch (e) {
//       await log(e, event.request)
//     }
//     return new Response('Logged!')
//   })
// })

async function log(err, request) {
  const body = JSON.stringify(toSentryEvent(err, request))

  for (let i = 0; i <= RETRIES; i++) {
    const res = await fetch(`https://sentry.io/api/${SENTRY_PROJECT_ID}/store/`, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'X-Sentry-Auth': [
          'Sentry sentry_version=7',
          `sentry_client=${CLIENT_NAME}/${CLIENT_VERSION}`,
          `sentry_key=${SENTRY_KEY}`,
        ].join(', '),
      },
      body,
    })
    if (res.status === 200) {
      return
    }
    // We couldn't send to Sentry, try to log the response at least
    console.error({ httpStatus: res.status, ...(await res.json()) }) // eslint-disable-line no-console
  }
}

function toSentryEvent(err, request) {
  const errType = err.name || (err.contructor || {}).name
  const frames = parse(err)
  const extraKeys = Object.keys(err).filter(key => !['name', 'message', 'stack'].includes(key))
  return {
    event_id: uuidv4(),
    message: errType + ': ' + (err.message || '<no message>'),
    exception: {
      values: [
        {
          type: errType,
          value: err.message,
          stacktrace: frames.length ? { frames: frames.reverse() } : undefined,
        },
      ],
    },
    extra: extraKeys.length
      ? {
          [errType]: extraKeys.reduce((obj, key) => ({ ...obj, [key]: err[key] }), {}),
        }
      : undefined,
    tags: TAGS,
    platform: 'javascript',
    environment: ENV,
    server_name: SERVER_NAME,
    timestamp: Date.now() / 1000,
    request:
      request && request.url
        ? {
            method: request.method,
            url: request.url,
            query_string: request.query,
            headers: request.headers,
            data: request.body,
          }
        : undefined,
    release: RELEASE,
  }
}

function parse(err) {
  return (err.stack || '')
    .split('\n')
    .slice(1)
    .map(line => {
      if (line.match(/^\s*[-]{4,}$/)) {
        return { filename: line }
      }

      // From https://github.com/felixge/node-stack-trace/blob/1ec9ba43eece124526c273c917104b4226898932/lib/stack-trace.js#L42
      const lineMatch = line.match(/at (?:(.+)\s+\()?(?:(.+?):(\d+)(?::(\d+))?|([^)]+))\)?/)
      if (!lineMatch) {
        return
      }

      return {
        function: lineMatch[1] || undefined,
        filename: lineMatch[2] || undefined,
        lineno: +lineMatch[3] || undefined,
        colno: +lineMatch[4] || undefined,
        in_app: lineMatch[5] !== 'native' || undefined,
      }
    })
    .filter(Boolean)
}

function uuidv4() {
  const bytes = new Uint8Array(16)
  crypto.getRandomValues(bytes)
  bytes[6] = (bytes[6] & 0x0f) | 0x40
  bytes[8] = (bytes[8] & 0x3f) | 0x80
  return [...bytes].map(b => ('0' + b.toString(16)).slice(-2)).join('') // to hex
}

license

Copyright 2019 Michael Hart

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.