fix: ensure mesages are always strings

License: MIT
Signed-off-by: Oli Evans <oli@protocol.ai>

README.md

@@ -2,16 +2,22 @@
 
 Post logs to loki from a Cloudflare [Tail Worker].
 
-It will convert your logs to JSON and send the to `env.LOKI_URL`
+![tail worker diagram](https://developers.cloudflare.com/assets/tail-workers_hu70389a70db4cc3aeffe45d478af42800_41597_1280x532_resize_q75_box_3-1cd0ba86.png)
+
+Converts your logs and errors to JSON and POSTs them to `env.LOKI_URL`.
 
 By using a Tail Worker we ship logs to Loki even in cases where the primary worker hits sub-request limits.
 
+A single instance of this worker on your account can ship all your logs to a shared loki instance.
+
+Each workers log stream is identified by a loki label `worker: 'your-worker-name'`.
+
 ## Getting started
 
 Deploy this worker to your account and set the secrets using `wrangler secret put`
 
 - LOKI_URL - the url to post to e.g `https://eg.grafana.net/loki/api/v1/push`
-- LOKI_TOKEN - basic auth token for loki
+- LOKI_TOKEN - basic auth token for loki: base64 encoded `user:pass` string
 
 Configure this worker as a `tail_consumer` in any other workers whose logs you want to send to Loki.
 
@@ -22,5 +28,4 @@ tail_consumers = [
 ]
 ```
 
-
 [Tail Worker]: https://developers.cloudflare.com/workers/observability/tail-workers/

src/worker.js

@@ -1,19 +1,26 @@
+/**
+* @typedef {object} Env
+* @prop {string} LOKI_URL - full url to post logs to
+* @prop {string} LOKI_TOKEN - basic auth token for loki url
+* @prop {string} DEBUG - log every request
+*/
+
 /**
  * POST tail events to Loki
  *
  * @see https://developers.cloudflare.com/workers/runtime-apis/tail-event/
  * @see https://developers.cloudflare.com/workers/observability/tail-workers/
  *
  * @type {ExportedHandler<Env>}
- * @typedef {object} Env
- * @prop {string} LOKI_URL - full url to post logs to
- * @prop {string} LOKI_TOKEN - basic auth token for loki url
  */
 export default {
   async tail (events, env) {
     const lokiBody = {
       streams: events.map(toLoki)
     }
+    if (env.DEBUG === 'true') {
+      console.log('POST', env.LOKI_URL, JSON.stringify(lokiBody))
+    }
     const res = await fetch(env.LOKI_URL, {
       method: 'POST',
       headers: {
@@ -23,9 +30,13 @@ export default {
       },
       body: JSON.stringify(lokiBody)
     })
-    if (!res.ok) {
-      console.error(`${res.status} ${res.statusText} ${res.url}`)
-      console.log(await res.text())
+    if (!res.ok || env.DEBUG === 'true') {
+      console.log(`${res.status} ${res.statusText} ${res.url}`)
+      const text = await res.text()
+      console.log(text)
+      if (!res.ok) {
+        throw new Error(`Failed to POST to loki ${res.status} ${res.url} ${text}`)
+      }
     }
   }
 }
@@ -37,6 +48,7 @@ export function toLoki (tailItem) {
   const req = formatRequest(tailItem)
   const logs = tailItem.logs.map(formatLog)
   const errs = tailItem.exceptions.map(formatException)
+  /** @type [string, string][] */
   const values = [...logs, ...errs]
   if (req !== undefined) {
     values.unshift(req)
@@ -52,30 +64,39 @@ export function toLoki (tailItem) {
 
 /** @param {number} ms epoch time in milliseconds */
 export function toNano (ms) {
-  const nano = BigInt(ms) * BigInt(10_000)
+  const nano = BigInt(ms) * BigInt(1_000_000)
   return nano.toString()
 }
 
-/** @param {TraceItem} item */
+/**
+ * @param {TraceItem} item
+ * @returns {[string, string] | undefined}
+ **/
 export function formatRequest ({ eventTimestamp, event }) {
   // @ts-expect-error checking for request here
   const request = event?.request
   if (eventTimestamp && request) {
     const { url, method, headers, cf } = request
-    return [toNano(eventTimestamp), { url, method, headers, cf, level: 'request' }]
+    return [toNano(eventTimestamp), JSON.stringify({ url, method, headers, cf, level: 'request' })]
   }
 }
 
-/** @param {TraceLog} log */
+/**
+ * @param {TraceLog} log
+ * @returns {[string, string]}
+ **/
 export function formatLog ({ timestamp, message, level }) {
   const [first, ...args] = message
   if (typeof first === 'object') {
-    return [toNano(timestamp), { ...first, args, level }]
+    return [toNano(timestamp), JSON.stringify({ ...first, args, level })]
   }
-  return [toNano(timestamp), { msg: first, args, level }]
+  return [toNano(timestamp), JSON.stringify({ msg: first, args, level })]
 }
 
-/** @param {TraceException} e */
+/**
+ * @param {TraceException} e
+ * @returns {[string, string]}
+ **/
 export function formatException ({ timestamp, name, message }) {
-  return [toNano(timestamp), { msg: message, name, level: 'fatal' }]
+  return [toNano(timestamp), JSON.stringify({ msg: message, name, level: 'fatal' })]
 }

test/worker.test.js

@@ -12,7 +12,8 @@ test('toLoki', t => {
   })
   t.is(values.length, 3)
 
-  t.is(values[0][0], '15870586420050000')
+  t.is(values[0][0].length, 19, 'should be nanoseconds since epoch')
+  t.is(values[0][0], '1587058642005000000')
   t.like(values[0][1], {
     url: 'https://example.com/some/requested/url',
     method: 'GET',
@@ -22,14 +23,14 @@ test('toLoki', t => {
     level: 'request'
   })
 
-  t.is(values[1][0], '15870586420060000')
+  t.is(values[1][0], '1587058642006000000')
   t.like(values[1][1], {
     msg: 'string passed to console.log()',
     args: [99, { woo: 'haa' }],
     level: 'log'
   })
 
-  t.is(values[2][0], '15870586420070000')
+  t.is(values[2][0], '1587058642007000000')
   t.like(values[2][1], {
     msg: 'Threw a sample exception',
     name: 'Error',

wrangler.toml

@@ -4,13 +4,15 @@ compatibility_date = "2023-07-17"
 
 [vars]
 ENV = "dev"
+DEBUG = "true"
 
 # STAGING!
 [env.staging]
 account_id = "fffa4b4363a7e5250af8357087263b3a"
 
 [env.staging.vars]
 ENV = "staging"
+DEBUG = "true"
 
 # PROD!
 [env.productuion]