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[workers] Fallback to plain text Discord message as a 429 workaround (#1154)

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**Tested by**

Deployed, and redelivered a few recent messages to see that they're
falling back to the fallback.
This commit is contained in:
Manav Rathi 2024-03-20 09:58:06 +05:30 committed by GitHub
parent 2bf03cbcaf 35ba5b6685
commit b77ac2a2d8
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GPG key ID: B5690EEEBB952194
2 changed files with 62 additions and 14 deletions
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74
infra/workers/github-discord-notifier/src/index.ts
View file

@ -3,16 +3,6 @@
*
* This worker receives webhooks from GitHub, filters out the ones we don't
* need, and forwards them to a Discord webhook.
*
* [Note: GitHub specific Discord Webhooks]
*
* By appending `/github` to the end of the webhook URL, we can get Discord to
* automatically parse the payload sent by GitHub.
* https://discord.com/developers/docs/resources/webhook#execute-githubcompatible-webhook
*
* Note that this doesn't work for all events. And sadly, the events it doesn't
* work for get silently ignored (Discord responds with a 204).
* https://github.com/discord/discord-api-docs/issues/6203#issuecomment-1608151265
*/
export default {
async fetch(request: Request, env: Env) {
@ -24,20 +14,78 @@ interface Env {
DISCORD_WEBHOOK_URL: string;
}
const handleRequest = async (request: Request, targetURL: string) => {
const handleRequest = async (request: Request, discordWebhookURL: string) => {
const requestBody = await request.text();
let sender = JSON.parse(requestBody)["sender"]["login"];
const requestJSON = JSON.parse(requestBody);
const sender = requestJSON["sender"]["login"];
if (sender === "cloudflare-pages[bot]" || sender === "CLAassistant") {
// Ignore pings from CF bot
return new Response(null, { status: 200 });
}
const response = await fetch(targetURL, {
// [Note: GitHub specific Discord Webhooks]
//
// By appending `/github` to the end of the webhook URL, we can get Discord
// to automatically parse the payload sent by GitHub.
// https://discord.com/developers/docs/resources/webhook#execute-githubcompatible-webhook
//
// Note that this doesn't work for all events. And sadly, the events it
// doesn't work for get silently ignored (Discord responds with a 204).
// https://github.com/discord/discord-api-docs/issues/6203#issuecomment-1608151265
let response = await fetch(`${discordWebhookURL}/github`, {
method: request.method,
headers: request.headers,
body: requestBody,
});
if (response.status === 429) {
// Sometimes Discord starts returning 429 Rate Limited responses when we
// try to invoke the webhook.
//
// Retry-After: 300
// X-Ratelimit-Global: true
// X-Ratelimit-Scope: global
//
// {"message": "You are being rate limited.", "retry_after": 0.3, "global": true}
//
// This just seems to be a bug on their end, and it goes away on its own
// after a while. My best guess is that the IP of the Cloudflare Worker
// somehow gets rate limited because of someone else trying to spam from
// a worker running on the same IP. But it's a guess. I'm not sure.
//
// Ref:
// https://discord.com/developers/docs/topics/rate-limits#global-rate-limit
//
// Interestingly, this only happens for the `/github` specific webhook.
// The normal webhook still works. So as a workaround, just send a
// normal text message to the webhook when we get a 429.
// The JSON sent by GitHub has a varied schema. This is a stop-gap
// arrangement (we shouldn't be getting 429s forever), so just try to
// see if we can extract a URL from something we recognize.
let activityURL: string | undefined;
if (requestJSON["issue"]) {
activityURL = requestJSON["issue"]["html_url"];
}
if (!activityURL && requestJSON["discussion"]) {
activityURL = requestJSON["discussion"]["html_url"];
}
// Ignore things like issue label changes.
const action = requestJSON["action"];
if (activityURL && ["created", "opened"].includes(action)) {
response = await fetch(discordWebhookURL, {
method: request.method,
headers: request.headers,
body: JSON.stringify({
content: `Activity in ${activityURL}`,
}),
});
}
}
const responseBody = await response.text();
const newResponse = new Response(responseBody, {
status: response.status,

2
infra/workers/github-discord-notifier/wrangler.toml
View file

@ -4,4 +4,4 @@ compatibility_date = "2024-03-14"
[vars]
# Added as a secret via the Cloudflare dashboard
# DISCORD_WEBHOOK_URL = "https://discord.com/api/webhooks/{webhook.id}/{webhook.token}/github"
# DISCORD_WEBHOOK_URL = "https://discord.com/api/webhooks/{webhook.id}/{webhook.token}"