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Debugging logs

Send debugging information in an errored response to a logging service.

export default {
async fetch(request, env, ctx) {
// Service configured to receive logs
const LOG_URL = "https://log-service.example.com/";
async function postLog(data) {
return await fetch(LOG_URL, {
method: "POST",
body: data,
});
}
let response;
try {
response = await fetch(request);
if (!response.ok && !response.redirected) {
const body = await response.text();
throw new Error(
"Bad response at origin. Status: " +
response.status +
" Body: " +
// Ensure the string is small enough to be a header
body.trim().substring(0, 10)
);
}
} catch (err) {
// Without ctx.waitUntil(), your fetch() to Cloudflare's
// logging service may or may not complete
ctx.waitUntil(postLog(err.toString()));
const stack = JSON.stringify(err.stack) || err;
// Copy the response and initialize body to the stack trace
response = new Response(stack, response);
// Add the error stack into a header to find out what happened
response.headers.set("X-Debug-stack", stack);
response.headers.set("X-Debug-err", err);
}
return response;
},
};

const handler: ExportedHandler = {
async fetch(request, env, ctx) {
// Service configured to receive logs
const LOG_URL = "https://log-service.example.com/";
async function postLog(data) {
return await fetch(LOG_URL, {
method: "POST",
body: data,
});
}
let response;
try {
response = await fetch(request);
if (!response.ok && !response.redirected) {
const body = await response.text();
throw new Error(
"Bad response at origin. Status: " +
response.status +
" Body: " +
// Ensure the string is small enough to be a header
body.trim().substring(0, 10)
);
}
} catch (err) {
// Without ctx.waitUntil(), your fetch() to Cloudflare's
// logging service may or may not complete
ctx.waitUntil(postLog(err.toString()));
const stack = JSON.stringify(err.stack) || err;
// Copy the response and initialize body to the stack trace
response = new Response(stack, response);
// Add the error stack into a header to find out what happened
response.headers.set("X-Debug-stack", stack);
response.headers.set("X-Debug-err", err);
}
return response;
},
};
export default handler;