Periodically check your website/url with Cloudflare worker

Here is the minimal example to show how to build your own website check with Cloudflare worker and send IM notice to LINE channel.

Create a new worker project

Quick Edit

const url_list = ["http://your.own.http.site", "https://your.own.https.site"];

async function gatherResponse(response) {
    const { headers } = response;
    // console.log(headers);
    const contentType = headers.get("content-type") || "";
    if (contentType.includes("application/json")) {
        return JSON.stringify(await response.json());
    } else if (contentType.includes("application/text")) {
        return response.text();
    } else if (contentType.includes("text/html")) {
        return response.text();
    } else {
        return response.text();
    }
}

async function handleScheduled(event) {
    const init = {
        headers: {
            "content-type": "text/html;charset=UTF-8",
        },
    };
    for (const url of url_list) {
        const response = await fetch(url, init);
        if (response.status === '301' || '302' || '200') {
            console.log(response.status);
        } else {
            await sendToLineChannel(response.status + ": " + url);
        };
    };
};

addEventListener("scheduled", (event) => {
    event.waitUntil(handleScheduled(event));
});

async function sendToLineChannel(msg) {
    // send to LINE
    const form = new FormData();
    form.append("message", msg);
    const init = {
        method: 'POST',
        headers: {
            "Authorization": "Bearer Your_channel_key"
        },
        body: form
    };
    const response = await fetch("https://notify-api.line.me/api/notify", init);
}

Config Triggers

config Cron Triggers to execute your Worker on a time-based, reoccurring schedule.

Reference

• https://developers.cloudflare.com/workers/learning/metrics-and-analytics/#requests
• Alternative solution: https://grafana.com/docs/grafana-cloud/synthetic-monitoring/

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