handlers_alternative.js

const axios = require("axios");

const colors = { firing: 0xd50000, resolved: 0x00c853 };
const maxEmbedsLength = 10;
const maxFieldsLength = 25;
const groupBy = (array, func) => {
    return array.reduce((group, item) => {
        const groupName = func(item);
        group[groupName] = group[groupName] ?? [];
        group[groupName].push(item);
        return group;
    }, {});
};
const getMentions = (alerts) => {
    return [...alerts].reduce((mentions, alert) => {
        if (alert.labels["mentions"]) {
            alert.labels["mentions"]
                .replace(/ /g, "")
                .split(",")
                .forEach((m) => mentions.push(`<@${m}>`));
        }
        return mentions;
    }, []);
};

async function handleHook(ctx) {
    let hook = ctx.routes[ctx.params.slug];

    if (ctx.request.body && Array.isArray(ctx.request.body.alerts)) {
        const raws = [];
        const groupByStatus = groupBy(ctx.request.body.alerts, (alert) => alert.status);
        for (const byStatus of Object.values(groupByStatus)) {
            const [first] = byStatus;
            if (first.annotations && (first.annotations.summary || first.annotations.description)) {
                const statusColor = first.status === "resolved" ? colors.resolved : colors.firing;
                const title = (a) =>
                    a.status === "resolved"
                        ? a.annotations["resolved_summary"] ?? a.annotations.summary
                        : a.annotations.summary;
                const desc = (a) =>
                    a.status === "resolved"
                        ? a.annotations["resolved_description"] ?? a.annotations.description
                        : a.annotations.description;
                if (first.annotations["field_name"] && first.annotations["field_value"]) {
                    let chunk = [];
                    while ((chunk = byStatus.splice(0, maxFieldsLength)) && chunk.length) {
                        raws.push({
                            mentions: getMentions(chunk),
                            embed: {
                                title: `${first.annotations["emoji"] ? first.annotations.emoji + " " : ""}${
                                    chunk.length
                                } ${title(first)}`,
                                url: statusColor === colors.firing ? first.annotations["url"] ?? "" : "",
                                description: desc(first),
                                color: statusColor,
                                fields: chunk.map((a) => ({
                                    name: a.annotations.field_name,
                                    value: a.annotations.field_value,
                                    inline: true,
                                })),
                                footer: {
                                    text: first.annotations.footer_text ?? "",
                                    icon_url: first.annotations.footer_icon_url ?? "",
                                },
                            },
                        });
                    }
                } else {
                    byStatus.forEach((a) => {
                        raws.push({
                            mentions: getMentions([a]),
                            embed: {
                                title: `${first.annotations["emoji"] ? first.annotations.emoji + " " : ""}${title(
                                    a
                                )}`,
                                url: statusColor === colors.firing ? first.annotations["url"] ?? "" : "",
                                description: desc(a),
                                color: statusColor,
                                footer: {
                                    text: first.annotations.footer_text ?? "",
                                    icon_url: first.annotations.footer_icon_url ?? "",
                                },
                            },
                        });
                    });
                }
            }
        }
        raws.sort((a) => (a.embed.color === colors.resolved ? -1 : 1));
        if (!raws.length) {
            ctx.status = 400;
            ctx.logger.warn("No data to write to embeds");
            return;
        }

        let chunk = [];
        while ((chunk = raws.splice(0, maxEmbedsLength)) && chunk.length) {
            // Discord displays only one embed if several embeds have the same url in one message.
            // Then only one (last fired) embed will have URL in each chunk
            chunk.forEach((e) =>
                chunk.filter((a) => a.embed.url === e.embed.url).length > 1 ? (e.embed.url = "") : undefined
            );
            const mentions = [...new Set(chunk.map((c) => c.mentions).flat())].join(" ");
            const payload = { embeds: chunk.map((c) => c.embed) };
            if (mentions.length !== 0) {
                payload.content = mentions;
                payload.allowed_mentions = { parse: ["users", "roles"] };
            }
            await axios
                .post(hook, payload)
                .then(() => {
                    ctx.status = 200;
                    ctx.logger.info(chunk.length + " embeds sent");
                })
                .catch((err) => {
                    ctx.status = 500;

                    const errorConfig = err.config || {};
                    const errorMessage = err.message
                      + (errorConfig.method != null ? `; Method: ${errorConfig.method}` : '')
                      + (errorConfig.data != null ? `; Request data length: ${
                        errorConfig.data.length
                      }; Request data: ${JSON.stringify(errorConfig.data)}` : '');

                    ctx.logger.error(`Axios error in "handlers_alternative.js": ${errorMessage}`);
                });
        }
    } else {
        ctx.status = 400;
        ctx.logger.error(`Unexpected request from Alertmanager: ${JSON.stringify(ctx.request.body)}`);
    }
}

module.exports = {
    handleHook,
};