@fiberplane/hono-otel/dist/exporter.js

Hono middleware to forward OpenTelemetry traces to a local instance of @fiberplane/studio

import { ExportResultCode } from "@opentelemetry/core";
import { OTLPExporterError, } from "@opentelemetry/otlp-exporter-base";
import { createExportTraceServiceRequest } from "@opentelemetry/otlp-transformer";
import { isWrapped } from "./utils/index.js";
const defaultHeaders = {
    // INVESTIGATE - add user agent in the same way the OTLPTraceExporter does
    accept: "application/json",
    "content-type": "application/json",
};
/**
 * @NOTE - We had to implement a custom SpanExporter because the OTLPTraceExporter
 *         was not working for us in Cloudflare Workers.
 *
 *         Specifically, the OTLPTraceExporter kept thinking that we were in the browser,
 *         _but only when we attached a `headers` object to the request._
 *
 *         The lack of browser APIs (XHR, sendBeacon) led to runtime errors.
 *
 *         Solution inspired by https://github.com/evanderkoogh/otel-cf-workers/blob/450435bc136d5b81aee655096aa4b8261f42d0c7/src/exporter.ts
 */
export class FPOTLPExporter {
    constructor(config, fetchFn, logger) {
        this.url = config.url;
        this.headers = Object.assign({}, defaultHeaders, config.headers);
        this.fetchFn = fetchFn;
        this.logger = logger;
        if (isWrapped(this.fetchFn)) {
            this.logger.error("FPOTLPExporter's fetch function is already instrumented, so we cannot send traces without causing an infinite loop");
            throw new Error("FPOTLPExporter fetchFn cannot be instrumented");
        }
    }
    export(items, resultCallback) {
        this._export(items)
            .then(() => {
            resultCallback({ code: ExportResultCode.SUCCESS });
        })
            .catch((error) => {
            resultCallback({ code: ExportResultCode.FAILED, error });
        });
    }
    _export(items) {
        return new Promise((resolve, reject) => {
            try {
                this.send(items, resolve, reject);
            }
            catch (e) {
                reject(e);
            }
        });
    }
    send(items, onSuccess, onError) {
        const exportMessage = createExportTraceServiceRequest(items, 
        /** useHex: */ true);
        // HACK - Convert timestamp fields to strings so that they are not parsed as numbers
        //        This gives us better support in the Fiberplane Rust ingestor
        //
        const body = JSON.stringify(exportMessage, (key, value) => {
            // Convert timestamp fields to strings
            if (key === "startTimeUnixNano" ||
                key === "endTimeUnixNano" ||
                key === "timeUnixNano") {
                return String(value);
            }
            return value;
        });
        const params = {
            method: "POST",
            headers: this.headers,
            body,
        };
        // NOTE - You can log the payload to the console for debugging purposes
        // this.logger.debug(`Payload to send to OTLP (${body.length})\n`, body);
        this.fetchFn(this.url, params)
            .then(async (response) => {
            if (response.ok) {
                onSuccess();
            }
            else {
                onError(new OTLPExporterError(`Exporter received a statusCode: ${response.status}`));
            }
        })
            .catch((error) => {
            onError(new OTLPExporterError(`Exception during export: ${error.toString()}`, error.code, error.stack));
        });
    }
    async shutdown() { }
}