Mohnish Kodnani mohnishkodnani

The trick is to design your common-layer value type as a strict subset of OTel's AttributeValue alternatives. If every alternative your variant can hold is also a native alternative of opentelemetry::common::AttributeValue, then the OTel conversion becomes identity-construction (a one-line visitor that just returns the value), while Prometheus visits the same variant and stringifies — paying the heap/map cost alone. The common header stays OTel-free, so ODR and the Prometheus build are unaffected.

OTel's AttributeValue includes bool, int64_t, double, std::string_view (among its 16 arms). Those are exactly the spec-blessed types — so make your variant those four.

Common layer (OTel-free) — common/include/ebay/observability/attributes.hpp

#pragma once
#include <concepts>
#include <cstdint>
#include <span>

	<!DOCTYPE html>
	<html lang="en">
	<head>
	<meta charset="UTF-8">
	<meta name="viewport" content="width=device-width, initial-scale=1.0">
	<title>eBay Evo \| DSBE Paradise Onboarding</title>
	<script src="https://cdn.tailwindcss.com"></script>
	<link href="https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&display=swap" rel="stylesheet">
	<style>
	body { font-family: 'Market Sans', 'Inter', sans-serif; -webkit-font-smoothing: antialiased; }

	container{
	client_name: "urn:ebay-marketplace-consumerid:13051638-8fe9-4380-8d03-c2b176530b4a",
	QueryTime: 1778172926,
	customer_experience: SRP,
	enable_approximate_histograms: true,
	summarize_response: 1,
	task_name: MainSearchInvokerTask
	}(
	query{
	"X-EBAY-C-ENDUSERCTX": "sec-ch-ua-model=%22%22,sec-ch-ua-full-version=%22147.0.7727.138%22,sec-ch-ua-platform-version=%2215.7.1%22,clientId=urn%3Aebay-marketplace-consumerid%3A13051638-8fe9-4380-8d03-c2b176530b4a,ip=216.113.170.107,userAgentAccept=text%2Fhtml%2Capplication%2Fxhtml%2Bxml%2Capplication%2Fxml%3Bq%3D0.9%2Cimage%2Favif%2Cimage%2Fwebp%2Cimage%2Fapng%2C%2F%3Bq%3D0.8%2Capplication%2Fsigned-exchange%3Bv%3Db3%3Bq%3D0.7,userAgentAcceptEncoding=identity,userAgent=Mozilla%2F5.0%20(Macintosh%3B%20Intel%20Mac%20OS%20X%2010_15_7)%20AppleWebKit%2F537.36%20(KHTML%2C%20like%20Gecko)%20Chrome%2F147.0.0.0%20Safari%2F537.36,uri=%2Fsch%2Fi.html,applicationURL=https%3A%2F%2Fwww.ebay.com%2Fsch%2Fi.html%3F_nkw%3D100%2525%2Bnorg%2Bsnow%2Bgoggles%26_sacat

	container{
	client_name: "urn:ebay-marketplace-consumerid:13051638-8fe9-4380-8d03-c2b176530b4a",
	QueryTime: 1777590256,
	customer_experience: SRP,
	enable_approximate_histograms: true,
	summarize_response: 1,
	task_name: MainSearchInvokerTask
	}(
	query{
	"X-EBAY-C-ENDUSERCTX": "sec-ch-ua-model=%22SM-A137F%22,sec-ch-ua-full-version=%22146.0.7680.177%22,sec-ch-ua-platform-version=%2214.0.0%22,clientId=urn%3Aebay-marketplace-consumerid%3A13051638-8fe9-4380-8d03-c2b176530b4a,ip=91.8.53.105,userAgentAccept=%2F,userAgentAcceptEncoding=identity,userAgent=Mozilla%2F5.0%20(Linux%3B%20Android%2010%3B%20K)%20AppleWebKit%2F537.36%20(KHTML%2C%20like%20Gecko)%20Chrome%2F146.0.0.0%20Mobile%20Safari%2F537.36,uri=%2Fsch%2Fajax%2Frefine,applicationURL=https%3A%2F%2Fwww.ebay.de%2Fsch%2Fajax%2Frefine%3F_nkw%3Diphone%252015%2520pro%2520max%26_sacat%3D0%26LH_BIN%3D1%26_udhi%3D500%26no_encode_refine_params%3D1%26modules%3DSEARCH_REFINEMENTS_MODEL_V2%26async%3Dtrue,referer=https%3A%2F%2Fwww.ebay.de%2Fsch%2Fi.html%3F_n

	// If I want to take the code here to build a Table using context functions and convert it to compile time check using macros, to validate rows / cell values etc how do i do that.
	// https://docs.scala-lang.org/scala3/reference/contextual/context-functions.html
	class Table:
	val rows = new ArrayBuffer[Row]
	def add(r: Row): Unit = rows += r
	override def toString = rows.mkString("Table(", ", ", ")")

	class Row:
	val cells = new ArrayBuffer[Cell]
	def add(c: Cell): Unit = cells += c

	package com.symphony.framework.akkastreams.v1;

	import akka.stream.Attributes;
	import akka.stream.FlowShape;
	import akka.stream.Inlet;
	import akka.stream.Outlet;
	import akka.stream.stage.GraphStage;
	import akka.stream.stage.GraphStageLogic;
	import akka.stream.stage.InHandler;
	import akka.stream.stage.OutHandler;

	sudo apt-get install --assume-yes python-software-properties
	sudo apt-add-repository ppa:chris-lea/node.js
	sudo apt-get update
	sudo apt-get install --assume-yes nodejs
	sudo apt-get install --assume-yes git

	# Install Graphite
	sudo apt-get install python-dev ruby-dev bundler build-essential libpcre3-dev graphite-carbon graphite-web
	cat >> /tmp/graphite-carbon << EOF
	# Change to true, to enable carbon-cache on boot