Deno

Traces	Metrics	App Logs	Custom Logs	Profiling
✅	✖	✖	✅	✖

Prerequisites

Deno 1.41.2+. Check using:
```
1deno --version
```
If you choose Host-based mode, ensure the Middleware Host Agent is running and reachable from your app (see Host Agent install). In containers, set MW_AGENT_SERVICE to route traffic to the agent:
- Docker: MW_AGENT_SERVICE=172.17.0.1 (default bridge gateway).
- Kubernetes: MW_AGENT_SERVICE=mw-service.mw-agent-ns.svc.cluster.local.

Choose your deployment

With Host Agent (same VM/pod as your app) → send OTLP to the local agent (http://localhost:9320).
Serverless (no agent) → send directly to Middleware ingest (https://<ACCOUNT-UID>.middleware.io:443).

Host-based

Serverless

1 Import the SDK and HTTP server

Add these imports at the top of your entry file (e.g., index.ts).

1// index.ts
2import { serve } from "https://deno.land/[email protected]/http/server.ts";
3import { track, httpTracer, info, warn, error, debug } from "https://deno.land/x/[email protected]/mod.ts";

2 Initialize tracing

Initialize once at startup. For host-based setups, send OTLP to the local Host Agent.

1// index.ts
2  track({
3    serviceName: "{APM-SERVICE-NAME}",
4    target: "http://localhost:9320",   // Host Agent OTLP HTTP endpoint
5    accessToken: "<MW_API_KEY>",
6  });

(The track(...) API mirrors the Middleware Deno doc; using a local collector is standard in host-based installs.)

3 Add a request handler

Define how your server responds to incoming HTTP requests with the following function:

1// index.ts
2function handler(_req: Request): Response {
3  const data = { message: "Hello world!" };
4  return new Response(JSON.stringify(data), { headers: { "Content-Type": "application/json" } });
5}

4 Start the server with tracing

Wrap the handler so incoming requests become spans; run with network permissions:

1// index.ts
2await serve(httpTracer(handler));
3deno run --allow-net index.ts

(Deno blocks network access by default; --allow-net grants it.)

5 (Optional) Send custom logs

Wrap the handler so incoming requests become spans; run with network permissions:

1Emit structured logs that correlate with the active trace:
2info("Sample Info Log");
3warn("Sample Warning Log");
4error("Sample Error Log");
5debug("Sample Debug Log");

(Logging helpers are part of the same Deno SDK.)

Everything else stays the same. Only change the target to send data straight to the Middleware’s serverless ingest:

1// Only the target differs for serverless:
2track({
3  serviceName: "{APM-SERVICE-NAME}",
4  target: "https://<MW_UID>.middleware.io:443",
5  accessToken: "<MW_API_KEY>",
6});

On platforms like Deno Deploy, you don’t manage the HTTP process flags locally; you’ll still run with --allow-net for testing.

Environment variables

Key/Option	Purpose	Example
`MW_AGENT_SERVICE`	In containers, routes app → Host Agent	`172.17.0.1` (Docker) / `mw-service.mw-agent-ns.svc.cluster.local` (K8s).
`serviceName (SDK option)`	Logical service name in APM	`orders-deno.`
`target` (SDK option)	OTLP endpoint	`http://localhost:9320` (Host) or `https://{ACCOUNT-UID}.middleware.io:443` (Serverless).
`accessToken` (SDK option)	Middleware API key	`<MW_API_KEY>`.
`--allow-net` (CLI)	Network permission for local runs	`deno run --allow-net index.ts.`

Troubleshooting

No traces/logs: Ensure track({...}) runs before requests and that you start via serve(httpTracer(handler)). In Host mode, confirm the Host Agent is running and the app can reach it (set MW_AGENT_SERVICE correctly in Docker/K8s).
Permission errors: Deno blocks the network by default. Run with --allow-net (you can scope it to specific hosts).
Imports drift: Pin remote module versions or use an import map in deno.json to centralize and lock dependencies.

Need assistance or want to learn more about Middleware? Contact our support team at [email protected] or join our Slack channel.