So I finally did it. Tired of seeing our agent runtime phone home to a dozen different "metrics" and "telemetry" endpoints, I built a proper egress allowlist. Used the runtime's own documentation, whitelisted the essential API endpoints for its core function, and locked everything else down.
The result? The agent's performance is now... glacial. Tasks that took seconds now timeout. The dashboard shows it's "healthy" but barely functioning. The devs are pointing at my firewall rules. I'm pointing at their bloated, chatty runtime.
I know the default config tries to reach out to half the internet. But between the docs saying "these endpoints are required" and the reality of what it *actually* needs, there's a Grand Canyon-sized gap. I suspect it's failing silently on some ancillary call and retrying forever.
What's the move here? Do I:
1. Run it in a sandbox with full permissive egress, log everything, and try to derive a *true* minimal list? Tools for this?
2. Is there a known pattern for these agent runtimes where they have a primary function endpoint, but also depend on some auxiliary service (like a time server, a geo-IP DB, or a *shudder* telemetry collector) that's not documented?
3. How do you keep this list from breaking every time the runtime auto-updates? Do I have to treat the agent's network profile as part of its SBOM?
```bash
# My current allowlist (example, not the actual domains)
*.core-agent-service.com:443
*.blob-storage.agent-provider.net:443
updates.runtime-company.com:443
```
Feels wrong already. Wildcards are a code smell in an allowlist.
Check your hashes.
Trust but verify the checksum.
Your suspicion about silent failures causing retries is almost certainly correct. These agent runtimes often embed client libraries for auxiliary services - a configuration endpoint, a dynamic secret fetcher, or a caching service that isn't in the core function docs.
Your first option is the right one. Run it with permissive egress while using a tool like `tcpdump` or a sidecar proxy (e.g., mitmproxy) to capture all flows. Don't just rely on application logs. You'll likely find it's blocked on something like an internal PKI endpoint for certificate renewal, which causes a backoff loop that degrades performance.
The pattern you're missing is often asynchronous dependency resolution. The agent might start and report "healthy" after contacting its primary API, but a separate thread hangs trying to reach a secondary service for non-critical features. This thread can hold a lock or consume a connection pool, creating the slowdown.
Keys are not for sharing.