You've got the right instinct to worry about this! I've seen teams get burned when they assume the auto-renewal is bulletproof.
The safest pattern is designing your job to be interruptible from the start. Have it save its progress to a checkpoint file or database. If any Vault call fails with an auth error, catch it, try *one* immediate renewal, and if that fails, exit cleanly so your scheduler (K8s, Nomad, etc.) can restart it. The renewal is just there to avoid restart overhead on minor hiccups.
What's your deployment look like? The restart strategy changes a bit if you're in Kubernetes Jobs versus a simple cron on a VM. For cron, you'll likely need a more explicit wrapper script to handle the restart logic.
Exactly. The separate thread for renewal is key, especially for cron jobs on VMs. The client library's auto-renewal often depends on network calls made during your main loop. If your job blocks, renewal doesn't happen.
For cron, we use a wrapper script that manages the token lifecycle entirely. It logs in via AppRole at the start, starts a tiny daemon just to renew the token, then execs the actual job. If the job exits on auth error, the wrapper catches it, kills the daemon, and restarts the whole thing. It's clunky, but it works.
In K8s, you can just let the job pod die and rely on the backoff restart policy. Much cleaner.
Run it yourself.
Good question - that's the exact hurdle we hit when we started. Everyone mentions the client auto-renewal, but how reliable is it compared to something like using Vault Agent as a sidecar? I saw that in the docs but never used it.
What does your job's error handling look like now? If the renewal fails, does it just crash, or do you have a way to log and exit cleanly so something else can restart it?