How Deployment Works

PUQ Web Hosting module WHMCS
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Orders return instantly — work happens in the background
When a service is created (a WHMCS order goes active, an admin clicks Create, or the API is called) the module does not try to build everything inside the HTTP request. It writes a service record, returns success to WHMCS immediately, and lets the cron‑driven task queue do the real work.
This is what the customer sees right after ordering — a live deployment splash that polls for progress and refreshes itself:

Each step is a queued task processed by the cron runner. As steps complete, the bar advances and the recent‑activity feed updates:

When the last step finishes the page flips to the live control panel:

This design makes provisioning resilient to slow panels, SSH timeouts, apt‑get locks and long operations — none of them block the order, and any failed step is simply retried.
The pipeline (Split example)
A Split service is built by a chain of idempotent tasks, roughly in this order:

Create the web package + web user on a Web node.

Add the web domain (and the web account's quota/PHP settings).

Create the mail user + mail domain on a Mail node (with DKIM).

Create the DNS user + zone and deploy the zone to every attached DNS node.

Seed Auto‑SSL so Let's Encrypt issues as soon as DNS resolves.

Unified runs the same idea with one combined account; Vanity runs a trimmed chain (one web account, one mailbox on the shared mail user, one DNS record). Every task is idempotent — re‑running it is safe — so the chain can resume from wherever it stopped.
Watching and driving it from the admin panel
The admin service panel's Deploy tab shows the live deploy status and a full timeline of every task with its duration and result, plus a Redeploy (hard reset) button:

The Tasks tab lists this service's tasks (action, server, attempts, timestamps); each row opens a detail modal with the streamed SSH log:

Retries, failures and tickets
A failed task is retried with exponential back‑off. Once all attempts are exhausted it is terminally failed, the service shows a deploy error, and — if you enabled it — the module can open a support ticket for your staff. The retry policy and the failure‑ticket behaviour are configured in addon Settings (see Cron & Automation → Task queue, retries & tickets).

Key takeaway: deployment is an asynchronous, idempotent, resumable pipeline. The order is accepted instantly, the queue does the work, failures self‑heal on retry, and both you and the customer get live progress.