Polls S3 for hot upgrades and applies them automatically.

This GenServer periodically checks S3 for new hot upgrades and applies them when detected. It compares the S3 state's source_image_ref with the local marker file to determine if an upgrade is needed.

Usage

Add to your application's supervision tree:

def start(_type, _args) do
  children = [
    {FlyDeploy, otp_app: :my_app},
    # ... rest of your children
  ]

  Supervisor.start_link(children, strategy: :one_for_one)
end

Options

• :otp_app - The OTP application name (required)
• :poll_interval - How often to poll S3 in ms (default: 1000)
• :suspend_timeout - Timeout for suspending processes during upgrade in ms (default: 10_000)

Important

Place {FlyDeploy, otp_app: :my_app} at the TOP of your children list. The poller blocks during init/1 to apply any pending hot upgrades before the rest of the supervision tree starts.

Efficiency

Uses ETag/If-None-Match headers to minimize bandwidth. When no upgrade is available, S3 returns a 304 Not Modified response.

Version Tracking

The poller maintains a "fingerprint" of the current code version in :persistent_term. Access it via FlyDeploy.current_vsn/0.