Live logs

The Live logs tab on a device page streams log files from the device while the page is open: Pantavisor's own log, each container's console, and whatever a container writes under its /var/log. Unlike the persisted logs Pantavisor pushes, nothing is stored: lines go from the device to your browser over the device's MQTT connection, for as long as you watch and no longer.

What you need

• A device managed by the Pantahub MQTT agent (pv-mqtt-sdk), connected over MQTT.
• You must be the device's owner. A token used from a script needs the full API scope or the devices.logs scope.

Using it

1. Open Live logs on the device page. The tab asks the device which log files it has (the LIST_LOG_SOURCES command) and shows them as a tree: one folder per container plus pantavisor, with the rotated .gz files of each.

2. Pick what to stream, up to 10 entries:

   • a file, such as pantavisor/pantavisor.log or myapp/lxc/console.log;
   • a folder, which streams every live file under it (a container's whole output);
   • All logs, the whole revision.

   A folder streams at most 64 files; rotated .gz files are picked one by one, and are read once rather than followed. Clear selection empties the picker.

3. Choose the revision. The running revision is followed live; older revisions and .gz files are read once.

4. Optionally type a filter. It is sent to the device, which then sends only the lines that contain the text (case-insensitive), so a busy device costs no bandwidth for lines you will not read. Changing the text while streaming restarts the session with the new filter; the initial tail counts matching lines.

5. Press Start. The last lines (200 by default) arrive first, then new ones as they are written. Pause, download what you have, or narrow the view by source.

A session ends when you leave the tab, after 30 minutes, or when the lease runs out (60 s after the tab is hidden).

How it works

Pantavisor has no API to read logs back, so the agent reads the files itself: its container has the mgmt role and sees every revision's logs read-only under /pantavisor/logs/<rev>/. A session is a lease the browser renews every 20 seconds; the device follows the selected files across rotation, batches lines every 500 ms or 32 KiB, and sends them at most at 64 KiB/s (lines above that are counted as dropped, never buffered forever). Batches are numbered, so a gap shows in the view.

The Hub keeps a batch for ten minutes so several API replicas can serve the long-poll; nothing goes into the persisted logs.

Limit	Value
Lease / hard limit	60 s renewed while visible / 30 min
Sessions	2 per device, 5 per user
Sources	10 entries, 64 files per session
Tail	up to 500 lines
Line	cut at 8 KiB
Rate	64 KiB/s per session
Filter	up to 256 bytes, case-insensitive substring, applied on the device

The endpoints are in the API Reference under devices (log-sessions); the wire contract is docs/logs.md in pv-mqtt-sdk.