A VM list showed what it read when it was loaded: a VM stopped from
inside its guest or with virsh, or made or removed elsewhere, showed only
after a reload, unlike the VM page, which reloads when its VM's state
changes. The lists of all VMs and of one host's VMs now poll the states
of their VMs, at once and then every 5 s as the VM page does, and reload
when an answer differs from the one before. The states come from one
libvirt call per host; a user who does not see hosts gets only their own
VMs. The page in use (a dialog, a field, an unsaved XML edit, a job
outcome shown) holds the reload until it is free; that check is shared
with the job panel.
Each stats answer carries a signed sample of the counters, bound to the VM,
its compute and UUID. The next poll sends it back and the rates are the
averages since then; a sample from another run of the VM (domain ID),
another host CPU count or device list, or older than 30 s falls back to
one second as before. Windows are measured on the monotonic clock.
Now that a poll is cheap, the Stats tab polls every 5 s like the host
graph, the first time as soon as it opens (pollWhileVisible takes the
delay of the first request).
A counter the host reports as unsupported (-1) or that went back gives no
value instead of 0 or a jump; a NIC without a target keeps its chart, a
pool volume disk is measured, and a disk or NIC attached after the page
loaded no longer stops the other charts. Disk rates are MB/s (they were
MiB/s labelled Mb/s), network Mbit/s; the CPU tooltip names the window.
The VM page polls the VM state every 5 s and, while its Stats tab is
open, the statistics every 10 s; the compute overview polls the host
graph every 5 s. All used setInterval:
- A new request went out on schedule while the previous one was still
open. When a host goes silent, a stats request waits up to 30-45 s,
so each open page held several sync workers at once.
- Each time the Stats tab was shown, the page made new charts and a
new interval without stopping the old ones, and polling went on on
the other tabs of the page.
- Hidden pages kept polling at full rate.
Measured in a browser against a test server (old code / new): Stats tab
shown 4 times, 31 s on it: 12 / 2 requests; 31 s on another tab of the
page: 12 / 0; page hidden for 31 s: 15 / 0, and the new code asks once
right after the page is shown again; with 25 s answers, at most 15 / 1
requests open at once.
static/js/poll.js repeats a request while the page is visible: the
next one 5 or 10 s after the previous answer, none while hidden, one at
once when shown again. The Stats tab makes its charts once and polls
only while shown. The answer handler runs after the poller's own
bookkeeping, so an error in it (a chart for a disk added meanwhile)
does not stop the polling. A Node test of poll.js runs with the test
suite when node is installed.
