viktor/infra
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions 1

android-emulator: sleep after 6h idle (activity-based), fix never-sleeping
All checks were successful
ci/woodpecker/push/default Pipeline was successful
Details

Browse source 
The emulator was meant to scale to zero when idle but had been up 6+ days
straight despite ~5 days with no real use. Two bugs:

1. The idle check counted ESTABLISHED TCP connections to the adb/noVNC
   ports. A forgotten `adb connect` (no disconnect) holds that transport
   open forever, so every 15-min run saw "active" and reset the counter --
   it never reached the sleep branch. (Right now: 4 such stale transports
   from pods on k8s-node3/node4.)
2. Even when it did reach the sleep branch, `kubectl scale --replicas=0`
   failed Forbidden -- the gate ServiceAccount can patch `deployments` but
   not `deployments/scale`.

Switch the sleeper to measure actual use: time since last user activity
(taps/keys/app-launches, incl. noVNC clicks) from `dumpsys power` vs guest
uptime. No interaction for 6h -> sleep. This ignores idle/forgotten
connections entirely. Scale down with a direct replicas patch on the named
deployment (same path the wake gate scales up), so it needs only the
existing `deployments` patch grant -- no `deployments/scale`. Now stateless
(drops the idle-counter annotation; gate.py no longer sets it) and lighter
on etcd. Fail-safe: any read error (e.g. mid-boot) does not sleep.

Requested by Viktor: turn the dev-only emulator off when it hasn't been
used for 6h.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Viktor Barzin 2026-06-24 08:49:23 +00:00
parent 566447a698
commit 839fdb33c2
3 changed files with 44 additions and 33 deletions
Download patch file Download diff file Expand all files Collapse all files

9
stacks/android-emulator/README.md
View file

@ -6,9 +6,12 @@ tenant: tripit). Decision record: `docs/adr/0001-android-emulator-in-cluster.md`
## On-demand lifecycle (since 2026-06-12)
The emulator **scales to zero when idle** (no adb/VNC connections for ~1h,
checked by the `android-emulator-idle-sleeper` CronJob) and **wakes on
visit**: the wake gate owns `/` on both hostnames. Warm boot is ~90s.
The emulator **scales to zero when idle** (no user interaction for 6h —
taps/keys/app-launches/noVNC clicks, read from `dumpsys power` by the
`android-emulator-idle-sleeper` CronJob) and **wakes on visit**: the wake
gate owns `/` on both hostnames. Warm boot is ~90s. Idle is measured from
real interaction, not connection count, so a forgotten `adb connect` (left
ESTABLISHED) no longer keeps it awake — but `adb disconnect` anyway.
- Humans: open https://android-emulator.viktorbarzin.me — it wakes the
emulator if needed, shows a self-refreshing boot page, then hands over to

10
stacks/android-emulator/gate.py
View file

@ -22,7 +22,6 @@ API = "https://%s:%s" % (
)
TOKEN_PATH = "/var/run/secrets/kubernetes.io/serviceaccount/token"
CA_PATH = "/var/run/secrets/kubernetes.io/serviceaccount/ca.crt"
IDLE_ANNOTATION = "emulator.viktorbarzin.me/idle-checks"
VNC_PATH = "/vnc.html?autoconnect=1&resize=scale"
WAKING_PAGE = """<!doctype html><html><head><title>Android emulator</title>
@ -57,13 +56,14 @@ def deployment_state():
def wake():
# Direct replicas patch on the named deployment — same path the idle
# sleeper uses to scale DOWN; needs only `deployments` patch, not
# `deployments/scale`. Idle is now measured from dumpsys power, so there
# is no idle-counter annotation to reset here.
kube(
"PATCH",
f"/apis/apps/v1/namespaces/{NS}/deployments/{DEPLOY}",
{
"spec": {"replicas": 1},
"metadata": {"annotations": {IDLE_ANNOTATION: "0"}},
},
{"spec": {"replicas": 1}},
)

58
stacks/android-emulator/gate.tf
View file

@ -152,11 +152,18 @@ resource "kubernetes_service" "gate" {
}
}
# Sleep side: every 15 min, look at established TCP connections to the
# emulator's adb (5555) and noVNC (6080) ports from OUTSIDE the pod
# (remote != 127.0.0.1 — the in-container adb server holds a permanent
# loopback connection to adbd that must not count as activity). Four
# consecutive idle checks (~1h) scale the deployment to zero.
# Sleep side: every 15 min, ask the emulator how long since it was actually
# USED — dumpsys power's last user-activity time (taps/keys/app-launches,
# including noVNC clicks) vs guest uptime. No activity for 6h → scale the
# deployment to zero. This deliberately IGNORES open adb/noVNC connections:
# a forgotten adb transport (connect with no disconnect) stays ESTABLISHED
# forever, so the old connection-count check kept resetting and the emulator
# never slept (up 6+ days while idle ~5). Reads activity via `kubectl exec`
# (the SA has pods/exec) and scales down with a direct replicas patch on the
# named deployment — the SAME path the wake gate scales UP — so it needs only
# the existing `deployments` patch grant, NOT `deployments/scale` (which the
# SA lacks; the old `kubectl scale` here failed Forbidden). Stateless: no
# idle-counter annotation. Fail-safe: any read error → do NOT sleep.
resource "kubernetes_cron_job_v1" "idle_sleeper" {
metadata {
name = "android-emulator-idle-sleeper"
@ -183,32 +190,33 @@ resource "kubernetes_cron_job_v1" "idle_sleeper" {
command = ["/bin/bash", "-c"]
args = [<<-EOT
set -euo pipefail
NS=android-emulator DEPLOY=android-emulator ANN=emulator.viktorbarzin.me/idle-checks
NS=android-emulator
DEPLOY=android-emulator
IDLE_LIMIT_SECONDS=21600 # 6h with no user activity -> sleep
spec=$(kubectl -n $NS get deploy $DEPLOY -o jsonpath='{.spec.replicas}')
[ "$spec" = "0" ] && { echo "already asleep"; exit 0; }
pod=$(kubectl -n $NS get pods -l app=$DEPLOY --field-selector=status.phase=Running -o name | head -1)
[ -z "$pod" ] && { echo "no running pod (booting?) — not counting"; exit 0; }
# /proc/net/tcp: count ESTABLISHED (st=01) conns with local port
# 5555 (0x15B3) or 6080 (0x17C0) whose remote is not loopback.
est=$(kubectl -n $NS exec $${pod#pod/} -- cat /proc/net/tcp | awk '
$4 == "01" {
split($2, l, ":"); split($3, r, ":")
if ((l[2] == "15B3" || l[2] == "17C0") && r[1] != "0100007F") n++
} END { print n+0 }')
if [ "$est" -gt 0 ]; then
echo "$est active connection(s) — resetting idle counter"
kubectl -n $NS annotate deploy $DEPLOY $ANN=0 --overwrite
[ -z "$pod" ] && { echo "no running pod (booting?) — not sleeping"; exit 0; }
pod=$${pod#pod/}
# How long since the emulator was actually used? Compare the
# last user-activity time from dumpsys power (taps/keys/app
# launches, incl. noVNC clicks) against current guest uptime,
# both in ms on the guest uptime clock. Fail-safe: if adb is
# not answering yet (cold boot) these come back empty and we
# must NOT sleep.
uptime_ms=$(kubectl -n $NS exec $pod -- sh -c 'adb shell cat /proc/uptime' 2>/dev/null | awk '{printf "%d", $1*1000}')
last_ms=$(kubectl -n $NS exec $pod -- sh -c 'adb shell dumpsys power' 2>/dev/null | awk -F= '/mLastUserActivityTime\(excludingAttention\)/{gsub(/[^0-9]/,"",$2); print $2; exit}')
if [ -z "$uptime_ms" ] || [ -z "$last_ms" ]; then
echo "could not read activity (emulator booting / adb not ready) — not sleeping"
exit 0
fi
n=$(kubectl -n $NS get deploy $DEPLOY -o jsonpath="{.metadata.annotations['emulator\.viktorbarzin\.me/idle-checks']}")
n=$(( $${n:-0} + 1 ))
if [ "$n" -ge 4 ]; then
echo "idle for $n checks (~1h) — scaling to zero"
kubectl -n $NS scale deploy $DEPLOY --replicas=0
kubectl -n $NS annotate deploy $DEPLOY $ANN=0 --overwrite
idle_s=$(( (uptime_ms - last_ms) / 1000 ))
echo "idle for $idle_s s (limit $IDLE_LIMIT_SECONDS s / 6h)"
if [ "$idle_s" -ge "$IDLE_LIMIT_SECONDS" ]; then
echo "idle >= 6h with no user activity — scaling to zero"
kubectl -n $NS patch deploy $DEPLOY --type=merge -p '{"spec":{"replicas":0}}'
else
echo "idle check $n/4"
kubectl -n $NS annotate deploy $DEPLOY $ANN=$n --overwrite
echo "used within 6h — staying up"
fi
EOT
]