hectic-lab/util.nix
2
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

feat(package): sentinèlla: switch peer discovery from A records to SRV records

Browse Source
This commit is contained in:
yukkop
2026-04-27 14:08:23 +00:00
parent 7268ec3704
commit 0c81c0454d
3 changed files with 43 additions and 38 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
package/sentinèlla/default.nix
View File

@@ -1,4 +1,4 @@
{ symlinkJoin, writeTextFile, socat, dash, hectic, curl, gawk, jq, inetutils, getent }:
{ symlinkJoin, writeTextFile, socat, dash, hectic, curl, gawk, jq, inetutils, getent, bind }:
let
shell = "${dash}/bin/dash";
bashOptions = [
@@ -36,7 +36,7 @@ let
watcher = hectic.writeShellApplication {
inherit shell bashOptions;
name = "watcher";
runtimeInputs = [ curl jq gawk inetutils getent ];
runtimeInputs = [ curl jq gawk inetutils getent bind.dnsutils ];
text = ''
${builtins.readFile ./log.sh}
${builtins.readFile ./colors.sh}

70
package/sentinèlla/watcher.sh
View File

@@ -1,26 +1,26 @@
#!/bin/dash
# watcher.sh — p2p peer monitor; polls all peers discovered via DNS and notifies on status change
# watcher.sh — p2p peer monitor; polls all peers discovered via DNS SRV records
# and notifies on status change via Telegram.
#
# Every node runs both probe (HTTP server) and watcher (this script).
# Peer discovery: a single DNS name with multiple A records is resolved via
# getent(1) on every poll cycle. Local IPs are detected automatically via
# hostname(1) and excluded so the node never polls itself.
# Peer discovery: a single SRV record name resolved on every poll cycle.
# Each SRV entry yields (priority, weight, port, target-hostname); the target
# is resolved to an IP via getent and excluded if it belongs to this node.
# No central coordinator; all nodes are equal.
#
# DNS setup (external, any registrar, TTL 60):
# peers.example.com A 1.2.3.4
# peers.example.com A 5.6.7.8
# peers.example.com A 9.10.11.12
# DNS setup (any registrar, TTL 60):
# _sentinella._tcp.example.com. SRV 0 10 5988 node-a.peers.example.com.
# _sentinella._tcp.example.com. SRV 0 10 5988 node-b.peers.example.com.
# node-a.peers.example.com. A 1.2.3.4
# node-b.peers.example.com. A 5.6.7.8
#
# Required env:
# PEERS_DNS DNS name that resolves to all peer IPs
# PEERS_SRV SRV record name (e.g. _sentinella._tcp.example.com)
# TG_TOKEN Telegram bot token
# TG_CHAT_ID Telegram chat ID
#
# Optional env:
# SELF Override auto-detected local IP (useful behind NAT
# or with floating IPs where hostname -I is unreliable)
# PEERS_PORT default 5988
# SELF Override auto-detected local IPs (space-separated)
# PEERS_SCHEME default http
# PEERS_TOKEN Basic Auth token sent to all peers; omit for no auth
# TIMEOUT curl timeout seconds (default 5)
@@ -35,9 +35,8 @@ PREFIX_FAIL="FAIL"
TIMEOUT=${TIMEOUT:-5}
POLLING_INTERVAL_SEC=${POLLING_INTERVAL_SEC:-3}
PEERS_DNS=${PEERS_DNS:-}
PEERS_SRV=${PEERS_SRV:-}
SELF=${SELF:-}
PEERS_PORT=${PEERS_PORT:-5988}
PEERS_SCHEME=${PEERS_SCHEME:-http}
PEERS_TOKEN=${PEERS_TOKEN:-}
TG_TOKEN=${TG_TOKEN:-}
@@ -50,14 +49,13 @@ mkdir -p "$STATE_DIR" 2>/dev/null || {
mkdir -p "$STATE_DIR"
}
[ -n "$PEERS_DNS" ] || { printf >&2 'PEERS_DNS not set\n'; exit 3; }
[ -n "$PEERS_SRV" ] || { printf >&2 'PEERS_SRV not set\n'; exit 3; }
[ -n "$TG_TOKEN" ] || { printf >&2 'TG_TOKEN not set\n'; exit 3; }
[ -n "$TG_CHAT_ID" ] || { printf >&2 'TG_CHAT_ID not set\n'; exit 3; }
# --- helpers ---
# local_ips — returns space-separated list of IPs assigned to local interfaces.
# If SELF is set it is used directly (useful behind NAT / floating IPs).
# local_ips — space-separated list of IPs assigned to this node.
local_ips() {
if [ -n "$SELF" ]; then
printf '%s' "$SELF"
@@ -76,14 +74,19 @@ is_local_ip() {
return 1
}
# resolve_peers — resolves PEERS_DNS to a newline-separated list of peer URLs,
# excluding all local IPs. Re-called every poll cycle so DNS changes are
# picked up without restarting the watcher.
# resolve_peers — SRV-resolves PEERS_SRV, then A-resolves each target.
# Emits "host port ip" per non-local peer, one per line.
resolve_peers() {
getent hosts "$PEERS_DNS" \
| awk '{print $1}' \
| while IFS= read -r ip; do
is_local_ip "$ip" || printf '%s://%s:%s\n' "$PEERS_SCHEME" "$ip" "$PEERS_PORT"
# host -t SRV output:
# <name> has SRV record <prio> <weight> <port> <target>.
host -t SRV "$PEERS_SRV" 2>/dev/null \
| awk '/has SRV record/ { sub(/\.$/, "", $NF); print $(NF-1), $NF }' \
| while IFS=' ' read -r port target; do
[ -n "$target" ] || continue
ip=$(getent hosts "$target" | awk '{print $1; exit}')
[ -n "$ip" ] || { log warn "could not resolve ${WHITE}${target}${NC}"; continue; }
is_local_ip "$ip" && continue
printf '%s %s %s\n' "$target" "$port" "$ip"
done
}
@@ -115,7 +118,7 @@ list_failures() {
'
}
# server_status_message(prefix, peer_url, ok, total, fail_list)
# server_status_message(prefix, peer_label, ok, total, fail_list)
server_status_message() {
printf '%s: %s [%s/%s]%s' "${1:?}" "${2:?}" "${3:?}" "${4:?}" "$5"
}
@@ -125,21 +128,24 @@ server_status_message() {
trap 'rm -f "$tmpb" 2>/dev/null' EXIT INT HUP
while :; do
log info "polling peers via ${WHITE}${PEERS_DNS}${NC} every ${WHITE}${POLLING_INTERVAL_SEC}${NC}s"
log info "polling peers via SRV ${WHITE}${PEERS_SRV}${NC} every ${WHITE}${POLLING_INTERVAL_SEC}${NC}s"
peers=$(resolve_peers) || peers=""
if [ -z "$peers" ]; then
log warn "no peers resolved from ${WHITE}${PEERS_DNS}${NC} (all IPs are local or DNS returned nothing)"
log warn "no peers resolved from ${WHITE}${PEERS_SRV}${NC} (all targets local or DNS empty)"
fi
printf '%s\n' "$peers" | while IFS= read -r url; do
[ -n "$url" ] || continue
printf '%s\n' "$peers" | while IFS=' ' read -r host port ip; do
[ -n "$host" ] || continue
url="${PEERS_SCHEME}://${ip}:${port}"
label="${host} (${ip})"
tmpb=$(mktemp) || exit 1
set -- curl -sS -m "$TIMEOUT" -w '%{http_code}' -o "$tmpb"
[ -n "$PEERS_TOKEN" ] && set -- "$@" -H "Authorization: Basic $PEERS_TOKEN"
set -- "$@" "$url"
set -- "$@" "${url}/status"
code=$("$@" 2>/dev/null) || code="000"
body=$(cat "$tmpb"); rm -f "$tmpb"
@@ -156,9 +162,9 @@ while :; do
fails=$(printf '%s' "$body" | list_failures | sed 's/[ ]$//')
[ -n "$fails" ] && fail_list=" — ${fails}"
fi
msg=$(server_status_message "$msg_prefix" "$url" "$good" "$total" "$fail_list")
msg=$(server_status_message "$msg_prefix" "$label" "$good" "$total" "$fail_list")
sfile="${STATE_DIR}/$(sid "$url").state"
sfile="${STATE_DIR}/$(sid "$host").state"
last=""; [ -f "$sfile" ] && last=$(cat "$sfile")
cur="${ok}:${good}/${total}:${code}"
if [ "$cur" != "$last" ] || [ "$SPAM" = "1" ]; then