#!/usr/bin/env bash
# T96 — GSLB flip(A→B) 순간 "진행 중(in-flight) 요청"의 운명: STRICT_DNS vs LOGICAL_DNS
#
# T92(Mode 1)는 1ms 요청이라 drain이 항상 요청 사이에 떨어져 in-flight 절단이 관측 불가였다
# (destroy_with_active_rq = 0). 이 실측은 30초짜리 응답(300KB @ 10KB/s)을 wire에 걸쳐 두고
# flip을 넣어 두 가설을 가른다:
#   (A) 즉시 절단  → curl rc!=0 / bytes<307200, upstream_cx_destroy_with_active_rq +1
#   (B) graceful  → curl rc=0 / bytes=307200 완주, destroy는 완주 후(with_active_rq 0)
#
# 전제: setup.sh 완료 + t96-backends-slow.yaml 적용 완료 상태.
set -uo pipefail
CTX="${CTX:-homelab}"; NS="${NS:-dns-lab}"
DIR="$(cd "$(dirname "$0")" && pwd)"
LAB="${LAB:-$DIR}"
K="kubectl --context=$CTX -n $NS"
CL="outbound|443||gslb.lab.internal"
SIZE=307200   # 300KB

IP_A="$($K get svc backend-a -o jsonpath='{.spec.clusterIP}')"
IP_B="$($K get svc backend-b -o jsonpath='{.spec.clusterIP}')"
echo "== T96 == backend-a=$IP_A backend-b=$IP_B  (기대 응답 크기 $SIZE bytes ≈ 30s)"

flip(){ $K exec deploy/lab-dns -c writer -- sh -c "printf '%s gslb.lab.internal\n' '$1' > /hosts/addn"; }
digq(){ $K exec deploy/netshoot -- dig +short gslb.lab.internal 2>/dev/null | tr '\n' ' '; }
eps(){  istioctl --context="$CTX" proxy-config endpoints "deploy/netshoot.$NS" --cluster "$CL" 2>/dev/null | tail -n +1; }
cstat(){
  $K exec deploy/netshoot -c istio-proxy -- pilot-agent request GET "stats?filter=gslb" 2>/dev/null \
    | grep -E 'cluster\.outbound\|443.*(upstream_cx_total|upstream_cx_destroy|upstream_cx_active|membership_change|upstream_rq_total)' \
    | sed 's#cluster.outbound|443||gslb.lab.internal.##' || echo "(none)"
}
snap(){
  echo "--- snap[$1] @ $(date +%H:%M:%S)  dig=$(digq)"
  echo "[endpoints]"; eps
  echo "[cluster|443 cx]"; cstat
}

run_variant(){
  local V=$1
  echo; echo "================ VARIANT=$V ================"
  $K delete serviceentry gslb-strict gslb-logical --ignore-not-found >/dev/null 2>&1
  case $V in
    strict)  $K apply -f "$LAB/40-serviceentry-strict.yaml"  >/dev/null ;;
    logical) $K apply -f "$LAB/41-serviceentry-logical.yaml" >/dev/null ;;
  esac
  $K apply -f "$LAB/42-virtualservice-80to443.yaml" >/dev/null
  $K apply -f "$LAB/43-destinationrule-tls.yaml"    >/dev/null
  flip "$IP_A"; sleep 8
  snap "S0 pre-request (gslb->A)"

  echo; echo ">> slow GET 시작 @ $(date +%H:%M:%S)  (완주 시 ~30s)"
  $K exec deploy/netshoot -- sh -c '
    curl -sS -o /dev/null -D /tmp/t96h -m 90 \
      -w "code=%{http_code} bytes=%{size_download} time=%{time_total}s" \
      http://gslb.lab.internal/slow/slow.bin; echo " rc=$?"
    grep -i "x-backend" /tmp/t96h' > "$DIR/curl-$V.txt" 2>&1 &
  CPID=$!

  sleep 8
  snap "S1 mid-flight, pre-flip (+8s)"
  echo ">> FLIP A->B @ $(date +%H:%M:%S)"
  flip "$IP_B"
  sleep 12
  snap "S2 post-flip (+12s; 절단이면 이미 죽음 / graceful이면 아직 전송 중)"

  wait $CPID 2>/dev/null
  echo; echo "[curl 결과 — $V] @ $(date +%H:%M:%S)"
  cat "$DIR/curl-$V.txt"
  sleep 2
  snap "S3 after"
}

run_variant strict
run_variant logical

echo; echo "== 판정 가이드 =="
echo "  절단(가설 A):   curl rc!=0(18=partial/56=reset), bytes<$SIZE, destroy_with_active_rq 델타 +1"
echo "  graceful(가설 B): curl rc=0, bytes=$SIZE, time≈30s, destroy는 완주 후 with_active_rq 0"