Completa il hardening autoscaler (Fase 4): budget, kill-switch e runbook.

Drain sicuro in scale-in, alert Ops su overflow e controlli admin senza abilitare il deploy in produzione.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/spec/services/streams/autoscaler_spec.rb

@@ -15,6 +15,7 @@ RSpec.describe Streams::Autoscaler do
 
   before do
     redis.del(Streams::Autoscaler::LOCK_KEY)
+    redis.del(Streams::Autoscaler::KILL_SWITCH_KEY)
     redis.del(Streams::DnsProviders::Lab::REDIS_KEY)
   end
 
@@ -116,10 +117,55 @@ RSpec.describe Streams::Autoscaler do
       )
 
       provisioner = instance_double(Streams::NodeProvisioner)
+      allow(provisioner).to receive(:drain!)
       expect(provisioner).to receive(:decommission!).with(idle)
 
       result = described_class.reconcile!(provisioner: provisioner)
       expect(result.actions.map(&:to_s)).to include("scale_in_ingest-lab-99")
     end
   end
+
+  it "skips when Redis kill-switch is engaged even if ENV is enabled" do
+    redis.del(described_class::KILL_SWITCH_KEY)
+    with_env("STREAM_AUTOSCALE_ENABLED" => "1") do
+      described_class.engage_kill_switch!
+      expect(described_class.enabled?).to eq(false)
+      result = described_class.reconcile!
+      expect(result.skipped).to eq(true)
+    ensure
+      described_class.clear_kill_switch!
+    end
+  end
+
+  it "blocks scale-out when next node would exceed monthly budget" do
+    with_env(
+      "STREAM_AUTOSCALE_ENABLED" => "1",
+      "STREAM_AUTOSCALE_SOFT_FREE_SLOTS" => "2",
+      "STREAM_AUTOSCALE_WARM_SPARE" => "0",
+      "STREAM_AUTOSCALE_KIND" => "lab",
+      "STREAM_AUTOSCALE_MAX_NODES" => "5",
+      "STREAM_AUTOSCALE_NODE_EUR_PER_HOUR" => "1",
+      "STREAM_AUTOSCALE_MONTHLY_BUDGET_EUR" => "10",
+      "STREAM_CLOUD_PROVIDER" => "local_lab",
+      "STREAM_DNS_PROVIDER" => "lab",
+      "STREAM_NODE_HOME_MAX_PUBLISHERS" => "1",
+      "MEDIAMTX_API_URL" => "http://mtx-home:9997",
+      "MEDIAMTX_RTMP_URL" => "rtmp://home.example:1935",
+      "HLS_PUBLIC_URL" => "https://home.example/hls"
+    ) do
+      home = Streams::NodeRegistry.ensure_home_from_env!
+      user = User.create!(email: "budget@example.com", name: "B", password: "Password123", role: "coach")
+      club = Club.create!(name: "Budget", sport: "volleyball")
+      team = club.teams.create!(name: "T", sport: "volleyball", slug: "budget-t")
+      match = team.matches.create!(opponent_name: "X", scheduled_at: 1.hour.from_now)
+      StreamSession.create!(match: match, user: user, platform: "matchlivetv", status: "live", stream_node: home)
+
+      provisioner = instance_double(Streams::NodeProvisioner)
+      expect(provisioner).not_to receive(:provision_lab!)
+
+      result = described_class.reconcile!(provisioner: provisioner)
+      expect(result.actions).to include(:blocked_capacity)
+      expect(described_class.metrics[:within_budget]).to eq(true)
+    end
+  end
 end