Add core-next and service-relay services to composition.

These services enable async host OS updates. When the release is
installed, the `core-next` takes over the running supervisor and
intercepts all communications between the supervisor and the API and
other services, allowing the progressive take over of new supervisor
features.

Change-type: major

Author: pipex

docker-compose.test.yml

@@ -20,7 +20,7 @@ services:
       - mock-systemd
     volumes:
       - dbus:/shared/dbus
-      - tmp:/mnt/root/tmp/balena-supervisor/services
+      - services:/mnt/root/tmp/balena-supervisor/services
       - ./test/data/root:/mnt/root
       - ./test/data/root/mnt/boot:/mnt/boot
       - ./test/lib/wait-for-it.sh:/wait-for-it.sh
@@ -78,7 +78,7 @@ services:
     stop_grace_period: 3s
     volumes:
       - dbus:/shared/dbus
-      - tmp:/mnt/root/tmp/balena-supervisor/services
+      - services:/mnt/root/tmp/balena-supervisor/services
     # Set required supervisor configuration variables here
     environment:
       DOCKER_HOST: tcp://docker:2375
@@ -110,7 +110,7 @@ volumes:
     driver_opts:
       type: tmpfs
       device: tmpfs
-  tmp:
+  services:
     driver_opts:
       type: tmpfs
       device: tmpfs

docker-compose.yml

@@ -1,5 +1,8 @@
 version: '2.3'
 
+x-helios-image: &helios-image
+  image: ghcr.io/balena-io/helios:0.25.21
+
 services:
   # This service can only be named `main`, `balena-supervisor` or `core`
   # in a multi-container supervisor, the API `supervisor_release` needs to be able to
@@ -8,10 +11,76 @@ services:
   core:
     build: ./
     privileged: true
-    tty: true
+    tty: false
     restart: always
     network_mode: host
     labels:
       io.balena.features.balena-api: '1'
       io.balena.features.dbus: '1'
       io.balena.features.balena-socket: '1'
+
+  # This is the next generation supervisor service. When started, it becomes a proxy
+  # for calls between the existing supervisor and the balenaAPI and containers
+  core-next:
+    <<: *helios-image
+    restart: on-failure
+    # required to distinguish between stderr/stdout, the supervisor defaults to true
+    tty: false
+    labels:
+      # Needed to get access to supervisor api variables
+      # and credentials
+      io.balena.features.supervisor-api: '1'
+      # Needed for access to DOCKER_HOST
+      io.balena.features.balena-socket: '1'
+      # Needed to stop the supervisor service
+      io.balena.features.dbus: '1'
+      # Needed to get access to the API credentials
+      io.balena.features.balena-api: '1'
+      # Needed to get Host OS metadata
+      io.balena.features.host-os.board-rev: '1'
+    environment:
+      - DBUS_SYSTEM_BUS_ADDRESS=unix:path=/host/run/dbus/system_bus_socket
+      # Needed for locks and balenahup. This needs to match the device
+      # used for the `runtime` volume
+      - BALENA_HOST_RUNTIME_DIR=/tmp/balena-supervisor
+    volumes:
+      # Critical configurations
+      - config:/config/helios
+      # Request caching
+      - cache:/cache/helios
+      # Persistent system state data that can be reconstructed from
+      # the target state
+      - state:/local/helios
+      # Runtime directory. Data here does not persist after reboots
+      - runtime:/tmp/run
+
+  # The service below relays requests between tcp port 48484 and the socket exposed by
+  # the core-next service
+  service-relay:
+    <<: *helios-image
+    command: socat TCP-LISTEN:48484,reuseaddr,fork UNIX-CONNECT:/tmp/run/helios.sock
+    # required to distinguish between stderr/stdout, the supervisor defaults to true
+    tty: false
+    ports:
+      - 48484
+    depends_on:
+      - core
+    volumes:
+      - runtime:/tmp/run
+    healthcheck:
+      test: ['CMD', 'wget', '-O', '-', '-q', 'http://127.0.0.1:48484/ping']
+
+volumes:
+  config:
+  state:
+    labels:
+      # the database version, can be bumped to re-create the state
+      io.balena.private.db-version: 0
+  cache:
+  runtime:
+    driver: local
+    driver_opts:
+      type: none
+      o: bind
+      # XXX: this directory needs to exist on the host before the container is started
+      device: /tmp/balena-supervisor