feat(update-server): Add bootId field to GET /server/update/health (#7404)

Author: SyntaxColoring

update-server/otupdate/buildroot/__init__.py

@@ -34,6 +34,7 @@ def get_version(version_file: str) -> Mapping[str, str]:
 def get_app(system_version_file: str = None,
             config_file_override: str = None,
             name_override: str = None,
+            boot_id_override: str = None,
             loop: asyncio.AbstractEventLoop = None) -> web.Application:
     """ Build and return the aiohttp.web.Application that runs the server
 
@@ -44,6 +45,7 @@ def get_app(system_version_file: str = None,
 
     version = get_version(system_version_file)
     name = name_override or name_management.get_name()
+    boot_id = boot_id_override or control.get_boot_id()
     config_obj = config.load(config_file_override)
 
     LOG.info("Setup: " + '\n\t'.join([
@@ -69,6 +71,7 @@ def get_app(system_version_file: str = None,
     app = web.Application(middlewares=[log_error_middleware])
     app[config.CONFIG_VARNAME] = config_obj
     app[constants.RESTART_LOCK_NAME] = asyncio.Lock()
+    app[constants.DEVICE_BOOT_ID_NAME] = boot_id
     app[constants.DEVICE_NAME_VARNAME] = name
     app.router.add_routes([
         web.get('/server/update/health',

update-server/otupdate/buildroot/constants.py

@@ -8,3 +8,17 @@
 
 DEVICE_NAME_VARNAME = APP_VARIABLE_PREFIX + 'name'
 #: Name for the device
+
+DEVICE_BOOT_ID_NAME = APP_VARIABLE_PREFIX + "boot_id"
+#: A random string that changes every time the device boots.
+#:
+#: Clients can poll this to detect when the OT-2 has rebooted. (Including both
+#: graceful reboots, like from clicking the soft "Restart" button, and
+#: unexpected reboots, like from interrupting the power supply).
+#:
+#: There are no guarantees about the returned ID's length or format. Equality
+#: comparison with other IDs returned from this endpoint is the only valid
+#: thing to do with it.
+#:
+#: This ID only changes when the whole OT-2 operating system reboots.
+#: It doesn't change if some internal process merely crashes and restarts.

update-server/otupdate/buildroot/control.py

@@ -6,11 +6,15 @@
 import asyncio
 import logging
 import subprocess
+from functools import lru_cache
+from pathlib import Path
 from typing import Callable, Coroutine, Mapping
 
 from aiohttp import web
 
-from .constants import (RESTART_LOCK_NAME, DEVICE_NAME_VARNAME)
+from .constants import (
+    RESTART_LOCK_NAME, DEVICE_BOOT_ID_NAME, DEVICE_NAME_VARNAME
+)
 
 LOG = logging.getLogger(__name__)
 
@@ -49,7 +53,8 @@ async def health(request: web.Request) -> web.Response:
                 'systemVersion': version_dict.get(
                     'buildroot_version', 'unknown'),
                 'capabilities': {'buildrootUpdate': '/server/update/begin',
-                                 'restart': '/server/restart'}
+                                 'restart': '/server/restart'},
+                'bootId': request.app[DEVICE_BOOT_ID_NAME]
             },
             headers={'Access-Control-Allow-Origin': '*'}
         )
@@ -59,7 +64,12 @@ async def health(request: web.Request) -> web.Response:
 def get_serial() -> str:
     """ Get the device serial number. """
     try:
-        with open('/var/serial') as vs:
-            return vs.read().strip()
+        return Path('/var/serial').read_text().strip()
     except OSError:
         return 'unknown'
+
+
+@lru_cache(maxsize=1)
+def get_boot_id() -> str:
+    # See the "/proc Interface" section in man(4) random.
+    return Path('/proc/sys/kernel/random/boot_id').read_text().strip()

update-server/tests/buildroot/conftest.py

@@ -123,10 +123,11 @@ async def test_cli(aiohttp_client, loop, otupdate_config, monkeypatch):
     Build an app using dummy versions, then build a test client and return it
     """
     app = buildroot.get_app(
-        os.path.join(HERE, "version.json"),
-        otupdate_config,
-        'opentrons-test',
-        loop)
+        system_version_file=os.path.join(HERE, "version.json"),
+        config_file_override=otupdate_config,
+        name_override='opentrons-test',
+        boot_id_override='dummy-boot-id-abc123',
+        loop=loop)
     client = await loop.create_task(aiohttp_client(app))
     return client
 

update-server/tests/buildroot/test_control.py

@@ -19,6 +19,7 @@ async def test_health(test_cli):
     assert body['apiServerVersion'] == version_dict['opentrons_api_version']
     assert body['smoothieVersion'] == 'unimplemented'
     assert body['systemVersion'] == version_dict['buildroot_version']
+    assert body['bootId'] == 'dummy-boot-id-abc123'
 
 
 async def test_restart(test_cli, monkeypatch):