snap switch subiquity to stable/ubuntu-XX.YY.Z

also support passing subquity-channel= on the kernel command line

examples/snaps/v2-changes-8/0000.json

@@ -0,0 +1,29 @@
+{
+  "type": "sync",
+  "status-code": 200,
+  "status": "OK",
+  "result": {
+    "id": "176",
+    "kind": "switch-snap",
+    "summary": "Switch \"subiquity\" snap to stable",
+    "status": "Done",
+    "tasks": [
+      {
+        "id": "4715",
+        "kind": "switch-snap",
+        "summary": "Switch snap \"subiquity\" to stable",
+        "status": "Done",
+        "progress": {
+          "label": "",
+          "done": 1,
+          "total": 1
+        },
+        "spawn-time": "2019-03-29T14:13:32.922119778+13:00",
+        "ready-time": "2019-03-29T14:13:32.941910157+13:00"
+      }
+    ],
+    "ready": true,
+    "spawn-time": "2019-03-29T14:13:32.922139818+13:00",
+    "ready-time": "2019-03-29T14:13:32.941911437+13:00"
+  }
+}

subiquity/controllers/refresh.py

@@ -16,6 +16,7 @@
 import enum
 import logging
 import os
+import time
 
 import requests.exceptions
 
@@ -36,6 +37,11 @@ class CheckState(enum.IntEnum):
     def is_definite(self):
         return self in [self.AVAILABLE, self.UNAVAILABLE]
 
+class SwitchState(enum.IntEnum):
+    NOT_STARTED = enum.auto()
+    SWITCHING = enum.auto()
+    SWITCHED = enum.auto()
+
 
 class RefreshController(BaseController):
 
@@ -47,11 +53,90 @@ class RefreshController(BaseController):
         super().__init__(common)
         self.snap_name = os.environ.get("SNAP_NAME", "subiquity")
         self.check_state = CheckState.NOT_STARTED
+        self.switch_state = SwitchState.NOT_STARTED
+        self.network_state = "down"
         self.view = None
         self.offered_first_time = False
         self.answers = self.all_answers.get("Refresh", {})
 
+    def start(self):
+        self.switch_state = SwitchState.SWITCHING
+        channel = self.get_refresh_channel()
+        self.run_in_bg(
+            lambda: self._bg_switch_snap(channel),
+            self._snap_switched)
+
+    def get_refresh_channel(self):
+        """Return the channel we should refresh subiquity to."""
+
+        with open('/proc/cmdline') as fp:
+            cmdline = fp.read()
+        prefix="subquity-channel="
+        for arg in cmdline.split():
+            if arg.startswith(prefix):
+                log.debug("found cmdline arg %s", arg)
+                return arg[len(prefix):]
+
+        info_file = '/cdrom/.disk/info'
+        try:
+            fp = open(info_file)
+        except FileNotFoundError:
+            if self.opts.dry_run:
+                info = (
+                    'Ubuntu-Server 18.04.2 LTS "Bionic Beaver" - '
+                    'Release amd64 (20190214.3)')
+            else:
+                log.debug("failed to find .disk/info file")
+                return
+        else:
+            with fp:
+                info = fp.read()
+        release = info.split()[1]
+        return 'stable/ubuntu-' + release
+
+    def _bg_switch_snap(self, channel):
+        log.debug("switching %s to %s", self.snap_name, channel)
+        try:
+            response = self.snapd_connection.post(
+                'v2/snaps/{}'.format(self.snap_name),
+                {'action': 'switch', 'channel': channel})
+            response.raise_for_status()
+        except requests.exceptions.RequestException as e:
+            log.exception("switching")
+            return
+        change = response.json()["change"]
+        while True:
+            try:
+                response = self.snapd_connection.get(
+                    'v2/changes/{}'.format(change))
+                response.raise_for_status()
+            except requests.exceptions.RequestException as e:
+                log.exception("checking switch")
+                return
+            if response.json()["result"]["status"] == "Done":
+                return
+            time.sleep(0.1)
+
+    def _snap_switched(self, fut):
+        log.debug("snap switching completed")
+        try:
+            fut.result()
+        except:
+            log.exception("_snap_switched")
+        self.switch_state = SwitchState.SWITCHED
+        self._maybe_check_for_update()
+
     def snapd_network_changed(self):
+        self.network_state = "up"
+        self._maybe_check_for_update()
+
+    def _maybe_check_for_update(self):
+        # If we have not yet switched to the right channel, wait.
+        if self.switch_state != SwitchState.SWITCHED:
+            return
+        # If the network is not yet up, wait.
+        if self.network_state == "down":
+            return
         # If we restarted into this version, don't check for a new version.
         if self.updated:
             return
@@ -98,7 +183,7 @@ class RefreshController(BaseController):
 
     def _bg_start_update(self):
         return self.snapd_connection.post(
-            'v2/snaps/subiquity', {'action': 'refresh'})
+            'v2/snaps/{}'.format(self.snap_name), {'action': 'refresh'})
 
     def update_started(self, fut, callback):
         try:

subiquity/snapd.py

@@ -132,6 +132,13 @@ class FakeSnapdConnection:
                 "status-code": 200,
                 "status": "OK",
                 })
+        if path == "v2/snaps/subiquity" and body['action'] == 'switch':
+            return _FakeMemoryResponse({
+                "type": "async",
+                "change": 8,
+                "status-code": 200,
+                "status": "Accepted",
+                })
         raise Exception(
             "Don't know how to fake POST response to {}".format((path, args)))