[Bug 2146422] Re: Installer UI crashed with ServerDisconnectedError

[Olivier Gayot]

I investigated the issue and managed to reproduce it once on amd64.

So this isn't strictly specific to riscv but only seems to occur if two
or more Subiquity clients run.

When testing on riscv, I get a subiquity client for serial and another
for the tty.

The --serial option of kvm-test allows having the same in amd64.


Observed behavior
-----------------
* A newly spawned client failed with ServerDisconnectedError right after a refresh.


* After refresh, I found 3 different server log files (and only expected two - one before refresh, and one after).
  lrwxrwxrwx 1 root root     31 Mar 26 16:53 subiquity-server-debug.log -> subiquity-server-debug.log.2342
  -rw------- 1 root root 134897 Mar 26 16:53 subiquity-server-debug.log.1716
  -rw------- 1 root root  26125 Mar 26 16:53 subiquity-server-debug.log.2240
  -rw------- 1 root root  45629 Mar 26 17:13 subiquity-server-debug.log.2342

* The hierarchy of processes also showed some inconsistency. Process
2240 was supposedly a server process (see above) but is now showing as a
shell process (which spawned a server).

   2204 root        20   0  2888  1816  1700 S   0.0  0.0  0:00.05 `- /bin/sh /snap/subiquity/7147/usr/bin/subiquity-server
   2240 root        20   0  2888  2036  1924 S   0.0  0.0  0:02.00 |  `- /bin/sh /snap/subiquity/7147/usr/bin/subiquity-server
   2342 root        20   0  392M 88488 21476 S   0.0  1.1  0:01.85 |     `- /snap/subiquity/7147/usr/bin/python3.12 -m subiquity.cmd.server


Explanation
-----------

* Server process 1716 was the server process before refresh
* Server process 2240 was the new server process after refresh. But it somehow was forced to restart and ended up executing os.execvp(["snap", "run", "subiquity-server"])
   * as a consequence, it "turned" into the "snap" process, and in turn ended up spawning yet another server process (i.e., PID 2342)


Why server 2240  was forced to restart?
---------------------------------------

* it turned out that GET refresh/progress?change_id="x" causes a server
restart if change x is a snap change ID in the "Done" state.

https://github.com/canonical/subiquity/blob/e422d4239fdc2491b3808e63bf77f165276c53a1/subiquity/server/controllers/refresh.py#L225-L242


[...]
2026-03-26 16:53:47,074 DEBUG curtin.reporting.start.subiquity/Refresh/progress_GET:45 start: subiquity/Refresh/progress_GET: 
2026-03-26 16:53:47,074 DEBUG subiquity.common.api.server:83 /refresh/progress waiting on start
[...]
2026-03-26 16:53:47,724 DEBUG subiquity.common.api.server:85 /refresh/progress resuming

* One of the clients likely didn't stop immediately upon refresh, and
ended sending a /refresh/progress query to the newly created server
process - triggering a restart.

* In the meantime, a newly created client crashed because the server
decided to restart.

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https://bugs.launchpad.net/bugs/2146422

Title:
  Installer UI crashed with ServerDisconnectedError

Status in subiquity package in Ubuntu:
  In Progress

Bug description:
  I tried to install current resolute-live-server-riscv64.iso. subiquity
  26.04-beta+git12.e422d423 failed with the error below. Full logs
  appended.

  SnapUpdated: True 
  SourcePackage: subiquity
  Tags: subiquity
  Title: Installer UI crashed with ServerDisconnectedError
  Traceback:
   Traceback (most recent call last):
     File "/snap/subiquity/7156/lib/python3.12/site-packages/subiquity/client/client.py", line 426, in run
       await super().run()
     File "/snap/subiquity/7156/lib/python3.12/site-packages/subiquitycore/tui.py", line 390, in run
       await super().run()
     File "/snap/subiquity/7156/lib/python3.12/site-packages/subiquitycore/core.py", line 133, in run
       raise exc
     File "/snap/subiquity/7156/lib/python3.12/site-packages/subiquity/client/client.py", line 367, in start
       variant = await self.client.meta.client_variant.GET()
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     File "/snap/subiquity/7156/lib/python3.12/site-packages/subiquity/common/api/client.py", line 75, in impl 
       async with make_request(
     File "/snap/subiquity/7156/usr/lib/python3.12/contextlib.py", line 210, in __aenter__
       return await anext(self.gen)
              ^^^^^^^^^^^^^^^^^^^^^
     File "/snap/subiquity/7156/lib/python3.12/site-packages/subiquity/common/api/client.py", line 168, in make_request
       async with session.request(
     File "/snap/subiquity/7156/usr/lib/python3/dist-packages/aiohttp/client.py", line 1187, in __aenter__
       self._resp = await self._coro
                    ^^^^^^^^^^^^^^^^
     File "/snap/subiquity/7156/usr/lib/python3/dist-packages/aiohttp/client.py", line 601, in _request
       await resp.start(conn)
     File "/snap/subiquity/7156/usr/lib/python3/dist-packages/aiohttp/client_reqrep.py", line 965, in start
       message, payload = await protocol.read()  # type: ignore[union-attr]
                          ^^^^^^^^^^^^^^^^^^^^^
     File "/snap/subiquity/7156/usr/lib/python3/dist-packages/aiohttp/streams.py", line 622, in read 
       await self._waiter
   aiohttp.client_exceptions.ServerDisconnectedError: Server disconnected

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