Public bug reported:
[Impact]
apt-daily.service is launched by a timer that depends on network-
online.target (after the fixes for bug 1686470 are in everywhere)
At boot that is mostly sufficient for it to have network online, but it
does not seem to work all the time, and we might be disagreeing with
network-manager and friends what online state means.
At resume time, network-online.target is still active, so the service is
started as soon as possible when it tries to catch up. Depending on the
timing, the network connectivity might not be there yet, and it will
fail and only retry 12 hours later.
[Proposed solution]
Introduce a new apt-helper wait-online that tries to connect() to remote hosts
specified in sources.list until one connection works or a TIMEOUT is reached.
The proposed algorithm looks something like this:
while (time elapsed < TIMEOUT):
for each entry:
host = gethostbyname()
if host failed:
continue
fd = connect to it
if fd is invalid:
continue
all fds += fd
if poll(all fds, 100 ms timeout) finds a connected one:
exit(0)
exit(42) # timeout
There are two things to consider:
* gethostbyname() and connect() may fail if network is not up yet, so we need
to retry (we might need to sleep somewhere)
* If poll() fails, we likely sleep enough, so no extra sleep needed.
I believe the time out should be something like 30s.
On the systemd service side, we add:
ExecStartPre=/usr/lib/apt/apt-helper wait-online
RestartForceExitStatus=42
RestartSec=15m
To retry the service after 15 minutes.
[Test case]
* Start apt-daily.service after turning off network -> It should wait (in
ExecStartPre)
* Turn on network -> apt-daily.service should start
[Regression potential]
There might be increased I/O activity after resume, if that did not work before.
** Affects: apt (Ubuntu)
Importance: High
Assignee: Julian Andres Klode (juliank)
Status: Triaged
** Changed in: apt (Ubuntu)
Assignee: (unassigned) => Julian Andres Klode (juliank)
** Description changed:
[Impact]
apt-daily.service is launched by a timer that depends on network-
online.target (after the fixes for 1686470 are in everywhere)
At boot that is mostly sufficient for it to have network online, but it
does not seem to work all the time, and we might be disagreeing with
network-manager and friends what online state means.
At resume time, network-online.target is still active, so the service is
started as soon as possible when it tries to catch up. Depending on the
timing, the network connectivity might not be there yet, and it will
fail and only retry 12 hours later.
[Proposed solution]
Introduce a new apt-helper wait-online that tries to connect() to remote
hosts specified in sources.list until one connection works or a TIMEOUT is
reached. The proposed algorithm looks something like this:
while (time elapsed < TIMEOUT):
- for each entry:
- host = gethostbyname()
- if host failed:
- continue
- fd = connect to it
- if fd is invalid:
- continue
+ for each entry:
+ host = gethostbyname()
+ if host failed:
+ continue
+ fd = connect to it
+ if fd is invalid:
+ continue
- all fds += fd
-
- if poll(all fds, 100 ms timeout) finds a connected one:
- exit(0)
+ all fds += fd
+
+ if poll(all fds, 100 ms timeout) finds a connected one:
+ exit(0)
exit(42) # timeout
There are two things to consider:
* gethostbyname() and connect() may fail if network is not up yet, so we need
to retry (we might need to sleep somewhere)
* If poll() fails, we likely sleep enough, so no extra sleep needed.
I believe the time out should be something like 30s.
On the systemd service side, we add:
- RestartForceExitStatus=42
- RestartSec=15m
+ ExecStartPre=/usr/lib/apt/apt-helper wait-online
+ RestartForceExitStatus=42
+ RestartSec=15m
To retry the service after 15 minutes.
+
+ [Test case]
+ * Start apt-daily.service after turning off network -> It should wait (in
ExecStartPre)
+ * Turn on network -> apt-daily.service should start
+
+ [Regression potential]
+ There might be increased I/O activity after resume, if that did not work
before.
** Changed in: apt (Ubuntu)
Status: New => Triaged
** Changed in: apt (Ubuntu)
Importance: Undecided => High
** Description changed:
[Impact]
apt-daily.service is launched by a timer that depends on network-
- online.target (after the fixes for 1686470 are in everywhere)
+ online.target (after the fixes for bug 1686470 are in everywhere)
At boot that is mostly sufficient for it to have network online, but it
does not seem to work all the time, and we might be disagreeing with
network-manager and friends what online state means.
At resume time, network-online.target is still active, so the service is
started as soon as possible when it tries to catch up. Depending on the
timing, the network connectivity might not be there yet, and it will
fail and only retry 12 hours later.
[Proposed solution]
Introduce a new apt-helper wait-online that tries to connect() to remote
hosts specified in sources.list until one connection works or a TIMEOUT is
reached. The proposed algorithm looks something like this:
while (time elapsed < TIMEOUT):
for each entry:
host = gethostbyname()
if host failed:
continue
fd = connect to it
if fd is invalid:
continue
all fds += fd
if poll(all fds, 100 ms timeout) finds a connected one:
exit(0)
exit(42) # timeout
There are two things to consider:
* gethostbyname() and connect() may fail if network is not up yet, so we need
to retry (we might need to sleep somewhere)
* If poll() fails, we likely sleep enough, so no extra sleep needed.
I believe the time out should be something like 30s.
On the systemd service side, we add:
- ExecStartPre=/usr/lib/apt/apt-helper wait-online
+ ExecStartPre=/usr/lib/apt/apt-helper wait-online
RestartForceExitStatus=42
RestartSec=15m
To retry the service after 15 minutes.
[Test case]
* Start apt-daily.service after turning off network -> It should wait (in
ExecStartPre)
* Turn on network -> apt-daily.service should start
[Regression potential]
There might be increased I/O activity after resume, if that did not work
before.
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https://bugs.launchpad.net/bugs/1699850
Title:
Reliable network connectivity for apt-daily
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