By default, `compose up` attaches to all services (i.e.
shows log output from every associated container). If
a service is specified, e.g. `compose up foo`, then
only `foo`'s logs are tailed. The `--attach-dependencies`
flag can also be used, so that if `foo` depended upon
`bar`, then `bar`'s logs would also be followed. It's
also possible to use `--no-attach` to filter out one
or more services explicitly, e.g. `compose up --no-attach=noisy`
would launch all services, including `noisy`, and would
show log output from every service _except_ `noisy`.
Lastly, it's possible to use `up --attach` to explicitly
restrict to a subset of services (or their dependencies).
How these flags interact with each other is also worth
thinking through.
There were a few different connected issues here, but
the primary issue was that running `compose up foo` was
always attaching dependencies regardless of `--attach-dependencies`.
The filtering logic here has been updated so that it
behaves predictably both when launching all services
(`compose up`) or a subset (`compose up foo`) as well
as various flag combinations on top of those.
Notably, this required making some changes to how it
watches containers. The logic here between attaching
for logs and monitoring for lifecycle changes is
tightly coupled, so some changes were needed to ensure
that the full set of services being `up`'d are _watched_
and the subset that should have logs shown are _attached_.
(This does mean faking the attach with an event but not
actually doing it.)
While handling that, I adjusted the context lifetimes
here, which improves error handling that gets shown to
the user and should help avoid potential leaks by getting
rid of a `context.Background()`.
Signed-off-by: Milas Bowman <milas.bowman@docker.com>
caad72713b