When we put something in the queue and respond "250 ok" to the client,
that is taken as accepting the email.
As part of putting something in the queue, we write it to disk, but
today we don't do an fsync on that file.
That leaves a gap where a badly timed crash on some systems could lead
to the file being empty, causing us to lose an email that we accepted.
To elliminate (or drastically reduce on some filesystems) the chances of
that situation, we call fsync on the file that gets written when we put
something in the queue.
Thanks to nolanl@github for reporting this in
https://github.com/albertito/chasquid/issues/78.
This patch adds tests to verify how safeio behaves when *os.File
operations return various errors.
To do this, we allow the possibility of wrapping os.CreateTemp, so we
can simulate the errors during testing.
This is not pretty, but the code is small enough that the readability
overhead is minimal, and we get a lot of tests from it.
ioutil package was deprecated in Go 1.16, replace all uses with their
respective replacements.
This patch was generated with a combination of `gofmt -r`, `eg`, and
manually (for `ioutil.ReadDir`).
We have many places in our tests where we create temporary directories,
which we later remove (most of the time). We have at least 3 helpers to
do this, and various places where it's done ad-hoc (and the cleanup is
not always present).
To try to reduce the clutter, and make the tests more uniform and
readable, this patch introduces two helpers in a new "testutil" package:
one for creating and one for removing temporary directories.
These new functions are safer, better tested, and make the tests more
consistent. All the tests are updated to use them.
This patch extends WriteFile to allow arbitrary operations to be applied
to the file before it is atomically renamed.
This will be used in upcoming patches to change the mtime of the file
before it is atomically renamed.
This patch adds a new internal/safeio package, which is meant to implement
safer version of some I/O related functions.
For now, only an atomic version of ioutil.WriteFile is implemented. More may
be added later if there's a need for them.
