Careful management of the journal read pointer is sufficient to ensure
that no entry is read more than once.
Unit test the journald logger without requiring a running journald by
using the systemd-journal-remote command to write arbitrary entries to
journal files.
Signed-off-by: Cory Snider <csnider@mirantis.com>
Wrap the libsystemd journal reading functionality in a more idiomatic Go
API and refactor the journald logging driver's ReadLogs implementation
to use the wrapper. Rewrite the parts of the ReadLogs implementation in
Go which were previously implemented in C as part of the cgo preamble.
Separating the business logic from the cgo minutiae should hopefully
make the code more accessible to a wider audience of developers for
reviewing the code and contributing improvements.
The structure of the ReadLogs implementation is retained with few
modifications. Any ignored errors were also ignored before the refactor;
the explicit error return values afforded by the sdjournal wrapper makes
this more obvious.
The package github.com/coreos/go-systemd/v22/sdjournal also provides a
more idiomatic Go wrapper around libsystemd. It is unsuitable for our
needs as it does not expose wrappers for the sd_journal_process and
sd_journal_get_fd functions.
Signed-off-by: Cory Snider <csnider@mirantis.com>
