The new behavior eliminates a couple unpleasant edge cases in which it
would never flush:
* if all recording stops, whatever was unflushed would stay that way
* if every recording attempt produces a 0-duration recording (such as if the
camera sends only one frame and thus no PTS delta can be calculated),
the list of recordings to flush would continue to grow
This is only the database schema, which I'm adding now in the hopes of
freezing schema version 3. There's no way yet to create users, much less
actually authenticate.
These are not actually populated by the code yet. I'm trying to get the
v3 schema frozen as soon as possible; actually using the fields can come
later.
Add some explanation of their value in time.md, along with some general
musing on leap seconds, and a correction on the frequency error of my cameras.
I want to be able to use it in etags without having to do a full scan of the
recording_playback in advance, which would greatly increase time to first
byte. I probably will even use it in urls to ensure the segments they point to
are stable. I haven't actually done this yet - it will wait until I implement
serving unflushed recordings - but I want to get the schema set up properly.
As noted in schema.sql, this can be used for disambiguation. It also may be
useful in diagnosing data integrity problems.
Also, sneak in a couple minor improvements: better diagnostics in a couple
places, fix to 1->2 upgrade procedure.
This improves the practicality of having many streams (including the doubling
of streams by having main + sub streams for each camera). With these tuned
properly, extra streams don't cause any extra write cycles in normal or error
cases. Consider the worst case in which each RTSP session immediately sends a
single frame and then fails. Moonfire retries every second, so this would
formerly cause one commit per second per stream. (flush_if_sec=0 preserves
this behavior.) Now the commits can be arbitrarily infrequent by setting
higher values of flush_if_sec.
WARNING: this isn't production-ready! I hacked up dir.rs to make tests pass
and "moonfire-nvr run" work in the best-case scenario, but it doesn't handle
errors gracefully. I've been debating what to do when writing a recording
fails. I considered "abandoning" the recording then either reusing or skipping
its id. (in the latter case, marking the file as garbage if it can't be
unlinked immediately). I think now there's no point in abandoning a recording.
If I can't write to that file, there's no reason to believe another will work
better. It's better to retry that recording forever, and perhaps put the whole
directory into an error state that stops recording until those writes go
through. I'm planning to redesign dir.rs to make this happen.
It should reduce compile time / memory usage to put quite a bit of the code
into a separate crate. I also intend to limit visibility of some things to
only within the db crate, but that's for a future change. This is the smallest
move that will compile.
