This commit changes the logic for managing the expiration of
objects in the database.
Before: There was a server-wide hashmap that stored the
collection key, id, and expiration timestamp for all objects
that had a TTL. The hashmap was occasionally probed at 20
random positions, looking for objects that have expired. Those
expired objects were immediately deleted, and if there was 5
or more objects deleted, then the probe happened again, with
no delay. If the number of objects was less than 5 then the
there was a 1/10th of a second delay before the next probe.
Now: Rather than a server-wide hashmap, each collection has
its own ordered priority queue that stores objects with TTLs.
Rather than probing, there is a background routine that
executes every 1/10th of a second, which pops the expired
objects from the collection queues, and deletes them.
The collection/queue method is a more stable approach than
the hashmap/probing method. With probing, we can run into
major cache misses for some cases where there is wide
TTL duration, such as in the hours or days. This may cause
the system to occasionally fall behind, leaving should-be
expired objects in memory. Using a queue, there is no
cache misses, all objects that should be expired will be
right away, regardless of the TTL durations.
Fixes#616
This commit includes updates that affects the build, testing, and
deployment of Tile38.
- The root level build.sh has been broken up into multiple scripts
and placed in the "scripts" directory.
- The vendor directory has been updated to follow the Go modules
rules, thus `make` should work on isolated environments. Also
some vendored packages may have been updated to a later
version, if needed.
- The Makefile has been updated to allow for making single
binaries such as `make tile38-server`. There is some scaffolding
during the build process, so from now on all binaries should be
made using make. For example, to run a development version of
the tile38-cli binary, do this:
make tile38-cli && ./tile38-cli
not this:
go run cmd/tile38-cli/main.go
- Travis.CI docker push script has been updated to address a
change to Docker's JSON repo meta output, which in turn fixes
a bug where new Tile38 versions were not being properly pushed
to Docker
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