Instead of spawning a new thread for every cache, we use a single thread
that will evict entries from all caches.
The thread keeps a weak reference to the caches, so that they can be
garbage collected.
A specialized date parser that can only handle ISO-8601 like dates
(2011-12-03T10:15:30.123Z or 2011-12-03T10:15:30+01:00) but does this
roughly 10 times faster than DateTimeFormatter and 5 times
faster than the FastDateParser of commons-lang3.
diskBlock.force() makes insertion speed very slow, because it adds
two digit ms to tree changes. I disabled it for now. The tree is not
crash resistent anyway.
Replaced Tags.filenameBytes with a SortedSet<Tag>. Tags are now
stored as longs (variable length encoded) in the PersistenMap.
Tags.filenameBytes was introduced to reduce memory consumption, when
all tags were hold in memory. Tags are now stored in a PersistentMap
and only read when needed.
Moved the VariableByteEncoder into its own project, because it was
needed by pdb-api.
Replaces the use of in-memory data structures with the PersistentMap.
This is the crucial step in reducing memory usage for both persistent
storage and main memory.
Before the offset of the root node was hard-coded.
Now the offset of the pointer to the root node is hard-coded.
That allows us to replace the root node.
The cache must remove/evict writers after a few seconds, but EhCache
only evicts entries when a new entry is added. That is not acceptable
for us, because that would leave lots of files open and we would need
a second mechanism to close them.
Therefore I write a simple wrapper for a ConcurrentHashMap that evicts
entries after timeToLive+5s.
- PdbFiles no longer require dates to be monotonically
increasing. Therefore TagsToFile does not have to ensure
this. => We only have one file per Tags.
- Use EhCache instead of HashMap.
We now support negative values. This will allow us to
store time/value sequences that are not monotonically
increasing, so that we do not have to create multiple
files just because some values were send out of order.
This is done by first transforming the values into
positive values by using interleaved encoding (there
is a name for it, but I don't remember it). We are
mapping values like this:
0 -> 1
1 -> 2
-1 -> 3
2 -> 4
-2 -> 5
...
Renamed LongSequenceEncoderDecoder to VariableByteEncoder.
Made methods static.
