So far we've been using Go's native time.Time for anything related to sample
timestamps. Since the range of time.Time is much bigger than what we need, this
has created two problems:
- there could be time.Time values which were out of the range/precision of the
time type that we persist to disk, therefore causing incorrectly ordered keys.
One bug caused by this was:
https://github.com/prometheus/prometheus/issues/367
It would be good to use a timestamp type that's more closely aligned with
what the underlying storage supports.
- sizeof(time.Time) is 192, while Prometheus should be ok with a single 64-bit
Unix timestamp (possibly even a 32-bit one). Since we store samples in large
numbers, this seriously affects memory usage. Furthermore, copying/working
with the data will be faster if it's smaller.
*MEMORY USAGE RESULTS*
Initial memory usage comparisons for a running Prometheus with 1 timeseries and
100,000 samples show roughly a 13% decrease in total (VIRT) memory usage. In my
tests, this advantage for some reason decreased a bit the more samples the
timeseries had (to 5-7% for millions of samples). This I can't fully explain,
but perhaps garbage collection issues were involved.
*WHEN TO USE THE NEW TIMESTAMP TYPE*
The new clientmodel.Timestamp type should be used whenever time
calculations are either directly or indirectly related to sample
timestamps.
For example:
- the timestamp of a sample itself
- all kinds of watermarks
- anything that may become or is compared to a sample timestamp (like the timestamp
passed into Target.Scrape()).
When to still use time.Time:
- for measuring durations/times not related to sample timestamps, like duration
telemetry exporting, timers that indicate how frequently to execute some
action, etc.
*NOTE ON OPERATOR OPTIMIZATION TESTS*
We don't use operator optimization code anymore, but it still lives in
the code as dead code. It still has tests, but I couldn't get all of them to
pass with the new timestamp format. I commented out the failing cases for now,
but we should probably remove the dead code soon. I just didn't want to do that
in the same change as this.
Change-Id: I821787414b0debe85c9fffaeb57abd453727af0f
This adds search domain support by trying to resolve a name by
appending each search domain configured in /etc/resolv.conf until
the query succeeds (NOERROR) and has at least one answer.
Change-Id: Ibdc5138c5d8cc049e11fab90c3d5243d5a06852c
* changes:
fix link to CONTRIBUTING.md in README.md
moved CONTRIBUTING.md to top of repo; link to CONTRIBUTING.md in README.md
change double quotes to backticks for md awesomeness
add contributing.md
Due to on going issues, we've decided to remove gorest. It started with gorest
not being thread-safe (it does introspection to create a new handler which is
an easy process to mess up with multiple threads of execution):
https://code.google.com/p/gorest/issues/detail?id=15
While the issue has been marked fixed, it looks like the patch has introduced
more problems than the original issue and simply doesn't work properly.
I'm not sure the behaviour was thought through properly. If a new instance is
needed every request then a handler-factory is needed or the library needs to
set expectations about how the new objects should interact with their
constructor state.
While it was tempting to try out another routing library, I think for now
it's better to use dumb vanilla Go routing. At least until we decide which
URL format we intend to standardize on.
Change-Id: Ica3da135d05f8ab8fc206f51eeca4f684f8efa0e
- Modified sample conf so it is useable by default, also added some
comments from the 'hello world' configuration.
- Updated README so there's a clear two step start for newbies.
- Added extra vim swap files to gitignore.
Change-Id: I76203973db4a7b332014662fcfb2ce5e7d137bd8
This fixes part 2) of https://github.com/prometheus/prometheus/issues/367
(uninitialized time.Time mapping to a higher LevelDB key than "normal"
timestamps).
Change-Id: Ib079974110a7b7c4757948f81fc47d3d29ae43c9
This fixes part 1) of https://github.com/prometheus/prometheus/issues/367 (the
storing of samples with the wrong fingerprint into a compacted chunk, thus
corrupting it).
Change-Id: I4c36d0d2e508e37a0aba90b8ca2ecc78ee03e3f1
