0.5.0 / 2015-05-06

• [BUGFIX] Removed a weakness in the fingerprinting aka signature code.
  This makes fingerprinting slower and more allocation-heavy, but the
  weakness was too severe to be tolerated.
• [CHANGE] As a result of the above, Metric.Fingerprint is now returning
  a different fingerprint. To keep the same fingerprint, the new method
  Metric.FastFingerprint was introduced, which will be used by the
  Prometheus server for storage purposes (implying that a collision
  detection has to be added, too).
• [ENHANCEMENT] The Metric.Equal and Metric.Before do not depend on
  fingerprinting anymore, removing the possibility of an undetected
  fingerprint collision.
• [FEATURE] The Go collector in the exposition library includes garbage
  collection stats.
• [FEATURE] The exposition library allows to create constant "throw-away"
  summaries and histograms.
• [CHANGE] A number of new reserved labels and prefixes.

0.4.0 / 2015-04-08

• [CHANGE] Return NaN when Summaries have no observations yet.
• [BUGFIX] Properly handle Summary decay upon Write().
• [BUGFIX] Fix the documentation link to the consumption library.
• [FEATURE] Allow the metric family injection hook to merge with existing
  metric families.
• [ENHANCEMENT] Removed cgo dependency and conditional compilation of procfs.
• [MAINTENANCE] Adjusted to changes in matttproud/golang_protobuf_extensions.

0.3.2 / 2015-03-11

• [BUGFIX] Fixed the receiver type of COWMetric.Set(). This method is
  only used by the Prometheus server internally.
• [CLEANUP] Added licenses of vendored code left out by godep.

0.3.1 / 2015-03-04

• [ENHANCEMENT] Switched fingerprinting functions from own free list to
  sync.Pool.
• [CHANGE] Makefile uses Go 1.4.2 now (only relevant for examples and tests).

0.3.0 / 2015-03-03

This is the big one that changes fingerprinting. See below.

As long as you build the Prometheus server only with make, nothing
can go wrong, as the client_golang is vendored then. But if you
build from your own sources (with go build), you will compile in
whatever you have checked out in client_golang.

Version 0.12.0 of the Prometheus server will have a guard to not
accidentally run from a storage with the old fingerprinting.

• [CHANGE] Changed the fingerprinting for metrics. THIS WILL INVALIDATE ALL
  PERSISTED FINGERPRINTS. IF YOU COMPILE THE PROMETHEUS SERVER WITH THIS
  VERSION, YOU HAVE TO WIPE THE PREVIOUSLY CREATED STORAGE.
• [CHANGE] LabelValuesToSignature removed. (Nobody had used it, and it was
  arguably broken.)
• [CHANGE] Vendored dependencies. Those are only used by the Makefile. If
  client_golang is used as a library, the vendoring will stay out of your way.
• [BUGFIX] Remove a weakness in the fingerprinting for metrics. (This made
  the fingerprinting change above necessary.)
• [FEATURE] Added new fingerprinting functions SignatureForLabels and
  SignatureWithoutLabels to be used by the Prometheus server. These functions
  require fewer allocations than the ones currently used by the server.

0.2.0 / 2015-02-23

client_golang 0.2.0 has been released, with the most prominent new feature being server-side histograms. (Documentations will be updated later today to explain usage.)

0.2.0 / 2015-02-23

• [FEATURE] Introduce new Histagram metric type.
• [CHANGE] Ignore process collector errors for now (better error handling
  pending).
• [CHANGE] Use clear error interface for process pidFn.
• [BUGFIX] Fix Go download links for several archs and OSes.
• [ENHANCEMENT] Massively improve Gauge and Counter performance.
• [ENHANCEMENT] Catch illegal label names for summaries in histograms.
• [ENHANCEMENT] Reduce allocations during fingerprinting.
• [ENHANCEMENT] Remove cgo dependency. procfs package will only be included if
  both cgo is available and the build is for an OS with procfs.
• [CLEANUP] Clean up code style issues.
• [CLEANUP] Mark slow test as such and exclude them from travis.
• [CLEANUP] Update protobuf library package name.
• [CLEANUP] Updated vendoring of beorn7/perks.

Early warning: The fingerprinting method has an embarrassing bug (#74), which will be fixed in v0.3.0, but that will obviously invalidate each and every persisted fingerprint. We thought long about a conversion path or allowing to continue with the old fingerprinting method but could not come up with anything feasible. So one more storage wipe is looming...

0.1.0 / 2015-02-02

0.1.0 / 2015-02-02

• [CLEANUP] Introduced semantic versioning and changelog. From now on,
  changes will be reported in this file.