0.9.4 / 2019-06-07

• [CHANGE] API client: Switch to alert values as strings. #585
• [FEATURE] Add a collector for Go module build information. #595
• [FEATURE] promhttp: Add an counter for internal errors during HTTP exposition. #594
• [FEATURE] API client: Support target metadata API. #590
• [FEATURE] API client: Support storage warnings. #562
• [ENHANCEMENT] API client: Improve performance handling JSON. #570
• [BUGFIX] Reduce test flakiness. #573

0.9.3 / 2019-05-16

• [CHANGE] Required Go version is now 1.9+. #561
• [FEATURE] API client: Add POST with get fallback for Query/QueryRange. #557
• [FEATURE] API client: Add alerts endpoint. #552
• [FEATURE] API client: Add rules endpoint. #508
• [FEATURE] push: Add option to pick metrics format. #540
• [ENHANCEMENT] Limit time the Go collector may take to collect memstats,
  returning results from the previous collection in case of a timeout. #568
• [ENHANCEMENT] Pusher now requires only a thin interface instead of a full
  http.Client, facilitating mocking and custom HTTP client implementation.
  #559
• [ENHANCEMENT] Memory usage improvement for histograms and summaries without
  objectives. #536
• [ENHANCEMENT] Summaries without objectives are now lock-free. #521
• [BUGFIX] promhttp: InstrumentRoundTripperTrace now takes into account a pre-set context. #582
• [BUGFIX] TestCounterAddLarge now works on all platforms. #567
• [BUGFIX] Fix promhttp examples. #535 #544
• [BUGFIX] API client: Wait for done before writing to shared response
  body. #532
• [BUGFIX] API client: Deal with discovered labels properly. #529

0.9.2 / 2018-12-06

• [FEATURE] Support for Go modules. #501
• [FEATURE] Timer.ObserveDuration returns observed duration. #509
• [ENHANCEMENT] Improved doc comments and error messages. #504
• [BUGFIX] Fix race condition during metrics gathering. #512
• [BUGFIX] Fix testutil metric comparison for Histograms and empty labels. #494 #498

0.9.1 / 2018-11-03

• [FEATURE] Add WriteToTextfile function to facilitate the creation of
  *.prom files for the textfile collector of the node exporter. #489
• [ENHANCEMENT] More descriptive error messages for inconsistent label
  cardinality. #487
• [ENHANCEMENT] Exposition: Use a GZIP encoder pool to avoid allocations in
  high-frequency scrape scenarios. #366
• [ENHANCEMENT] Exposition: Streaming serving of metrics data while encoding.
  #482
• [ENHANCEMENT] API client: Add a way to return the body of a 5xx response.
  #479

0.9.0 / 2018-10-15

• [CHANGE] Go1.6 is no longer supported.
• [CHANGE] More refinements of the Registry consistency checks: Duplicated
  labels are now detected, but inconsistent label dimensions are now allowed.
  Collisions with the “magic” metric and label names in Summaries and
  Histograms are detected now. #108 #417 #471
• [CHANGE] Changed ProcessCollector constructor. #219
• [CHANGE] Changed Go counter go_memstats_heap_released_bytes_total to gauge
  go_memstats_heap_released_bytes. #229
• [CHANGE] Unexported LabelPairSorter. #453
• [CHANGE] Removed the Untyped metric from direct instrumentation. #340
• [CHANGE] Unexported MetricVec. #319
• [CHANGE] Removed deprecated Set method from Counter #247
• [CHANGE] Removed deprecated RegisterOrGet and MustRegisterOrGet. #247
• [CHANGE] API client: Introduced versioned packages.
• [FEATURE] A Registerer can be wrapped with prefixes and labels. #357
• [FEATURE] “Describe by collect” helper function. #239
• [FEATURE] Added package testutil. #58
• [FEATURE] Timestamp can be explicitly set for const metrics. #187
• [FEATURE] “Unchecked” collectors are possible now without cheating. #47
• [FEATURE] Pushing to the Pushgateway reworked in package push to support
  many new features. (The old functions are still usable but deprecated.) #372
  #341
• [FEATURE] Configurable connection limit for scrapes. #179
• [FEATURE] New HTTP middlewares to instrument http.Handler and
  http.RoundTripper. The old middlewares and the pre-instrumented /metrics
  handler are (strongly) deprecated. #316 #57 #101 #224
• [FEATURE] “Currying” for metric vectors. #320
• [FEATURE] A Summary can be created without quantiles. #118
• [FEATURE] Added a Timer helper type. #231
• [FEATURE] Added a Graphite bridge. #197
• [FEATURE] Help strings are now optional. #460
• [FEATURE] Added process_virtual_memory_max_bytes metric. #438 #440
• [FEATURE] Added go_gc_cpu_fraction and go_threads metrics. #281 #277
• [FEATURE] Added promauto package with auto-registering metrics. #385 #393
• [FEATURE] Add SetToCurrentTime method to Gauge. #259
• [FEATURE] API client: Add AlertManager, Status, and Target methods. #402
• [FEATURE] API client: Add admin methods. #398
• [FEATURE] API client: Support series API. #361
• [FEATURE] API client: Support querying label values.
• [ENHANCEMENT] Smarter creation of goroutines during scraping. Solves memory
  usage spikes in certain situations. #369
• [ENHANCEMENT] Counters are now faster if dealing with integers only. #367
• [ENHANCEMENT] Improved label validation. #274 #335
• [BUGFIX] Creating a const metric with an invalid Desc returns an error. #460
• [BUGFIX] Histogram observations don't race any longer with exposition. #275
• [BUGFIX] Fixed goroutine leaks. #236 #472
• [BUGFIX] Fixed an error message for exponential histogram buckets. #467
• [BUGFIX] Fixed data race writing to the metric map. #401
• [BUGFIX] API client: Decode JSON on a 4xx respons but do not on 204
  responses. #476 #414

0.8.0 / 2016-08-17

• [CHANGE] Registry is doing more consistency checks. This might break
  existing setups that used to export inconsistent metrics.
• [CHANGE] Pushing to Pushgateway moved to package push and changed to allow
  arbitrary grouping.
• [CHANGE] Removed SelfCollector.
• [CHANGE] Removed PanicOnCollectError and EnableCollectChecks methods.
• [CHANGE] Moved packages to the prometheus/common repo: text, model,
  extraction.
• [CHANGE] Deprecated a number of functions.
• [FEATURE] Allow custom registries. Added Registerer and Gatherer
  interfaces.
• [FEATURE] Separated HTTP exposition, allowing custom HTTP handlers (package
  promhttp) and enabling the creation of other exposition mechanisms.
• [FEATURE] MustRegister is variadic now, allowing registration of many
  collectors in one call.
• [FEATURE] Added HTTP API v1 package.
• [ENHANCEMENT] Numerous documentation improvements.
• [ENHANCEMENT] Improved metric sorting.
• [ENHANCEMENT] Inlined fnv64a hashing for improved performance.
• [ENHANCEMENT] Several test improvements.
• [BUGFIX] Handle collisions in MetricVec.

0.7.0 / 2015-07-27

• [CHANGE] Rename ExporterLabelPrefix to ExportedLabelPrefix.
• [BUGFIX] Closed gaps in metric consistency check.
• [BUGFIX] Validate LabelName/LabelSet on JSON unmarshaling.
• [ENHANCEMENT] Document the possibility to create "empty" metrics in
  a metric vector.
• [ENHANCEMENT] Fix and clarify various doc comments and the README.md.
• [ENHANCEMENT] - (Kind of) solve "The Proxy Problem" of http.InstrumentHandler.
• [ENHANCEMENT] Change responseWriterDelegator.written to int64.

0.6.0 / 2015-06-01

• [CHANGE] Rename process_goroutines to go_goroutines.
• [ENHANCEMENT] Validate label names during YAML decoding.
• [ENHANCEMENT] Add LabelName regular expression.
• [BUGFIX] Ensure alignment of struct members for 32-bit systems.

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.