3.0.0-rc1

Breaking Changes:

• invalid_metric_arity tuple changed. Added metric real arity to invalid_metric_arity error tuple;
• fix histogram,summary:observe_duration arguments order (Registry now goes first);
• changed collect_mf/3,2 args order;
• default collectors env key changed to 'collectors';
• default instrumenters env key changed to 'instrumenters';
• prometheus_buckets removed deprecations
  generate_linear/3,
  generate_exponential/3;
• prometheus_histogram: removed deprecated bounds config support;
• tweak histogram_invalid_buckets error tuple. It always has three elements now;
• prometheus_histogram:*_buckets functions are private.

Deprecations:

• deprecate prometheus_collector:register/deregister;
• deprecate metric:new,declare/2.

What's new:

• added metric real arity to invalid_metric_arity error tuple;
• :value returns undefined for unknown label set;
• :set,reset,value raise unknown_metric|invalid_metric_arity;
• :observe,observe_duration,track_inprogress raise unknown_metric|invalid_metric_arity;
• :d functions raise unknown_metric|invalid_metric_arity before gen_server:cast;
• :new,declare/1 accept registry key;
• prometheus_registry:register_collector(s),deregister_collector/1;
• prometheus_registry:collector_registeredp/1;
• gauge:set accepts undefined which is rendered as NaN;
• new error messages;
• track_inprogress/observe_duration raise invalid_value error when Fun is not a function;
• gauge (d)inc/(d)dec;
• gauge:set_duration;
• :remove - can remove series for a given label set;
• untyped metric support;
• erlang_vm_system_info_collector;
• new time measurement system #32;
• gen_server:call support with custom timeout #33.

Other

• rebar3 updated;
• coveralls integration;
• tests, refactors;
• docs.