add metrics collector for BEAM VM

instrumentation/opentelemetry_beam/.gitignore

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+.rebar3
+_build
+_checkouts
+_vendor
+.eunit
+*.o
+*.beam
+*.plt
+*.swp
+*.swo
+.erlang.cookie
+ebin
+log
+erl_crash.dump
+.rebar
+logs
+.idea
+*.iml
+rebar3.crashdump
+*~

instrumentation/opentelemetry_beam/README.md

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+# opentelemetry_beam
+
+Metrics collector to export statistics from the BEAM VM.
+
+The metrics and their names are heavily borrowed from [prometheus.erl](https://github.com/deadtrickster/prometheus.erl).
+
+After installing, setup the desired metrics in your application behaviour before your
+top-level supervisor starts. Make sure the API and SDK applications are started before
+your application.
+
+```erlang
+opentelemetry_beam_metrics:setup(),
+...
+```
+
+Metrics that are based on microstate accounting need to be enabled explicitly with the `msacc` setting in the `opt_in` option:
+
+```erlang
+opentelemetry_beam_metrics:setup(#{opt_in => #{msacc => true}}),
+...
+```

instrumentation/opentelemetry_beam/priv/dev.config

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+%%-*-Erlang-*-
+[{kernel,
+  [{logger_level, debug},
+   {logger,
+    [{handler, default, logger_std_h,
+      #{level => debug,
+        formatter =>
+            {logger_formatter,
+             #{single_line => true,
+               legacy_header => false,
+               template => [time," ",pid," ",level,": ",msg,"\n"]
+              }},
+        config =>
+            #{sync_mode_qlen => 10000,
+              drop_mode_qlen => 10000,
+              flush_qlen     => 10000}
+       }
+     }
+    ]}
+  ]},
+
+ {opentelemetry_experimental,
+  [{readers,
+    [
+     #{module => otel_metric_reader_periodic,
+       config => #{export_interval_ms => 1000,
+                   exporter => {otel_metric_exporter_console, undefined}}}
+    ]}
+  ]}
+].

instrumentation/opentelemetry_beam/rebar.config

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+%%-*-Erlang-*-
+{erl_opts, [debug_info]}.
+{deps, [
+        {opentelemetry_api, "~> 1.3.0"},
+        {opentelemetry_api_experimental, "~> 0.5.1"}
+       ]}.
+
+{plugins, [rebar3_fmt]}.
+
+{xref_checks, [undefined_function_calls, undefined_functions,
+               deprecated_function_calls, deprecated_functions]}.
+{xref_ignores, []}.
+
+%% development setting
+{shell, [{config, "priv/dev.config"}]}.

instrumentation/opentelemetry_beam/src/opentelemetry_beam.app.src

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+{application, opentelemetry_beam,
+ [{description, "OpenTelemetry BEAM VM Instrumentation"},
+  {vsn, "0.1.0"},
+  {registered, []},
+  {applications,
+   [kernel,
+    stdlib,
+    opentelemetry_api,
+    opentelemetry_api_experimental
+   ]},
+  {env,[]},
+  {modules, []},
+  {licenses, ["Apache-2.0"]},
+  {links, []}
+ ]}.