Add Utility to Collect Platform Information (#2097)

* Add host information utility

* fixup! Add host information utility

* Rename file to platform

* fixup! Rename file to platform

* Require etc in file

lib/datadog/core/environment/platform.rb

@@ -0,0 +1,40 @@
+# typed: false
+
+require 'etc'
+
+require 'datadog/core/environment/identity'
+
+module Datadog
+  module Core
+    module Environment
+      # For gathering information about the platform
+      module Platform
+        module_function
+
+        # @return [String] name of host; `uname -n`
+        def hostname
+          Identity.lang_version >= '2.2' ? Etc.uname[:nodename] : nil
+        end
+
+        # @return [String] name of kernel; `uname -s`
+        def kernel_name
+          Identity.lang_version >= '2.2' ? Etc.uname[:sysname] : Gem::Platform.local.os.capitalize
+        end
+
+        # @return [String] kernel release; `uname -r`
+        def kernel_release
+          if Identity.lang_engine == 'jruby'
+            Etc.uname[:version] # Java's `os.version` maps to `uname -r`
+          elsif Identity.lang_version >= '2.2'
+            Etc.uname[:release]
+          end
+        end
+
+        # @return [String] kernel version; `uname -v`
+        def kernel_version
+          Etc.uname[:version] if Identity.lang_engine != 'jruby' && Identity.lang_version >= '2.2'
+        end
+      end
+    end
+  end
+end

spec/datadog/core/environment/platform_spec.rb

@@ -0,0 +1,57 @@
+# typed: false
+
+require 'spec_helper'
+require 'datadog/core/environment/platform'
+
+RSpec.describe Datadog::Core::Environment::Platform do
+  describe '::hostname' do
+    subject(:hostname) { described_class.hostname }
+
+    context 'when Ruby version < 2.2', if: Datadog::Core::Environment::Ext::LANG_VERSION < '2.2' do
+      it { is_expected.to be_nil }
+    end
+
+    context 'when Ruby version >= 2.2', if: Datadog::Core::Environment::Ext::LANG_VERSION >= '2.2' do
+      it { is_expected.to be_a_kind_of(String) }
+      it { is_expected.to eql(`uname -n`.strip) }
+    end
+  end
+
+  describe '::kernel_name' do
+    subject(:kernel_name) { described_class.kernel_name }
+    it { is_expected.to be_a_kind_of(String) }
+    it { is_expected.to eql(`uname -s`.strip) }
+  end
+
+  describe '::kernel_release' do
+    subject(:kernel_release) { described_class.kernel_release }
+
+    context 'when Ruby version < 2.2', if: Datadog::Core::Environment::Ext::LANG_VERSION < '2.2' do
+      it { is_expected.to be_nil }
+    end
+
+    context 'when Ruby version >= 2.2', if: Datadog::Core::Environment::Ext::LANG_VERSION >= '2.2' do
+      it { is_expected.to be_a_kind_of(String) }
+      it { is_expected.to eql(`uname -r`.strip) }
+    end
+  end
+
+  describe '::kernel_version' do
+    subject(:kernel_version) { described_class.kernel_version }
+
+    context 'when using JRuby', if: Datadog::Core::Environment::Ext::RUBY_ENGINE == 'jruby' do
+      it { is_expected.to be_nil }
+    end
+
+    context 'when not using JRuby', unless: Datadog::Core::Environment::Ext::RUBY_ENGINE == 'jruby' do
+      context 'when Ruby version < 2.2', if: Datadog::Core::Environment::Ext::LANG_VERSION < '2.2' do
+        it { is_expected.to be_nil }
+      end
+
+      context 'when Ruby version >= 2.2', if: Datadog::Core::Environment::Ext::LANG_VERSION >= '2.2' do
+        it { is_expected.to be_a_kind_of(String) }
+        it { is_expected.to eql(`uname -v`.strip) }
+      end
+    end
+  end
+end