Address machineType not being returned in GCP metadata

lib/elastic_apm/metadata/cloud_info.rb

@@ -94,15 +94,18 @@ def fetch_gcp
         return unless resp.status == 200
         return unless (metadata = JSON.parse(resp.body.to_s))
 
-        zone = metadata["instance"]["zone"]&.split("/")&.at(-1)
-
         self.provider = "gcp"
-        self.instance_id = metadata["instance"]["id"].to_s
-        self.instance_name = metadata["instance"]["name"]
         self.project_id = metadata["project"]["projectId"]
+
+        return unless metadata['instance']
+
+        zone = metadata["instance"]["zone"]&.split("/")&.at(-1)
         self.availability_zone = zone
         self.region = zone.split("-")[0..-2].join("-")
-        self.machine_type = metadata["instance"]["machineType"].split("/")[-1]
+
+        self.instance_id = metadata["instance"]["id"].to_s
+        self.instance_name = metadata["instance"]["name"]
+        self.machine_type = metadata["instance"]["machineType"]&.split("/")&.at(-1)
       rescue HTTP::TimeoutError, HTTP::ConnectionError
         nil
       end

spec/elastic_apm/metadata/cloud_info_spec.rb

@@ -54,6 +54,22 @@ module CloudExamples
         }
       JSON
 
+      GCP_NO_MACHINE_EXAMPLE =  <<-JSON
+        {
+          "instance": {
+            "id": 4306570268266786072,
+            "name": "basepi-test",
+            "zone": "projects/513326162531/zones/us-west3-a"
+          },
+          "project": {"numericProjectId": 513326162531, "projectId": "elastic-apm"}
+        }
+      JSON
+
+      GCP_NO_INSTANCE_EXAMPLE =  <<-JSON
+        { "project": {"numericProjectId": 513326162531, "projectId": "elastic-apm"} }
+      JSON
+
+
       AZURE_EXAMPLE = <<-JSON
         {
           "location": "westus2",
@@ -118,6 +134,52 @@ module CloudExamples
         end
       end
 
+      context 'gcp no machine_type' do
+        let (:config) { Config.new(cloud_provider: 'gcp') }
+        before do
+          @gcp_mock =
+            WebMock.stub_request(:get, Metadata::CloudInfo::GCP_URI)
+              .to_return(body: CloudExamples::GCP_NO_MACHINE_EXAMPLE)
+        end
+
+        it 'fetches metadata from gcp' do
+          subject.fetch!
+
+          expect(subject.provider).to eq('gcp')
+          expect(subject.instance_id).to eq("4306570268266786072")
+          expect(subject.instance_name).to eq("basepi-test")
+          expect(subject.project_id).to eq('elastic-apm')
+          expect(subject.availability_zone).to eq('us-west3-a')
+          expect(subject.region).to eq('us-west3')
+          expect(subject.machine_type).to be nil
+
+          expect(@gcp_mock).to have_been_requested
+        end
+      end
+
+      context 'gcp no instance' do
+        let (:config) { Config.new(cloud_provider: 'gcp') }
+        before do
+          @gcp_mock =
+            WebMock.stub_request(:get, Metadata::CloudInfo::GCP_URI)
+              .to_return(body: CloudExamples::GCP_NO_INSTANCE_EXAMPLE)
+        end
+
+        it 'fetches metadata from gcp' do
+          subject.fetch!
+
+          expect(subject.provider).to eq('gcp')
+          expect(subject.project_id).to eq('elastic-apm')
+          expect(subject.instance_id).to be nil
+          expect(subject.instance_name).to be nil
+          expect(subject.availability_zone).to be nil
+          expect(subject.region).to be nil
+          expect(subject.machine_type).to be nil
+
+          expect(@gcp_mock).to have_been_requested
+        end
+      end
+
       context 'azure' do
         let(:config) { Config.new(cloud_provider: 'azure') }