Support retrieval of disk statistics from Gitaly

Add a rudimentary client implementation for the new gitaly
disk_statistics grpc.

Add unit tests.

New gitaly server methods include disk_used and
disk_available.  This commit adds unit testing
for those methods.

Add default server response on error

When the remote service is unavailable, times out,
or otherwise causes a service call failure, return
a default response with trivial values set to its
fields.

changelogs/unreleased/integrate-gitaly-disk_statistics-grpc.yml

+---
+title: "Support retrieval of disk statistics from Gitaly"
+merge_request: 22226
+author: Nels Nelson
+type: added

lib/gitaly/server.rb

@@ -53,6 +53,20 @@ module Gitaly
       storage_status&.fs_type
     end
 
+    def disk_used
+      disk_statistics_storage_status&.used
+    end
+
+    def disk_available
+      disk_statistics_storage_status&.available
+    end
+
+    # Simple convenience method for when obtaining both used and available
+    # statistics at once is preferred.
+    def disk_stats
+      disk_statistics_storage_status
+    end
+
     def address
       Gitlab::GitalyClient.address(@storage)
     rescue RuntimeError => e
@@ -65,6 +79,10 @@ module Gitaly
       @storage_status ||= info.storage_statuses.find { |s| s.storage_name == storage }
     end
 
+    def disk_statistics_storage_status
+      @disk_statistics_storage_status ||= disk_statistics.storage_statuses.find { |s| s.storage_name == storage }
+    end
+
     def matches_sha?
       match = server_version.match(SHA_VERSION_REGEX)
       return false unless match
@@ -76,7 +94,19 @@ module Gitaly
       @info ||=
         begin
           Gitlab::GitalyClient::ServerService.new(@storage).info
-        rescue GRPC::Unavailable, GRPC::DeadlineExceeded
+        rescue GRPC::Unavailable, GRPC::DeadlineExceeded => ex
+          Gitlab::ErrorTracking.track_exception(ex)
+          # This will show the server as being out of date
+          Gitaly::ServerInfoResponse.new(git_version: '', server_version: '', storage_statuses: [])
+        end
+    end
+
+    def disk_statistics
+      @disk_statistics ||=
+        begin
+          Gitlab::GitalyClient::ServerService.new(@storage).disk_statistics
+        rescue GRPC::Unavailable, GRPC::DeadlineExceeded => ex
+          Gitlab::ErrorTracking.track_exception(ex)
           # This will show the server as being out of date
           Gitaly::ServerInfoResponse.new(git_version: '', server_version: '', storage_statuses: [])
         end

lib/gitlab/gitaly_client.rb

@@ -432,10 +432,7 @@ module Gitlab
     end
 
     def self.filesystem_id(storage)
-      response = Gitlab::GitalyClient::ServerService.new(storage).info
-      storage_status = response.storage_statuses.find { |status| status.storage_name == storage }
-
-      storage_status&.filesystem_id
+      Gitlab::GitalyClient::ServerService.new(storage).storage_info&.filesystem_id
     end
 
     def self.filesystem_id_from_disk(storage)
@@ -446,6 +443,14 @@ module Gitlab
       nil
     end
 
+    def self.filesystem_disk_available(storage)
+      Gitlab::GitalyClient::ServerService.new(storage).storage_disk_statistics&.available
+    end
+
+    def self.filesystem_disk_used(storage)
+      Gitlab::GitalyClient::ServerService.new(storage).storage_disk_statistics&.used
+    end
+
     def self.timeout(timeout_name)
       Gitlab::CurrentSettings.current_application_settings[timeout_name]
     end

lib/gitlab/gitaly_client/server_service.rb

@@ -13,6 +13,24 @@ module Gitlab
       def info
         GitalyClient.call(@storage, :server_service, :server_info, Gitaly::ServerInfoRequest.new, timeout: GitalyClient.fast_timeout)
       end
+
+      def disk_statistics
+        GitalyClient.call(@storage, :server_service, :disk_statistics, Gitaly::DiskStatisticsRequest.new, timeout: GitalyClient.fast_timeout)
+      end
+
+      def storage_info
+        storage_specific(info)
+      end
+
+      def storage_disk_statistics
+        storage_specific(disk_statistics)
+      end
+
+      private
+
+      def storage_specific(response)
+        response.storage_statuses.find { |status| status.storage_name == @storage }
+      end
     end
   end
 end

spec/lib/gitaly/server_spec.rb

@@ -66,6 +66,53 @@ describe Gitaly::Server do
     end
   end
 
+  context "when examining disk statistics for a given server" do
+    let(:disk_available) { 42 }
+    let(:disk_used) { 42 }
+    let(:storage_status) { double('storage_status') }
+
+    before do
+      allow(storage_status).to receive(:storage_name).and_return('default')
+      allow(storage_status).to receive(:available).and_return(disk_available)
+      allow(storage_status).to receive(:used).and_return(disk_used)
+      response = double("response")
+      allow(response).to receive(:storage_statuses).and_return([storage_status])
+      allow_next_instance_of(Gitlab::GitalyClient::ServerService) do |instance|
+        allow(instance).to receive(:disk_statistics).and_return(response)
+      end
+    end
+
+    describe '#disk_available' do
+      subject { server.disk_available }
+
+      it { is_expected.to be_present }
+
+      it "returns disk available for the storage of the instantiated server" do
+        is_expected.to eq(disk_available)
+      end
+    end
+
+    describe '#disk_used' do
+      subject { server.disk_used }
+
+      it { is_expected.to be_present }
+
+      it "returns disk used for the storage of the instantiated server" do
+        is_expected.to eq(disk_used)
+      end
+    end
+
+    describe '#disk_stats' do
+      subject { server.disk_stats }
+
+      it { is_expected.to be_present }
+
+      it "returns the storage of the instantiated server" do
+        is_expected.to eq(storage_status)
+      end
+    end
+  end
+
   describe '#expected_version?' do
     using RSpec::Parameterized::TableSyntax
 

spec/lib/gitlab/gitaly_client_spec.rb

@@ -52,7 +52,7 @@ describe Gitlab::GitalyClient do
   end
 
   describe '.filesystem_id' do
-    it 'returns an empty string when the storage is not found in the response' do
+    it 'returns an empty string when the relevant storage status is not found in the response' do
       response = double("response")
       allow(response).to receive(:storage_statuses).and_return([])
       allow_next_instance_of(Gitlab::GitalyClient::ServerService) do |instance|
@@ -63,6 +63,63 @@ describe Gitlab::GitalyClient do
     end
   end
 
+  context 'when the relevant storage status is not found' do
+    before do
+      response = double('response')
+      allow(response).to receive(:storage_statuses).and_return([])
+      allow_next_instance_of(Gitlab::GitalyClient::ServerService) do |instance|
+        allow(instance).to receive(:disk_statistics).and_return(response)
+        expect(instance).to receive(:storage_disk_statistics)
+      end
+    end
+
+    describe '.filesystem_disk_available' do
+      it 'returns nil when the relevant storage status is not found in the response' do
+        expect(described_class.filesystem_disk_available('default')).to eq(nil)
+      end
+    end
+
+    describe '.filesystem_disk_used' do
+      it 'returns nil when the relevant storage status is not found in the response' do
+        expect(described_class.filesystem_disk_used('default')).to eq(nil)
+      end
+    end
+  end
+
+  context 'when the relevant storage status is found' do
+    let(:disk_available) { 42 }
+    let(:disk_used) { 42 }
+    let(:storage_status) { double('storage_status') }
+
+    before do
+      allow(storage_status).to receive(:storage_name).and_return('default')
+      allow(storage_status).to receive(:used).and_return(disk_used)
+      allow(storage_status).to receive(:available).and_return(disk_available)
+      response = double('response')
+      allow(response).to receive(:storage_statuses).and_return([storage_status])
+      allow_next_instance_of(Gitlab::GitalyClient::ServerService) do |instance|
+        allow(instance).to receive(:disk_statistics).and_return(response)
+      end
+      expect_next_instance_of(Gitlab::GitalyClient::ServerService) do |instance|
+        expect(instance).to receive(:storage_disk_statistics).and_return(storage_status)
+      end
+    end
+
+    describe '.filesystem_disk_available' do
+      it 'returns disk available when the relevant storage status is found in the response' do
+        expect(storage_status).to receive(:available)
+        expect(described_class.filesystem_disk_available('default')).to eq(disk_available)
+      end
+    end
+
+    describe '.filesystem_disk_used' do
+      it 'returns disk used when the relevant storage status is found in the response' do
+        expect(storage_status).to receive(:used)
+        expect(described_class.filesystem_disk_used('default')).to eq(disk_used)
+      end
+    end
+  end
+
   describe '.stub_class' do
     it 'returns the gRPC health check stub' do
       expect(described_class.stub_class(:health_check)).to eq(::Grpc::Health::V1::Health::Stub)