Merge branch 'bvl-circuitbreaker-backoff' into 'master'

Circuitbreaker backoff and retries

Closes #37383 and #38231

See merge request gitlab-org/gitlab-ce!14933

app/helpers/application_settings_helper.rb

@@ -120,6 +120,15 @@ module ApplicationSettingsHelper
     message.html_safe
   end
 
+  def circuitbreaker_access_retries_help_text
+    _('The number of attempts GitLab will make to access a storage.')
+  end
+
+  def circuitbreaker_backoff_threshold_help_text
+    _("The number of failures after which GitLab will start temporarily "\
+      "disabling access to a storage shard on a host")
+  end
+
   def circuitbreaker_failure_wait_time_help_text
     _("When access to a storage fails. GitLab will prevent access to the "\
       "storage for the time specified here. This allows the filesystem to "\
@@ -144,6 +153,8 @@ module ApplicationSettingsHelper
       :akismet_api_key,
       :akismet_enabled,
       :auto_devops_enabled,
+      :circuitbreaker_access_retries,
+      :circuitbreaker_backoff_threshold,
       :circuitbreaker_failure_count_threshold,
       :circuitbreaker_failure_reset_time,
       :circuitbreaker_failure_wait_time,

app/helpers/storage_health_helper.rb

@@ -16,17 +16,16 @@ module StorageHealthHelper
   def message_for_circuit_breaker(circuit_breaker)
     maximum_failures = circuit_breaker.failure_count_threshold
     current_failures = circuit_breaker.failure_count
-    permanently_broken = circuit_breaker.circuit_broken? && current_failures >= maximum_failures
 
     translation_params = { number_of_failures: current_failures,
                            maximum_failures: maximum_failures,
                            number_of_seconds: circuit_breaker.failure_wait_time }
 
-    if permanently_broken
+    if circuit_breaker.circuit_broken?
       s_("%{number_of_failures} of %{maximum_failures} failures. GitLab will not "\
          "retry automatically. Reset storage information when the problem is "\
          "resolved.") % translation_params
-    elsif circuit_breaker.circuit_broken?
+    elsif circuit_breaker.backing_off?
       _("%{number_of_failures} of %{maximum_failures} failures. GitLab will "\
         "block access for %{number_of_seconds} seconds.") % translation_params
     else

app/models/application_setting.rb

@@ -153,13 +153,25 @@ class ApplicationSetting < ActiveRecord::Base
             presence: true,
             numericality: { greater_than_or_equal_to: 0 }
 
-  validates :circuitbreaker_failure_count_threshold,
+  validates :circuitbreaker_backoff_threshold,
+            :circuitbreaker_failure_count_threshold,
             :circuitbreaker_failure_wait_time,
             :circuitbreaker_failure_reset_time,
             :circuitbreaker_storage_timeout,
             presence: true,
             numericality: { only_integer: true, greater_than_or_equal_to: 0 }
 
+  validates :circuitbreaker_access_retries,
+            presence: true,
+            numericality: { only_integer: true, greater_than_or_equal_to: 1 }
+
+  validates_each :circuitbreaker_backoff_threshold do |record, attr, value|
+    if value.to_i >= record.circuitbreaker_failure_count_threshold
+      record.errors.add(attr, _("The circuitbreaker backoff threshold should be "\
+                                "lower than the failure count threshold"))
+    end
+  end
+
   SUPPORTED_KEY_TYPES.each do |type|
     validates :"#{type}_key_restriction", presence: true, key_restriction: { type: type }
   end

app/views/admin/application_settings/_form.html.haml

@@ -533,11 +533,23 @@
   %fieldset
     %legend Git Storage Circuitbreaker settings
     .form-group
-      = f.label :circuitbreaker_failure_count_threshold, _('Maximum git storage failures'), class: 'control-label col-sm-2'
+      = f.label :circuitbreaker_access_retries, _('Number of access attempts'), class: 'control-label col-sm-2'
       .col-sm-10
-        = f.number_field :circuitbreaker_failure_count_threshold, class: 'form-control'
+        = f.number_field :circuitbreaker_access_retries, class: 'form-control'
         .help-block
-          = circuitbreaker_failure_count_help_text
+          = circuitbreaker_access_retries_help_text
+    .form-group
+      = f.label :circuitbreaker_storage_timeout, _('Seconds to wait for a storage access attempt'), class: 'control-label col-sm-2'
+      .col-sm-10
+        = f.number_field :circuitbreaker_storage_timeout, class: 'form-control'
+        .help-block
+          = circuitbreaker_storage_timeout_help_text
+    .form-group
+      = f.label :circuitbreaker_backoff_threshold, _('Number of failures before backing off'), class: 'control-label col-sm-2'
+      .col-sm-10
+        = f.number_field :circuitbreaker_backoff_threshold, class: 'form-control'
+        .help-block
+          = circuitbreaker_backoff_threshold_help_text
     .form-group
       = f.label :circuitbreaker_failure_wait_time, _('Seconds to wait after a storage failure'), class: 'control-label col-sm-2'
       .col-sm-10
@@ -545,17 +557,17 @@
         .help-block
           = circuitbreaker_failure_wait_time_help_text
     .form-group
-      = f.label :circuitbreaker_failure_reset_time, _('Seconds before reseting failure information'), class: 'control-label col-sm-2'
+      = f.label :circuitbreaker_failure_count_threshold, _('Maximum git storage failures'), class: 'control-label col-sm-2'
       .col-sm-10
-        = f.number_field :circuitbreaker_failure_reset_time, class: 'form-control'
+        = f.number_field :circuitbreaker_failure_count_threshold, class: 'form-control'
         .help-block
-          = circuitbreaker_failure_reset_time_help_text
+          = circuitbreaker_failure_count_help_text
     .form-group
-      = f.label :circuitbreaker_storage_timeout, _('Seconds to wait for a storage access attempt'), class: 'control-label col-sm-2'
+      = f.label :circuitbreaker_failure_reset_time, _('Seconds before reseting failure information'), class: 'control-label col-sm-2'
       .col-sm-10
-        = f.number_field :circuitbreaker_storage_timeout, class: 'form-control'
+        = f.number_field :circuitbreaker_failure_reset_time, class: 'form-control'
         .help-block
-          = circuitbreaker_storage_timeout_help_text
+          = circuitbreaker_failure_reset_time_help_text
 
   %fieldset
     %legend Repository Checks

changelogs/unreleased/bvl-circuitbreaker-backoff.yml

+---
+title: Make the circuitbreaker more robust by adding higher thresholds, and multiple
+  access attempts.
+merge_request: 14933
+author:
+type: fixed

db/migrate/20171017145932_add_new_circuitbreaker_settings_to_application_settings.rb

+class AddNewCircuitbreakerSettingsToApplicationSettings < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  def change
+    add_column :application_settings,
+               :circuitbreaker_access_retries,
+               :integer,
+               default: 3
+    add_column :application_settings,
+               :circuitbreaker_backoff_threshold,
+               :integer,
+               default: 80
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20171012101043) do
+ActiveRecord::Schema.define(version: 20171017145932) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -138,6 +138,8 @@ ActiveRecord::Schema.define(version: 20171012101043) do
     t.integer "circuitbreaker_failure_wait_time", default: 30
     t.integer "circuitbreaker_failure_reset_time", default: 1800
     t.integer "circuitbreaker_storage_timeout", default: 30
+    t.integer "circuitbreaker_access_retries", default: 3
+    t.integer "circuitbreaker_backoff_threshold", default: 80
   end
 
   create_table "audit_events", force: :cascade do |t|

doc/administration/repository_storage_paths.md

@@ -109,6 +109,11 @@ This can be configured from the admin interface:
 
 ![circuitbreaker configuration](img/circuitbreaker_config.png)
 
+**Number of access attempts**: The number of attempts GitLab will make to access a
+storage when probing a shard.
+
+**Number of failures before backing off**: The number of failures after which
+GitLab will start temporarily disabling access to a storage shard on a host.
 
 **Maximum git storage failures:** The number of failures of after which GitLab will
 completely prevent access to the storage. The number of failures can be reset in
@@ -126,6 +131,15 @@ mount is reset.
 **Seconds to wait for a storage access attempt:** The time in seconds GitLab will
 try to access storage. After this time a timeout error will be raised.
 
+To enable the circuitbreaker for repository storage you can flip the feature flag from a rails console:
+
+```
+Feature.enable('git_storage_circuit_breaker')
+```
+
+Alternatively it can be enabled by setting `true` in the `GIT_STORAGE_CIRCUIT_BREAKER` environment variable.
+This approach would be used when enabling the circuit breaker on a single host.
+
 When storage failures occur, this will be visible in the admin interface like this:
 
 ![failing storage](img/failing_storage.png)

doc/api/settings.md

@@ -69,6 +69,8 @@ PUT /application/settings
 | `after_sign_up_text`                     | string           | no                                            | Text shown to the user after signing up                                                                                                                                                                                                                                                                                                                                                                                                                   |
 | `akismet_api_key`                        | string           | no                                            | API key for akismet spam protection                                                                                                                                                                                                                                                                                                                                                                                                                       |
 | `akismet_enabled`                        | boolean          | no                                            | Enable or disable akismet spam protection                                                                                                                                                                                                                                                                                                                                                                                                                 |
+| `circuitbreaker_access_retries           | integer          | no                                            | The number of attempts GitLab will make to access a storage.                                                                                                                                                                                                                                                                                                                                                                                              |
+| `circuitbreaker_backoff_threshold        | integer          | no                                            | The number of failures after which GitLab will start temporarily disabling access to a storage shard on a host.                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
 | `circuitbreaker_failure_count_threshold` | integer          | no                                            | The number of failures of after which GitLab will completely prevent access to the storage.                                                                                                                                                                                                                                                                                                                                                               |
 | `circuitbreaker_failure_reset_time`      | integer          | no                                            | Time in seconds GitLab will keep storage failure information. When no failures occur during this time, the failure information is reset.                                                                                                                                                                                                                                                                                                                  |
 | `circuitbreaker_failure_wait_time`       | integer          | no                                            | Time in seconds GitLab will block access to a failing storage to allow it to recover.                                                                                                                                                                                                                                                                                                                                                                     |

lib/gitlab/git/storage.rb

@@ -12,6 +12,7 @@ module Gitlab
 
       CircuitOpen = Class.new(Inaccessible)
       Misconfiguration = Class.new(Inaccessible)
+      Failing = Class.new(Inaccessible)
 
       REDIS_KEY_PREFIX = 'storage_accessible:'.freeze
 

lib/gitlab/git/storage/circuit_breaker.rb

@@ -54,7 +54,7 @@ module Gitlab
         end
 
         def perform
-          return yield unless Feature.enabled?('git_storage_circuit_breaker')
+          return yield unless enabled?
 
           check_storage_accessible!
 
@@ -64,10 +64,27 @@ module Gitlab
         def circuit_broken?
           return false if no_failures?
 
+          failure_count > failure_count_threshold
+        end
+
+        def backing_off?
+          return false if no_failures?
+
           recent_failure = last_failure > failure_wait_time.seconds.ago
-          too_many_failures = failure_count > failure_count_threshold
+          too_many_failures = failure_count > backoff_threshold
 
-          recent_failure || too_many_failures
+          recent_failure && too_many_failures
+        end
+
+        private
+
+        # The circuitbreaker can be enabled for the entire fleet using a Feature
+        # flag.
+        #
+        # Enabling it for a single host can be done setting the
+        # `GIT_STORAGE_CIRCUIT_BREAKER` environment variable.
+        def enabled?
+          ENV['GIT_STORAGE_CIRCUIT_BREAKER'].present? || Feature.enabled?('git_storage_circuit_breaker')
         end
 
         def failure_info
@@ -83,7 +100,7 @@ module Gitlab
           return @storage_available if @storage_available
 
           if @storage_available = Gitlab::Git::Storage::ForkedStorageCheck
-                                    .storage_available?(storage_path, storage_timeout)
+                                    .storage_available?(storage_path, storage_timeout, access_retries)
             track_storage_accessible
           else
             track_storage_inaccessible
@@ -94,7 +111,11 @@ module Gitlab
 
         def check_storage_accessible!
           if circuit_broken?
-            raise Gitlab::Git::Storage::CircuitOpen.new("Circuit for #{storage} is broken", failure_wait_time)
+            raise Gitlab::Git::Storage::CircuitOpen.new("Circuit for #{storage} is broken", failure_reset_time)
+          end
+
+          if backing_off?
+            raise Gitlab::Git::Storage::Failing.new("Backing off access to #{storage}", failure_wait_time)
           end
 
           unless storage_available?
@@ -131,12 +152,6 @@ module Gitlab
           end
         end
 
-        def cache_key
-          @cache_key ||= "#{Gitlab::Git::Storage::REDIS_KEY_PREFIX}#{storage}:#{hostname}"
-        end
-
-        private
-
         def get_failure_info
           last_failure, failure_count = Gitlab::Git::Storage.redis.with do |redis|
             redis.hmget(cache_key, :last_failure, :failure_count)
@@ -146,6 +161,10 @@ module Gitlab
 
           FailureInfo.new(last_failure, failure_count.to_i)
         end
+
+        def cache_key
+          @cache_key ||= "#{Gitlab::Git::Storage::REDIS_KEY_PREFIX}#{storage}:#{hostname}"
+        end
       end
     end
   end

lib/gitlab/git/storage/circuit_breaker_settings.rb

@@ -18,6 +18,14 @@ module Gitlab
           application_settings.circuitbreaker_storage_timeout
         end
 
+        def access_retries
+          application_settings.circuitbreaker_access_retries
+        end
+
+        def backoff_threshold
+          application_settings.circuitbreaker_backoff_threshold
+        end
+
         private
 
         def application_settings

lib/gitlab/git/storage/forked_storage_check.rb

@@ -4,8 +4,17 @@ module Gitlab
       module ForkedStorageCheck
         extend self
 
-        def storage_available?(path, timeout_seconds = 5)
-          status = timeout_check(path, timeout_seconds)
+        def storage_available?(path, timeout_seconds = 5, retries = 1)
+          partial_timeout = timeout_seconds / retries
+          status = timeout_check(path, partial_timeout)
+
+          # If the status check did not succeed the first time, we retry a few
+          # more times to avoid one-off failures
+          current_attempts = 1
+          while current_attempts < retries && !status.success?
+            status = timeout_check(path, partial_timeout)
+            current_attempts += 1
+          end
 
           status.success?
         end

lib/gitlab/git/storage/null_circuit_breaker.rb

@@ -25,6 +25,10 @@ module Gitlab
           !!@error
         end
 
+        def backing_off?
+          false
+        end
+
         def last_failure
           circuit_broken? ? Time.now : nil
         end

spec/lib/gitlab/git/storage/circuit_breaker_spec.rb

@@ -79,7 +79,9 @@ describe Gitlab::Git::Storage::CircuitBreaker, clean_gitlab_redis_shared_state:
       stub_application_setting(circuitbreaker_failure_count_threshold: 0,
                                circuitbreaker_failure_wait_time: 1,
                                circuitbreaker_failure_reset_time: 2,
-                               circuitbreaker_storage_timeout: 3)
+                               circuitbreaker_storage_timeout: 3,
+                               circuitbreaker_access_retries: 4,
+                               circuitbreaker_backoff_threshold: 5)
     end
 
     describe '#failure_count_threshold' do
@@ -105,14 +107,43 @@ describe Gitlab::Git::Storage::CircuitBreaker, clean_gitlab_redis_shared_state:
         expect(circuit_breaker.storage_timeout).to eq(3)
       end
     end
+
+    describe '#access_retries' do
+      it 'reads the value from settings' do
+        expect(circuit_breaker.access_retries).to eq(4)
+      end
+    end
+
+    describe '#backoff_threshold' do
+      it 'reads the value from settings' do
+        expect(circuit_breaker.backoff_threshold).to eq(5)
+      end
+    end
   end
 
   describe '#perform' do
-    it 'raises an exception with retry time when the circuit is open' do
-      allow(circuit_breaker).to receive(:circuit_broken?).and_return(true)
+    it 'raises the correct exception when the circuit is open' do
+      set_in_redis(:last_failure, 1.day.ago.to_f)
+      set_in_redis(:failure_count, 999)
+
+      expect { |b| circuit_breaker.perform(&b) }
+        .to raise_error do |exception|
+        expect(exception).to be_kind_of(Gitlab::Git::Storage::CircuitOpen)
+        expect(exception.retry_after).to eq(1800)
+      end
+    end
+
+    it 'raises the correct exception when backing off' do
+      Timecop.freeze do
+        set_in_redis(:last_failure, 1.second.ago.to_f)
+        set_in_redis(:failure_count, 90)
 
         expect { |b| circuit_breaker.perform(&b) }
-        .to raise_error(Gitlab::Git::Storage::CircuitOpen)
+          .to raise_error do |exception|
+          expect(exception).to be_kind_of(Gitlab::Git::Storage::Failing)
+          expect(exception.retry_after).to eq(30)
+        end
+      end
     end
 
     it 'yields the block' do
@@ -122,6 +153,7 @@ describe Gitlab::Git::Storage::CircuitBreaker, clean_gitlab_redis_shared_state:
 
     it 'checks if the storage is available' do
       expect(circuit_breaker).to receive(:check_storage_accessible!)
+                                   .and_call_original
 
       circuit_breaker.perform { 'hello world' }
     end
@@ -137,201 +169,124 @@ describe Gitlab::Git::Storage::CircuitBreaker, clean_gitlab_redis_shared_state:
         .to raise_error(Rugged::OSError)
     end
 
-    context 'with the feature disabled' do
-      it 'returns the block without checking accessibility' do
-        stub_feature_flags(git_storage_circuit_breaker: false)
-
-        expect(circuit_breaker).not_to receive(:circuit_broken?)
+    it 'tracks that the storage was accessible' do
+      set_in_redis(:failure_count, 10)
+      set_in_redis(:last_failure, Time.now.to_f)
 
-        result = circuit_breaker.perform { 'hello' }
+      circuit_breaker.perform { '' }
 
-        expect(result).to eq('hello')
-      end
-    end
+      expect(value_from_redis(:failure_count).to_i).to eq(0)
+      expect(value_from_redis(:last_failure)).to be_empty
+      expect(circuit_breaker.failure_count).to eq(0)
+      expect(circuit_breaker.last_failure).to be_nil
     end
 
-  describe '#circuit_broken?' do
-    it 'is working when there is no last failure' do
-      set_in_redis(:last_failure, nil)
-      set_in_redis(:failure_count, 0)
+    it 'only performs the accessibility check once' do
+      expect(Gitlab::Git::Storage::ForkedStorageCheck)
+        .to receive(:storage_available?).once.and_call_original
 
-      expect(circuit_breaker.circuit_broken?).to be_falsey
+      2.times { circuit_breaker.perform { '' } }
     end
 
-    it 'is broken when there was a recent failure' do
-      Timecop.freeze do
-        set_in_redis(:last_failure, 1.second.ago.to_f)
-        set_in_redis(:failure_count, 1)
-
-        expect(circuit_breaker.circuit_broken?).to be_truthy
-      end
-    end
+    it 'calls the check with the correct arguments' do
+      stub_application_setting(circuitbreaker_storage_timeout: 30,
+                               circuitbreaker_access_retries: 3)
 
-    it 'is broken when there are too many failures' do
-      set_in_redis(:last_failure, 1.day.ago.to_f)
-      set_in_redis(:failure_count, 200)
+      expect(Gitlab::Git::Storage::ForkedStorageCheck)
+        .to receive(:storage_available?).with(TestEnv.repos_path, 30, 3)
+              .and_call_original
 
-      expect(circuit_breaker.circuit_broken?).to be_truthy
+      circuit_breaker.perform { '' }
     end
 
-    context 'the `failure_wait_time` is set to 0' do
+    context 'with the feature disabled' do
       before do
-        stub_application_setting(circuitbreaker_failure_wait_time: 0)
-      end
-
-      it 'is working even when there is a recent failure' do
-        Timecop.freeze do
-          set_in_redis(:last_failure, 0.seconds.ago.to_f)
-          set_in_redis(:failure_count, 1)
-
-          expect(circuit_breaker.circuit_broken?).to be_falsey
-        end
-      end
-    end
+        stub_feature_flags(git_storage_circuit_breaker: false)
       end
 
-  describe "storage_available?" do
-    context 'the storage is available' do
-      it 'tracks that the storage was accessible an raises the error' do
-        expect(circuit_breaker).to receive(:track_storage_accessible)
-
-        circuit_breaker.storage_available?
-      end
+      it 'returns the block without checking accessibility' do
+        expect(circuit_breaker).not_to receive(:check_storage_accessible!)
 
-      it 'only performs the check once' do
-        expect(Gitlab::Git::Storage::ForkedStorageCheck)
-          .to receive(:storage_available?).once.and_call_original
+        result = circuit_breaker.perform { 'hello' }
 
-        2.times { circuit_breaker.storage_available? }
-      end
+        expect(result).to eq('hello')
       end
 
-    context 'storage is not available' do
-      let(:storage_name) { 'broken' }
-
-      it 'tracks that the storage was inaccessible' do
-        expect(circuit_breaker).to receive(:track_storage_inaccessible)
-
-        circuit_breaker.storage_available?
-      end
-    end
-  end
+      it 'allows enabling the feature using an ENV var' do
+        stub_env('GIT_STORAGE_CIRCUIT_BREAKER', 'true')
+        expect(circuit_breaker).to receive(:check_storage_accessible!)
 
-  describe '#check_storage_accessible!' do
-    it 'raises an exception with retry time when the circuit is open' do
-      allow(circuit_breaker).to receive(:circuit_broken?).and_return(true)
+        result = circuit_breaker.perform { 'hello' }
 
-      expect { circuit_breaker.check_storage_accessible! }
-        .to raise_error do |exception|
-        expect(exception).to be_kind_of(Gitlab::Git::Storage::CircuitOpen)
-        expect(exception.retry_after).to eq(30)
+        expect(result).to eq('hello')
       end
     end
 
     context 'the storage is not available' do
       let(:storage_name) { 'broken' }
 
-      it 'raises an error' do
+      it 'raises the correct exception' do
         expect(circuit_breaker).to receive(:track_storage_inaccessible)
 
-        expect { circuit_breaker.check_storage_accessible! }
+        expect { circuit_breaker.perform { '' } }
           .to raise_error do |exception|
           expect(exception).to be_kind_of(Gitlab::Git::Storage::Inaccessible)
           expect(exception.retry_after).to eq(30)
         end
       end
-    end
-  end
-
-  describe '#track_storage_inaccessible' do
-    around do |example|
-      Timecop.freeze { example.run }
-    end
-
-    it 'records the failure time in redis' do
-      circuit_breaker.track_storage_inaccessible
 
-      failure_time = value_from_redis(:last_failure)
-
-      expect(Time.at(failure_time.to_i)).to be_within(1.second).of(Time.now)
-    end
-
-    it 'sets the failure time on the breaker without reloading' do
-      circuit_breaker.track_storage_inaccessible
+      it 'tracks that the storage was inaccessible' do
+        Timecop.freeze do
+          expect { circuit_breaker.perform { '' } }.to raise_error(Gitlab::Git::Storage::Inaccessible)
 
-      expect(circuit_breaker).not_to receive(:get_failure_info)
-      expect(circuit_breaker.last_failure).to eq(Time.now)
+          expect(value_from_redis(:failure_count).to_i).to eq(1)
+          expect(value_from_redis(:last_failure)).not_to be_empty
+          expect(circuit_breaker.failure_count).to eq(1)
+          expect(circuit_breaker.last_failure).to be_within(1.second).of(Time.now)
         end
-
-    it 'increments the failure count in redis' do
-      set_in_redis(:failure_count, 10)
-
-      circuit_breaker.track_storage_inaccessible
-
-      expect(value_from_redis(:failure_count).to_i).to be(11)
       end
-
-    it 'increments the failure count on the breaker without reloading' do
-      set_in_redis(:failure_count, 10)
-
-      circuit_breaker.track_storage_inaccessible
-
-      expect(circuit_breaker).not_to receive(:get_failure_info)
-      expect(circuit_breaker.failure_count).to eq(11)
     end
   end
 
-  describe '#track_storage_accessible' do
-    it 'sets the failure count to zero in redis' do
-      set_in_redis(:failure_count, 10)
-
-      circuit_breaker.track_storage_accessible
+  describe '#circuit_broken?' do
+    it 'is working when there is no last failure' do
+      set_in_redis(:last_failure, nil)
+      set_in_redis(:failure_count, 0)
 
-      expect(value_from_redis(:failure_count).to_i).to be(0)
+      expect(circuit_breaker.circuit_broken?).to be_falsey
     end
 
-    it 'sets the failure count to zero on the breaker without reloading' do
-      set_in_redis(:failure_count, 10)
-
-      circuit_breaker.track_storage_accessible
+    it 'is broken when there are too many failures' do
+      set_in_redis(:last_failure, 1.day.ago.to_f)
+      set_in_redis(:failure_count, 200)
 
-      expect(circuit_breaker).not_to receive(:get_failure_info)
-      expect(circuit_breaker.failure_count).to eq(0)
+      expect(circuit_breaker.circuit_broken?).to be_truthy
     end
-
-    it 'removes the last failure time from redis' do
-      set_in_redis(:last_failure, Time.now.to_i)
-
-      circuit_breaker.track_storage_accessible
-
-      expect(circuit_breaker).not_to receive(:get_failure_info)
-      expect(circuit_breaker.last_failure).to be_nil
   end
 
-    it 'removes the last failure time from the breaker without reloading' do
-      set_in_redis(:last_failure, Time.now.to_i)
+  describe '#backing_off?' do
+    it 'is true when there was a recent failure' do
+      Timecop.freeze do
+        set_in_redis(:last_failure, 1.second.ago.to_f)
+        set_in_redis(:failure_count, 90)
 
-      circuit_breaker.track_storage_accessible
+        expect(circuit_breaker.backing_off?).to be_truthy
+      end
+    end
 
-      expect(value_from_redis(:last_failure)).to be_empty
+    context 'the `failure_wait_time` is set to 0' do
+      before do
+        stub_application_setting(circuitbreaker_failure_wait_time: 0)
       end
 
-    it 'wont connect to redis when there are no failures' do
-      expect(Gitlab::Git::Storage.redis).to receive(:with).once
-                                              .and_call_original
-      expect(circuit_breaker).to receive(:track_storage_accessible)
-                           .and_call_original
+      it 'is working even when there are failures' do
+        Timecop.freeze do
+          set_in_redis(:last_failure, 0.seconds.ago.to_f)
+          set_in_redis(:failure_count, 90)
 
-      circuit_breaker.track_storage_accessible
+          expect(circuit_breaker.backing_off?).to be_falsey
         end
       end
-
-  describe '#no_failures?' do
-    it 'is false when a failure was tracked' do
-      set_in_redis(:last_failure, Time.now.to_i)
-      set_in_redis(:failure_count, 1)
-
-      expect(circuit_breaker.no_failures?).to be_falsey
     end
   end
 
@@ -351,10 +306,4 @@ describe Gitlab::Git::Storage::CircuitBreaker, clean_gitlab_redis_shared_state:
       expect(circuit_breaker.failure_count).to eq(7)
     end
   end
-
-  describe '#cache_key' do
-    it 'includes storage and host' do
-      expect(circuit_breaker.cache_key).to eq(cache_key)
-    end
-  end
 end

spec/lib/gitlab/git/storage/forked_storage_check_spec.rb

@@ -33,6 +33,21 @@ describe Gitlab::Git::Storage::ForkedStorageCheck, broken_storage: true, skip_da
       expect(runtime).to be < 1.0
     end
 
+    it 'will try the specified amount of times before failing'  do
+      allow(described_class).to receive(:check_filesystem_in_process) do
+        Process.spawn("sleep 10")
+      end
+
+      expect(Process).to receive(:spawn).with('sleep 10').twice
+                           .and_call_original
+
+      runtime = Benchmark.realtime do
+        described_class.storage_available?(existing_path, 0.5, 2)
+      end
+
+      expect(runtime).to be < 1.0
+    end
+
     describe 'when using paths with spaces' do
       let(:test_dir) { Rails.root.join('tmp', 'tests', 'storage_check') }
       let(:path_with_spaces) { File.join(test_dir, 'path with spaces') }

spec/lib/gitlab/git/storage/null_circuit_breaker_spec.rb

@@ -65,17 +65,6 @@ describe Gitlab::Git::Storage::NullCircuitBreaker do
     ours = described_class.public_instance_methods
     theirs = Gitlab::Git::Storage::CircuitBreaker.public_instance_methods
 
-    # These methods are not part of the public API, but are public to allow the
-    # CircuitBreaker specs to operate. They should be made private over time.
-    exceptions = %i[
-      cache_key
-      check_storage_accessible!
-      no_failures?
-      storage_available?
-      track_storage_accessible
-      track_storage_inaccessible
-    ]
-
-    expect(theirs - ours).to contain_exactly(*exceptions)
+    expect(theirs - ours).to be_empty
   end
 end

spec/models/application_setting_spec.rb

@@ -115,7 +115,8 @@ describe ApplicationSetting do
     end
 
     context 'circuitbreaker settings' do
-      [:circuitbreaker_failure_count_threshold,
+      [:circuitbreaker_backoff_threshold,
+       :circuitbreaker_failure_count_threshold,
        :circuitbreaker_failure_wait_time,
        :circuitbreaker_failure_reset_time,
        :circuitbreaker_storage_timeout].each do |field|
@@ -125,6 +126,16 @@ describe ApplicationSetting do
                            .is_greater_than_or_equal_to(0)
         end
       end
+
+      it 'requires the `backoff_threshold` to be lower than the `failure_count_threshold`' do
+        setting.circuitbreaker_failure_count_threshold = 10
+        setting.circuitbreaker_backoff_threshold = 15
+        failure_message = "The circuitbreaker backoff threshold should be lower "\
+                          "than the failure count threshold"
+
+        expect(setting).not_to be_valid
+        expect(setting.errors[:circuitbreaker_backoff_threshold]).to include(failure_message)
+      end
     end
 
     context 'repository storages' do