ensure timestamp updates are atomic and applied in order

Gemfile

@@ -66,6 +66,7 @@ gem 'workflow-activerecord'
 gem 'em-mqtt'
 
 group :test do
+  gem "database_cleaner-active_record"
   gem 'simplecov', require: false
   gem 'timecop'
   gem 'vcr'

Gemfile.lock

@@ -131,6 +131,10 @@ GEM
     css_parser (1.14.0)
       addressable
     dalli (3.2.4)
+    database_cleaner-active_record (2.2.0)
+      activerecord (>= 5.a)
+      database_cleaner-core (~> 2.0.0)
+    database_cleaner-core (2.0.1)
     date (3.3.3)
     date_validator (0.12.0)
       activemodel (>= 3)
@@ -545,6 +549,7 @@ DEPENDENCIES
   cane
   countries
   dalli
+  database_cleaner-active_record
   date_validator
   diffy
   doorkeeper (~> 5)
@@ -616,4 +621,4 @@ RUBY VERSION
    ruby 3.0.6p216
 
 BUNDLED WITH
-   2.5.6
+   2.5.17

app/models/device.rb

@@ -245,8 +245,8 @@ def remove_mac_address_for_newly_registered_device!
 
   def update_component_timestamps(timestamp, sensor_ids)
     components.select {|c| sensor_ids.include?(c.sensor_id) }.each do |component|
-      component.transaction do
-        component.lock!
+      component.lock! if self.class.connection.transaction_open?
+      if !component.reload.last_reading_at || timestamp > component.last_reading_at
         component.update_column(:last_reading_at, timestamp)
       end
     end

app/models/storer.rb

@@ -23,18 +23,20 @@ def store device, reading, do_update = true
 
   def update_device(device, parsed_ts, sql_data)
     return if parsed_ts <= Time.at(0)
+    device.transaction(isolation: :serializable) do
+      device.lock!
+      if device.reload.last_reading_at.present?
+        # Comparison errors if device.last_reading_at is nil (new devices).
+        # Devices can post multiple readings, in a non-sorted order.
+        # Do not update data with an older timestamp.
+        return if parsed_ts < device.last_reading_at
+      end
 
-    if device.last_reading_at.present?
-      # Comparison errors if device.last_reading_at is nil (new devices).
-      # Devices can post multiple readings, in a non-sorted order.
-      # Do not update data with an older timestamp.
-      return if parsed_ts < device.last_reading_at
+      sql_data = device.data.present? ? device.data.merge(sql_data) : sql_data
+      device.update_columns(last_reading_at: parsed_ts, data: sql_data, state: 'has_published')
+      sensor_ids = sql_data.select { |k, v| k.is_a?(Integer) }.keys.compact.uniq
+      device.update_component_timestamps(parsed_ts, sensor_ids)
     end
-
-    sql_data = device.data.present? ? device.data.merge(sql_data) : sql_data
-    device.update_columns(last_reading_at: parsed_ts, data: sql_data, state: 'has_published')
-    sensor_ids = sql_data.select { |k, v| k.is_a?(Integer) }.keys.compact.uniq
-    device.update_component_timestamps(parsed_ts, sensor_ids)
   end
 
   def kairos_publish(reading_data)

spec/rails_helper.rb

@@ -74,7 +74,7 @@
   # If you're not using ActiveRecord, or you'd prefer not to run each of your
   # examples within a transaction, remove the following line or assign false
   # instead of true.
-  config.use_transactional_fixtures = true
+  config.use_transactional_fixtures = false
 
   # RSpec Rails can automatically mix in different behaviours to your tests
   # based on their file location, for example enabling you to call `get` and

spec/spec_helper.rb

@@ -14,7 +14,7 @@
 # users commonly want.
 #
 # See http://rubydoc.info/gems/rspec-core/RSpec/Core/Configuration
-
+require "database_cleaner/active_record"
 RSpec.configure do |config|
   # rspec-expectations config goes here. You can use an alternate
   # assertion/expectation library such as wrong or the stdlib/minitest
@@ -40,6 +40,18 @@
     mocks.verify_partial_doubles = true
   end
 
+  DatabaseCleaner.strategy = :truncation
+
+  config.before(:suite) do
+    DatabaseCleaner.clean
+  end
+
+  config.around(:each) do |example|
+    DatabaseCleaner.cleaning do
+      example.run
+    end
+  end
+
 # The settings below are suggested to provide a good initial experience
 # with RSpec, but feel free to customize to your heart's content.