Add a new checks type: new_bad_data

app/models/blazer/check.rb

@@ -49,7 +49,7 @@ def update_state(result)
             "passing"
           end
         elsif result.rows.any?
-          check_type == "missing_data" ? "passing" : "failing"
+          %w[bad_data new_bad_data].include?(check_type) ? 'failing' : 'passing'
         else
           check_type == "missing_data" ? "failing" : "passing"
         end
@@ -66,8 +66,16 @@ def update_state(result)
         end
       end
 
+      condition = state != state_was
+
+      if respond_to?(:last_results_hash)
+        results_hash = Digest::MD5.hexdigest(result.rows.to_json)
+        condition =  results_hash != last_result if check_type == 'new_bad_data'
+        self.last_results_hash = results_hash
+      end
+
       # do not notify on creation, except when not passing
-      if (state_was != "new" || state != "passing") && state != state_was
+      if (state_was != "new" || state != "passing") && condition
         Blazer::CheckMailer.state_change(self, state, state_was, result.rows.size, message, result.columns, result.rows.first(10).as_json, result.column_types, check_type).deliver_now if emails.present?
         Blazer::SlackNotifier.state_change(self, state, state_was, result.rows.size, message, check_type)
       end

app/views/blazer/check_mailer/state_change.html.erb

@@ -6,7 +6,7 @@
     <p><%= link_to "View", query_url(@check.query_id) %></p>
     <% if @error %>
       <p><%= @error %></p>
-    <% elsif @rows_count > 0 && @check_type == "bad_data" %>
+    <% elsif @rows_count > 0 && %w[bad_data new_bad_data].include?(@check_type) %>
       <p>
         <% if @rows_count <= 10 %>
           <%= pluralize(@rows_count, "row") %>

app/views/blazer/checks/_form.html.erb

@@ -25,6 +25,7 @@
       <%= f.label :check_type, "Alert if" %>
       <div class="hide">
         <% check_options = [["Any results (bad data)", "bad_data"], ["No results (missing data)", "missing_data"]] %>
+        <% check_options <<  ["Any new results (more bad data)", "new_bad_data"] if @check.respond_to?(:last_results_hash) %>
         <% check_options << ["Anomaly (most recent data point)", "anomaly"] if Blazer.anomaly_checks %>
         <%= f.select :check_type, check_options %>
       </div>

lib/blazer/slack_notifier.rb

@@ -7,7 +7,7 @@ def self.state_change(check, state, state_was, rows_count, error, check_type)
         text =
           if error
             error
-          elsif rows_count > 0 && check_type == "bad_data"
+          elsif rows_count > 0 && %w[bad_data new_bad_data].include?(check_type)
             pluralize(rows_count, "row")
           end
 

lib/generators/blazer/templates/install.rb.tt

@@ -39,6 +39,7 @@ class <%= migration_class_name %> < ActiveRecord::Migration<%= migration_version
       t.text :emails
       t.text :slack_channels
       t.string :check_type
+      t.string :last_results_hash
       t.text :message
       t.datetime :last_run_at
       t.timestamps null: false

test/checks_test.rb

@@ -66,6 +66,25 @@ def test_emails
     end
   end
 
+  def test_emails_for_new_bad_data
+    query = create_query
+    check = create_check(query: query, check_type: "new_bad_data", emails: "hi@example.org,hi2@example.org")
+
+    assert_emails 1 do
+      Blazer.run_checks(schedule: "5 minutes")
+    end
+
+    assert_emails 0 do
+      Blazer.run_checks(schedule: "5 minutes")
+    end
+
+    query.update!(statement: "SELECT 1 LIMIT 0")
+
+    assert_emails 1 do
+      Blazer.run_checks(schedule: "5 minutes")
+    end
+  end
+
   def test_slack
     query = create_query
     check = create_check(query: query, check_type: "bad_data", slack_channels: "#general,#random")
@@ -83,6 +102,25 @@ def test_slack
     end
   end
 
+  def test_slack_for_new_bad_data
+    query = create_query
+    check = create_check(query: query, check_type: "new_bad_data", slack_channels: "#general,#random")
+
+    assert_slack_messages 2 do
+      Blazer.run_checks(schedule: "5 minutes")
+    end
+
+    assert_slack_messages 0 do
+      Blazer.run_checks(schedule: "5 minutes")
+    end
+
+    query.update!(statement: "SELECT 1 LIMIT 0")
+
+    assert_slack_messages 2 do
+      Blazer.run_checks(schedule: "5 minutes")
+    end
+  end
+
   def assert_slack_messages(expected)
     count = 0
     Blazer::SlackNotifier.stub :post_api, ->(*) { count += 1 } do

test/internal/db/schema.rb

@@ -38,6 +38,7 @@
     t.text :emails
     t.text :slack_channels
     t.string :check_type
+    t.string :last_results_hash
     t.text :message
     t.datetime :last_run_at
     t.timestamps null: false