Handle severity for generic alert payloads more gracefully

Allow values being case-insensitive and use `critical` as fallback
for unmapped values.

changelogs/unreleased/pl-generic-payload-severity.yml

+---
+title: Handle severity for generic payloads more gracefully
+merge_request: 53999
+author:
+type: fixed

ee/spec/lib/ee/gitlab/alert_management/payload/generic_spec.rb

@@ -53,7 +53,7 @@ RSpec.describe Gitlab::AlertManagement::Payload::Generic do
     describe '#severity' do
       subject { parsed_payload.severity }
 
-      it { is_expected.to eq('low') }
+      it { is_expected.to eq(:low) }
     end
 
     describe '#environment_name' do
@@ -178,7 +178,7 @@ RSpec.describe Gitlab::AlertManagement::Payload::Generic do
           describe '#severity' do
             subject { parsed_payload.severity }
 
-            it { is_expected.to eq('high') }
+            it { is_expected.to eq(:high) }
           end
 
           describe '#environment_name' do

lib/gitlab/alert_management/payload/base.rb

@@ -44,11 +44,25 @@ module Gitlab
           :title
         ].freeze
 
+        private_constant :EXPECTED_PAYLOAD_ATTRIBUTES
+
         # Define expected API for a payload
         EXPECTED_PAYLOAD_ATTRIBUTES.each do |key|
           define_method(key) {}
         end
 
+        SEVERITY_MAPPING = {
+          'critical' => :critical,
+          'high' => :high,
+          'medium' => :medium,
+          'low' => :low,
+          'info' => :info
+        }.freeze
+
+        # Handle an unmapped severity value the same way we treat missing values
+        # so we can fallback to alert's default severity `critical`.
+        UNMAPPED_SEVERITY = nil
+
         # Defines a method which allows access to a given
         # value within an alert payload
         #
@@ -131,9 +145,21 @@ module Gitlab
           true
         end
 
+        def severity
+          severity_mapping.fetch(severity_raw.to_s.downcase, UNMAPPED_SEVERITY)
+        end
+
         private
 
-        def plain_gitlab_fingerprint; end
+        def plain_gitlab_fingerprint
+        end
+
+        def severity_raw
+        end
+
+        def severity_mapping
+          SEVERITY_MAPPING
+        end
 
         def truncate_hosts(hosts)
           return hosts if hosts.join.length <= ::AlertManagement::Alert::HOSTS_MAX_LENGTH

lib/gitlab/alert_management/payload/generic.rb

@@ -6,7 +6,6 @@ module Gitlab
     module Payload
       class Generic < Base
         DEFAULT_TITLE = 'New: Incident'
-        DEFAULT_SEVERITY = 'critical'
 
         attribute :description, paths: 'description'
         attribute :ends_at, paths: 'end_time', type: :time
@@ -15,10 +14,12 @@ module Gitlab
         attribute :monitoring_tool, paths: 'monitoring_tool'
         attribute :runbook, paths: 'runbook'
         attribute :service, paths: 'service'
-        attribute :severity, paths: 'severity', fallback: -> { DEFAULT_SEVERITY }
         attribute :starts_at, paths: 'start_time', type: :time, fallback: -> { Time.current.utc }
         attribute :title, paths: 'title', fallback: -> { DEFAULT_TITLE }
 
+        attribute :severity_raw, paths: 'severity'
+        private :severity_raw
+
         attribute :plain_gitlab_fingerprint, paths: 'fingerprint'
         private :plain_gitlab_fingerprint
       end

lib/gitlab/alert_management/payload/prometheus.rb

@@ -5,6 +5,8 @@ module Gitlab
     module Payload
       # Attribute mapping for alerts via prometheus alerting integration.
       class Prometheus < Base
+        extend Gitlab::Utils::Override
+
         attribute :alert_markdown, paths: %w(annotations gitlab_incident_markdown)
         attribute :annotations, paths: 'annotations'
         attribute :description, paths: %w(annotations description)
@@ -35,12 +37,7 @@ module Gitlab
 
         METRIC_TIME_WINDOW = 30.minutes
 
-        SEVERITY_MAP = {
-          'critical' => :critical,
-          'high' => :high,
-          'medium' => :medium,
-          'low' => :low,
-          'info' => :info,
+        ADDITIONAL_SEVERITY_MAPPING = {
           's1' => :critical,
           's2' => :high,
           's3' => :medium,
@@ -65,10 +62,6 @@ module Gitlab
           'page' => :high
         }.freeze
 
-        # Handle an unmapped severity value the same way we treat missing values
-        # so we can fallback to alert's default severity `critical`.
-        UNMAPPED_SEVERITY = nil
-
         def monitoring_tool
           Gitlab::AlertManagement::Payload::MONITORING_TOOLS[:prometheus]
         end
@@ -101,14 +94,13 @@ module Gitlab
           project && title && starts_at_raw
         end
 
-        def severity
-          return unless severity_raw
+        private
 
-          SEVERITY_MAP.fetch(severity_raw.to_s.downcase, UNMAPPED_SEVERITY)
+        override :severity_mapping
+        def severity_mapping
+          super.merge(ADDITIONAL_SEVERITY_MAPPING)
         end
 
-        private
-
         def plain_gitlab_fingerprint
           [starts_at_raw, title, full_query].join('/')
         end

spec/lib/gitlab/alert_management/payload/generic_spec.rb

@@ -19,7 +19,34 @@ RSpec.describe Gitlab::AlertManagement::Payload::Generic do
   describe '#severity' do
     subject { parsed_payload.severity }
 
-    it_behaves_like 'parsable alert payload field with fallback', 'critical', 'severity'
+    context 'when set' do
+      using RSpec::Parameterized::TableSyntax
+
+      let(:raw_payload) { { 'severity' => payload_severity } }
+
+      where(:payload_severity, :expected_severity) do
+        'critical' | :critical
+        'high'     | :high
+        'medium'   | :medium
+        'low'      | :low
+        'info'     | :info
+
+        'CRITICAL' | :critical
+        'cRiTiCaL' | :critical
+
+        'unmapped' | nil
+        1          | nil
+        nil        | nil
+      end
+
+      with_them do
+        it { is_expected.to eq(expected_severity) }
+      end
+    end
+
+    context 'without key' do
+      it { is_expected.to be_nil }
+    end
   end
 
   describe '#monitoring_tool' do

spec/lib/gitlab/alert_management/payload/prometheus_spec.rb

@@ -239,13 +239,13 @@ RSpec.describe Gitlab::AlertManagement::Payload::Prometheus do
   end
 
   describe '#severity' do
-    using RSpec::Parameterized::TableSyntax
-
-    let(:raw_payload) { { 'labels' => { 'severity' => payload_severity } } }
-
     subject { parsed_payload.severity }
 
     context 'when set' do
+      using RSpec::Parameterized::TableSyntax
+
+      let(:raw_payload) { { 'labels' => { 'severity' => payload_severity } } }
+
       where(:payload_severity, :expected_severity) do
         'critical' | :critical
         'high'     | :high
@@ -293,8 +293,6 @@ RSpec.describe Gitlab::AlertManagement::Payload::Prometheus do
     end
 
     context 'without key' do
-      let(:raw_payload) { {} }
-
       it { is_expected.to be_nil }
     end
   end