FIX: skips caching a generated secret key base token if skip_redis is true. (#29029)

Allows for `SKIP_DB_AND_REDIS` env var to be used without a secret key setup in
global setting env.

app/models/global_setting.rb

@@ -18,6 +18,7 @@ class GlobalSetting
   # This method will
   # - use existing token if already set in ENV or discourse.conf
   # - generate a token on the fly if needed and cache in redis
+  # - skips caching generated token to redis if redis is skipped
   # - enforce rules about token format falling back to redis if needed
   def self.safe_secret_key_base
     if @safe_secret_key_base && @token_in_redis &&
@@ -31,6 +32,9 @@ class GlobalSetting
       begin
         token = secret_key_base
         if token.blank? || token !~ VALID_SECRET_KEY
+          if GlobalSetting.skip_redis?
+            token = SecureRandom.hex(64)
+          else
             @token_in_redis = true
             @token_last_validated = Time.now
 
@@ -40,6 +44,7 @@ class GlobalSetting
               Discourse.redis.without_namespace.set(REDIS_SECRET_KEY, token)
             end
           end
+        end
         if !secret_key_base.blank? && token != secret_key_base
           STDERR.puts "WARNING: DISCOURSE_SECRET_KEY_BASE is invalid, it was re-generated"
         end

spec/models/global_setting_spec.rb

@@ -46,6 +46,22 @@ RSpec.describe GlobalSetting do
       new_token = Discourse.redis.without_namespace.get(GlobalSetting::REDIS_SECRET_KEY)
       expect(new_token).to eq(token)
     end
+
+    context "when a secret key is not provided and redis is not used" do
+      before do
+        GlobalSetting.skip_redis = true
+        GlobalSetting.stubs(:secret_key_base).returns("")
+        # Fail tests if redis calls are made
+        Discourse.stubs(:redis).returns(nil)
+      end
+
+      it "generates a new random key in memory without redis" do
+        GlobalSetting.reset_secret_key_base!
+        token = GlobalSetting.safe_secret_key_base
+        new_token = GlobalSetting.safe_secret_key_base
+        expect(new_token).to eq(token)
+      end
+    end
   end
 
   describe ".add_default" do