Support Hash-Based Routing by hoffmaen · Pull Request #4696 · cloudfoundry/cloud_controller_ng

hoffmaen · 2025-12-09T08:48:46Z

This Pull-Request adds support for hash-based routing to Cloud Controller.

Summary:
The routes model is enhanced as follows:

hash is added as a valid loadbalancing option
hash_header is added as a per-route option. The option is mandatory when loadbalancing=hash
hash_balance is added as a per-route option. The option is optional when loadbalancing=hash

Validation of these options is added when creating and updating both via API and via manifest. When hash_balance is provided as an option, its value must be a float or a string representing a float.

The options are still stored as a raw JSON string in the routes table. The value for hash_balance is always stored as a string inside the JSON for consistency.

Logic is introduced to remove hash_balance and hash_header when switching from hash to another load-balancing algorithm. Incremental updates on per-route options are allowed, e.g. only updating hash_header or hash_balance while keeping other previously set per-route options is possible.

Links:

capi-release implementation issue
routing-release Pull-Request for hash-based routing support
RFC-0042
I have reviewed the contributing guide
I have viewed, signed, and submitted the Contributor License Agreement
I have made this pull request to the main branch
I have run all the unit tests using bundle exec rake
I have run CF Acceptance Tests

philippthun

Did not look at the spec files so far...

philippthun · 2025-12-09T09:25:53Z

app/actions/route_update.rb

      Route.db.transaction do
-        route.options = route.options.symbolize_keys.merge(message.options).compact if message.requested?(:options)
+        if message.requested?(:options)
+          merged_options = message.options.compact


Isn't the merge missing, i.e. route.options.merge(message.options)?

philippthun · 2025-12-09T09:32:21Z

app/controllers/v3/routes_controller.rb


  def update
-    message = RouteUpdateMessage.new(hashed_params[:body])
+    params = hashed_params[:body]


The controller should not manipulate the params and the message should reflect what has been provided by the user. Isn't this redundant with RouteUpdate.update anyway?

philippthun · 2025-12-09T09:35:41Z

app/actions/manifest_route_update.rb

          elsif manifest_route[:options] && route[:options] != manifest_route[:options]
-            # remove nil values from options
-            manifest_route[:options] = manifest_route[:options].compact
+            # Merge existing route options with manifest options for partial updates


I would move the merge to RouteUpdate.update to have it in a single place.

On route updates, we need to validate after merging, as we need to allow incremental route option updates. E.g., only setting hash_balance would be invalid for a new route, but is valid for a route that is already properly setup with hash-based routing. RouteUpdate.update is the last step in this chain, so we would also need to migrate the validation logic to RouteUpdate. I think the OptionsValidator is the better place to have the validation, and thus also the merging. Would you agree?

philippthun · 2025-12-09T09:40:16Z

app/messages/manifest_routes_update_message.rb

+      return if options[:hash_balance].blank?
+
+      errors.add(:base, message: "Route '#{route[:route]}': hash_balance can only be set when loadbalancing is hash")


Why not errors.add(...) if options[:hash_balance].present? as above?

philippthun · 2025-12-09T09:44:29Z

app/messages/route_options_message.rb

+    VALID_LOADBALANCING_ALGORITHMS_WITH_HASH = %w[round-robin least-connection hash].freeze
+    VALID_LOADBALANCING_ALGORITHMS_WITHOUT_HASH = %w[round-robin least-connection].freeze


Would it make sense to define VALID_LOADBALANCING_ALGORITHMS_WITH_HASH as VALID_LOADBALANCING_ALGORITHMS_WITHOUT_HASH + 'hash'?

philippthun · 2025-12-09T09:53:06Z

app/models/runtime/route.rb

+      if hash_balance_value.present?
+        # Always convert to string for consistent storage in JSON
+        normalized[hash_balance_key] = hash_balance_value.to_s
+      end
+
+      normalized


Suggestion:

return opts if hash_balance_value.blank? normalized = opts.dup normalized[hash_balance_key] = hash_balance_value.to_s normalized

philippthun · 2025-12-09T09:57:23Z

app/presenters/v3/app_manifest_presenters/route_properties_presenter.rb

              if route_mapping.route.options
+                opts = route_mapping.route.options
+
                route_hash[:options] = {}


Why not route_hash[:options] = route_mapping.route.options?

philippthun · 2025-12-09T10:25:48Z

app/messages/route_options_message.rb

+      return if hash_balance.blank?
+
+      errors.add(:hash_balance, 'can only be set when loadbalancing is hash')


I would prefer errors.add(...) if hash_balance.present?.

philippthun · 2025-12-09T10:26:40Z

app/messages/route_options_message.rb

+    end
+
+    def validate_hash_balance_format
+      return if hash_balance.nil?


Should we use blank? instead of nil? as in other places?

hoffmaen · 2026-01-09T17:17:22Z

Closing in lieu of #4746

hoffmaen force-pushed the hash-based-routing branch 2 times, most recently from f181a31 to 6ae8cb9 Compare December 9, 2025 09:33

Support hash-based routing

fe3a37a

hoffmaen force-pushed the hash-based-routing branch from 6ae8cb9 to fe3a37a Compare December 9, 2025 09:39

philippthun reviewed Dec 9, 2025

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hoffmaen mentioned this pull request Jan 9, 2026

Support Hash-Based Routing #4746

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hoffmaen closed this Jan 9, 2026

hoffmaen deleted the hash-based-routing branch January 12, 2026 14:03

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Support Hash-Based Routing#4696

Support Hash-Based Routing#4696
hoffmaen wants to merge 1 commit intocloudfoundry:mainfrom
sap-contributions:hash-based-routing

hoffmaen commented Dec 9, 2025 •

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		return if options[:hash_balance].blank?

		errors.add(:base, message: "Route '#{route[:route]}': hash_balance can only be set when loadbalancing is hash")

		VALID_LOADBALANCING_ALGORITHMS_WITH_HASH = %w[round-robin least-connection hash].freeze
		VALID_LOADBALANCING_ALGORITHMS_WITHOUT_HASH = %w[round-robin least-connection].freeze

		return if hash_balance.blank?

		errors.add(:hash_balance, 'can only be set when loadbalancing is hash')

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hoffmaen commented Dec 9, 2025 •

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