Sub-block targeting and validation by SikaGrr · Pull Request #5405 · GoogleCloudPlatform/cluster-toolkit

SikaGrr · 2026-03-25T15:07:06Z

Multiple sub-blocks can be specified. Validation (and url forming) only occurs if the variables are defined and super-slicing is enabled.

gemini-code-assist · 2026-03-25T15:07:33Z

Summary of Changes

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This pull request enhances the GKE node pool module by introducing the capability to target specific reservation sub-blocks. This allows for more granular control over resource allocation, particularly for advanced "super-slicing" topologies. The changes include new configuration variables, a data source to fetch sub-block information, and robust pre-conditions to validate that sub-block targeting is enabled correctly, has adequate capacity, and points to healthy resources.

Highlights

Sub-block Targeting: Implemented support for targeting specific reservation sub-blocks within GKE node pools, allowing for more granular resource allocation.
New Configuration Variables: Introduced new input variables reservation_block, reservation_sub_block, and enable_slice_controller to manage the configuration of sub-block targeting.
Enhanced Validation: Added comprehensive validation logic to ensure correct usage, sufficient capacity, and health of targeted reservation sub-blocks before node pool creation.
Dynamic Reservation URL Formation: Updated the logic for constructing reservation URLs to incorporate sub-block identifiers when the enable_slice_controller is active.

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Code Review

This pull request introduces support for GKE Slice Controller, reservation blocks, and reservation sub-blocks in the GKE node pool module. It adds new variables for reservation_block, reservation_sub_block, and enable_slice_controller, along with new data sources and updated logic to construct reservation resource names based on these new parameters. The review comments suggest an improvement opportunity to enhance readability and maintainability by extracting the complex conditional logic related to enable_slice_controller and reservation block/sub-block variables into a local variable, as this logic is repeated across multiple parts of the code.

gemini-code-assist · 2026-03-25T15:11:45Z

modules/compute/gke-node-pool/reservation_definitions.tf

+
+locals {
+  requested_nodes = coalesce(var.static_node_count, var.initial_node_count, var.autoscaling_total_max_nodes, 0)
+}


To improve readability and reduce repetition, consider extracting the complex conditional logic for enable_slice_controller and reservation block/sub-block variables into a local variable. This makes the code easier to understand and maintain.

This aligns with the repository's focus on "Maintainability: Code should be easy to understand, modify, and extend." (Repository Style Guide, line 6).

requested_nodes = coalesce(var.static_node_count, var.initial_node_count, var.autoscaling_total_max_nodes, 0) is_sub_block_targeting_enabled = var.enable_slice_controller && var.reservation_block != null && var.reservation_block != "" && var.reservation_sub_block != null && var.reservation_sub_block != ""

References

Code should be easy to understand, modify, and extend. ^(link)

gemini-code-assist · 2026-03-25T15:11:45Z

modules/compute/gke-node-pool/reservation_definitions.tf


+data "google_compute_reservation_sub_block" "this" {
+  for_each = (
+    (var.enable_slice_controller && var.reservation_block != null && var.reservation_block != "" && var.reservation_sub_block != null && var.reservation_sub_block != "") ?


Using the newly introduced is_sub_block_targeting_enabled local variable here improves readability by abstracting the complex conditional logic. This makes the for_each condition more concise and easier to grasp at a glance.

This aligns with the repository's focus on "Maintainability: Code should be easy to understand, modify, and extend." (Repository Style Guide, line 6).

local.is_sub_block_targeting_enabled ?

References

Code should be easy to understand, modify, and extend. ^(link)

gemini-code-assist · 2026-03-25T15:11:45Z

modules/compute/gke-node-pool/reservation_definitions.tf

-    length(local.input_reservation_suffixes[i]) > 0 ?
-    format("%s%s", r.name, local.input_reservation_suffixes[i]) :
-    "projects/${r.project}/reservations/${r.name}"
+    (var.enable_slice_controller && var.reservation_block != null && var.reservation_block != "" && var.reservation_sub_block != null && var.reservation_sub_block != "") ?


Using the is_sub_block_targeting_enabled local variable here enhances readability by simplifying the conditional expression for active_reservation_values. This reduces duplication and makes the intent clearer.

This aligns with the repository's focus on "Maintainability: Code should be easy to understand, modify, and extend." (Repository Style Guide, line 6).

local.is_sub_block_targeting_enabled ?

References

Code should be easy to understand, modify, and extend. ^(link)

gemini-code-assist · 2026-03-25T15:11:45Z

modules/compute/gke-node-pool/reservation_definitions.tf

+  specific_reservation_name = length(local.input_reservation_names) > 0 ? local.input_reservation_names[0] : ""
+  default_reservation_values = [
+    for zone in try(var.zones, []) :
+    (var.enable_slice_controller && var.reservation_block != null && var.reservation_block != "" && var.reservation_sub_block != null && var.reservation_sub_block != "") ?


Replacing the repeated conditional logic with the is_sub_block_targeting_enabled local variable in default_reservation_values improves code clarity and maintainability. This helps in avoiding errors if the underlying logic needs to change in the future.

This aligns with the repository's focus on "Maintainability: Code should be easy to understand, modify, and extend." (Repository Style Guide, line 6).

local.is_sub_block_targeting_enabled ?

References

Code should be easy to understand, modify, and extend. ^(link)

gemini-code-assist · 2026-03-25T15:11:45Z

modules/compute/gke-node-pool/main.tf

      error_message = "Spot consumption option only works with reservation_affinity consume_reservation_type NO_RESERVATION."
    }
+    precondition {
+      condition     = (var.reservation_sub_block == null || var.reservation_sub_block == "") || (var.enable_slice_controller && var.reservation_block != null && var.reservation_block != "")


Leveraging the is_sub_block_targeting_enabled local variable here simplifies the precondition's condition expression. This makes the validation logic more readable and consistent with other parts of the module where this complex condition is used.

This aligns with the repository's focus on "Maintainability: Code should be easy to understand, modify, and extend." (Repository Style Guide, line 6).

condition = (var.reservation_sub_block == null || var.reservation_sub_block == "") || local.is_sub_block_targeting_enabled

References

Code should be easy to understand, modify, and extend. ^(link)

SikaGrr added 3 commits March 24, 2026 14:44

add subblock variables and validation

249a7dd

Merge branch 'develop' into origin/subblock

c5008d3

multiple blocks

a1b0a4e

gemini-code-assist bot reviewed Mar 25, 2026

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Sub-block targeting and validation#5405

Sub-block targeting and validation#5405
SikaGrr wants to merge 3 commits intoGoogleCloudPlatform:developfrom
SikaGrr:origin/subblock

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SikaGrr commented Mar 25, 2026

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