feat(gke-node-pool): Add support for "registry_hosts" by marcmillien · Pull Request #2563 · terraform-google-modules/terraform-google-kubernetes-engine

marcmillien · 2026-03-25T13:17:19Z

Implements registry_hosts.
Cf.:

gemini-code-assist · 2026-03-25T13:17:39Z

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the GKE node pool module by integrating support for containerd registry host configurations. This new feature allows users to precisely define how their GKE nodes interact with container image registries, enabling advanced scenarios such as private registry access, custom certificate authorities, and client authentication. It provides granular control over registry communication, aligning the module with the latest GKE capabilities for container runtime customization.

Highlights

GKE Node Pool Configuration: Implemented support for registry_hosts within the containerd_config block for GKE node pools.
Container Registry Customization: Introduced comprehensive configuration options for registry_hosts, including server definitions, host-specific settings, headers, and CA/client certificate management via GCP Secret Manager.

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gemini-code-assist

Code Review

This pull request introduces new functionality to configure Containerd registry hosts within GKE node pools, allowing for detailed specification of host settings, including advanced authentication via GCP Secret Manager for CA certificates and client certificates/keys. A critical issue was identified in modules/gke-node-pool/main.tf where a typo (host.value.client instead of hosts.value.client) in a for_each expression for the client dynamic block will cause a Terraform error.

modules/gke-node-pool/main.tf

gemini-code-assist

Code Review

This pull request introduces new functionality to the GKE node pool module, enabling advanced Containerd registry host configuration. This includes support for private registry access and detailed host settings, with integration for GCP Secret Manager to manage certificates. The review feedback indicates that the README.md documentation for the node_config variable is outdated and needs to be updated to reflect the newly added registry_hosts attribute.

modules/gke-node-pool/variables.tf

marcmillien · 2026-03-25T13:57:56Z

/gemini review

gemini-code-assist

Code Review

This pull request introduces the capability to configure custom container registry hosts for GKE node pools, enhancing flexibility for image management. It also refactors the existing private_registry_access_config to use dynamic blocks for improved robustness. A high-severity issue was identified where the certificate_authority_domain_config block within private_registry_access_config should also be dynamic to prevent errors when it's optional but not provided.

gemini-code-assist · 2026-03-25T14:06:22Z

modules/gke-node-pool/main.tf

+              certificate_authority_domain_config {
+                fqdns = private_registry_access_config.value.certificate_authority_domain_config.fqdns
+                gcp_secret_manager_certificate_config {
+                  secret_uri = private_registry_access_config.value.certificate_authority_domain_config.gcp_secret_manager_certificate_config.secret_uri
+                }
+              }


The certificate_authority_domain_config block is optional within private_registry_access_config. To prevent potential errors when private_registry_access_config is enabled but certificate_authority_domain_config is not provided, this block should be created dynamically. This will make the configuration more robust and prevent unexpected failures.

dynamic "certificate_authority_domain_config" { for_each = private_registry_access_config.value.certificate_authority_domain_config != null ? [private_registry_access_config.value.certificate_authority_domain_config] : [] content { fqdns = certificate_authority_domain_config.value.fqdns gcp_secret_manager_certificate_config { secret_uri = certificate_authority_domain_config.value.gcp_secret_manager_certificate_config.secret_uri } } }

@gemini-code-assist I am going to check it, but this is not related to my changes

You are correct that the primary focus of your changes is the addition of registry_hosts. However, the change you made to wrap private_registry_access_config in a dynamic block (lines 242-252 in main.tf in the AFTER DIFF section) makes the certificate_authority_domain_config block, which is nested inside it, susceptible to errors if private_registry_access_config is provided but certificate_authority_domain_config is not. My suggestion aims to make the certificate_authority_domain_config block also dynamic to align with this new structure and prevent potential issues, ensuring the configuration remains robust. This is a direct follow-up improvement related to the refactoring you introduced for private_registry_access_config.

Cf.: https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/container_cluster#certificate_authority_domain_config-1 > certificate_authority_domain_config (Optional) - List of configuration objects for CA and domains. Each object identifies a certificate and its assigned domains.

marcmillien · 2026-03-25T14:43:39Z

/gemini review

gemini-code-assist

Code Review

This pull request enhances the GKE node pool module by introducing support for containerd_config.registry_hosts and updating certificate_authority_domain_config to be a list. The review suggests adding a description for the new registry_hosts block in the README.md to improve clarity and usability for module consumers.

gemini-code-assist · 2026-03-25T14:45:23Z

modules/gke-node-pool/README.md

 | name\_prefix | Creates a unique name for the node pool beginning with the specified prefix. Conflicts with name. | `string` | `null` | no |
 | network\_config | The network configuration of the pool. | <pre>object({<br>    create_pod_range     = optional(bool)<br>    enable_private_nodes = optional(bool)<br>    pod_ipv4_cidr_block  = optional(string)<br>    pod_range            = optional(string)<br>    additional_node_network_configs = optional(list(object({<br>      network    = string<br>      subnetwork = string<br>    })))<br>    additional_pod_network_configs = optional(list(object({<br>      subnetwork          = string<br>      secondary_pod_range = string<br>      max_pods_per_node   = number<br>    })))<br>    pod_cidr_overprovision_config = optional(object({<br>      disabled = bool<br>    }))<br>    network_performance_config = optional(object({<br>      total_egress_bandwidth_tier = string<br>    }))<br>  })</pre> | `null` | no |
-| node\_config | Parameters used in creating the node pool. | <pre>object({<br>    confidential_nodes = optional(object({<br>      enabled = bool<br>    }))<br>    disk_size_gb                = optional(number)<br>    disk_type                   = optional(string)<br>    enable_confidential_storage = optional(bool)<br>    local_ssd_encryption_mode   = optional(string)<br>    ephemeral_storage_config = optional(object({<br>      local_ssd_count = number<br>    }))<br>    ephemeral_storage_local_ssd_config = optional(object({<br>      local_ssd_count  = number<br>      data_cache_count = optional(number)<br>    }))<br>    fast_socket = optional(object({<br>      enabled = bool<br>    }))<br>    local_nvme_ssd_block_config = optional(object({<br>      local_ssd_count = number<br>    }))<br>    logging_variant = optional(string)<br>    secondary_boot_disks = optional(object({<br>      disk_image = string<br>      mode       = optional(string)<br>    }))<br>    gcfs_config = optional(object({<br>      enabled = bool<br>    }))<br>    gvnic = optional(object({<br>      enabled = bool<br>    }))<br>    guest_accelerator = optional(object({<br>      type  = string<br>      count = number<br>      gpu_driver_installation_config = optional(object({<br>        gpu_driver_version = string<br>      }))<br>      gpu_partition_size = optional(string)<br>      gpu_sharing_config = optional(object({<br>        gpu_sharing_strategy       = string<br>        max_shared_clients_per_gpu = number<br>      }))<br>    }))<br>    image_type       = optional(string)<br>    labels           = optional(map(string))<br>    resource_labels  = optional(map(string))<br>    max_run_duration = optional(string)<br>    flex_start       = optional(bool)<br>    local_ssd_count  = optional(number)<br>    machine_type     = optional(string)<br>    metadata         = optional(map(string))<br>    min_cpu_platform = optional(string)<br>    oauth_scopes     = optional(list(string))<br>    preemptible      = optional(bool)<br>    reservation_affinity = optional(object({<br>      consume_reservation_type = string<br>      key                      = optional(string)<br>      values                   = optional(list(string))<br>    }))<br>    spot = optional(bool)<br>    sandbox_config = optional(object({<br>      sandbox_type = string<br>    }))<br>    boot_disk_kms_key = optional(string)<br>    service_account   = optional(string)<br>    shielded_instance_config = optional(object({<br>      enable_secure_boot          = optional(bool)<br>      enable_integrity_monitoring = optional(bool)<br>    }))<br>    storage_pools         = optional(list(string))<br>    tags                  = optional(list(string))<br>    resource_manager_tags = optional(map(string))<br>    taint = optional(list(object({<br>      key    = string<br>      value  = string<br>      effect = string<br>    })))<br>    workload_metadata_config = optional(object({<br>      mode = optional(string)<br>    }))<br>    kubelet_config = optional(object({<br>      cpu_manager_policy                     = optional(string)<br>      cpu_cfs_quota                          = optional(bool)<br>      cpu_cfs_quota_period                   = optional(string)<br>      insecure_kubelet_readonly_port_enabled = optional(bool)<br>      pod_pids_limit                         = optional(number)<br>      container_log_max_size                 = optional(string)<br>      container_log_max_files                = optional(number)<br>      image_gc_low_threshold_percent         = optional(number)<br>      image_gc_high_threshold_percent        = optional(number)<br>      image_minimum_gc_age                   = optional(string)<br>      allowed_unsafe_sysctls                 = optional(list(string))<br>    }))<br>    linux_node_config = optional(object({<br>      sysctls     = optional(map(string))<br>      cgroup_mode = optional(string)<br>      hugepages_config = optional(object({<br>        hugepage_size_2m = optional(number)<br>        hugepage_size_1g = optional(number)<br>      }))<br>    }))<br>    windows_node_config = optional(object({<br>      osversion = string<br>    }))<br>    containerd_config = optional(object({<br>      private_registry_access_config = optional(object({<br>        enabled = bool<br>        certificate_authority_domain_config = optional(object({<br>          fqdns = list(string)<br>          gcp_secret_manager_certificate_config = object({<br>            secret_uri = string<br>          })<br>        }))<br>      }))<br>    }))<br>    node_group = optional(string)<br>    sole_tenant_config = optional(object({<br>      node_affinity = optional(object({<br>        key      = string<br>        operator = string<br>        values   = list(string)<br>      }))<br>    }))<br>  })</pre> | <pre>{<br>  "disk_size_gb": 100,<br>  "disk_type": "pd-standard",<br>  "image_type": "COS_CONTAINERD",<br>  "kubelet_config": {<br>    "insecure_kubelet_readonly_port_enabled": false<br>  },<br>  "machine_type": "e2-medium",<br>  "workload_metadata_config": {<br>    "mode": "GKE_METADATA"<br>  }<br>}</pre> | no |
+| node\_config | Parameters used in creating the node pool. | <pre>object({<br>    confidential_nodes = optional(object({<br>      enabled = bool<br>    }))<br>    disk_size_gb                = optional(number)<br>    disk_type                   = optional(string)<br>    enable_confidential_storage = optional(bool)<br>    local_ssd_encryption_mode   = optional(string)<br>    ephemeral_storage_config = optional(object({<br>      local_ssd_count = number<br>    }))<br>    ephemeral_storage_local_ssd_config = optional(object({<br>      local_ssd_count  = number<br>      data_cache_count = optional(number)<br>    }))<br>    fast_socket = optional(object({<br>      enabled = bool<br>    }))<br>    local_nvme_ssd_block_config = optional(object({<br>      local_ssd_count = number<br>    }))<br>    logging_variant = optional(string)<br>    secondary_boot_disks = optional(object({<br>      disk_image = string<br>      mode       = optional(string)<br>    }))<br>    gcfs_config = optional(object({<br>      enabled = bool<br>    }))<br>    gvnic = optional(object({<br>      enabled = bool<br>    }))<br>    guest_accelerator = optional(object({<br>      type  = string<br>      count = number<br>      gpu_driver_installation_config = optional(object({<br>        gpu_driver_version = string<br>      }))<br>      gpu_partition_size = optional(string)<br>      gpu_sharing_config = optional(object({<br>        gpu_sharing_strategy       = string<br>        max_shared_clients_per_gpu = number<br>      }))<br>    }))<br>    image_type       = optional(string)<br>    labels           = optional(map(string))<br>    resource_labels  = optional(map(string))<br>    max_run_duration = optional(string)<br>    flex_start       = optional(bool)<br>    local_ssd_count  = optional(number)<br>    machine_type     = optional(string)<br>    metadata         = optional(map(string))<br>    min_cpu_platform = optional(string)<br>    oauth_scopes     = optional(list(string))<br>    preemptible      = optional(bool)<br>    reservation_affinity = optional(object({<br>      consume_reservation_type = string<br>      key                      = optional(string)<br>      values                   = optional(list(string))<br>    }))<br>    spot = optional(bool)<br>    sandbox_config = optional(object({<br>      sandbox_type = string<br>    }))<br>    boot_disk_kms_key = optional(string)<br>    service_account   = optional(string)<br>    shielded_instance_config = optional(object({<br>      enable_secure_boot          = optional(bool)<br>      enable_integrity_monitoring = optional(bool)<br>    }))<br>    storage_pools         = optional(list(string))<br>    tags                  = optional(list(string))<br>    resource_manager_tags = optional(map(string))<br>    taint = optional(list(object({<br>      key    = string<br>      value  = string<br>      effect = string<br>    })))<br>    workload_metadata_config = optional(object({<br>      mode = optional(string)<br>    }))<br>    kubelet_config = optional(object({<br>      cpu_manager_policy                     = optional(string)<br>      cpu_cfs_quota                          = optional(bool)<br>      cpu_cfs_quota_period                   = optional(string)<br>      insecure_kubelet_readonly_port_enabled = optional(bool)<br>      pod_pids_limit                         = optional(number)<br>      container_log_max_size                 = optional(string)<br>      container_log_max_files                = optional(number)<br>      image_gc_low_threshold_percent         = optional(number)<br>      image_gc_high_threshold_percent        = optional(number)<br>      image_minimum_gc_age                   = optional(string)<br>      allowed_unsafe_sysctls                 = optional(list(string))<br>    }))<br>    linux_node_config = optional(object({<br>      sysctls     = optional(map(string))<br>      cgroup_mode = optional(string)<br>      hugepages_config = optional(object({<br>        hugepage_size_2m = optional(number)<br>        hugepage_size_1g = optional(number)<br>      }))<br>    }))<br>    windows_node_config = optional(object({<br>      osversion = string<br>    }))<br>    containerd_config = optional(object({<br>      private_registry_access_config = optional(object({<br>        enabled = bool<br>        certificate_authority_domain_config = optional(list(object({<br>          fqdns = list(string)<br>          gcp_secret_manager_certificate_config = object({<br>            secret_uri = string<br>          })<br>        })))<br>      }))<br>      registry_hosts = optional(list(object({<br>        server = string<br>        hosts = list(object({<br>          host          = string<br>          capabilities  = optional(list(string))<br>          override_path = optional(bool)<br>          dial_timeout  = optional(string)<br>          header = optional(list(object({<br>            key   = string<br>            value = list(string)<br>          })))<br>          ca = optional(list(object({<br>            gcp_secret_manager_secret_uri = string<br>          })))<br>          client = optional(list(object({<br>            cert = object({<br>              gcp_secret_manager_secret_uri = string<br>            })<br>            key = object({<br>              gcp_secret_manager_secret_uri = string<br>            })<br>          })))<br>        }))<br>      })))<br>    }))<br>    node_group = optional(string)<br>    sole_tenant_config = optional(object({<br>      node_affinity = optional(object({<br>        key      = string<br>        operator = string<br>        values   = list(string)<br>      }))<br>    }))<br>  })</pre> | <pre>{<br>  "disk_size_gb": 100,<br>  "disk_type": "pd-standard",<br>  "image_type": "COS_CONTAINERD",<br>  "kubelet_config": {<br>    "insecure_kubelet_readonly_port_enabled": false<br>  },<br>  "machine_type": "e2-medium",<br>  "workload_metadata_config": {<br>    "mode": "GKE_METADATA"<br>  }<br>}</pre> | no |


The node_config variable has been updated to include the containerd_config.registry_hosts block. While the type definition is correctly reflected, adding a brief description for registry_hosts and its purpose would greatly improve the clarity and usability of this module for consumers. This helps users understand what this new configuration option does without needing to consult external documentation.

This is not done for other configs under node_config, I don't think this comment is relevant here, am I wrong?

apeabody

Thanks for the contribution @marcmillien

From the initial lint test:

Checking submodule's files generation
diff -r '--exclude=.terraform' '--exclude=.kitchen' '--exclude=.git' /workspace/modules/gke-node-pool/metadata.yaml /tmp/tmp.OaPGXUVVRT/workspace/modules/gke-node-pool/metadata.yaml
302c302
<                   certificate_authority_domain_config = optional(object({
---
>                   certificate_authority_domain_config = optional(list(object({
307c307
<                   }))
---
>                   })))
308a309,332
>                 registry_hosts = optional(list(object({
>                   server = string
>                   hosts = list(object({
>                     host          = string
>                     capabilities  = optional(list(string))
>                     override_path = optional(bool)
>                     dial_timeout  = optional(string)
>                     header = optional(list(object({
>                       key   = string
>                       value = list(string)
>                     })))
>                     ca = optional(list(object({
>                       gcp_secret_manager_secret_uri = string
>                     })))
>                     client = optional(list(object({
>                       cert = object({
>                         gcp_secret_manager_secret_uri = string
>                       })
>                       key = object({
>                         gcp_secret_manager_secret_uri = string
>                       })
>                     })))
>                   }))
>                 })))
Error: submodule's files generation has not been run, please run the
'make build' command and commit changes

Please see the contribution template section: https://github.com/terraform-google-modules/terraform-google-kubernetes-engine/blob/main/CONTRIBUTING.md#templating

marcmillien · 2026-03-25T16:00:38Z

Thanks 🤗 , I check/fix it :)

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feat(gke-node-pool): Add support for "registry_hosts"

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fix(gke-node-pool): Typo on hosts

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GKE Support spegel-org/spegel#38

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doc(gke-node-pool): Update for registry_hosts

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marcmillien force-pushed the feat_add_support_for_registry_hosts branch from cc373ae to 7a8decd Compare March 25, 2026 14:43

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marcmillien marked this pull request as ready for review March 25, 2026 14:52

marcmillien requested review from a team, apeabody, ayushmjain, ericyz, krprabhat-eng and q2w as code owners March 25, 2026 14:52

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fix(gke-node-pool): Update metadata.yaml instead of changing tf files…

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marcmillien marked this pull request as ready for review March 27, 2026 15:46

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