Add configurable swapfile for memory-constrained test VMs

Author: Kwaizer

alts/shared/models.py

@@ -154,6 +154,8 @@ class OpennebulaConfig(BaseModel):
     vm_group: Optional[str] = None
     default_vm_disk_size: Optional[int] = 15360
     default_vm_ram_size: Optional[int] = 1536
+    # Swapfile size in MB created during provisioning; 0 disables it
+    default_vm_swap_size: Optional[int] = 0
     network: Optional[str] = None
     # Quota checking configuration
     quota_check_enabled: bool = False

alts/worker/runners/base.py

@@ -356,6 +356,13 @@ def vm_ram_size(self) -> int:
             CONFIG.opennebula_config.default_vm_ram_size,
         )
 
+    @property
+    def vm_swap_size(self) -> int:
+        return self._test_env.get(
+            'vm_swap_size',
+            getattr(CONFIG.opennebula_config, 'default_vm_swap_size', 0),
+        )
+
     @property
     def dist_arch(self):
         return self._dist_arch
@@ -745,6 +752,7 @@ def initial_provision(self, verbose=False):
             'integrity_tests_dir': self._integrity_tests_dir,
             'connection_type': self.ansible_connection_type,
             'pytest_is_needed': self.pytest_is_needed,
+            'vm_swap_size': self.vm_swap_size,
             'development_mode': CONFIG.development_mode,
             'package_proxy': CONFIG.package_proxy,
             'third_party_repo_ssh_hosts': [

alts/worker/runners/opennebula.py

@@ -203,6 +203,7 @@ def _render_tf_main_file(self):
             template_id=template_id,
             vm_disk_size=self.vm_disk_size,
             vm_ram_size=self.vm_ram_size,
+            vm_swap_size=self.vm_swap_size,
             opennebula_network=CONFIG.opennebula_config.network,
         )
 

configs/example_config.yaml

@@ -42,6 +42,7 @@ opennebula_config:
   # in MB
   default_vm_disk_size:
   default_vm_ram_size:
+  default_vm_swap_size:
   network:
 
 bs_host:

resources/opennebula/opennebula.tf.tmpl

@@ -36,9 +36,9 @@ locals {
   # Disk configuration
   disk_0 = data.opennebula_template.selected_template.disk[0]
   disk_size = max(
-    local.disk_0.size,        # Original disk size from template
-    15360,                    # Minimum required size
-    local.disk_0.size + 5120  # Original size + 5GB
+    local.disk_0.size,                          # Original disk size from template
+    15360,                                      # Minimum required size
+    local.disk_0.size + 5120 + ${vm_swap_size}  # Original size + 5GB + swapfile (MB)
   )
   # Determine network_id: use template network if available, otherwise use test_system_network
   network_id = local.template_has_network ? data.opennebula_virtual_network.template_network[0].id : data.opennebula_virtual_network.test_system_network.id

resources/roles/preparation/defaults/main.yml

@@ -10,3 +10,6 @@ third_party_repo_ssh_hosts: []
 # and is passed in as an extra-var by the runner. Empty list here is a
 # no-op fallback so the role still works if invoked standalone.
 cached_test_repos: []
+# Swapfile size in MB, passed in as an extra-var by the runner from the
+# platform's `vm_swap_size`. 0 (the default) disables swapfile creation.
+vm_swap_size: 0

resources/roles/preparation/tasks/main.yml

@@ -21,6 +21,45 @@
   tags:
     - initial_provision
 
+# Some platforms (e.g. CL7h) carry many available kernels across repos, and
+# dnf/yum can exhaust memory while resolving kernel-module dependencies.
+# A swapfile sized from the platform's `vm_swap_size` gives them headroom.
+# VM-only (Docker envs share the host kernel and can't swapon) and a no-op
+# when vm_swap_size is 0.
+- name: Provide swap space for memory-constrained platforms
+  when:
+    - connection_type != 'docker'
+    - (vm_swap_size | int) > 0
+  tags:
+    - initial_provision
+  block:
+    - name: Allocate swapfile
+      ansible.builtin.command:
+        cmd: "fallocate -l {{ vm_swap_size }}M /swapfile"
+        creates: /swapfile
+
+    - name: Restrict swapfile permissions
+      ansible.builtin.file:
+        path: /swapfile
+        owner: root
+        group: root
+        mode: '0600'
+
+    - name: Format swapfile
+      ansible.builtin.command:
+        cmd: mkswap /swapfile
+      register: _mkswap
+      changed_when: _mkswap.rc == 0
+
+    - name: Enable swapfile
+      ansible.builtin.command:
+        cmd: swapon /swapfile
+      register: _swapon
+      changed_when: _swapon.rc == 0
+      failed_when:
+        - _swapon.rc != 0
+        - "'already active' not in _swapon.stderr"
+
 # SSH client config is only needed where the third-party repo is cloned
 # *inside* the environment (VMs cloned over SSH). Docker envs receive the
 # repo via `docker cp` from the worker, so they never clone and need no