feat: allow unlimited memory_swap in docker_container (#138)

* feat: allow unlimited memory_swap in docker_container

summary: in docker_container, allow `memory_swap: values
`unlimited` and `-1` for unlimited container swap usage.

`--memory-swap=-1` is a valid docker run value allowing
unlimited swap usage. `docker_container` should allow
setting this value via `memory_swap` values `unlimited`
and `-1` as it sometimes must explicitly be set to prevent
docker from attempting to limit swap usage to double the
`--memory` value by default. In rootless docker environments,
attempting to set `memory-swap` usage limits will result in an error
if the user doesn't have the ability to do so. Allowing explicit
unlimited swap usage via docker_container will prevent these errors.

https://docs.docker.com/config/containers/resource_constraints/#--memory-swap-details

* Update tests/integration/targets/docker_container/tasks/tests/options.yml

* Apply suggestions from code review

Co-authored-by: Felix Fontein <felix@fontein.de>

changelogs/fragments/138-docker_container-allow-memory-swap-unlimited.yml

@@ -0,0 +1,2 @@
+minor_changes:
+- "docker_container - allow ``memory_swap: -1`` to set memory swap limit to unlimited. This is useful when the user cannot set memory swap limits due to cgroup limitations or other reasons, as by default Docker will try to set swap usage to two times the value of ``memory`` (https://github.com/ansible-collections/community.docker/pull/138)."

plugins/modules/docker_container.py

@@ -458,7 +458,8 @@ options:
     type: str
   memory_swap:
     description:
-      - "Total memory limit (memory + swap) in format C(<number>[<unit>]).
+      - "Total memory limit (memory + swap) in format C(<number>[<unit>]), or
+        the special values C(unlimited) or C(-1) for unlimited swap usage.
         Number is a positive integer. Unit can be C(B) (byte), C(K) (kibibyte, 1024B),
         C(M) (mebibyte), C(G) (gibibyte), C(T) (tebibyte), or C(P) (pebibyte)."
       - Omitting the unit defaults to bytes.
@@ -1413,10 +1414,13 @@ class TaskParameters(DockerBaseClass):
 
         for param_name in REQUIRES_CONVERSION_TO_BYTES:
             if client.module.params.get(param_name):
-                try:
-                    setattr(self, param_name, human_to_bytes(client.module.params.get(param_name)))
-                except ValueError as exc:
-                    self.fail("Failed to convert %s to bytes: %s" % (param_name, to_native(exc)))
+                if param_name == 'memory_swap' and client.module.params.get(param_name) in ['unlimited', '-1']:
+                    setattr(self, param_name, -1)
+                else:
+                    try:
+                        setattr(self, param_name, human_to_bytes(client.module.params.get(param_name)))
+                    except ValueError as exc:
+                        self.fail("Failed to convert %s to bytes: %s" % (param_name, to_native(exc)))
 
         self.publish_all_ports = False
         self.published_ports = self._parse_publish_ports()

tests/integration/targets/docker_container/tasks/tests/options.yml

@@ -2520,6 +2520,32 @@ avoid such warnings, please quote the value.' in log_options_2.warnings"
     debug: yes
   register: memory_swap_3
 
+- name: memory_swap (unlimited)
+  docker_container:
+    image: "{{ docker_test_image_alpine }}"
+    command: '/bin/sh -c "sleep 10m"'
+    name: "{{ cname }}"
+    # Docker daemon does not accept memory_swap if memory is not specified
+    memory: 32M
+    memory_swap: unlimited
+    state: started
+    force_kill: yes
+    debug: yes
+  register: memory_swap_4
+
+- name: memory_swap (unlimited via -1)
+  docker_container:
+    image: "{{ docker_test_image_alpine }}"
+    command: '/bin/sh -c "sleep 10m"'
+    name: "{{ cname }}"
+    # Docker daemon does not accept memory_swap if memory is not specified
+    memory: 32M
+    memory_swap: -1
+    state: started
+    force_kill: yes
+    debug: yes
+  register: memory_swap_5
+
 - name: cleanup
   docker_container:
     name: "{{ cname }}"
@@ -2534,6 +2560,11 @@ avoid such warnings, please quote the value.' in log_options_2.warnings"
     # on a proper VM), memory_swap cannot be set and will be -1 afterwards.
     - memory_swap_2 is not changed or memory_swap_2.container.HostConfig.MemorySwap == -1
     - memory_swap_3 is changed
+    # Unlimited memory_swap (using 'unlimited') should be allowed
+    # (If the value was already -1 because of the above reasons, it won't change)
+    - (memory_swap_4 is changed or memory_swap_3.container.HostConfig.MemorySwap == -1) and memory_swap_4.container.HostConfig.MemorySwap == -1
+    # Unlimited memory_swap (using '-1') should be allowed
+    - memory_swap_5 is not changed and memory_swap_5.container.HostConfig.MemorySwap == -1
 
 - debug: var=memory_swap_1
   when: memory_swap_2 is changed