feat: add new tail_lines parameter to k8s_log module (#488) (#489)

feat: add new tail_lines parameter to k8s_log module (#488)

SUMMARY

Add new tail_lines parameter to k8s_log module to limit the number of lines to be retrieved from the end of the logs.
Closes #488.

ISSUE TYPE


Feature Pull Request

COMPONENT NAME

kubernetes.core.k8s_log
ADDITIONAL INFORMATION


Thanks for useful collection 😃
This is the first time to send PR to this collection, so please let me know if I'm on the wrong way.

The version_added is set to 2.4.0, but I'm not aware of the roadmap for this collection, so I'd like to know this is the right version to specify.
Changelog and simple integration test is also added.
It seems that the end of log_lines always contains an empty element, so if tail_lines is set to 5, the length of log_lines will be 6, as noted in the comment in the test. I've considered that truncating the trailing empty element, but decided not to for the following reasons.

It is inconsistent and unnatural to remove trailing empty elements only when tail_lines is specified.
Removing trailing empty elements always with or without tail_lines is a destructive change and should not be done because it would break backward compatibility.




Example tasks in playbook:
  tasks: 
    - name: create a job that has 10 lines of log
      kubernetes.core.k8s:
        state: present
        wait: yes
        wait_timeout: "{{ k8s_wait_timeout | default(omit) }}"
        wait_condition:
          type: Complete
          status: 'True'
        definition:
          apiVersion: batch/v1
          kind: Job
          metadata:
            name: multiline-log
            namespace: test
          spec:
            template:
              spec:
                containers:
                  - name: busybox
                    image: busybox
                    command: ['sh']
                    args: ['-c', 'for i in $(seq 0 9); do echo $i; done']
                restartPolicy: Never
            backoffLimit: 4

    - name: retrieve all logs from the job
      kubernetes.core.k8s_log:
        api_version: batch/v1
        kind: Job
        namespace: test
        name: multiline-log
      register: full_log

    - name: retrieve last 5 lines of log from the job
      kubernetes.core.k8s_log:
        api_version: batch/v1
        kind: Job
        namespace: test
        name: multiline-log
        tail_lines: 5
      register: tailed_log

    - ansible.builtin.debug:
        var: full_log.log_lines

    - ansible.builtin.debug:
        var: tailed_log.log_lines
Example output:
TASK [create a job that has 10 lines of log] *****************************************************************************************
ok: [localhost]

TASK [retrieve all logs from the job] ************************************************************************************************
ok: [localhost]

TASK [retrieve last 5 lines of log from the job] *************************************************************************************
ok: [localhost]

TASK [ansible.builtin.debug] *********************************************************************************************************
ok: [localhost] => 
  full_log.log_lines:
  - '0'
  - '1'
  - '2'
  - '3'
  - '4'
  - '5'
  - '6'
  - '7'
  - '8'
  - '9'
  - ''

TASK [ansible.builtin.debug] *********************************************************************************************************
ok: [localhost] => 
  tailed_log.log_lines:
  - '5'
  - '6'
  - '7'
  - '8'
  - '9'
  - ''

PLAY RECAP ***************************************************************************************************************************
localhost                  : ok=5    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Reviewed-by: Bikouo Aubin <None>
Reviewed-by: Mike Graves <[email protected]>

changelogs/fragments/488-add-support-for-tail-logs.yaml

@@ -0,0 +1,3 @@
+---
+minor_changes:
+- k8s_log - added the `tail_lines` parameter to limit the number of lines to be retrieved from the end of the logs (https://github.com/ansible-collections/kubernetes.core/issues/488).

plugins/modules/k8s_log.py

@@ -67,6 +67,12 @@
     type: bool
     default: False
     version_added: '2.4.0'
+  tail_lines:
+    description:
+    - A number of lines from the end of the logs to retrieve.
+    required: no
+    type: int
+    version_added: '2.4.0'
 
 requirements:
   - "python >= 3.6"
@@ -106,6 +112,7 @@
     kind: DeploymentConfig
     namespace: testing
     name: example
+    tail_lines: 100
   register: log
 """
 
@@ -156,6 +163,7 @@ def argspec():
             since_seconds=dict(),
             label_selectors=dict(type="list", elements="str", default=[]),
             previous=dict(type="bool", default=False),
+            tail_lines=dict(type="int"),
         )
     )
     return args
@@ -204,6 +212,11 @@ def execute_module(svc, params):
     if params.get("previous"):
         kwargs.setdefault("query_params", {}).update({"previous": params["previous"]})
 
+    if params.get("tail_lines"):
+        kwargs.setdefault("query_params", {}).update(
+            {"tailLines": params["tail_lines"]}
+        )
+
     response = resource.log.get(
         name=name, namespace=namespace, serialize=False, **kwargs
     )

tests/integration/targets/k8s_log/tasks/main.yml

@@ -112,6 +112,46 @@
       assert:
         that: job_logs.log_lines[0] == "7"
 
+    - name: create a job that has 10 log lines
+      k8s:
+        state: present
+        wait: yes
+        wait_timeout: "{{ k8s_wait_timeout | default(omit) }}"
+        wait_condition:
+          type: Complete
+          status: 'True'
+        definition:
+          apiVersion: batch/v1
+          kind: Job
+          metadata:
+            name: multiline-log
+            namespace: "{{ test_namespace }}"
+          spec:
+            template:
+              spec:
+                containers:
+                  - name: busybox
+                    image: busybox
+                    command: ['sh']
+                    args: ['-c', 'for i in $(seq 0 9); do echo $i; done']
+                restartPolicy: Never
+            backoffLimit: 4
+
+    - name: retrieve last 5 log lines from the job
+      k8s_log:
+        api_version: batch/v1
+        kind: Job
+        namespace: "{{ test_namespace }}"
+        name: multiline-log
+        tail_lines: 5
+      register: tailed_log
+
+    # The log_lines by k8s_log always contain a trailing empty element,
+    # so if "tail"ing 5 lines, the length will be 6.
+    - name: verify that specific number of logs have been retrieved
+      assert:
+        that: tailed_log.log_lines | length == 5 + 1
+
   always:
     - name: ensure that namespace is removed
       k8s: