Do not fail on empty log line

[YevheniiSemendiak]

If we have a job with empty log line, for instance (simple STR):
n run ubuntu -- bash -c "echo; echo hi;"

platform cannot handle its logs, since fluent-bit omits "log" in logs entry:

and logs from k8s:

Corresponding error from service:

2023-07-05 18:41:57,671 - platform_monitoring.logs - ERROR - Invalid log entry: b'{"time":"2023-07-05T18:39:49.720424314Z","stream":"stdout","logtag":"F","kubernetes":{"pod_name":"job-b34af07f-0418-4e12-8529-906c6c284f68","namespace_name":"platform-jobs","pod_id":"f06694a3-1c4e-4bfb-93ce-60f4a5ccc9c6","labels":{"platform.neuromation.io/gpu-model":"nvidia-tesla-v100","platform.neuromation.io/job":"job-b34af07f-0418-4e12-8529-906c6c284f68","platform.neuromation.io/org":"no_org","platform.neuromation.io/preset":"gpu-small","platform.neuromation.io/user":"yevheniisemendiak"},"annotations":{"cni.projectcalico.org/containerID":"4588e23019d34ca8ae8194ab98f1eed4c2ddc3666b88c49b08836418809181fc","cni.projectcalico.org/podIP":"","cni.projectcalico.org/podIPs":""},"host":"master-1","container_name":"job-b34af07f-0418-4e12-8529-906c6c284f68","docker_id":"0a85ee521ae55eaa8dadadd396875cbbd05c58037cb0f306886acbd5f8fba03b","container_hash":"0bced47fffa3361afa981854fcabcd4577cd43cebbb808cea2b1f33a3dd7f508"}}'
Traceback (most recent call last):
  File "/root/.local/lib/python3.9/site-packages/platform_monitoring/logs.py", line 364, in _iterate
    log = event["log"]
KeyError: 'log'
2023-07-05 18:41:57,674 - asyncio - ERROR - Task exception was never retrieved
future: <Task finished name='Task-448227' coro=<_forward_bytes_iterating() done, defined at /root/.local/lib/python3.9/site-packages/platform_monitoring/api.py:492> exception=KeyError('log')>
Traceback (most recent call last):
  File "/root/.local/lib/python3.9/site-packages/platform_monitoring/api.py", line 495, in _forward_bytes_iterating
    async for chunk in it:
  File "/root/.local/lib/python3.9/site-packages/platform_monitoring/logs.py", line 441, in get_pod_log_reader
    async for chunk in it:
  File "/root/.local/lib/python3.9/site-packages/platform_monitoring/logs.py", line 364, in _iterate
    log = event["log"]
KeyError: 'log'

Maybe, we could configure fluent-bit properly, but I haven't found how to do it.
It also might close #719

[codecov]

Codecov Report

Merging #818 (2ddc4e0) into master (96ed14d) will not change coverage.
The diff coverage is 100.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #818   +/-   ##
=======================================
  Coverage   86.05%   86.05%           
=======================================
  Files          12       12           
  Lines        2094     2094           
  Branches      287      287           
=======================================
  Hits         1802     1802           
  Misses        179      179           
  Partials      113      113           

Flag	Coverage Δ
integration	79.41% <100.00%> (-1.20%)	⬇️
unit	47.27% <100.00%> (+1.09%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
platform_monitoring/logs.py	87.52% <100.00%> (+0.47%)	⬆️

... and 3 files with indirect coverage changes

[dalazx]

great!

we should probably try to add a test.

[YevheniiSemendiak]

great!

we should probably try to add a test.

It took too much time to add such a simple test, but I did it :D
Please, take a look once more.

[dalazx]

thank you!