With Kubernetes Container running a Python script:
import time
while True:
try:
for i in range(10):
if i==0:
raise Exception('Exception occurred!')
except:
pass
time.sleep(1)
I would like to pass the Exception's message 'Exception occurred!' down to the Container so this error message could be seen with:
kubectl describe pod pod_id
Would it be possible?
Anything you print() will be visible in kubectl logs. (You may need to set an environment variable PYTHONUNBUFFERED=1 in your pod spec.)
Your code as you've written it will never print anything. The construct
try:
...
except:
pass
silently ignores any and all exceptions out of the try block. The bare except: even captures some system-level exceptions like SystemExit or KeyboardInterrupt; this is almost always wrong. Often you want your except blocks to be as tightly scoped as you can, and the Python tutorial on user-defined exceptions is a helpful pattern.
(The exception to this, particularly in a Kubernetes context, is that you will often want a very broad exception handler to do something like return an HTTP 500 error to a network request, rather than crashing the application.)
A better example might look like:
import time
class OneException(Exception):
pass
def iteration():
for i in range(10):
try:
if i == 1:
raise OneException("it is one")
print(i, math.sqrt(i), math.sqrt(-i))
# will work when i==0 but fail when i==2
except OneException as e:
print(i, repr(e))
# and proceed to the next iteration
if __name__ == '__main__':
while True:
# The top-level loop. We want a very broad catch here.
try:
iteration()
except Exception as e:
print('iteration failed', repr(e))
time.sleep(1)
PYTHONUNBUFFERED=1 did the trick for me, thank you!
kubectl logs ... if you want it in the output ofkubectl describe pod..., you'll need to write it to create it as a kubernetes event.