candlerb opened a new issue #5518: python functions cannot find python3 interpreter URL: https://github.com/apache/pulsar/issues/5518 **Describe the bug** python functions do not start if the system has "python3" but not "python" (which is the case for modern Ubuntu systems - "python" is python2 and is not installed by default) **To Reproduce** Write a simple function `func1.py` ``` from pulsar import Function class FirstFunction(Function): def process(self, item, context): log = context.get_logger() log.info("Got %r with properties %r" % (item, context.get_message_properties())) ``` Deploy it: ``` apache-pulsar-2.4.1/bin/pulsar-admin functions create --name womble --inputs my-topic \ --py /home/ubuntu/func1.py --classname FirstFunction --log-topic pulsar-log ``` (side note: have to give absolute path to function, pulsar-admin changes the working directory) Check its status: ``` $ apache-pulsar-2.4.1/bin/pulsar-admin functions status --name womble { "numInstances" : 1, "numRunning" : 0, "instances" : [ { "instanceId" : 0, "status" : { "running" : false, "error" : "Cannot run program \"python\": error=2, No such file or directory", "numRestarts" : 16, "numReceived" : 0, "numSuccessfullyProcessed" : 0, "numUserExceptions" : 0, "latestUserExceptions" : [ ], "numSystemExceptions" : 0, "latestSystemExceptions" : [ ], "averageLatency" : 0.0, "lastInvocationTime" : 0, "workerId" : "c-standalone-fw-ldex-pulsar.int.example.net-8080" } } ] } ``` Note error: **Cannot run program "python": error=2, No such file or directory** **Expected behavior** I would expect the function to deploy. **Screenshots** N/A **Desktop (please complete the following information):** N/A **Additional context** This may be the same problem as #5369 - however in that case, it's the shebang line in pulsar's own python code, whereas this one is my own function which is not starting. I cannot find it stated in Pulsar documentation whether Pulsar supports python2, python3 or both. However python2 is [very shortly](https://pythonclock.org/) going to be end-of-life. **Workarounds** Install python2 and write my code in python2. I really don't want to do that, with python2 being end-of-life in 2 months' time. Symlink python to python3. However in Ubuntu systems, symlinking python to python3 has the potential to cause all sorts of problems. Many applications and scripts depend on `python` meaning `python2` (in which case they will depend on the `python-XXX` packages rather than `python3-XXX`). More content [here](https://askubuntu.com/questions/320996/how-to-make-python-program-command-execute-python-3#answer-475815). Ideally pulsar would try python3 and fallback to python. If pulsar were to be hard-coded to run "python3" instead of "python" that would also be fine IMO, given the impending EOL of python2.
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