KAFKA-4566: multiple changes $(dirname "$0.. to $(dirname "$(readlink -f "$0..

[itfromblighty]

This PR allows people to symlink to e.g. /opt/kafka/bin/kafka-console-consumer.sh and when they execute the script it does not fail due to exec $(dirname $0.. when the directory of the symlink is not the same i.e. the symlink is in a separate directory so that binaries don't have to be cloned when a separate directory is used for e.g. configuration. This was raised as a bug in 2016 and was never fixed since the original proposal was not platform agnostic (MacOS vs Linux) and further proposals were heavy-handed. However, "readlink -f" is platform portable (across MacOS and Linux i.e. official docker container) and neatly solves the problem with symlinking to /opt/kafka/bin scripts.
This is my original work and I license this work to the project under the project's open source license.

[edoardocomar]

@itfromblighty if I search the repo for "$(dirname $0 I still get some hits, can you please take another look ?

[itfromblighty]

@edoardocomar, yes, in several places there are/is basedir=$(dirname $0) for example relative directory to config - I thought the purpose of this 'bug' was to continue to allow the user/admin to use (e.g.) config relative to where they'd symlink-ed the kafka .sh script from, as opposed to locking-in all subsequent 'paths' into the kafka/bin directory?.. However, on second thoughts, I see that every time the base_dir is used, it's only when an environment variable isn't defined. So I think it makes sense to apply this readlink logic to everything (now). There are (were) (still) matches for "$(dirname $0)" yes:

bin/connect-mirror-maker.sh [candidate#1]
bin/zookeeper-server-start.sh [candidate#2]
bin/connect-standalone.sh [candidate#3]
bin/connect-distributed.sh [candidate#4]
bin/kafka-run-class.sh [candidate#5]
bin/kafka-server-start.sh [candidate#6]
vagrant/package-base-box.sh
vagrant/aws/aws-init.sh
tests/bootstrap-test-env.sh
jmh-benchmarks/jmh.sh
examples/bin/java-producer-consumer-demo.sh [candidate#7]
examples/bin/exactly-once-demo.sh [candidate#8]
raft/bin/test-kraft-server-start.sh [candidate#9]

However, since this 'bug' was for "Kafka bins", I'd limited the change/s to bin/.sh only. I've updated candidates 1 through 5 as-per my adjusted understanding at the top of this comment, and updated candidates 7 through 9 as while these are outside the kafka/bin directory, they look, smell, and feel the same as the majority of the rest of the kafka/bin/.sh scripts. I've also taken the liberty to surround ALL instances of $base_dir with double-quotes (except when they're already in double-quotes)

[itfromblighty]

@mumrah, hi. I see you're a committer on this project. Is there anything I can do, to help with getting this PR merged with trunk?

[cmccabe]

readlink -f doesn't exist on Macs prior to macOS 12.3. More details here:

https://stackoverflow.com/questions/1055671/how-can-i-get-the-behavior-of-gnus-readlink-f-on-a-mac

I don't know what our policy is for older MacOS versions, but it seems too soon to drop support for 2022-era MacOS.

[mumrah]

I don't think we have official supported versions of Mac or Linux, but I agree we should not break a version of MacOS that is still supported. It looks like Mac OS 12 will be EoL later this year, so maybe we can make this change in a future release like 4.1.

I'm going to close this PR for now. @itfromblighty I've updated the ticket with a fix version of 4.1, so we can re-open this PR once we're closer to that release. Thanks for the fix btw!