Having a bit of trouble trying to get a readiness probe command working. Every external service / app of ours exposes an /up endpoint whose body contains the SHA of the current release. I’m trying to create a readiness probe that hits this URL locally and then compares the content of the response body against the expected release. Basically, if 200 OK && ${BODY} == ${RELEASE} then we’re good to go.

I’m trying to translate this to the following probe, but I’m having constant issues:

... heaps of yaml ...
                command: [ "/bin/sh", "-c", "wget", "-q", "-O", "//RELEASE", "localhost:5000/up", "&&", "grep", "-E", "'^${DEPLOYMENT_RELEASE}$'", "//RELEASE" ]
... even more heaps of yaml meight ...

Which results in the following error:

Readiness probe failed: wget: unrecognized option: E BusyBox v1.28.4 (2018-07-17 15:21:40 UTC) multi-call binary. Usage: wget [-c|--continue] [--spider] [-q|--quiet] [-O|--output-document FILE] [--header 'header: value'] [-Y|--proxy on/off] [-P DIR] [-S|--server-response] [-U|--user-agent AGENT] [-T SEC] URL... Retrieve files via HTTP or FTP --spider    Only check URL existence: $? is 0 if exists -c  Continue retrieval of aborted transfer -q   Quiet -P DIR    Save to DIR (default .) -S Show server response -T SEC Network read timeout is SEC seconds -O FILE  Save to FILE ('-' for stdout) -U STR    Use STR for User-Agent header -Y on/off Use proxy

I’ve tried a few variations on the above, all resulting in similar errors:

wget -q -O /RELEASE localhost:5000/up; grep -E '^${DEPLOYMENT_RELEASE}$' /RELEASE

and even:

[[ $(wget -qO- localhost:5000/up) == ${DEPLOYMENT_RELEASE} ]]

Breaking the command up into a list doesn’t seem to help either. It has to be some mundane syntactic error, or some misinterpretation of the manual.

This command works if I execute it from within a running pod.

Unfortunately, I can't modify the images directly, so I have to find out some other way to perform this check. Perhaps via a side car or something?

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