Why do images like `cloudnativelabs/whats-my-ip` not run on Cloud Run?

Question

I tried to run cloudnativelabs/whats-my-ip on GCP (Cloud Run), but it failed:

/home/server: line 1: syntax error: unexpected "("
Container called exit(2).

The image contains a Go program, but this looks like it tries to run it as a script. Because there's no syntax when you run a binary.

What's happening here? Why does it fail? Does it really think the entrypoint is a script? A shell script? Why?

Is this a duplicate of the exec format error? No, at least the message is different. And as far as I can tell architectures on Docker Hub and Cloud Run match.

Steps to reproduce:

resource "google_cloud_run_v2_service" "cloud-run-test" {
    name = "cloud-run-test"
    location = "europe-central2"
    template {
        containers {
            image = "cloudnativelabs/whats-my-ip"
        }
    }
}

$ terraform init
$ terraform apply
$ gcloud logging read 'logName:projects/PROJECT_ID/logs/run.googleapis.com%2F' --format 'text(logName, textPayload, timestamp)' --project PROJECT_ID
---
log_name:     projects/PROJECT_ID/logs/run.googleapis.com%2Fvarlog%2Fsystem
text_payload: Container called exit(2).
timestamp:    2023-12-09T03:40:23.628609204Z
---
log_name:     projects/PROJECT_ID/logs/run.googleapis.com%2Fstderr
text_payload: /home/server: line 1: syntax error: unexpected "("
timestamp:    2023-12-09T03:40:22.632415Z

I moved my experiments with the image to this gist.

Answer 1

This is not exactly the reason (depends on your definition) but this is as close as I could probably hope to get. According to the fragment of the docs John Hanley quoted:

Executables in the container image must be compiled for Linux 64-bit. Cloud Run specifically supports the Linux x86_64 ABI format.

$ docker container create cloudnativelabs/whats-my-ip
$ docker cp 97bd786fbc2dd1df6925121ae8c0febebaf1a6f8785c10a7a7237e5799791289:/home/server /tmp/server
$ docker rm 97bd786fbc2dd1df6925121ae8c0febebaf1a6f8785c10a7a7237e5799791289

$ file /tmp/server
/tmp/server: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), statically linked, Go BuildID=edc3254ee8543cb3d51767295b041bc44368d286, with debug_info, not stripped

The reason is apparently because /home/server is a 32-bit binary.