Truncated response on Alpine

[ContinentalGuy]

Hi!

I run jsonschema in Docker container with enabled tty on Alpine + Node JS using this command:

docker run \
      --volume "$DIRECTORY:/$VOLUME_NAME" \
      --user "$UID":"$GID" \
      --workdir "/$VOLUME_NAME" \
      --entrypoint jsonschema \
      -t \
      $JSONSCHEMA_DOCKER_IMAGE \
      test --extension ".test.json"

But I get partial response that differs from what I got on my local PC on Linux Mint.

I tried to pipe response and cat it:

docker run \
      --volume "$DIRECTORY:/$VOLUME_NAME" \
      --user "$UID":"$GID" \
      --workdir "/$VOLUME_NAME" \
      --entrypoint jsonschema \
      -t \
      $JSONSCHEMA_DOCKER_IMAGE \
      test --extension ".test.json" 2>&1 | cat

But the answer still turns out to be truncated.

What should I do to avoid this error?

[jviotti]

Hey @ContinentalGuy ,

That sounds strange. I know of a couple of people using the Docker image without troubles.

• Did you try without enabling TTY? As per https://github.com/sourcemeta/jsonschema?tab=readme-ov-file#from-dockerfile I remember some issues where enabling TTY was actually the problem
• Is only the output truncated by the results of the tool are fine? I wonder if it is a flushing problem. Do you get the same if you open a shell into the container and run it there?

[ContinentalGuy]

Did you try without enabling TTY?

Yes. At first I tried to run it without TTY. The problem persists.

--interactive instead of -t gives the same result.

Is only the output truncated by the results of the tool are fine?

If I understood the question correctly, then yes. The changes only affect the output.
Response is ok, there are no unexpected errors.

Do you get the same if you open a shell into the container and run it there?

Yes.

[jviotti]

Is it a custom Docker image? How did you set it up? Any chance you can share the exact same Dockerfile for me to try? Do you get the same with the Docker image we publish out of this repo? https://github.com/sourcemeta/jsonschema/pkgs/container/jsonschema

[ContinentalGuy]

Is it a custom Docker image? How did you set it up?

Not really. I took this image and installed jsonschema like this:

FROM node:24.11.1-alpine3.21

ARG JSONSCHEMA_VERSION=v14.4.0

RUN apk add --no-cache libc6-compat && \
    npm install --global @sourcemeta/jsonschema@${JSONSCHEMA_VERSION} && \
    npm cache clean --force

ENTRYPOINT ["jsonschema"]

Then I built it:

docker build -t jsonschema-mcve:latest .

And ran it recursively on a large number of tests like this:

docker run --rm --volume ./:/schemas --workdir /schemas jsonschema-mcve:latest test --extension ".test.json"

Result also looks like this:

<more tests here>
/schemas/a/v1/tests/x.test.json: PASS 16/16
/schemas/b/v1/tests/y.test.json: PASS 7/7
/schemas/b/v1/tests/z.test.json: PASS 3/3
/schemas/b/v1/tests/z.test.json

[jviotti]

Ha. very interesting. Different output on a GLIBC image vs a MUSL image. And it seems to have something to do with libc6-compat. Debugging more...

[jviotti]

Seems to be related to -D_FORTIFY_SOURCE=2. When the CLI is compiled with that, it will hit different symbols for some of the libc functions that are not properly handled by libc6-compat.

Any reason why you are installing over NPM? We provide pre-built binaries for Alpine in GitHub Releases, which might work better.

[jviotti]

I confirm the musl binary here (https://github.com/sourcemeta/jsonschema/releases/tag/v14.6.1) works fine but:

• We don't publish musl binaries for arm64
• We don't publish musl binaries on the NPM package

Is arm64 or NPM a requirement here? Just trying to figure out how to fix it!