I have this command to start a Node.js webserver like this:

node --inspect=0.0.0.0:9229 --preserve-symlinks /app/api/dist/server.js | pino-pretty

I'm placing it into a Dockerfile as the CMD:

CMD ["node", "--inspect=0.0.0.0:9229", "--preserve-symlinks" ,"/app/api/dist/server.js", "|","pino-pretty"]

The service starts when calling docker run but the | is ignored so no logs are forwarded to pino-pretty.

What am I doing wrong here?

I could put the whole command into a start.sh or use CMD ["npm", "run", "start:prod"] but I want to understand the core problem.

CodePudding user response：

I could put the whole command into a start.sh or use CMD ["npm", "run", "start:prod"] but I want to understand the core problem.

A pipe is a shell construct, e.g. a feature of /bin/sh, /bin/bash, and similar shells. When you define CMD with the json/exec syntax, you are explicitly telling docker to run the command without a shell. Therefore you need to either run the command in a script, call a shell explicitly, or run with the string/shell syntax to have docker execute the command with a shell:

CMD node --inspect=0.0.0.0:9229 --preserve-symlinks /app/api/dist/server.js | pino-pretty