Detecting Docker Environment in Java: A Simple Approach

This code is checking whether the current environment is running within a Docker container. It does this by examining two potential indicators of a Docker environment:

1. Checking /proc/1/cgroup:
   • It reads the contents of the /proc/1/cgroup file, which typically contains information about the control groups in the system. If the file exists and contains the term “docker” (case-insensitive) in any line, checkCgrpFile is set to true.
2. Checking for /.dockerenv file:
   • It checks for the existence of the / directory’s .dockerenv file. If the file exists, checkDockerenv is set to true.

The function then returns true if either checkCgrpFile or checkDockerenv is true, indicating that the code is running within a Docker container. If both are false, it implies that the code is not running in a Docker environment.

        boolean checkCgrpFile = false;
        boolean checkDockerenv = false;

        File cgrpFile = new File("/proc/1/cgroup");
        if (cgrpFile.exists()) {
            try (BufferedReader br = new BufferedReader(new FileReader(cgrpFile))) {
                String line;
                while ((line = br.readLine()) != null) {
                    if (line.toLowerCase().contains("docker".toLowerCase())) {
                        checkCgrpFile = true;
                        break;
                    }
                }

            } catch (IOException e) {
            }
        }


        try {
            if (new File("/.dockerenv").exists()) {
                checkDockerenv = true;
            }
        } catch (Exception e) {
            checkDockerenv = false;
        }

        return (checkCgrpFile || checkDockerenv);