apache/cassandra · error · IOException

Exception while executing the command:

Error message

Exception while executing the command:

What it means

FBUtilities.exec (the ProcessBuilder-based helper) runs an external command and throws this IOException when the process exits with a non-zero error code, embedding the command line, exit code, and combined stdout/stderr output. It indicates the external tool invocation failed.

Solutions

  1. Read the 'command output' section of the message to see the underlying tool's stderr
  2. Verify the command and its arguments are correct for the current platform
  3. Run the command manually on the host to reproduce and diagnose
  4. Handle the specific exit code in the caller or add the required tool/dependency on the host

Example fix

// before: FBUtilities.exec("fio", "--name=test", "--bad-option")
// after:  FBUtilities.exec("fio", "--name=test", "--rw=read", "--size=1G") // valid args
Defensive patterns

Strategy: try-catch

Validate before calling

if (!new File(command[0]).canExecute() && FBUtilities.exec("which", command[0]).isEmpty()) throw new IllegalStateException("tool not found: " + command[0]);

Try / catch

try { FBUtilities.exec(cmd); } catch (IOException e) { logger.error("External command failed: {}", e.getMessage()); throw new RuntimeException(e); }

Prevention

When it happens

Trigger: Calling FBUtilities.exec(cmd) or execTimeout(...) where the spawned process returns a non-zero exit code, e.g. executing a native tool script that fails, missing arguments to the command, or a tool that errors on the host.

Common situations: Calls to external tools during repair/backup tooling, empty or wrong arguments to the command, the tool not supporting the requested operation on this OS, or environment issues (PATH, permissions) making the command fail after starting.

Related errors

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/fbd1c8bd92fd446e. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/utils/FBUtilities.java:1221

    public static void exec(ProcessBuilder pb) throws IOException
    {
        Process p = pb.start();
        try
        {
            int errCode = p.waitFor();
            if (errCode != 0)
            {
                try (BufferedReader in = new BufferedReader(new InputStreamReader(p.getInputStream()));
                     BufferedReader err = new BufferedReader(new InputStreamReader(p.getErrorStream())))
                {
                    String lineSep = LINE_SEPARATOR.getString();
                    StringBuilder sb = new StringBuilder();
                    String str;
                    while ((str = in.readLine()) != null)
                        sb.append(str).append(lineSep);
                    while ((str = err.readLine()) != null)
                        sb.append(str).append(lineSep);
                    throw new IOException("Exception while executing the command: " + StringUtils.join(pb.command(), " ") +
                                          ", command error Code: " + errCode +
                                          ", command output: " + sb);
                }
            }
        }
        catch (InterruptedException e)
        {
            throw new UncheckedInterruptedException(e);
        }
    }

    /**
     * Starts and waits for the given <code>cmd</code> to finish. If the process does not finish within <code>timeout</code>,
     * it will be destroyed.
     *
     * @param env        additional environment variables to set
     * @param timeout    timeout for the process to finish, or zero/null to wait forever
     * @param outBufSize the maximum size of the collected std output; the overflow will be discarded

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