RATIS-2260. AtomicFileOutputStream should truncate temp file

[adoroszlai]

What changes were proposed in this pull request?

AtomicFileOutputStream should reject overwriting existing temp file.

https://issues.apache.org/jira/browse/RATIS-2260

How was this patch tested?

CI:
https://github.com/adoroszlai/ratis/actions/runs/13900762173

[szetszwo]

@adoroszlai , thanks a lot for working on this! Please see the comment inlined.

[szetszwo]

Let's pass a createNew parameter. Usually, we don't care about overwriting tmp file since it is just tmp. On the other hand, we don't want to throw an exception when server starting because of a leftover tmp file. The leftover tmp file may be due to killing the previous run.

[adoroszlai]

If we allow the file to exist, at least we should truncate it. Otherwise leftover content may be included in the final file.

[szetszwo]

You are right -- we need TRUNCATE_EXISTING.

  0: 0123456789
  0: aaaaaa6789
  0: bbb

  static void main(String[] args) throws Exception {
    final File f = new File("a.txt");
    try(OutputStream out = newOutputStreamForceAtClose(f, StandardOpenOption.CREATE_NEW, StandardOpenOption.WRITE)) {
      out.write("0123456789".getBytes(StandardCharsets.UTF_8));
    }
    dump(f);
    try(OutputStream out = newOutputStreamForceAtClose(f, StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {
      out.write("aaaaaa".getBytes(StandardCharsets.UTF_8));
    }
    dump(f);
    try(OutputStream out = newOutputStreamForceAtClose(f, StandardOpenOption.CREATE, StandardOpenOption.WRITE, StandardOpenOption.TRUNCATE_EXISTING)) {
      out.write("bbb".getBytes(StandardCharsets.UTF_8));
    }
    dump(f);
  }

  static void dump(File f) throws Exception {
    try(BufferedReader in = new BufferedReader(new InputStreamReader(
        newInputStream(f.toPath()), StandardCharsets.UTF_8))) {
      String line;
      for(int i = 0; (line = in.readLine()) != null; i++) {
        System.out.printf("%3d: %s%n", i, line);
      }
    }
  }

[szetszwo]

+1 the change looks good.

[adoroszlai]

Thanks @szetszwo for reviewing and merging this.