How to modify the filename of the S3 object?

[matias-dls]

Hi, I've been using the S3 connector for a couple of weeks now, and I want to change the way the connector names each file. I am using the HourlyBasedPartition, so the path to each file is already enough for me to find each file, and I want the filenames to be something generic for all the files, like just 'Data.json.gzip' (with the respective path from the partitioner).

For example, I want to go from this:
<prefix>/<topic>/<HourlyBasedPartition>/<topic>+<kafkaPartition>+<startOffset>.<format>

To this:
<prefix>/<topic>/<HourlyBasedPartition>/Data.<format>

The objective of this is to only make one call to S3 to download the files later, instead of having to look for the filename first and then download it.

[matias-dls]

Searching through the files from the repo called 'kafka-connect-s3', I found this file:
https://github.com/confluentinc/kafka-connect-storage-cloud/blob/master/kafka-connect-s3/src/main/java/io/confluent/connect/s3/TopicPartitionWriter.java which at the end has some of the following functions:

private RecordWriter getWriter(SinkRecord record, String encodedPartition)
      throws ConnectException {
    if (writers.containsKey(encodedPartition)) {
      return writers.get(encodedPartition);
    }
    String commitFilename = getCommitFilename(encodedPartition);
    log.debug(
        "Creating new writer encodedPartition='{}' filename='{}'",
        encodedPartition,
        commitFilename
    );
    RecordWriter writer = writerProvider.getRecordWriter(connectorConfig, commitFilename);
    writers.put(encodedPartition, writer);
    return writer;
  }

  private String getCommitFilename(String encodedPartition) {
    String commitFile;
    if (commitFiles.containsKey(encodedPartition)) {
      commitFile = commitFiles.get(encodedPartition);
    } else {
      long startOffset = startOffsets.get(encodedPartition);
      String prefix = getDirectoryPrefix(encodedPartition);
      commitFile = fileKeyToCommit(prefix, startOffset);
      commitFiles.put(encodedPartition, commitFile);
    }
    return commitFile;
  }

  private String fileKey(String topicsPrefix, String keyPrefix, String name) {
    String suffix = keyPrefix + dirDelim + name;
    return StringUtils.isNotBlank(topicsPrefix)
           ? topicsPrefix + dirDelim + suffix
           : suffix;
  }

  private String fileKeyToCommit(String dirPrefix, long startOffset) {
    String name = tp.topic()
                      + fileDelim
                      + tp.partition()
                      + fileDelim
                      + String.format(zeroPadOffsetFormat, startOffset)
                      + extension;
    return fileKey(topicsDir, dirPrefix, name);
  }

I don't know if this can be customized to what I want to do but seems to be somehow near/related to my intentions. Hope it helps.

[OneCricketeer]

Worth pointing out that the sink connector does not append into files, so you would be overriding those files if you were to change these lines

+ String name = "Data"
- String name = tp.topic()
-                      + fileDelim
-                      + tp.partition()
-                      + fileDelim
-                      + String.format(zeroPadOffsetFormat, startOffset)
                      + extension;