Documentation says :
errors.log.enable: When set to true, both errors that are tolerated (determined by the errors.tolerance setting) and not tolerated are written.
But:
When settings errors.tolerance=all and errors.log.enable=true Then only MongoException are logged.
Cause probably is in catch block in com.mongodb.kafka.connect.sink.MongoSinkTask.processSinkRecords(MongoSinkTopicConfig config, List<SinkRecord> batch)
private void processSinkRecords(final MongoSinkTopicConfig config, final List<SinkRecord> batch) { ... try { ... } catch (MongoException e) { ... handleMongoException(config, e); } catch (Exception e) { if (!config.tolerateErrors()) { ... } } } private void handleMongoException(final MongoSinkTopicConfig config, final MongoException e) { ... if (config.logErrors()) { ... } if (!config.tolerateErrors()) { ... } ... }