File writer/sender doesn't fsync

[KristianLyng]

When writing, the file sender doesn't issue a fsync, which means it will return before data is comitted to disk. This isn't normally a problem, but with a one-off receiver chain it easily leads to incomplete writes.

E.g.:

{
    "receivers": {
        "dbpoll": {
            "type": "sql",
            "connstr": "...",
            "driver": "mysql",
            "handler": "dbp",
            "query": "select .... (large query)"
        }
    },
    "handlers": {
        "dbp": {
            "parser": "json",
            "transformers": ["now"],
            "sender": "tofile"
        }
    },
    "senders": {
        "tofile": {
            "type": "file",
            "encoder": "skogul",
            "path": "dump.json"
        }
    }
}

This will break if the query returns large amounts of data, since the receiver will return and skogul will exit before data is committed. Or at least, I am assuming that's the reason.