How can a TextWriter be used as a source for Serilog?

Question

StackExchange.Redis writes log messages to a TextWriter. It does not use the ILogger interface for logging.

I would like to turn messages written to a TextWriter, into Serilog debug level messages.

Thoughts?

What about creating a class inheriting from `TextWriter` overriding the `Write___()` methods to write to the Serilog logger? — thepirat000, Dec 13 '18 at 19:30
Did this turn into a more generic solution? (preferably to be shared). Have the same issue, logging mechanism in 3. party library, that takes TextWriter as parameter, and want to pass on to Serilog from there. — Toke Breer-Mortensen, Apr 30 '21 at 21:59

score 3 · Answer 1 · answered Oct 01 '20 at 22:05

3

Something like the following (only smoke tested, but seems to work):

public class TextWriterLogger : TextWriter
{
    private ILogger logger;
    private StringBuilder builder = new StringBuilder();
    private bool terminatorStarted = false;

    public TextWriterLogger(ILoggerFactory log)
    {
        logger = log.CreateLogger("RedisTrace");
    }

    public override void Write(string value)
    {
        logger.LogDebug(value);
    }

    public override void Write(char value)
    {
        builder.Append(value);
        if (value == NewLine[0])
            if (NewLine.Length == 1)
                Flush2Log();
            else
                terminatorStarted = true;
        else if (terminatorStarted)
            if (terminatorStarted = NewLine[1] == value)
                Flush2Log();
    }

    private void Flush2Log()
    {
        if (builder.Length > NewLine.Length)
            logger.LogDebug(builder.ToString());
        builder.Clear();
        terminatorStarted = false;
    }


    public override Encoding Encoding
    {
        get { return Encoding.Default; }
    }
}

answered Oct 01 '20 at 22:05

d_f

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`if (terminatorStarted = NewLine[1] == value)` - don't do this, you're assigning terminatorStarted to the condition NewLine[1] == value being true. It's confusing to read, and breaks SOLID principle L: https://en.wikipedia.org/wiki/SOLID. I presume you actually meant to write something like `if (terminatorStarted == (NewLine[1] == value))` or even `else if (terminatorStarted && NewLine[1] == value)`. If you provide to your buffer as chars "\", then "\" and "n" your buffer will essentially escape the newline, you can overflow your buffer with providing constant backslashes... – NotoriousPyro Mar 06 '21 at 15:00
Instead you should check that adding to StringBuilder would not exceed its maximum implementation capacity. Flush the buffer if it would exceed the capacity of StringBuilder or a reasonable capacity for a string... Otherwise your application will easily overflow. – NotoriousPyro Mar 06 '21 at 15:01
1

"you're assigning terminatorStarted to the condition `NewLine[1] == value`" -- something like that. that's a one-liner for: `if (NewLine[1] == value){Flush2Log();}else{terminatorStarted = false;}` when the second character of a possible terminator is not `NewLine[1]` -- it's not a terminator, so I clear the flag. The implementation is not generic, but it works fine with the Redis's constructor -- my only goal here – d_f Mar 07 '21 at 19:48
Note for those looking to make this slightly more generic: if you don't necessarily want to use `LogDebug`, you can add a `LogLevel logLevel` field to the class, fill it in the constructor, and then call `logger.Log(logLevel, value)` in the Write function instead. – Ben Seymour Mar 11 '22 at 14:15

How can a TextWriter be used as a source for Serilog?

1 Answers1