/// <summary>
/// When overriden, return the header fields for the log file with a given <paramref name="context"/>,
/// or 'null' if none is found
/// </summary>
protected virtual async Task <string[]> TryGetHeaderFields(DelimitedTextLogContext context, CancellationToken stopToken)
{
var position = 0;
long lineNumber = 0;
using (var stream = new FileStream(context.FilePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
using (var reader = new LineReader(stream, _encoding, _bufferSize))
{
while (position < context.Position)
{
stopToken.ThrowIfCancellationRequested();
var(line, consumed) = await reader.ReadAsync(stopToken);
if (line is null)
{
break;
}
lineNumber++;
position += consumed;
if (IsHeaders(line, lineNumber))
{
return(ParseHeadersLine(line));
}
}
}
return(null);
}
protected override async Task <string[]> TryGetHeaderFields(DelimitedTextLogContext context, CancellationToken stopToken)
{
if (_defaultHeaders is not null)
{
return(ParseHeadersLine(_defaultHeaders));
}
return(await base.TryGetHeaderFields(context, stopToken));
}
protected override W3SVCRecord CreateRecord(DelimitedTextLogContext context, Dictionary <string, string> data)
{
var timestamp = DateTime.UtcNow;
if (data.TryGetValue("date", out var date) && data.TryGetValue("time", out var time))
{
// date and time field is UTC-based: https://docs.microsoft.com/en-us/windows/win32/http/w3c-logging
timestamp = DateTime.Parse(date + "T" + time + "Z", null, DateTimeStyles.RoundtripKind);
}
return(new W3SVCRecord(timestamp, data));
}
protected override KeyValueLogRecord CreateRecord(DelimitedTextLogContext context, Dictionary <string, string> data)
{
var timestamp = DateTime.Now;
if (data.TryGetValue("TimestampUtc", out var timestampText))
{
timestamp = DateTime.Parse(timestampText, null, DateTimeStyles.AssumeUniversal);
}
else if (data.TryGetValue("Timestamp", out timestampText))
{
timestamp = DateTime.Parse(timestampText, null, DateTimeStyles.AssumeLocal);
}
return(new KeyValueLogRecord(timestamp, data));
}
/// <inheritdoc/>
public async Task ParseRecordsAsync(DelimitedTextLogContext context, IList <IEnvelope <TData> > output,
int recordCount, CancellationToken stopToken = default)
{
if (context.Fields is null)
{
context.Fields = await TryGetHeaderFields(context, stopToken);
}
var count = 0;
using (var stream = new FileStream(context.FilePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
{
stream.Position = context.Position;
using (var reader = new LineReader(stream, _encoding, _bufferSize))
{
while (count < recordCount)
{
stopToken.ThrowIfCancellationRequested();
var(line, consumed) = await reader.ReadAsync(stopToken);
_logger.LogTrace("File: '{0}', line: '{1}', bytes: {2}", context.FilePath, line, consumed);
context.Position += consumed;
if (line is null)
{
break;
}
if (ShouldStopAndRollback(line, context))
{
context.Position -= consumed;
return;
}
context.LineNumber++;
if (IsHeaders(line, context.LineNumber))
{
context.Fields = ParseHeadersLine(line);
continue;
}
else if (IsComment(line))
{
continue;
}
try
{
// 'ParseDataFragments' and 'CreateRecord' might throw error, so we need to catch it and skip the record
var fragments = ParseDataFragments(line);
if (context.Fields is null)
{
_logger.LogWarning("Unknown field mapping, skipping line {0}", context.LineNumber);
continue;
}
var dict = new Dictionary <string, string>();
for (var i = 0; i < context.Fields.Length; i++)
{
if (i >= fragments.Length)
{
break;
}
var(key, val) = KeyValueSelector(context.Fields[i], fragments[i]);
dict[key] = val;
}
var record = CreateRecord(context, dict);
var envelope = new LogEnvelope <TData>(record, record.Timestamp, line, context.FilePath, context.Position, context.LineNumber);
output.Add(envelope);
count++;
}
catch (Exception ex)
{
_logger.LogError(ex, "Error processing record '{0}'", line);
continue;
}
}
}
}
}
/// <summary> /// When immplemented, create a record based on the parsed key-value pairs. /// </summary> protected abstract TData CreateRecord(DelimitedTextLogContext context, Dictionary <string, string> data);
/// <summary> /// When implemented, returns true iff the line indicates that the reader should stop and rewind. /// </summary> protected virtual bool ShouldStopAndRollback(string line, DelimitedTextLogContext context) => false;
