test/Serilog.PerformanceTests/Support/DictionaryMessageTemplateCache.cs - dev - aprogrammer/serilog

test/Serilog.PerformanceTests/Support/DictionaryMessageTemplateCache.cs

50 строк2 KB

Evgeny Peshkov

By reference string comparison in template cache (#1947)

09 окт 2023, 10:05

09 окт 2023, 10:0588f76a8

namespace Serilog.PerformanceTests.Support;

class DictionaryMessageTemplateCache : IMessageTemplateParser
{
    readonly IMessageTemplateParser _innerParser;
    readonly object _templatesLock = new();

    readonly Dictionary<string, MessageTemplate> _templates = new(ByReferenceStringComparer.Instance);

    const int MaxCacheItems = 1000;
    const int MaxCachedTemplateLength = 1024;

    public DictionaryMessageTemplateCache(IMessageTemplateParser innerParser)
    {
        _innerParser = Guard.AgainstNull(innerParser);
    }

    public MessageTemplate Parse(string messageTemplate)
    {
        Guard.AgainstNull(messageTemplate);

        if (messageTemplate.Length > MaxCachedTemplateLength)
            return _innerParser.Parse(messageTemplate);

        MessageTemplate? result;
        lock (_templatesLock)
            if (_templates.TryGetValue(messageTemplate, out result))
                return result;

        result = _innerParser.Parse(messageTemplate);

        lock (_templatesLock)
        {
            // Exceeding MaxCacheItems is *not* the sunny day scenario; all we're doing here is preventing out-of-memory
            // conditions when the library is used incorrectly. Correct use (templates, rather than
            // direct message strings) should barely, if ever, overflow this cache.

            // Changing workloads through the lifecycle of an app instance mean we can gain some ground by
            // potentially dropping templates generated only in startup, or only during specific infrequent
            // activities.

            if (_templates.Count == MaxCacheItems)
                _templates.Clear();

            _templates[messageTemplate] = result;
        }

        return result;
    }
}