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MessageTemplateCache.cs
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MessageTemplateCache.cs
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// Copyright 2013-2015 Serilog Contributors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
using System;
using Serilog.Events;
#if HASHTABLE
using System.Collections;
#else
using System.Collections.Generic;
#endif
namespace Serilog.Core.Pipeline
{
class MessageTemplateCache : IMessageTemplateParser
{
readonly IMessageTemplateParser _innerParser;
readonly object _templatesLock = new object();
#if HASHTABLE
readonly Hashtable _templates = new Hashtable();
#else
readonly Dictionary<string, MessageTemplate> _templates = new Dictionary<string, MessageTemplate>();
#endif
const int MaxCacheItems = 1000;
const int MaxCachedTemplateLength = 1024;
public MessageTemplateCache(IMessageTemplateParser innerParser)
{
if (innerParser == null) throw new ArgumentNullException(nameof(innerParser));
_innerParser = innerParser;
}
public MessageTemplate Parse(string messageTemplate)
{
if (messageTemplate == null) throw new ArgumentNullException(nameof(messageTemplate));
if (messageTemplate.Length > MaxCachedTemplateLength)
return _innerParser.Parse(messageTemplate);
#if HASHTABLE
var result = (MessageTemplate)_templates[messageTemplate];
if (result != null)
return result;
#else
MessageTemplate result;
lock(_templatesLock)
if (_templates.TryGetValue(messageTemplate, out result))
return result;
#endif
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;
}
}
}