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Fix performance issues, esp regarding saving tags

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This commit is contained in:
Robert McRackan 2019-11-18 14:37:17 -05:00
parent 6734dec55c
commit f3128b562d
12 changed files with 142 additions and 176 deletions
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4
FileManager/FileManager.csproj
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@ -4,6 +4,10 @@
<TargetFramework>netstandard2.1</TargetFramework>
</PropertyGroup>
<ItemGroup>
<PackageReference Include="Polly" Version="7.1.1" />
</ItemGroup>
<ItemGroup>
<ProjectReference Include="..\..\Dinah.Core\Dinah.Core\Dinah.Core.csproj" />
</ItemGroup>

69
FileManager/UNTESTED/TagsPersistence.cs
View file

@ -3,64 +3,57 @@ using System.Collections.Generic;
using System.IO;
using System.Linq;
using Newtonsoft.Json;
using Polly;
using Polly.Retry;
namespace FileManager
{
/// <summary>
/// Tags must also be stored in db for search performance. Stored in json file to survive a db reset.
/// json is only read when a product is first loaded
/// json is only read when a product is first loaded into the db
/// json is only written to when tags are edited
/// json access is infrequent and one-off
/// all other reads happen against db. No volitile storage
/// </summary>
public static class TagsPersistence
{
public static string TagsFile => Path.Combine(Configuration.Instance.LibationFiles, "BookTags.json");
private static string TagsFile => Path.Combine(Configuration.Instance.LibationFiles, "BookTags.json");
private static object locker { get; } = new object();
// if failed, retry only 1 time after a wait of 100 ms
// 1st save attempt sometimes fails with
// The requested operation cannot be performed on a file with a user-mapped section open.
private static RetryPolicy policy { get; }
= Policy.Handle<Exception>()
.WaitAndRetry(new[] { TimeSpan.FromMilliseconds(100) });
public static void Save(string productId, string tags)
=> System.Threading.Tasks.Task.Run(() => save_fireAndForget(productId, tags));
private static void save_fireAndForget(string productId, string tags)
{
ensureCache();
cache[productId] = tags;
lock (locker)
{
// get all
var allDictionary = retrieve();
// update/upsert tag list
allDictionary[productId] = tags;
// re-save:
// this often fails the first time with
// The requested operation cannot be performed on a file with a user-mapped section open.
// 2nd immediate attempt failing was rare. So I added sleep. We'll see...
void resave() => File.WriteAllText(TagsFile, JsonConvert.SerializeObject(allDictionary, Formatting.Indented));
try { resave(); }
catch (IOException debugEx)
{
// 1000 was always reliable but very slow. trying other values
var waitMs = 100;
System.Threading.Thread.Sleep(waitMs);
resave();
}
}
policy.Execute(() => File.WriteAllText(TagsFile, JsonConvert.SerializeObject(cache, Formatting.Indented)));
}
private static Dictionary<string, string> cache;
public static string GetTags(string productId)
{
var dic = retrieve();
return dic.ContainsKey(productId) ? dic[productId] : null;
ensureCache();
cache.TryGetValue(productId, out string value);
return value;
}
private static Dictionary<string, string> retrieve()
{
if (!FileUtility.FileExists(TagsFile))
return new Dictionary<string, string>();
lock (locker)
return JsonConvert.DeserializeObject<Dictionary<string, string>>(File.ReadAllText(TagsFile));
}
}
private static void ensureCache()
{
if (cache is null)
lock (locker)
cache = !FileUtility.FileExists(TagsFile)
? new Dictionary<string, string>()
: JsonConvert.DeserializeObject<Dictionary<string, string>>(File.ReadAllText(TagsFile));
}
}
}