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141 lines
5.3 KiB
C#
141 lines
5.3 KiB
C#
// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
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// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
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using System;
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using System.Linq;
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using System.Threading;
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using Microsoft.EntityFrameworkCore.Storage;
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using osu.Framework.Platform;
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namespace osu.Game.Database
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{
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public class DatabaseContextFactory : IDatabaseContextFactory
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{
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private readonly Storage storage;
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private const string database_name = @"client";
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private ThreadLocal<OsuDbContext> threadContexts;
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private readonly object writeLock = new object();
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private bool currentWriteDidWrite;
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private bool currentWriteDidError;
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private int currentWriteUsages;
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private IDbContextTransaction currentWriteTransaction;
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public DatabaseContextFactory(Storage storage)
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{
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this.storage = storage;
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recycleThreadContexts();
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}
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/// <summary>
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/// Get a context for the current thread for read-only usage.
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/// If a <see cref="DatabaseWriteUsage"/> is in progress, the existing write-safe context will be returned.
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/// </summary>
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public OsuDbContext Get() => threadContexts.Value;
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/// <summary>
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/// Request a context for write usage. Can be consumed in a nested fashion (and will return the same underlying context).
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/// This method may block if a write is already active on a different thread.
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/// </summary>
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/// <param name="withTransaction">Whether to start a transaction for this write.</param>
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/// <returns>A usage containing a usable context.</returns>
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public DatabaseWriteUsage GetForWrite(bool withTransaction = true)
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{
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Monitor.Enter(writeLock);
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OsuDbContext context;
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try
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{
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if (currentWriteTransaction == null && withTransaction)
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{
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// this mitigates the fact that changes on tracked entities will not be rolled back with the transaction by ensuring write operations are always executed in isolated contexts.
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// if this results in sub-optimal efficiency, we may need to look into removing Database-level transactions in favour of running SaveChanges where we currently commit the transaction.
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if (threadContexts.IsValueCreated)
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recycleThreadContexts();
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context = threadContexts.Value;
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currentWriteTransaction = context.Database.BeginTransaction();
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}
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else
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{
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// we want to try-catch the retrieval of the context because it could throw an error (in CreateContext).
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context = threadContexts.Value;
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}
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}
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catch (Exception e)
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{
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// retrieval of a context could trigger a fatal error.
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Monitor.Exit(writeLock);
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throw;
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}
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Interlocked.Increment(ref currentWriteUsages);
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return new DatabaseWriteUsage(context, usageCompleted) { IsTransactionLeader = currentWriteTransaction != null && currentWriteUsages == 1 };
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}
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private void usageCompleted(DatabaseWriteUsage usage)
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{
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int usages = Interlocked.Decrement(ref currentWriteUsages);
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try
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{
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currentWriteDidWrite |= usage.PerformedWrite;
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currentWriteDidError |= usage.Errors.Any();
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if (usages == 0)
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{
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if (currentWriteDidError)
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currentWriteTransaction?.Rollback();
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else
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currentWriteTransaction?.Commit();
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if (currentWriteDidWrite || currentWriteDidError)
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{
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// explicitly dispose to ensure any outstanding flushes happen as soon as possible (and underlying resources are purged).
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usage.Context.Dispose();
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// once all writes are complete, we want to refresh thread-specific contexts to make sure they don't have stale local caches.
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recycleThreadContexts();
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}
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currentWriteTransaction = null;
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currentWriteDidWrite = false;
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currentWriteDidError = false;
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}
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}
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finally
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{
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Monitor.Exit(writeLock);
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}
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}
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private void recycleThreadContexts()
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{
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// Contexts for other threads are not disposed as they may be in use elsewhere. Instead, fresh contexts are exposed
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// for other threads to use, and we rely on the finalizer inside OsuDbContext to handle their previous contexts
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threadContexts?.Value.Dispose();
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threadContexts = new ThreadLocal<OsuDbContext>(CreateContext, true);
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}
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protected virtual OsuDbContext CreateContext() => new OsuDbContext(storage.GetDatabaseConnectionString(database_name))
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{
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Database = { AutoTransactionsEnabled = false }
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};
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public void ResetDatabase()
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{
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lock (writeLock)
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{
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recycleThreadContexts();
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storage.DeleteDatabase(database_name);
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}
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}
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}
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}
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