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Improved locking code.

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- Moved DatabaseLock into Framework and making it the default lock provider.
- Removed unnecessary thread synchronization code.
- Allowing multiple lock acquisitions from the same machine (simulating a "lease").
- Updated unit tests.
This commit is contained in:
Sipke Schoorstra
2015-08-11 16:43:48 +01:00
parent cb6835aba3
commit 77b8df516a
19 changed files with 106 additions and 105 deletions
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9
src/Orchard.Web/Modules/Orchard.TaskLease/Migrations.cs
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@@ -17,14 +17,5 @@ namespace Orchard.TaskLease {
return 1;
}
public int UpdateFrom1() {
SchemaBuilder.CreateTable("DatabaseLockRecord", table => table
.Column<int>("Id", column => column.PrimaryKey().Identity())
.Column<string>("Name", column => column.NotNull().WithLength(256))
.Column<DateTime>("AcquiredUtc"));
return 2;
}
}
}

9
src/Orchard.Web/Modules/Orchard.TaskLease/Models/DatabaseLockRecord.cs
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@@ -1,9 +0,0 @@
using System;
namespace Orchard.TaskLease.Models {
public class DatabaseLockRecord {
public virtual int Id { get; set; }
public virtual string Name { get; set; }
public virtual DateTime? AcquiredUtc { get; set; }
}
}

3
src/Orchard.Web/Modules/Orchard.TaskLease/Module.txt
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@@ -4,5 +4,6 @@ Author: The Orchard Team
Website: http://orchardtasklease.codeplex.com
Version: 1.9.1
OrchardVersion: 1.9
Description: Provides services to synchronize tasks in a farm environment
LifecycleStatus: Deprecated
Description: Provides services to synchronize tasks in a farm environment.
Category: Hosting

2
src/Orchard.Web/Modules/Orchard.TaskLease/Orchard.TaskLease.csproj
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@@ -76,7 +76,6 @@
</ItemGroup>
<ItemGroup>
<Content Include="Web.config" />
<Compile Include="Models\DatabaseLockRecord.cs" />
<Compile Include="Properties\AssemblyInfo.cs" />
<Content Include="Module.txt" />
</ItemGroup>
@@ -86,7 +85,6 @@
</Compile>
<Compile Include="Models\TaskLeaseRecord.cs" />
<Compile Include="Services\ITaskLeaseService.cs" />
<Compile Include="Services\DatabaseLock.cs" />
<Compile Include="Services\TaskLeaseService.cs" />
</ItemGroup>
<ItemGroup />

125
src/Orchard.Web/Modules/Orchard.TaskLease/Services/DatabaseLock.cs
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@@ -1,125 +0,0 @@
using System;
using System.Data;
using System.Linq;
using Autofac;
using Orchard.Data;
using Orchard.Environment.Extensions;
using Orchard.Exceptions;
using Orchard.Logging;
using Orchard.Services;
using Orchard.TaskLease.Models;
using Orchard.Tasks.Locking;
using Orchard.Validation;
namespace Orchard.TaskLease.Services {
/// <summary>
/// Provides a database driven implementation of <see cref="IDistributedLock" />
/// </summary>
[OrchardSuppressDependency("Orchard.Tasks.Locking.DefaultLock")]
public class DatabaseLock : IDistributedLock {
private readonly ILifetimeScope _lifetimeScope;
private readonly IClock _clock;
private string _name;
private bool _isAcquired;
private int _id;
private bool _isDisposed;
private ILifetimeScope _scope;
public DatabaseLock(ILifetimeScope lifetimeScope, IClock clock) {
_lifetimeScope = lifetimeScope;
_clock = clock;
Logger = NullLogger.Instance;
}
public ILogger Logger { get; set; }
public bool TryAcquire(string name, TimeSpan maxLifetime) {
if(_isDisposed)
throw new ObjectDisposedException("DatabaseLock");
Argument.ThrowIfNullOrEmpty(name, "name");
if (name.Length > 256)
throw new ArgumentException("The lock's name can't be longer than 256 characters.");
try {
var scope = EnsureLifetimeScope(name);
scope.Resolve<ITransactionManager>().RequireNew(IsolationLevel.ReadCommitted);
// This way we can create a nested transaction scope instead of having the unwanted effect
// of manipulating the transaction of the caller.
var repository = scope.Resolve<IRepository<DatabaseLockRecord>>();
var record = repository.Table.FirstOrDefault(x => x.Name == name);
if (record != null) {
// There is a nexisting lock, but check if it has expired.
var isExpired = record.AcquiredUtc + maxLifetime < _clock.UtcNow;
if (isExpired) {
repository.Delete(record);
record = null;
}
}
var canAcquire = record == null;
if (canAcquire) {
record = new DatabaseLockRecord {
Name = name,
AcquiredUtc = _clock.UtcNow
};
repository.Create(record);
repository.Flush();
_name = name;
_isAcquired = true;
_id = record.Id;
}
return canAcquire;
}
catch (Exception ex) {
Logger.Error(ex, "An error occurred while trying to acquire a lock.");
DisposeLifetimeScope();
throw;
}
}
// This will be called at least and at the latest by the IoC container when the request ends.
public void Dispose() {
if (_scope == null)
return;
if (!_isDisposed) {
_isDisposed = true;
if (_isAcquired) {
try {
var repository = _scope.Resolve<IRepository<DatabaseLockRecord>>();
var record = repository.Get(_id);
if (record != null) {
repository.Delete(record);
repository.Flush();
}
}
catch (Exception ex) {
if (ex.IsFatal()) throw;
Logger.Error(ex, "An non-fatal error occurred while trying to dispose the database lock.");
}
}
_scope.Dispose();
}
}
private ILifetimeScope EnsureLifetimeScope(string name) {
return _scope ?? (_scope = _lifetimeScope.BeginLifetimeScope("Orchard.Tasks.Locking.Database." + name));
}
private void DisposeLifetimeScope() {
if (_scope != null)
_scope.Dispose();
}
}
}