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FunctionAssemblyLoader.cs
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FunctionAssemblyLoader.cs
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// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the MIT License. See License.txt in the project root for license information.
using System;
using System.Collections.Concurrent;
using System.Globalization;
using System.Linq;
using System.Reflection;
using System.Text.RegularExpressions;
using Microsoft.Azure.WebJobs.Host;
namespace Microsoft.Azure.WebJobs.Script.Description
{
/// <summary>
/// Manages runtime assembly resolution for managed code functions,
/// loading assemblies from their respective <see cref="FunctionAssemblyLoadContext"/>.
/// </summary>
public class FunctionAssemblyLoader : IDisposable
{
// Prefix that uniquely identifies our assemblies
// i.e.: "f-<functionname>"
public const string AssemblyPrefix = "f-";
public const string AssemblySeparator = "__";
private readonly ConcurrentDictionary<string, FunctionAssemblyLoadContext> _functionContexts = new ConcurrentDictionary<string, FunctionAssemblyLoadContext>();
private readonly Regex _functionNameFromAssemblyRegex;
private readonly Uri _rootScriptUri;
public FunctionAssemblyLoader(string rootScriptPath)
{
_rootScriptUri = new Uri(rootScriptPath, UriKind.RelativeOrAbsolute);
AppDomain.CurrentDomain.AssemblyResolve += ResolveAssembly;
_functionNameFromAssemblyRegex = new Regex(string.Format(CultureInfo.InvariantCulture, "^{0}(?<name>.*?){1}", AssemblyPrefix, AssemblySeparator), RegexOptions.Compiled);
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
private void Dispose(bool disposing)
{
if (disposing)
{
AppDomain.CurrentDomain.AssemblyResolve -= ResolveAssembly;
}
}
internal Assembly ResolveAssembly(object sender, ResolveEventArgs args)
{
FunctionAssemblyLoadContext context = GetFunctionContext(args.RequestingAssembly);
Assembly result = null;
try
{
if (context != null)
{
result = context.ResolveAssembly(args.Name);
}
// If we were unable to resolve the assembly, apply the current App Domain policy and attempt to load it.
// This allows us to correctly handle retargetable assemblies, redirects, etc.
if (result == null)
{
string assemblyName = ((AppDomain)sender).ApplyPolicy(args.Name);
// If after applying the current policy, we now have a different target assembly name, attempt to load that
// assembly
if (string.Compare(assemblyName, args.Name) != 0)
{
result = Assembly.Load(assemblyName);
}
}
}
catch (Exception e)
{
if (context != null)
{
context.TraceWriter.Warning(string.Format(CultureInfo.InvariantCulture,
"Exception during runtime resolution of assembly '{0}': '{1}'", args.Name, e.ToString()));
}
}
// If we have an function context and failed to resolve a function assembly dependency,
// log the failure as this is usually caused by missing private assemblies.
if (context != null && result == null)
{
context.TraceWriter.Warning(string.Format(CultureInfo.InvariantCulture,
"Unable to find assembly '{0}'. Are you missing a private assembly file?", args.Name));
}
return result;
}
[CLSCompliant(false)]
public FunctionAssemblyLoadContext CreateOrUpdateContext(FunctionMetadata metadata, Assembly functionAssembly, IFunctionMetadataResolver metadataResolver, TraceWriter traceWriter)
{
if (metadata == null)
{
throw new ArgumentNullException("metadata");
}
if (functionAssembly == null)
{
throw new ArgumentNullException("functionAssembly");
}
if (metadataResolver == null)
{
throw new ArgumentNullException("metadataResolver");
}
if (traceWriter == null)
{
throw new ArgumentNullException("traceWriter");
}
var context = new FunctionAssemblyLoadContext(metadata, functionAssembly, metadataResolver, traceWriter);
return _functionContexts.AddOrUpdate(metadata.Name, context, (s, o) => context);
}
public bool ReleaseContext(FunctionMetadata metadata)
{
FunctionAssemblyLoadContext context;
return _functionContexts.TryRemove(metadata.Name, out context);
}
private FunctionAssemblyLoadContext GetFunctionContext(Assembly requestingAssembly)
{
if (requestingAssembly == null)
{
return null;
}
FunctionAssemblyLoadContext context = null;
string functionName = GetFunctionNameFromAssembly(requestingAssembly);
if (functionName != null)
{
context = GetFunctionContext(functionName);
// If the context is for a different assembly
if (context != null && context.FunctionAssembly != requestingAssembly)
{
return null;
}
}
else
{
context = GetFunctionContextFromDependency(requestingAssembly);
}
return context;
}
private FunctionAssemblyLoadContext GetFunctionContextFromDependency(Assembly requestingAssembly)
{
// If this is a private reference, get the context based on the CodeBase
string assemblyCodeBase = requestingAssembly.GetCodeBase();
if (Uri.IsWellFormedUriString(assemblyCodeBase, UriKind.RelativeOrAbsolute))
{
var codebaseUri = new Uri(assemblyCodeBase, UriKind.RelativeOrAbsolute);
if (_rootScriptUri.IsBaseOf(codebaseUri))
{
return _functionContexts.Values.FirstOrDefault(c => c.FunctionBaseUri.IsBaseOf(codebaseUri));
}
}
return _functionContexts.Values.FirstOrDefault(c => c.LoadedAssemblies.Any(a => a == requestingAssembly));
}
private FunctionAssemblyLoadContext GetFunctionContext(string functionName)
{
FunctionAssemblyLoadContext context;
_functionContexts.TryGetValue(functionName, out context);
return context;
}
public static string GetAssemblyNameFromMetadata(FunctionMetadata metadata, string suffix)
{
return AssemblyPrefix + metadata.Name + AssemblySeparator + suffix.GetHashCode().ToString();
}
public string GetFunctionNameFromAssembly(Assembly assembly)
{
if (assembly != null)
{
Match match = _functionNameFromAssemblyRegex.Match(assembly.FullName);
if (match.Success)
{
return match.Groups["name"].Value;
}
}
return null;
}
}
}