.NET Core runtime

Function Compute supports the .NET Core 2.1 (runtime = .NET Core 2.1) runtime. Functions are written in C#. This topic describes the .NET Core 2.1 runtime. It is divided into the following parts:

• Use logger
• Use third-party libraries
• Handle errors

Use logger

The content that is printed by C# functions by using context.Logger is collected to the logstore of Log Service that is specified when a service is created.

Log levels

You can change log levels by modifying the logger property EnabledLogLevel. Log levels are sorted as follows, in descending order:

For more information about log levels, see LogLevel Enum.

For more information about function logs, see Function logs.

Logger example 1

using System;
using System.IO;
using System.Text;
using Aliyun.Serverless.Core;
using Microsoft.Extensions.Logging;
namespace FC.Examples
{
    public class TestLogger
    {
        public Stream Echo(Stream input, IFcContext context)
        {
            context.Logger.LogInformation(string.Format("detail = {0} ", "hello world"));
            using (MemoryStream output = new MemoryStream(100))
            {
                byte[] hello = Encoding.UTF8.GetBytes("hello world");
                output.Write(hello, 0, hello.Length);
                return output;
            }
        }
    }
}

The output log is as follows:

2019-03-15T03:09:59.812Z 8ba1a2a2-0eb7-9e79-c3c6-ee6606c5beaf [INFO] detail = hello world

Logger example 2

using System;
using System.IO;
using System.Text;
using Aliyun.Serverless.Core;
using Microsoft.Extensions.Logging;
namespace FC.Examples
{
    public class TestLogger
    {
        public Stream Echo(Stream input, IFcContext context)
        {
            context.Logger.EnabledLogLevel = LogLevel.Error;
            context.Logger.LogError("console error 1");
            context.Logger.LogInformation("console info 1");
            context.Logger.LogWarning("console warn 1");
            context.Logger.LogDebug("console debug 1");
            context.Logger.EnabledLogLevel = LogLevel.Warning;
            context.Logger.LogError("console error 2");
            context.Logger.LogInformation("console info 2");
            context.Logger.LogWarning("console warn 2");
            context.Logger.LogDebug("console debug 2");
            context.Logger.EnabledLogLevel = LogLevel.Information;
            using (MemoryStream output = new MemoryStream(100))
            {
                byte[] hello = Encoding.UTF8.GetBytes("hello world");
                output.Write(hello, 0, hello.Length);
                return output;
            }
        }
    }
}

The output log is as follows:

2019-03-15T03:09:31.047Z f4ddc314-d3e9-91c9-b774-4b08c91a977d [ERROR]: console error 1
2019-03-15T03:09:31.047Z f4ddc314-d3e9-91c9-b774-4b08c91a977d [ERROR]: console error 2
2019-03-15T03:09:31.047Z f4ddc314-d3e9-91c9-b774-4b08c91a977d [WARNING]: console warn 2

Use third-party libraries

It is easy to apply third-party libraries to C#-written functions.

• Edit the .csproj file of the corresponding project to add the desired package, for example:

  <ItemGroup>
        <PackageReference Include="Aliyun.Serverless.Core" Version="1.0.1" />
        <PackageReference Include="Aliyun.OSS.SDK.NetCore" Version="2.9.1" />
    </ItemGroup>

• Add the corresponding NuGet package on the GUI of Visual Studio IDE.

Handle errors

Function Compute captures exceptions that occur when C# functions are executed and returns the corresponding error messages. The following sample code returns the oops error:

using System;
using System.IO;
using Aliyun.Serverless.Core;
namespace FC.Examples
{
    public class TestException
    {
        public Stream Echo(Stream input, IFcContext context)
        {
            throw new Exception("oops");
        }
    }
}

The following response may be returned when functions are called:

{
    "ErrorMessage": "oops",
    "ErrorType": "System.Exception",
    "StackTrace": [...]
}

When an error occurs, the HTTP header in the response message of the function call contains X-Fc-Error-Type: UnhandledInvocationError. For information about more error types in Function Compute, see Error types.