Exception caught when writing error log to fileSystem.IO.IOException: Read-only file system : '/var/task/aws-logger-errors.txt'

[pponzano]

Describe the bug

I've introduced serilog to some AWS lambda I wrote... when I run them I got this... any suggestion?

Here's my code

  public static void InitializeLogger()
        {
            AWSLoggerConfig configuration = new AWSLoggerConfig();

            Log.Logger = new LoggerConfiguration()
                .WriteTo.AWSSeriLog(configuration)
                .CreateLogger();

            var serviceCollection = new ServiceCollection();
            ConfigureServices(serviceCollection);

            serviceCollection.AddLogging(loggingBuilder =>
                loggingBuilder.AddSerilog(dispose: true));
        }

and when I log it's something as

   Log.Logger.Information($"Request inserted with Token: {guid}\n");

Any suggestion?
Thanks

Expected Behavior

The fact that the logs are correcly written to the CloudWatch

Current Behavior

This error is written in cloudwatch but no other application logs are written

Reproduction Steps

see up

Possible Solution

No response

Additional Information/Context

No response

AWS .NET SDK and/or Package version used

AWS Lambda core 2.1.0

Targeted .NET Platform

.NET6

Operating System and version

Windows 10

[ashishdhingra]

Hi @pponzano,

Good morning.

Could you please share your .csproj file, appSettings.json and Serilog configuration (if not using appSettings.json)? Looks like you have Serilog:LibraryLogErrors set to true in your config. This flag enables Serilog extension to log any service errors to local log file. When executing in Lambda environment, looks like there are some library errors (such as inability to log to CloudWatch logs may be due to lack of permissions) and it's unable to write to this file since Lambda code is executing with /var/task as current directory.

This setting is typically used for development environment. So you should have this setting enabled instead in appSettings.Development.json, not in production appSettings.json.

Thanks,
Ashish