为什么我的.NET Core Web API（在AWS Lambda上部署）返回502 Bad Gateway错误？

Question

I am new to .NET Core, Entity Framework, AWS, and pretty much everything here (please comment and let me know if anything needs to be added to the post).

What I am trying to do is deploy a .NET Core Web API with AWS Lambda. My API seems to be working locally, as I tested it (I have an Angular frontend app, with which I am able to successfully execute all the APIs). However, when I deploy with AWS and run a few of the APIs on Postman, I get a "502 Bad Gateway" error.

My serverless.yml file looks like this:

service: angularawardwebapi

provider: 
  name: aws
  runtime: dotnetcore2.1
  region: us-east-1

package:
  artifact: bin/release/netcoreapp2.1/deploy-package.zip

functions:
  api:
    handler: angularawardwebapi::angularawardwebapi.LambdaEntryPoint::FunctionHandlerAsync
    events: 
      - http:
          path: /{proxy+}
          method: ANY

My Model Class looks something like this:

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace angularawardwebapi.Models {
    public class Student {
        [Key]
        public int StudentId{get;set;}

        [Required]
        [Column(TypeName="nvarchar(50)")]
        public string StudentFirstName{get;set;}

        [Required]
        [Column(TypeName="varchar(50)")]
        public string StudentLastName{get;set;}
    }
}

My DbContext file looks like this:

public class DatabaseContext:DbContext {
        public DatabaseContext(DbContextOptions<DatabaseContext> options):base(options) {

        }

        public DbSet<Student> Students {get;set;} 
   }
}

I have two methods in my Controller:

        [HttpGet("temp")]
        public ActionResult<List<String>> GetTemp() {
            return Ok("here");
        } 


        [HttpGet]
        public ActionResult<IEnumerable<Student>> GetStudent()
        {
            return Ok(_context.Students);
        }

The first of which works without a hitch (as expected). However, when I try to return a list of the Students that are in the DB, it seems that I'm encountering issues.

I tried using the second API locally as well, and received the appropriate response:

[
    {
        "StudentId": 1,
        "StudentFirstName": "John",
        "StudentLastName": "Doe"
    }
]

I also checked the AWS CloudWatch Logs, which showed something like this:

[Information] Microsoft.AspNetCore.Hosting.Internal.WebHost: Request starting GET https://[myurl]/dev/api/Student/ 
[Information] Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker: Route matched with {action = "GetStudent", controller = "Student"}. Executing action WebApi.Controllers.StudentController.GetStudent ([myprojectname]) 
[Information] Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker: Executing action method WebApi.Controllers.StudentController.GetStudent ([myprojectname]) - Validation state: Valid 
[Information] Microsoft.EntityFrameworkCore.Infrastructure: Entity Framework Core 2.1.8-servicing-32085 initialized 'DatabaseContext' using provider 'Microsoft.EntityFrameworkCore.SqlServer' with options: None 
END RequestId: f57417d3-4075-4680-a78d-e90e2c710760
REPORT RequestId: f57417d3-4075-4680-a78d-e90e2c710760  Duration: 6006.80 ms    Billed Duration: 6000 ms Memory Size: 1024 MB   Max Memory Used: 141 MB 
2019-06-06T14:19:41.116Z f57417d3-4075-4680-a78d-e90e2c710760 Task timed out after 6.01 seconds

This time out issue is not seen when I run the API locally, as I immediately get the correct response (as specified above).

---

Update

So I now have an RDS Database, which I can successfully connect to and play around with in SSMS. Running APIs locally also still work. However, after I deploy it using serverless deploy -v , I'm still facing the previous issue. As suggested, I tried modifying the permissions for the DB, although I'm not sure I'm doing the right thing there either. What I've done is:

• Went into SSMS and modified the database permissions by right-clicking the server, going to Permissions, selecting my login (that I set up while configuring the RDS), and granted the "Alter any database" option. I then went to the database itself and modified some permissions (Delete, Insert and Update).
• I also enabled the Windows Management Instrumentation (WMI-In) Windows Firewall rule.

Neither of these seems to have solved my problem.

Answer 1

You're probably using the same connection string you used for testing in your local Db, you should change it to use some database that the api can access to from aws. If that's the case then your api is trying to access to a local db (which obviously it's not going to find), that would explain the timeout issue.

In order to fix it you should probably deploy your database to AWS as well and change the connection string of the project to the connection string of that database inside of AWS.