EF Core - System.InvalidOperationException: ExecuteReader requires an open and available Connection. The connection's current state is closed

问题

I'm running an ASP.NET Core 1.0 web app with Entity Framework Core. When the app has been running for a while (24 - 48 hours), the app starts crashing on every request to any endpoint or static resource throwing the error System.InvalidOperationException: ExecuteReader requires an open and available Connection. The connection's current state is closed. I can only recover from this by restarting the App Pool.

I am configuring Entity Framework like this:

Startup.cs

public void ConfigureServices(IServiceCollection services)
{
        services.AddDbContext<ApplicationDbContext>(options =>
            options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));   
}

I am loading data in the owin pipeline with an extension method like this like this:

Startup.cs

app.LoadTenantData();

AppBuilderExtensions.cs:

public static void LoadTenantData(this IApplicationBuilder app)
    {
        app.Use(async (context, next) =>
        {
            var dbContext = app.ApplicationServices.GetService<ApplicationDbContext>();        
            var club = dbContext.Clubs.Single(c => c.Id == GetClubIdFromUrl(context));
            context.Items[PipelineConstants.ClubKey] = club;
            await next();
        });
    }

Since the error only occurs when the app has been running for a long time, it is hard to reproduce, but I'm assuming it has something to do with EF opening and closing connections incorrectly.

How can I go about to debug this? Am I using EF incorrectly?

回答1:

I got same issue.

I think it is likely that the same dbcontext instance is being used concurrently by multiple threads.

You may need this: services.AddDbContext<ApplicationDbContext>(options => options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")),ServiceLifetime.Transient); There is a issue about that. https://github.com/aspnet/EntityFramework/issues/6491

回答2:

My app is very basic (write it fast, run it once, then forget), so a solution to the problem above was to simply introduce lock around the section that was doing multi-table inserts.

    public void CallGooglePlacesAPIAndSetCallback(string websiteName)
    {
        using (var db = new WebAnalyzerEntities())
        {
            IList<IRecord> addressesToBeSearched = db.Rent.Where<IRecord>(o => o.Url.Contains(websiteName) && o.SpatialAnalysis.Count == 0).ToList().Union(db.Sale.Where<IRecord>(oo => oo.Url.Contains(websiteName) && oo.SpatialAnalysis.Count == 0)).ToList();
            foreach (var locationTobeSearched in addressesToBeSearched)
            {
                try
                {
           //this is where I introduced the lock
                    lock (_lock)
                    {
                        dynamic res = null;
                        using (var client = new HttpClient())
                        {
                            while (res == null || HasProperty(res, "next_page_token"))
                            {
                                var url = $"https://maps.googleapis.com/maps/api/geocode/json?address={locationTobeSearched.Address}&key={googlePlacesApiKey}&bounds=51.222,-11.0133788|55.636,-5.6582363";
                                if (res != null && HasProperty(res, "next_page_token"))
                                    url += "&pagetoken=" + res["next_page_token"];
                                var response = client.GetStringAsync(url).Result;
                                JavaScriptSerializer json = new JavaScriptSerializer();
                                res = json.Deserialize<dynamic>(response);
                                if (res["status"] == "OK")
                                {
                                    Tuple<decimal?, decimal?, string> coordinatesAndPostCode = ReadResponse(res["results"][0]);
                                    if (coordinatesAndPostCode != null && coordinatesAndPostCode.Item1.HasValue && coordinatesAndPostCode.Item2.HasValue)
                                    {
           //this is the line where exception was thrown
                                        locationTobeSearched.SpatialAnalysis.Add(new SpatialAnalysis() { Point = CreatePoint(coordinatesAndPostCode.Item1.Value, coordinatesAndPostCode.Item2.Value) });
                                        locationTobeSearched.PostCode = coordinatesAndPostCode.Item3;
                                    }
                                }
                                else if (res["status"] == "OVER_QUERY_LIMIT")
                                {
                                    return;
                                }
                            }
                        }
                    }
                }
                catch (Exception e)
                {

                }

                db.SaveChanges();
            }
        }
    }

来源：https://stackoverflow.com/questions/38697965/ef-core-system-invalidoperationexception-executereader-requires-an-open-and-a