Deploying to Azure - Cannot connect to database

Question

I have recently subscribed for Azure free trial, and I'm currently trying to publish my website.

However, as I got my website published I encountered the following error:

[NullReferenceException: Object reference not set to an instance of an object.]
MySql.Data.MySqlClient.MySqlProviderServices.GetDbProviderManifestToken(DbConnection connection) +56
   System.Data.Entity.Core.Common.DbProviderServices.GetProviderManifestToken(DbConnection connection) +276
   System.Data.Entity.Utilities.DbProviderServicesExtensions.GetProviderManifestTokenChecked(DbProviderServices providerServices, DbConnection connection) +27
   System.Data.Entity.Infrastructure.<>c__DisplayClass1.<ResolveManifestToken>b__0(Tuple`3 k) +32
   System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory) +72
   System.Data.Entity.Infrastructure.DefaultManifestTokenResolver.ResolveManifestToken(DbConnection connection) +251
   System.Data.Entity.Utilities.DbConnectionExtensions.GetProviderInfo(DbConnection connection, DbProviderManifest& providerManifest) +56
   System.Data.Entity.DbModelBuilder.Build(DbConnection providerConnection) +43
   System.Data.Entity.Internal.LazyInternalContext.CreateModel(LazyInternalContext internalContext) +62
   System.Data.Entity.Internal.RetryLazy`2.GetValue(TInput input) +123
   System.Data.Entity.Internal.LazyInternalContext.InitializeContext() +610
   System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType(Type entityType) +18
   System.Data.Entity.Internal.Linq.InternalSet`1.Initialize() +53
   System.Data.Entity.Internal.Linq.InternalSet`1.get_InternalContext() +15
   System.Data.Entity.Infrastructure.DbQuery`1.System.Linq.IQueryable.get_Provider() +38

When I run this locally with the connection-string to my remote database it works fine, but as soon as I publish it it doesn't work.

My connection strings look like this:

<add name="DefaultConnection" connectionString="user id=****;password=****;persistsecurityinfo=False;server=**** ;database=iprospect_tools" providerName="MySql.Data.MySqlClient" />
<add name="ToolsEntities" connectionString="metadata=res://*/ToolsModel.csdl|res://*/ToolsModel.ssdl|res://*/ToolsModel.msl;provider=MySql.Data.MySqlClient;provider connection string=&quot;user id=****;password=****;persistsecurityinfo=False;server=****;database=tools&quot;" providerName="System.Data.EntityClient" />

When I remote debug my application, this is the error evaluation:

Any idea what might be causing this error?

Where is your database & website hosted in Azure (which service)? And are you able to ping the database from you instance in azure. — Kaushal Kumar Panday, Aug 09 '17 at 13:38
My website is hosted as a web app and my database is hosted as a MySQL database. I'm not sure where to ping the database from my instance in Azure - could you tell me where I can do that? — Frederik Hansen, Aug 11 '17 at 13:48
You can use the command console via the kudu. To access kudu browse to https://sitename.scm.azurewebsites.net/DebugConsole. Here you can use tcpping.exe to ping the hostname on a specific port. `tcpping hostname:port` — Kaushal Kumar Panday, Aug 11 '17 at 14:05
Is the server specified in the connection string fully qualified? if not, then provide the full name. — Kaushal Kumar Panday, Aug 11 '17 at 15:09
I will suggest you try remote debugging to see what is causing this to fail — Kaushal Kumar Panday, Aug 11 '17 at 15:10
The connection string should be fine - after all it works when I run it locally, but fails as soon as it's published to Azure. I've added the VS evaluation of the error causing my problems to the post. — Frederik Hansen, Aug 14 '17 at 10:58
I'm not sure - I've succesfully tried pinging the database as @KaushalKumarPanday suggested. Where would I grant access to MySQL? — Frederik Hansen, Aug 14 '17 at 20:22
Did you setup the connection string in settings or only web.config - https://azure.microsoft.com/en-us/resources/videos/configuration-and-app-settings-of-azure-web-sites/ and also look @ https://azure.microsoft.com/en-us/blog/windows-azure-web-sites-how-application-strings-and-connection-strings-work/ — Arun Vinoth-Precog Tech - MVP, Aug 15 '17 at 16:32
https://stackoverflow.com/questions/14459748/how-do-i-set-an-ado-net-entity-framework-connection-string-via-the-windows-azure — Arun Vinoth-Precog Tech - MVP, Aug 15 '17 at 16:43
https://stackoverflow.com/questions/31149693/setting-ef-connection-string-in-azure-web-app — Arun Vinoth-Precog Tech - MVP, Aug 15 '17 at 16:43

score 6 · Answer 1 · answered Aug 16 '17 at 21:25

There is some informatin missing form your question that would make providing a consice answer easier, but here is what I would do:

Figure out where the db is being hosted

The first thing to do here is to figure out what service you are using for your MySQL database. In Azure there are at least four ways to host a MySQL database and each one might require different steps.

MySQL in App Since you are doing a remote connection from your desktop I don't think you are using this option.
MySQL provided by ClearDB If you are using this, then server name would be something like: us-cdbr-azure-*.cloudapp.net
MySQL provided by Microsoft If you are using this, then server name would be something like: *.mysql.database.azure.com
MySQL hosted in an IaaS VM If you are using this, then server name would be something like: *.cloudapp.net

If the database is not hosted in Azure, then you should check network configuration.

Create a simplest app possible to test connectivity.

Assuming your DB is hosted in Azure the next step is to reduce your dependencies in an effort to identify if the issue lies with the Db server, network config, your code, or another dependency.

 string myConnectionString = "your-connectionstring-goes-here";
    try{
        using (var con = new MySqlConnection { ConnectionString = myConnectionString }){
            con.Open();

            if (!con.Ping()){
                System.Diagnostics.Trace.TraceError("MySQL Ping Failed:");
            }
            else{
                System.Diagnostics.Trace.TraceInformation("MySQL Successfull");
            }
        }
    }
    catch (Exception exep){
        System.Diagnostics.Trace.TraceError("Could not connect to MySQL: " + exep.Message);
    }

Note that in this example we are hard-coding the connection string into the code to bypass even web-config.

If this is working then we know connectivity to the DB is good and the app service app can reach the DB. Skip step (3) and go to step (4)

If it's not working then the we still have a bit more debugging to do. Go to step (3)

Fix network/firewall on DB server
- If your DB is being hosted by Microsoft MySQL check to make sure the Firewall is allowing your app to connect to it and repeat step (2)
- If your DB is being hosted in an IaaS VM make sure the ports and network are open to accepct connections and repeat step (2)

Once you get step (2) to work then try with your code again.

Debug your code

Once you get step (2) working and then that rules out connectivity issues. That means that the bug is in your code, connection string config or the way you are using Entity Framework.

Hope this helps

score 1 · Answer 2 · answered Aug 15 '17 at 17:27

1

If the website is working locally, and database connection failing after publishing to Azure - definitely config is missing in Azure website Settings.

Check out these SO thread 1 and SO thread 2

answered Aug 15 '17 at 17:27

Arun Vinoth-Precog Tech - MVP

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Deploying to Azure - Cannot connect to database

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