I have an application in Delphi under fireDac(fdconnection, Datasource...ect) which uses an access database stored on a server via an SMB share.
When I create a connection to an Access database, no problem for the connection or the requests.
However, if I stop and restart the service, it seems that the connection does not work anymore.
Although the service is ok, it seems that the connection is stuck on the old connection and the only way to restore this is to restart the application.
Is there a way to refreshing the connection ?
i used closeConnectionDef(https://docwiki.embarcadero.com/Libraries/Sydney/en/FireDAC.Comp.Client.TFDCustomManager.CloseConnectionDef) but no result
Related
I was testing my SpringBoot app which connects to a remote SQL database. I was also using MySQL workbench to view the tables. Then when I tried to run my app, it gave an error message as follows:
Data source rejected establishment of connection, message from server: "Too many connections"
I have tried restarting my PC but it still gives the same error. How can I solve it? I believe the previous connection was not properly closed. What can I do now?
The connections are automatically closed (or return to the connection pool) if you are using Spring Data Repository or JdbcTemplate. Your application may really need too many connections compared to your database limit, in that case you should check your database configuration. You can also check your connection properties in application.properties (pool size, idle time, timeout). Please add more details like code or configuration.
Last night AWS RDS had an "Internet Connectivity Issue" that was resolved a short time later. However, my app (which runs in .NET Core and connects to an RDS MySQL instance via Pomelo.EntityFrameworkCore.MySql) could never re-establish a connection to the database even though the MySQL server was back online. I tested connecting from my own local machine and it worked just fine. I then re-deployed the .NET Core app it everything started working again.
Is there something that I need to re-create (the db context perhaps), or is there something that is being cached that I need to flush to try to connect again? I connect via hostname, and my connection string looks something like this:
server=something.somewhere.us-east-2.rds.amazonaws.com;userid=XXXX;password=YYYYY;database=ZZZZ
Here is the Exception being thrown:
MySqlException: Unable to connect to any of the specified MySQL hosts.
at MySqlConnector.Core.ServerSession+<ConnectAsync>d__56.MoveNext (C:\projects\mysqlconnector\src\MySqlConnector\Core\ServerSession.cs:239)
and here is how I create my db context in Startup.cs:
services.AddDbContext<BlayFapContext>(opt => opt.UseMySql(Settings.Instance.SQLConnectionString));
Any help would be greatly appreciated.
Giawa
Okay, we worked out what happened. Pomelo's MySQL wrapper had an issue as outlined in their git repo here: https://github.com/PomeloFoundation/Pomelo.EntityFrameworkCore.MySql/issues/434
Basically, if a MySQL database is not available when the connection string is first used then it will be cached as invalid and will never work again. You can easily confirm this by launching a service with no MySQL connectivity, verify it doesn't work, then launch MySQL and confirm that the service still doesn't work. It can never establish a MySQL connection after the first connection string is found to be invalid.
They patched it shortly after the 2.0.1 release, but they haven't updated Nuget with a new version since then, despite the issue being found 6 months ago. So, the fix is to checkout their repository source code, and patch it ourselves. We found the fix here works just fine: https://github.com/PomeloFoundation/Pomelo.EntityFrameworkCore.MySql/pull/456
So, why was the connection string retried? We already had a successful connection! It turns out that the internet connectivity issue with the Ohio data center was not limited to RDS, but also affected EC2. Our EC2 instance was rebooted as part of the fix, and the MySQL connection wasn't valid when it reboot due to the continued connectivity issues. The state of that connection was cached, and even though the MySQL server came back online our service was toast.
Giawa
I'm using Outsystems Service Studio to develop a web application. I need to configure a connection to access a local server database. I get "Connection String test failed: Unable to connect to any of the specified MySQL hosts." I just figured out I can't connect using "localhost", because the Outsystems server is not local, but I'm not able to find a solution. what is wrong? Other details:
MySQL Server is up and running
I selected MySQL in DBMS
Inserted my schema name
Inserted the username (with all privileges granted)
Inserted the user password
Tried both basic and advanced configuration. I inserted j"dbc:mysql://127.0.0.1:3306/mydb?user=outsystems2" as connection string parameters and I get "Connection String test failed: Keyword not supported.Parameter name: mysql://127.0.0.1:3306/mydb?user". I know this connection string can't work , but I'm not able to find a functioning one. I've read many guides about this configuration, but no solution was found. Thank you all for your time and help, feel free to ask for more details
Luciano,
Is your OutSystems environment on-premises or in the cloud? Either way, you need to make sure that this server is able to reach - it as connectivity - to your MySQL database server. Using localhost or 127.0.0.1 is pretty much the same thing as this is an address for the machine where the request is running, which is, in this case, the OutSystems server. Do you have the MySQL database on your local machine? This is not a good approach as you will need to have an address that won't change otherwise the connection won't be stable and you'd have to reconfigure it all the time.
Regards
I have a mysql backend and a ms access 2013 frontend, I configured a odbc connection at system level so it´s available to all users in the computer. But Now I realized that you can easily just open a new database and pull all my tables from that odbc connection and see the credentials.
I´ve already try with user level odbc, the database simply doesn´t log.
How can I stop the users from being able to do such a thing?
Use a DSN-less connection plus connection caching.
Both are explained in this answer: https://stackoverflow.com/a/23430539/3820271
Then distribute your frontend as accde, so the source code isn't available.
I am running Ghost as a web service on Microsoft azure. I am using MySql Database for storage instead of the default Sqlite. Every time i open the blog i get a Econnreset error with status as 500, and Sql query is being shown.
I have MySql Running in a virtual machine. But everything works out fine on refresh. I am also using connection pooling.
How to rectify this, or what can be the probable reason for Ghost to drop connection with database.
Solved the problem. Issue is with the underlying Knex MySql Driver. When the connection remains Idle Azure closes the connection, when the request is made again knex does not check if the connection is still there or not leading to Econnreset Error.
You can fix this by setting min number of connections to be zero in knex.
For more details follow this issue:
https://github.com/tgriesser/knex/issues/975
Is the mysql database hosted on another azure instance ?
If so you will need to make it available to the outside (Open the required ports).