![]() ![]() Clear connections with a proxy functionĮven without SUPER privilege, RDS does allow SHOW PROCESSLIST which lets you view all open connections. ![]() This will throw an error in your Lambda function, but it is possible for you to gracefully handle that error with a Too many connections response or something else. MAX USER_CONNECTIONS can be limited to a number less than the max connections allowed by the RDS instance. Limit connections per usernameĪnother strategy is to set a resource limit on the number of connections a given db user can have. ![]() This isn’t necessarily ideal, since it will impact your users during high traffic situations, but it will prevent the database from maxing out connections. If your database only supports 1,000 concurrent connections, limit your Lambda function’s concurrent connections to something less that that. My code is always designed to reconnect if the connection drops, so even if “warm” containers lose their connection, this isn’t an issue. I’ve set these to 10 minutes in certain implementations and it seems to work well. RDS doesn’t give your root account the SUPER privilege, but you can create “RDS DB Parameter Groups” that allow you to set the wait_timeout and interactive_timeout to values more appropriate for serverless applications (the default is 8 hours). Your connect() call should always be INSIDE your handler and only called when your flow requires a connection. It’s possible that your thousands of concurrent requests might not actually need a database connection if they get data from a cache or are performing another action. You should also design your application to ONLY create a connection to RDS when you need to. REDIS’s maxclient default is 65,000, far greater than the connection limits for RDS. Implement a good caching strategyĪs your application scales, use something like REDIS to cache common data queries. Overall, I’ve found that Lambda is pretty good about closing database connections when the container expires, but even if it does it reliably, it still doesn’t solve the MAX CONNECTIONS problem. Here are several strategies that I’ve used to deal with this issue. Update August 9, 2018: Aurora Serverless is now Generally Available! Update September 2, 2018: I wrote an NPM module that manages MySQL connections for you in serverless environments. At the time of this writing it is still in preview mode. □♂️ Zombie RDS connections leftover on container expiration can become a problem when you start to reach a high number of concurrent Lambda executions. My guess is that this is why AWS is launching Aurora Serverless, to deal with relational databases at scale. I was wondering, is there some way to manage and/or end the connections without needing to wait for them to end on their own? The main issue I’m worried about is that these unused connections would remain for an excessive amount of time and prevent new connections that will actually be used from being made due to the limit on the number of connections. I found before that sometimes the connections would just die eventually. I’m playing around with AWS lambda and connections to an RDS database and am finding that for the containers that are not reused the connection remains. Someone asked a great question on my How To: Reuse Database Connections in AWS Lambda post about how to end the unused connections left over by expired Lambda functions: To make the above described scenario working we have to do a copule of things: Create user on MySQL instanceĬonnect to the instance and issue the following commands: mysql> CREATE USER '' IDENTIFIED WITH AWSAuthenticationPlugin as 'RDS' I’ve spent way too much time to solve the problem, but the documentation and examples on the Internet are lacking and wrong in some places… It’s time to document it right! Recently I’ve tried to write a lambda function in Go, which connects to MySQL database on RDS instance and use IAM Authentication instead of “traditional” approach with passwords (which I think is an anti-pattern in cloud environments). ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |