CODEWITHSUNDEEP
typescriptaws-lambdaamazon-rdstypeormamazon-rds-proxy
Rafael J Silva
Rafael J Silva

Reputation: 71

How to check if a connection is still established to the database using TypeORM?

I'm using typeorm "typeorm": "0.3.9" in a serverless architecture using AWS lambdas + RDS Proxy.

Following some suggestions I found on the internet, I chose to keep a connection open after the lambdas are executed so that it can be reused by the next lambda execution.

My problem is that there is a scenario where my RDS Proxy closes a connection (which it considers idle) but the reference of that connection is still being used by a lambda and then an error occurs.

To solve this problem I tried using typeorm to check if there is an active connection with the following code:

// Returns true even when the RDS Proxy has already killed the connection.
if (!this.dataSource.isInitialized) {
  await this.dataSource.initialize();
}

When I tested it I noticed that this validation understands that there is an established connection even when the RDS Proxy has already killed the connection.

Can anyone suggest me a way to check if there is an established connection to the database before opening a new connection?

Upvotes: 1

Views: 1426

Answers (1)

David Parish
David Parish

Reputation: 131

I was able to find a good solution for this. Just run a query and re-establish the connection if it fails.

This is a snippet from a middy middleware but you should be able to see what I mean....

      if (datasource) {
        try {
          // run a quick query to validate the connection, the lambda may have destroyed it
          await datasource.query('select version()');
          request.context.datasource = datasource;
          // We have a valid connection we can return;
          return;
        } catch (e) {
          console.warn('check connection failed, re-establishing connection', e);
          datasource = undefined;
        }
      }
      ... establish a connection

Upvotes: 0

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