从本地机器到 AWS RDS PostgreSQL 数据库的连接速度非常慢

Question

I've looked everywhere for an answer to this problem. I found a similar (unanswered) question on SO but not related to Java or SSL issues.

Important Information:

• The database I connect to is PostgreSQL on RDS.
• I can actually connect to the DB (it takes about 3 minutes to establish the connection). After the connection is established, simple queries take between 15-120 seconds.
• The problem only happens when connecting from my code.
• Connecting from Postico (on the same machine) works perfectly.
• Deploying to AWS EC2 the exact same connection works perfectly.
• I have added the RDS certificates to the keystore.
• The RDS force_ssl parameter is set to true.
• Notice the + "?ssl=true" parameter at the end of the connection string.
• Tested replacing the domain by the direct IP (to rule out DNS problems). Same thing.

I suspect it has something to do with SSL but can't confirm it.

This is my connection (pretty standard):

    String dbUriString = ConfigUtils.getEnv("DATABASE_URL");

    URI dbUri = new URI(dbUriString);

    String username = dbUri.getUserInfo().split(":")[0];
    String password = dbUri.getUserInfo().split(":")[1];
    String dbUrl = "jdbc:postgresql://" + dbUri.getHost() + ':' + dbUri.getPort() + dbUri.getPath() + "?ssl=true";

    ComboPooledDataSource datasource = new ComboPooledDataSource();

    datasource.setUser(username);
    datasource.setPassword(password);
    datasource.setJdbcUrl(dbUrl);
    datasource.setDriverClass("org.postgresql.Driver");

    datasource.setMaxPoolSize(20);
    datasource.setMinPoolSize(5);
    datasource.setAcquireIncrement(1);
    datasource.setAcquireRetryAttempts(3);
    datasource.setInitialPoolSize(5);
    datasource.setTestConnectionOnCheckout(true);

    return datasource;

A little more information:

• It's a Play Framework application.
• Java 8.
• DataSource connector c3p0.

Any help is deeply appreciated.

Answer 1

Connecting to our Postgres database on AWS took up to a minute or two to estabilish a connection, then it worked fine.

The reason turned out to be DNS resolution.

I ran telnet <database host> 5432 and discovered it was trying to connect to an IPv6 connection. After a minute or so, it would time out and try the IPv4 connection, which worked instantly.

Running dscacheutil -q host -a name <database host> on my macOS machine indeed showed the database host was resolved to an IPv6 and IPv4 address.

I changed the DNS settings on my machine. Specifically, I told my VPN client to use Google's DNS servers for the amazonaws.com domain. After that, everything worked perfectly. Indeed, on rerunning dscacheutil -q host -a name <database host> , I only saw the IPv4 address this time.

No idea by the IPv6 connection wasn't working, but the short of it was that DNS was part of the issue.