"The connection attempt failed" Postgres at AWS Lambda

Question

I have a Postgres DB on AWS that is available outside. The connection works fine when I launch my app locally.

When I launch it on AWS lambda it gives me this error:

org.postgresql.util.PSQLException: The connection attempt failed.
    at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:292)
    at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49)
    at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:195)
    at org.postgresql.Driver.makeConnection(Driver.java:454)
    at org.postgresql.Driver.connect(Driver.java:256)
    at java.sql.DriverManager.getConnection(DriverManager.java:664)
    at java.sql.DriverManager.getConnection(DriverManager.java:270)
    at ninja.majewski.AmazonDbService.getRemoteConnection(AmazonDbService.java:84)
    at ninja.majewski.AmazonDbService.removeOldDeals(AmazonDbService.java:63)
    at ninja.majewski.ChinaStuffLambdaHandler.handleRequest(ChinaStuffLambdaHandler.java:19)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at lambdainternal.EventHandlerLoader$PojoMethodRequestHandler.handleRequest(EventHandlerLoader.java:259)
    at lambdainternal.EventHandlerLoader$PojoHandlerAsStreamHandler.handleRequest(EventHandlerLoader.java:178)
    at lambdainternal.EventHandlerLoader$2.call(EventHandlerLoader.java:888)
    at lambdainternal.AWSLambda.startRuntime(AWSLambda.java:292)
    at lambdainternal.AWSLambda.<clinit>(AWSLambda.java:64)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:348)
    at lambdainternal.LambdaRTEn
    try.main(LambdaRTEntry.java:94)

This is the code that fails:

private Connection getRemoteConnection() throws Exception {
    Class.forName("org.postgresql.Driver");
    String dbName = System.getenv("RDS_DB_NAME");
    String userName = System.getenv("RDS_USERNAME");
    String password = System.getenv("RDS_PASSWORD");
    String hostname = System.getenv("RDS_HOSTNAME");
    String port = System.getenv("RDS_PORT");
    String jdbcUrl = "jdbc:postgresql://" + hostname + ":" + port + "/" + dbName + "?user=" + userName + "&password=" + password;
    log.info(String.format("Logging to DB: %s", jdbcUrl));
    return DriverManager.getConnection(jdbcUrl);
}

What could be the reason for this?

Is RDS_HOSTNAME set? Try to print it out, it could be null, the error shows that there is no suitable database host. — Karol Dowbecki
– Karol Dowbecki, Commented Nov 2, 2018 at 16:47
I print jdbcUrl variable and it is correct. If I copy it to IntelliJ it connects to DB correctly. All of these env variables are set — Krzysztof Majewski
– Krzysztof Majewski, Commented Nov 2, 2018 at 16:48
Is your RDS publicly accesible? If not, did you configured your lambda so it can access it? — yorodm
– yorodm, Commented Nov 2, 2018 at 16:51

Aweuzegaga · Accepted Answer · 2019-05-22 09:00:06Z

1

In your lambda you have to configurate the Network parameter. You have to add a VPC and a Security Group.

Once this Security Group is added to your lambda, you go to your EC2 Management Console in NETWORK & SECURITY -> Security Groups. Here you select the Security Group of your RDS Instance and you Edit the Inbound parameter. You add a Type PostgreSQL with a Custom Source with the name of the Security Group you just added to your Lambda.

answered May 22, 2019 at 9:00

Aweuzegaga

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