Dataproc trying to connect to Postgres through JDBC, missing permissions

Question

Thanks in advance...

1. I want to connect/write using JDBC APIs to a Postgres SQL instance running using Cloud SQL programmatically. I have used following jars:
   1. postgresql
   2. postgres-socket-factory
   3. postgres-socket-factory-1.0.11-jar-with-dependencies.jar

I am running Dataproc which will try to connect using step #1, but I get following exception:

2019-04-01 11:05:03.998 IST
Something unusual has occurred to cause the driver to fail. Please report this exception.
    at org.postgresql.Driver.connect(Driver.java:277)
    at java.sql.DriverManager.getConnection(DriverManager.java:664)
    at java.sql.DriverManager.getConnection(DriverManager.java:270)
    at rdsConnector$.getConnection(rdsConnector.scala:33) 
    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 org.apache.spark.deploy.yarn.ApplicationMaster$$anon$4.run(ApplicationMaster.scala:721)
Caused by: java.lang.RuntimeException: Unable to retrieve information about Cloud SQL instance [projectID:us-east1:dB]
    at com.google.cloud.sql.core.SslSocketFactory.obtainInstanceMetadata(SslSocketFactory.java:459)
    at com.google.cloud.sql.core.SslSocketFactory.fetchInstanceSslInfo(SslSocketFactory.java:333)
    at com.google.cloud.sql.core.SslSocketFactory.getInstanceSslInfo(SslSocketFactory.java:313)
    at com.google.cloud.sql.core.SslSocketFactory.createAndConfigureSocket(SslSocketFactory.java:194)
    at com.google.cloud.sql.core.SslSocketFactory.create(SslSocketFactory.java:160)
    at com.google.cloud.sql.postgres.SocketFactory.createSocket(SocketFactory.java:96)
    at org.postgresql.core.PGStream.<init>(PGStream.java:62)
    at org.postgresql.core.v3.ConnectionFactoryImpl.tryConnect(ConnectionFactoryImpl.java:91)
    at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:192)
    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)
    ... 11 more
Caused by: com.google.api.client.googleapis.json.GoogleJsonResponseException: 403 Forbidden

2019-04-01 11:05:03.000 IST
User class threw exception: org.postgresql.util.PSQLException: Something unusual has occurred to cause the driver to fail. Please report this exception.

I understand this as a permission issue, but since I am using Dataproc to connect to Postgres what permission is missing? if I was running from a local laptop machine then I have to set GOOGLE_APPLICATION_CREDENTIALS to a json file. But what is the process in case of Dataproc?

Answer 1

The JDBC SocketFactory uses the Application Default Credentials strategy for accessing account credentials.

For Cloud Dataproc, a default service account is provided for you at [project-number][email protected]. You grant this account the "Cloud SQL Client" IAM role, the JDBC SocketFactory will use it to authenticate, and thus you will be able to connect to your application.