GaussDB(DWS) Source Table

Function

DLI reads data of Flink jobs from GaussDB(DWS). GaussDB(DWS) database kernel is compliant with PostgreSQL. The PostgreSQL database can store data of more complex types and deliver space information services, multi-version concurrent control (MVCC), and high concurrency. It applies to location applications, financial insurance, and e-Commerce.

GaussDB(DWS) is an online data processing database based on the cloud infrastructure and platform and helps you mine and analyze massive sets of data. For more information about GaussDB(DWS), see Data Warehouse Service Management Guide.

Prerequisites

• You have created a GaussDB(DWS) cluster.

  For details about how to create a GaussDB(DWS) cluster, see Creating a Cluster in the Data Warehouse Service Management Guide.

• You have created a GaussDB(DWS) database table.
• An enhanced datasource connection has been created for DLI to connect to GaussDB(DWS) clusters, so that jobs can run on the dedicated queue of DLI and you can set the security group rules as required.
  • For details about how to set up an enhanced datasource connection, see Enhanced Datasource Connections in the Data Lake Insight User Guide.
  • For details about how to configure security group rules, see Security Group Overview in the Virtual Private Cloud User Guide.
• In Flink cross-source development scenarios, there is a risk of password leakage if datasource authentication information is directly configured. You are advised to use the datasource authentication provided by DLI.

  For details about datasource authentication, see Introduction to Datasource Authentication.

Precautions

When creating a Flink OpenSource SQL job, you need to set Flink Version to 1.12 on the Running Parameters tab of the job editing page, select Save Job Log, and set the OBS bucket for saving job logs.

Syntax

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create table dwsSource (
  attr_name attr_type 
  (',' attr_name attr_type)* 
  (','PRIMARY KEY (attr_name, ...) NOT ENFORCED)
  (',' watermark for rowtime_column_name as watermark-strategy_expression)
)
with (
  'connector' = 'gaussdb',
  'url' = '',
  'table-name' = '',
  'username' = '',
  'password' = ''
);

Parameters

Example

In this example, data is read from the GaussDB(DWS) data source and written to the Print result table. The procedure is as follows:

1. Create a table named dws_order in GaussDB(DWS).

   create table public.dws_order(
     order_id VARCHAR,
     order_channel VARCHAR,
     order_time VARCHAR,
     pay_amount FLOAT8,
     real_pay FLOAT8,
     pay_time VARCHAR,
     user_id VARCHAR,
     user_name VARCHAR,
     area_id VARCHAR);

   Insert data into the dws_order table.

   insert into public.dws_order
     (order_id,
     order_channel,
     order_time,
     pay_amount,
     real_pay,
     pay_time,
     user_id,
     user_name,
     area_id) values
     ('202103241000000001', 'webShop', '2021-03-24 10:00:00', '100.00', '100.00', '2021-03-24 10:02:03', '0001', 'Alice', '330106'),
     ('202103251202020001', 'miniAppShop', '2021-03-25 12:02:02', '60.00', '60.00', '2021-03-25 12:03:00', '0002', 'Bob', '330110');

2. Create an enhanced datasource connection in the VPC and subnet where GaussDB(DWS) locates, and bind the connection to the required Flink elastic resource pool. For details, see Enhanced Datasource Connections.
3. Set GaussDB(DWS) security groups and add inbound rules to allow access from the Flink queue. Test the connectivity using the GaussDB(DWS) address by referring to Testing Address Connectivity. If the connection is successful, the datasource is bound to the queue. Otherwise, the binding fails.
4. Create a Flink OpenSource SQL job. Enter the following job script and submit the job. The job script uses the GaussDB(DWS) data source and the Print result table.
   When you create a job, set Flink Version to 1.12 on the Running Parameters tab. Select Save Job Log, and specify the OBS bucket for saving job logs. Change the values of the parameters in bold as needed in the following script.

   CREATE TABLE dwsSource (
     order_id string,
     order_channel string,
     order_time string,
     pay_amount double,
     real_pay double,
     pay_time string,
     user_id string,
     user_name string,
     area_id string
   ) WITH (
     'connector' = 'gaussdb',
     'url' = 'jdbc:postgresql://DWSIP:DWSPort/DWSdbName',
     'table-name' = 'dws_order',
     'driver' = 'org.postgresql.Driver',
     'username' = 'DWSUserName',
     'password' = 'DWSPassword'
   );
   
   CREATE TABLE printSink (
     order_id string,
     order_channel string,
     order_time string,
     pay_amount double,
     real_pay double,
     pay_time string,
     user_id string,
     user_name string,
     area_id string
   ) WITH (
     'connector' = 'print'
   );
   
   insert into printSink select * from dwsSource;

5. Perform the following operations to view the data result in the taskmanager.out file:
   1. Log in to the DLI console. In the navigation pane, choose Job Management > Flink Jobs.
   2. Click the name of the corresponding Flink job, choose Run Log, click OBS Bucket, and locate the folder of the log you want to view according to the date.
   3. Go to the folder of the date, find the folder whose name contains taskmanager, download the taskmanager.out file, and view result logs.

   The data result is as follows:

   +I(202103241000000001,webShop,2021-03-24 10:00:00,100.0,100.0,2021-03-24 10:02:03,0001,Alice,330106)
   +I(202103251202020001,miniAppShop,2021-03-25 12:02:02,60.0,60.0,2021-03-25 12:03:00,0002,Bob,330110)

FAQ

• Q: What should I do if the job execution fails and the log contains the following error information?

  java.io.IOException: unable to open JDBC writer
  ...
  Caused by: org.postgresql.util.PSQLException: The connection attempt failed.
  ...
  Caused by: java.net.SocketTimeoutException: connect timed out

  A: The datasource connection is not bound or the binding fails.

  • To reconfigure datasource connections, refer to Enhanced Datasource Connection. Rectify the fault by referring to DLI Failed to Connect to GaussDB(DWS) Through an Enhanced Datasource Connection.