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Bundle: dbsched

The dbsched bundle is preconfigured with the Pado scheduler to periodically execute jobs that dump database tables to CSV files from which it automatically extracts column information to generate the corresponding VersionedPortable classes. It then transforms the CSV records to objects using the generated classes before ingesting them into Hazelcast.

Installing Bundle

install_bundle -download  bundle-hazelcast-3n4n5-app-pado_dbsched-perf_test_dbsched-docker-mysql

Use Case

In this use case, to control the system load, the IT department has put restrictions on applications from accessing the database in real time, especially during the business hours. Only select applications are allowed to read the database in a batch mode. Writes are not permitted. Our task is to download the data from the database and feed it to Hazelcast as follows:

1. Dump table contents to CSV files
2. Create VersionedPortable classes based on CSV file contents
3. Transform CSV records to objects
4. Ingest the transformed data into Hazelcast
5. Automate and schedule jobs to periodically repeat the above steps

Bundle Contents

apps
├── pado_dbsched
└── perf_test_dbsched

docker
└── mysql

Hazelcast Cluster

Let's create a new Hazelcast cluster. Make sure to name the cluster dbsched. The scheduler has been preconfigured with the dbsched cluster. See Step 3 in Configuring and Running Pado Scheduler.

# Create dbsched
create_cluster -product hazelcast -cluster dbsched

# Switch to the dbsched cluster so that we are in the Hazelcast cluster context
switch_cluster dbsched

Job Scheduler and ETL

This bundle includes the Pado scheduler to simplify the ETL process. The Pado scheduler offers the following:

1. Schedule jobs that execute SQL queries and dump the results to CSV files.
2. Automatically generate Hazelcast VersionedPortable classes based on CSV file contents.
3. Automatically generate schema (metadata) files for ingesting VersionedPortable objects into Hazelcast maps.
4. Transform CSV file contents to VersionedPortable objects.
5. Ingest VersionedPortable objects into Hazelcast.

We could also use the popular schedulers like Spring Cloud Data Flow and Apache Nifi but we would need to manually perform data transformation.

Database: nw Schema

Open MySQL Workbench and create the nw schema. When you run the test_group script (see below), the customers and orders tables will automatically be created by Hibernate.

MySQL Docker Container

If you prefer to use Docker to start MySQL, start the MySQL container as follows.

cd_docker mysql
docker compose up -d

MySQL root account is setup as follows:

Parameter	Value
Adminer URL	http://localhost:8080
MySQL User	root
MySQL Password	rootpw
MySQL Port	3306

Create the nw database using Adminer.

• Login to MySQL from Adminer URL
• Select SQL command from Adminer
• Execute the following:

create database nw; 

Building perf_test_dbsched

We need to download the MySQL binary files by building perf_test_dbsched as follows.

cd_app perf_test_dbsched/bin_sh
./build_app

Configuring Hibernate

The perf_test_dbsched app has been preconfigured to connect to MySQL on localhost with the user name root and the password rootpw. You can change the user name and password in etc/hibernate.cfg-mysql.xml. We will be using the perf_test app to load data directly into the database tables. After the database has been loaded with data, we will execute the use case by first dumping database tables to CSV files.

# Change database user name and password in the Hibernate config file.
cd_app perf_test_dbsched
vi etc/hibernate.cfg-mysql.xml

Loading Data into Database

Let's load mock data into the nw.customers and nw.oders tables by executing the test_group -db command. The -db option directly loads data into the database instead of Hazelcast.

cd_app perf_test_dbsched/bin_sh
./test_group -db -run -prop ../etc/group-factory.properties

Building Pado App

cd_app pado_dbsched/bin_sh
./build_app

Configuring and Running Pado Scheduler

1. Encrypt the database password. Copy the encrypted password.

cd_app pado_dbsched
cd pado_<version>/bin_sh/tools
./encryptor

2. Copy the included scheduler job to the scheduler's data directory.

cd_app pado_dbsched
cp -r scheduler pado_<version>/data/

3. Edit the job file and enter the user name and encrypted password.

cd pado_<version>/data/scehduler/etc
vi mysql.json

The mysql.json file contents are shown below. It configures the Pado scheduler to import the nw.customers table once a day at midnight and the nw.orders table every hour.

Note that the GridId attribute must be set to the Hazelcast cluster name. In our case, it is set to dbsched.

{
        "Driver": "com.mysql.cj.jdbc.Driver",
        "Url": "jdbc:mysql://localhost:3306/nw?allowPublicKeyRetrieval=true&serverTimezone=America/New_York",
        "User": "root",
        "Password": "",
        "Delimiter": ",",
        "Null": "'\\N'",
        "GridId": "dbsched",
        "Paths": [
                {
                        "Path": "nw/customers",
                        "Columns": "customerId, address, city, companyName, contactName, contactTitle, country, fax, phone, postalCode, region",
                        "Query": "select * from nw.customers",
                        "Day": "Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday",                                "Time": "00:00:00"
                },
                {
                        "Path": "nw/orders",
                        "Columns": "orderId, customerId, employeeId, freight, orderDate, requiredDate, shipAddress, shipCity, shipCountry, shipName, shipPostalCode, shipRegion, shipVia, shippedDate",
                        "Query": "select * from nw.orders",
                        "Day": "Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday",                                "Time": "00:00:00, 01:00:00, 02:00:00, 03:00:00, 04:00:00, 05:00:00, 06:00:00, 07:00:00, 08:00:00, 09:00:00, 10:00:00, 11:00:00, 12:00:00, 13:00:00, 14:00:00, 15:00:00, 16:00:00, 17:00:00, 18:00:00, 19:00:00, 20:00:00, 21:00:00, 22:00:00, 23:00:00"
                }
        ]
}

❗️ Note that serverTimezone is set to America/New_York for the JDBC URL. Without it, you may see the following exception if your MySQL uses the system timezone and unable to calculate the dates due to the leap year.

com.mysql.cj.exceptions.WrongArgumentException: HOUR_OF_DAY: 2 -> 3

4. We need to first execute the mysql.json job without scheduling it to generate the schema files. Run the following command to download data into CSV files in the default data/scheduler/import directory.

cd_app pado_dbsched
cd pado_<version>/bin_sh/hazelcast
./import_scheduler -now

5. Generate schema files using the downloaded data files.

./generate_schema -schemaDir data/scheduler/schema -dataDir data/scheduler/import -package org.hazelcast.data.demo.nw

6. Generate the corresponding VersionedPortable source code in the default src/generated directory.

./generate_versioned_portable -schemaDir data/scheduler/schema -fid 20000 -cid 20000

7. Add the generated factory class information in the cluster's configuration file.

switch_cluster dbsched
vi etc/hazelcast.xml

Add the following towards the bottom of the etc/hazelcast.xml file:

   <serialization>
   ...
      <portable-factory factory-id="20000">
       org.hazelcast.data.demo.nw.PortableFactoryImpl
      </portable-factory>
   </serialization>

8. Compile the generated code and deploy the generated jar file to the workspace plugins directory so that it will be included in the cluster class path.

cd_app pado_dbsched
cd pado_<version>/bin_sh/hazelcast
./compile_generated_code
cp ../../dropins/generated.jar $PADOGRID_WORKSPACE/plugins/

9. Start Hazelcast cluster.

# Stat cluster
start_cluster

10. Import the downloaded data into the cluster.

cd_app pado_dbsched
cd pado_<version>/bin_sh/hazelcast
./import_scheduler -import

11. Execute the read_cache command to verify the data in the Hazelcast cluster.

cd_app perf_test_dbsched
./read_cache nw/customers
./read_cache nw/orders

12. Execute the following SQL statements in your database to verify the data.

select * from nw.customers;
select * from nw.orders;

13. Once you are satisfied with the results, you can schedule the job by executing the following.

cd_app pado_dbsched
cd pado_<version>/bin_sh/hazelcast
./import_scheduler -sched

Output:

./import_scheduler started. Please see the following log files for status:
   /Users/dpark/Padogrid/workspaces/rwe-bundles/bundle-hazelcast-3n4n5-app-pado_dbsched-perf_test_dbsched-docker-mysql/apps/pado_dbsched/pado_0.5.0-B1-SNAPSHOT/log/./import_scheduler.log

14. Check the scheduler's log file to verify the scheduled jobs.

 cat  /Users/dpark/Padogrid/workspaces/rwe-bundles/bundle-hazelcast-3n4n5-app-pado_dbsched-perf_test_dbsched-docker-mysql/apps/pado_dbsched/pado_0.5.0-B1-SNAPSHOT/log/./import_scheduler.log

Output:

[info 2024/03/19 11:41:12.809 EDT <main main> tid=1] ImportScheduler started. All import results are logged in this file.
isSched=true
isNow=false
isImport=false
[config 2024/03/19 11:41:13.079 EDT <main main> tid=1] com.netcrest.pado.tools.db.DbManager.logScheduledList(DbManager.java:394): DB import tasks scheduled:
1. SUNDAY 00:00:00 dbsched//nw/customers [select * from nw.customers]
2. SUNDAY 00:00:00 dbsched//nw/orders [select * from nw.orders]
3. SUNDAY 01:00:00 dbsched//nw/orders [select * from nw.orders]
4. SUNDAY 02:00:00 dbsched//nw/orders [select * from nw.orders]
...
174. SATURDAY 22:00:00 dbsched//nw/orders [select * from nw.orders]
175. SATURDAY 23:00:00 dbsched//nw/orders [select * from nw.orders]

As you can see from the above log output, the nw.customers table is scheduled to be imported to the nw/customers map every Sunday at 00:00:00. The nw.orders table, on the other hand, is secheduled to be imported to the nw/orders map every hour.

15. Try updating the database to see if the updates get imported into Hazelcast. Keep in mind that you will need to wait up to an hour before the updates make to Hazelcast.

Tearing Down

# Stop the Hazelcast cluster
stop_cluster

# Run jps to find and kill the 'HazelcastImportScheduler' process
jps |grep HazelcastImportScheduler | kill -9 $(awk '{print $1}')

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