Java Access Apache Kudu: Table Creation to CRUD (Includin...

Dependency Import

<dependency>
  <groupId>org.apache.kudu</groupId>
  <artifactId>kudu-client</artifactId>
  <version>1.4.0</version>
</dependency>

Create Table

package icu.wzk.kudu;
public class KuduCreateTable {
    public static void main(String[] args) throws KuduException {
        String masterAddress = "localhost:7051,localhost:7151,localhost:7251";
        KuduClient.KuduClientBuilder kuduClientBuilder = new KuduClient.KuduClientBuilder(masterAddress);
        KuduClient kuduClient = kuduClientBuilder.build();
        String tableName = "student";
        List<ColumnSchema> columnSchemas = new ArrayList<>();
        ColumnSchema id = new ColumnSchema
                .ColumnSchemaBuilder("id", Type.INT32)
                .key(true)
                .build();
        columnSchemas.add(id);
        ColumnSchema name = new ColumnSchema
                .ColumnSchemaBuilder("name", Type.STRING)
                .key(false)
                .build();
        columnSchemas.add(name);
        Schema schema = new Schema(columnSchemas);
        CreateTableOptions options = new CreateTableOptions();
        options.setNumReplicas(1);
        List<String> colrule = new ArrayList<>();
        colrule.add("id");
        options.addHashPartitions(colrule, 3);
        kuduClient.createTable(tableName, schema, options);
        kuduClient.close();
    }
}

Delete Table

package icu.wzk.kudu;
public class KuduDeleteTable {
    public static void main(String[] args) throws KuduException {
        String masterAddress = "localhost:7051,localhost:7151,localhost:7251,";
        KuduClient client = new KuduClient.KuduClientBuilder(masterAddress)
                .defaultAdminOperationTimeoutMs(5000)
                .build();
        client.deleteTable("student");
        client.close();
    }
}

Insert Data

package icu.wzk.kudu;
public class KuduInsert {
    public static void main(String[] args) throws KuduException {
        String masterAddr = "localhost:7051,localhost:7151,localhost:7251";
        KuduClient client = new KuduClient
                .KuduClientBuilder(masterAddr)
                .defaultAdminOperationTimeoutMs(5000)
                .build();
        KuduTable stuTable = client.openTable("student");
        KuduSession kuduSession = client.newSession();
        kuduSession.setFlushMode(SessionConfiguration.FlushMode.MANUAL_FLUSH);
        Insert insert = stuTable.newInsert();
        insert.getRow().addInt("id", 1);
        insert.getRow().addString("name", "wzk");
        kuduSession.flush();
        kuduSession.apply(insert);
        kuduSession.close();
        client.close();
    }
}

KuduSession Flush Mode Notes:

• AUTO_FLUSH_SYNC (default): After calling apply, client refreshes to server before returning, doesn’t support batch insert
• AUTO_FLUSH_BACKGROUND: Returns immediately after calling apply, sends in background, may be out of order (KUDU-1767)
• MANUAL_FLUSH: Returns quickly after calling apply, write operations not sent, requires user to call flush function

Query Data

package icu.wzk.kudu;
public class KuduSelect {
    public static void main(String[] args) throws KuduException {
        String masterAddr = "localhost:7051,localhost:7151,localhost:7251";
        KuduClient client = new KuduClient
                .KuduClientBuilder(masterAddr)
                .build();
        KuduTable kuduTable = client.openTable("user");
        KuduScanner kuduScanner = client.newScannerBuilder(kuduTable).build();
        while (kuduScanner.hasMoreRows()) {
            for (RowResult result : kuduScanner.nextRows()) {
                int id = result.getInt("id");
                String name = result.getString("name");
                int age = result.getInt("age");
                System.out.println("id: " + id + ", name: " + name + ", age: " + age);
            }
        }
        client.close();
    }
}

Update Data

package icu.wzk.kudu;
public class KuduUpdate {
    public static void main(String[] args) throws KuduException {
        String masterAddress = "localhost:7051,localhost:7151,localhost:7251";
        KuduClient client = new KuduClient
                .KuduClientBuilder(masterAddress)
                .build();
        KuduTable stuTable = client.openTable("student");
        KuduSession kuduSession = client.newSession();
        kuduSession.setFlushMode(SessionConfiguration.FlushMode.MANUAL_FLUSH);
        Update update = stuTable.newUpdate();
        update.getRow().addInt("id", 1);
        update.getRow().addString("name", "wzk_icu");
        kuduSession.apply(update);
        kuduSession.close();
        client.close();
    }
}

Delete Data

package icu.wzk.kudu;
public class KuduDelete {
    public static void main(String[] args) throws KuduException {
        String masterAddress = "localhost:7051,localhost:7151,localhost:7251";
        KuduClient client = new KuduClient
                .KuduClientBuilder(masterAddress)
                .build();
        KuduSession kuduSession = client.newSession();
        KuduTable stuTable = client.openTable("student");
        kuduSession.setFlushMode(SessionConfiguration.FlushMode.MANUAL_FLUSH);
        Delete delete = stuTable.newDelete();
        PartialRow row = delete.getRow();
        row.addInt("id", 1);
        kuduSession.flush();
        kuduSession.apply(delete);
        kuduSession.close();
        client.close();
    }
}

Error Quick Reference

Symptom	Root Cause Location	Fix
No error in console but data not in table	MANUAL_FLUSH called flush before apply, order reversed	Change to apply before flush
UnknownHostException/connection exception	Extra comma at end of Master address	Remove trailing comma
Not found: table user	Query table name different from creation	Unify table names
Column read error	Schema doesn’t contain that column	Add to Schema
Read update/delete ineffective	MANUAL_FLUSH not flushed	Explicit flush after apply
Out of order	AUTO_FLUSH_BACKGROUND concurrent send	Change to sync/manual batch
Cannot connect to Leader Master	Master not started/wrong port	Check Master status
Insert/update lost writes	Not checking errors	Check getPendingErrors() after each flush