Java

{template ingester-lib-introduction%

The Java ingester SDK provided by GreptimeDB is a lightweight library with the following features:

• SPI-based extensible network transport layer, which provides the default implementation using the gRPC framework.
• Non-blocking, purely asynchronous API that is easy to use.
• Automatic collection of various performance metrics by default. You can then configure and write them to local files.
• Ability to take in-memory snapshots of critical objects, configure them, and write them to local files. This is helpful for troubleshooting complex issues.

%}

{template ingester-lib-installation%

1. Install the Java Development Kit(JDK)

Make sure that your system has JDK 8 or later installed. For more information on how to check your version of Java and install the JDK, see the Oracle Overview of JDK Installation documentation

2. Add GreptiemDB Java SDK as a Dependency

If you are using Maven, add the following to your pom.xml dependencies list:

<dependency>
    <groupId>io.greptime</groupId>
    <artifactId>ingester-all</artifactId>
    <version><%java-sdk-version%></version>
</dependency>

The latest version can be viewed here.

After configuring your dependencies, make sure they are available to your project. This may require refreshing the project in your IDE or running the dependency manager.

%}

{template ingester-lib-connect%

The following code demonstrates how to connect to GreptimeDB with the simplest configuration. For customizing the connection options, please refer to API Documentation. Please pay attention to the accompanying comments for each option, as they provide detailed explanations of their respective roles.

// GreptimeDB has a default database named "public" in the default catalog "greptime",
// we can use it as the test database
String database = "public";
// By default, GreptimeDB listens on port 4001 using the gRPC protocol.
// We can provide multiple endpoints that point to the same GreptimeDB cluster.
// The client will make calls to these endpoints based on a load balancing strategy.
String[] endpoints = {"127.0.0.1:4001"};
// Sets authentication information.
AuthInfo authInfo = new AuthInfo("username", "password");
GreptimeOptions opts = GreptimeOptions.newBuilder(endpoints, database)
        // If the database does not require authentication, we can use AuthInfo.noAuthorization() as the parameter.
        .authInfo(authInfo)
        // Enable secure connection if your server is secured by TLS
        //.tlsOptions(new TlsOptions())
        // A good start ^_^
        .build();

GreptimeDB client = GreptimeDB.create(opts);

For customizing the connection options, please refer to API Documentation.

%}

{template low-level-object%

// Construct the table schema for CPU metrics
TableSchema cpuMetricSchema = TableSchema.newBuilder("cpu_metric")
        .addTag("host", DataType.String) // Identifier for the host
        .addTimestamp("ts", DataType.TimestampMillisecond) // Timestamp in milliseconds
        .addField("cpu_user", DataType.Float64) // CPU usage by user processes
        .addField("cpu_sys", DataType.Float64) // CPU usage by system processes
        .build();

// Create the table from the defined schema
Table cpuMetric = Table.from(cpuMetricSchema);

// Example data for a single row
String host = "127.0.0.1"; // Host identifier
long ts = System.currentTimeMillis(); // Current timestamp
double cpuUser = 0.1; // CPU usage by user processes (in percentage)
double cpuSys = 0.12; // CPU usage by system processes (in percentage)

// Insert the row into the table
// NOTE: The arguments must be in the same order as the columns in the defined schema: host, ts, cpu_user, cpu_sys
cpuMetric.addRow(host, ts, cpuUser, cpuSys);

%}

{template create-rows%

// Creates schemas
TableSchema cpuMetricSchema = TableSchema.newBuilder("cpu_metric")
        .addTag("host", DataType.String)
        .addTimestamp("ts", DataType.TimestampMillisecond)
        .addField("cpu_user", DataType.Float64)
        .addField("cpu_sys", DataType.Float64)
        .build();

TableSchema memMetricSchema = TableSchema.newBuilder("mem_metric")
        .addTag("host", DataType.String)
        .addTimestamp("ts", DataType.TimestampMillisecond)
        .addField("mem_usage", DataType.Float64)
        .build();

Table cpuMetric = Table.from(cpuMetricSchema);
Table memMetric = Table.from(memMetricSchema);

// Adds row data items
for (int i = 0; i < 10; i++) {
    String host = "127.0.0." + i;
    long ts = System.currentTimeMillis();
    double cpuUser = i + 0.1;
    double cpuSys = i + 0.12;
    cpuMetric.addRow(host, ts, cpuUser, cpuSys);
}

for (int i = 0; i < 10; i++) {
    String host = "127.0.0." + i;
    long ts = System.currentTimeMillis();
    double memUsage = i + 0.2;
    memMetric.addRow(host, ts, memUsage);
}

%}

{template insert-rows%

// Saves data

// For performance reasons, the SDK is designed to be purely asynchronous.
// The return value is a future object. If you want to immediately obtain
// the result, you can call `future.get()`.
CompletableFuture<Result<WriteOk, Err>> future = greptimeDB.write(cpuMetric, memMetric);

Result<WriteOk, Err> result = future.get();

if (result.isOk()) {
    LOG.info("Write result: {}", result.getOk());
} else {
    LOG.error("Failed to write: {}", result.getErr());
}

%}

{template streaming-insert%

StreamWriter<Table, WriteOk> writer = greptimeDB.streamWriter();

// write data into stream
writer.write(cpuMetric);
writer.write(memMetric);

// You can perform operations on the stream, such as deleting the first 5 rows.
writer.write(cpuMetric.subRange(0, 5), WriteOp.Delete);

Close the stream writing after all data has been written. In general, you do not need to close the stream writing when continuously writing data.

// complete the stream
CompletableFuture<WriteOk> future = writer.completed();
WriteOk result = future.get();
LOG.info("Write result: {}", result);

%}

{template update-rows%

Update data

Please refer to update data for the updating mechanism. In the following code, we first save a row and then use the same tag and time index to identify the row for updating.

Table cpuMetric = Table.from(myMetricCpuSchema);
// insert a row data
long ts = 1703832681000L;
cpuMetric.addRow("host1", ts, 0.23, 0.12);
Result<WriteOk, Err> putResult = greptimeDB.write(cpuMetric).get();

// update the row data
Table newCpuMetric = Table.from(myMetricCpuSchema);
// The same tag `host1`
// The same time index `1703832681000`
// The new value: cpu_user = `0.80`, cpu_sys = `0.11`
long ts = 1703832681000L;
myMetricCpuSchema.addRow("host1", ts, 0.80, 0.11);

// overwrite the existing data
CompletableFuture<Result<WriteOk, Err>> future = greptimeDB.write(myMetricCpuSchema);
Result<WriteOk, Err> result = future.get();

%}

{template high-level-style-object%

GreptimeDB Java Ingester SDK allows us to use basic POJO objects for writing. This approach requires the use of Greptime's own annotations, but they are easy to use.

@Metric(name = "cpu_metric")
public class Cpu {
    @Column(name = "host", tag = true, dataType = DataType.String)
    private String host;

    @Column(name = "ts", timestamp = true, dataType = DataType.TimestampMillisecond)
    private long ts;

    @Column(name = "cpu_user", dataType = DataType.Float64)
    private double cpuUser;
    @Column(name = "cpu_sys", dataType = DataType.Float64)
    private double cpuSys;

    // getters and setters
    // ...
}

@Metric(name = "mem_metric")
public class Memory {
    @Column(name = "host", tag = true, dataType = DataType.String)
    private String host;

    @Column(name = "ts", timestamp = true, dataType = DataType.TimestampMillisecond)
    private long ts;

    @Column(name = "mem_usage", dataType = DataType.Float64)
    private double memUsage;
    // getters and setters
    // ...
}

// Add rows
List<Cpu> cpus = new ArrayList<>();
for (int i = 0; i < 10; i++) {
    Cpu c = new Cpu();
    c.setHost("127.0.0." + i);
    c.setTs(System.currentTimeMillis());
    c.setCpuUser(i + 0.1);
    c.setCpuSys(i + 0.12);
    cpus.add(c);
}

List<Memory> memories = new ArrayList<>();
for (int i = 0; i < 10; i++) {
    Memory m = new Memory();
    m.setHost("127.0.0." + i);
    m.setTs(System.currentTimeMillis());
    m.setMemUsage(i + 0.2);
    memories.add(m);
}

%}

{template high-level-style-insert-data%

Write data with POJO objects:

// Saves data

CompletableFuture<Result<WriteOk, Err>> puts = greptimeDB.writeObjects(cpus, memories);

Result<WriteOk, Err> result = puts.get();

if (result.isOk()) {
    LOG.info("Write result: {}", result.getOk());
} else {
    LOG.error("Failed to write: {}", result.getErr());
}

%}

{template high-level-style-streaming-insert%

StreamWriter<List<?>, WriteOk> writer = greptimeDB.objectsStreamWriter();

// write data into stream
writer.write(cpus);
writer.write(memories);

// You can perform operations on the stream, such as deleting the first 5 rows.
writer.write(cpus.subList(0, 5), WriteOp.Delete);

Close the stream writing after all data has been written. In general, you do not need to close the stream writing when continuously writing data.

// complete the stream
CompletableFuture<WriteOk> future = writer.completed();
WriteOk result = future.get();
LOG.info("Write result: {}", result);

%}

{template high-level-style-update-data%

Update data

Please refer to update data for the updating mechanism. In the following code, we first save a row and then use the same tag and time index to identify the row for updating.

Cpu cpu = new Cpu();
cpu.setHost("host1");
cpu.setTs(1703832681000L);
cpu.setCpuUser(0.23);
cpu.setCpuSys(0.12);

// insert a row data
Result<WriteOk, Err> putResult = greptimeDB.writeObjects(cpu).get();

// update the row data
Cpu newCpu = new Cpu();
// The same tag `host1`
newCpu.setHost("host1");
// The same time index `1703832681000`
newCpu.setTs(1703832681000L);
// The new value: cpu_user = `0.80`, cpu_sys = `0.11`
cpu.setCpuUser(0.80);
cpu.setCpuSys(0.11);

// overwrite the existing data
Result<WriteOk, Err> updateResult = greptimeDB.writeObjects(newCpu).get();

%}

{template ingester-lib-debug-logs%

Debug logs

The ingester SDK provides metrics and logs for debugging. Please refer to Metrics & Display and Magic Tools to learn how to enable or disable the logs.

%}

{template more-ingestion-examples%

For fully runnable code snippets and the complete code of the demo, please refer to the Examples.

%}

{template ingester-lib-reference%

• API Documentation

%}

{template recommended-query-library%

Java database connectivity (JDBC) is the JavaSoft specification of a standard application programming interface (API) that allows Java programs to access database management systems.

Many databases, such as MySQL or PostgreSQL, have implemented their own drivers based on the JDBC API. Since GreptimeDB supports multiple protocols, we use MySQL as an example to demonstrate how to use JDBC. If you want to use other protocols, just replace the MySQL driver with the corresponding driver.

%}

{template query-library-installation%

If you are using Maven, add the following to your pom.xml dependencies list:

<!-- MySQL usage dependency -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.33</version>
</dependency>

%}

{template query-library-connect%

Here we will use MySQL as an example to demonstrate how to connect to GreptimeDB.

public static Connection getConnection() throws IOException, ClassNotFoundException, SQLException {
    Properties prop = new Properties();
    prop.load(QueryJDBC.class.getResourceAsStream("/db-connection.properties"));

    String dbName = (String) prop.get("db.database-driver");

    String dbConnUrl = (String) prop.get("db.url");
    String dbUserName = (String) prop.get("db.username");
    String dbPassword = (String) prop.get("db.password");

    Class.forName(dbName);
    Connection dbConn = DriverManager.getConnection(dbConnUrl, dbUserName, dbPassword);

    return Objects.requireNonNull(dbConn, "Failed to make connection!");
}

You need a properties file to store the DB connection information. Place it in the Resources directory and name it db-connection.properties. The file content is as follows:

# DataSource
db.database-driver=com.mysql.cj.jdbc.Driver
db.url=jdbc:mysql://localhost:4002/public
db.username=
db.password=

Or you can just get the file from here.

%}

{template query-library-raw-sql%

try (Connection conn = getConnection()) {
    Statement statement = conn.createStatement();

    // DESC table;
    ResultSet rs = statement.executeQuery("DESC cpu_metric");
    LOG.info("Column | Type | Key | Null | Default | Semantic Type ");
    while (rs.next()) {
        LOG.info("{} | {} | {} | {} | {} | {}",
                rs.getString(1),
                rs.getString(2),
                rs.getString(3),
                rs.getString(4),
                rs.getString(5),
                rs.getString(6));
    }

    // SELECT COUNT(*) FROM cpu_metric;
    rs = statement.executeQuery("SELECT COUNT(*) FROM cpu_metric");
    while (rs.next()) {
        LOG.info("Count: {}", rs.getInt(1));
    }

    // SELECT * FROM cpu_metric ORDER BY ts DESC LIMIT 5;
    rs = statement.executeQuery("SELECT * FROM cpu_metric ORDER BY ts DESC LIMIT 5");
    LOG.info("host | ts | cpu_user | cpu_sys");
    while (rs.next()) {
        LOG.info("{} | {} | {} | {}",
                rs.getString("host"),
                rs.getTimestamp("ts"),
                rs.getDouble("cpu_user"),
                rs.getDouble("cpu_sys"));
    }
}

For the complete code of the demo, please refer to here.

%}

{template query-lib-doc-link%

• JDBC Online Tutorials

%}