QuestDB Client Library for Java

This is the official Java client library for QuestDB, a high-performance time-series database.

The client uses the InfluxDB Line Protocol (ILP) to insert data into QuestDB over HTTP, TCP, or UDP.

Transport	Description
HTTP	Recommended. Provides feedback on errors and supports authentication and TLS.
TCP	Legacy. No error feedback from server. Useful for compatibility.
UDP	Fire-and-forget. No error feedback or delivery guarantees. Supports multicast.

Quick Start

Add Dependency

Maven:

<dependency>
    <groupId>org.questdb</groupId>
    <artifactId>client</artifactId>
    <version>1.0.0</version>
</dependency>

Gradle:

implementation 'org.questdb:client:1.0.0'

Replace 1.0.0 with the latest version from Maven Central.

Start QuestDB

docker run -p 9000:9000 questdb/questdb

Insert Data

import io.questdb.client.Sender;

public class Main {
    public static void main(String[] args) {
        try (Sender sender = Sender.fromConfig("http::addr=localhost:9000;")) {
            sender.table("trades")
                    .symbol("symbol", "ETH-USD")
                    .symbol("side", "sell")
                    .doubleColumn("price", 2615.54)
                    .doubleColumn("amount", 0.00044)
                    .atNow();
        }
    }
}

More Examples

Using the Builder API

import io.questdb.client.Sender;

try (Sender sender = Sender.builder(Sender.Transport.HTTP)
        .address("localhost:9000")
        .autoFlushRows(1000)
        .autoFlushIntervalMillis(5000)
        .build()) {
    sender.table("trades")
            .symbol("symbol", "ETH-USD")
            .doubleColumn("price", 2615.54)
            .atNow();
}

TCP Transport

try (Sender sender = Sender.fromConfig("tcp::addr=localhost:9009;")) {
    sender.table("trades")
            .symbol("symbol", "ETH-USD")
            .symbol("side", "sell")
            .doubleColumn("price", 2615.54)
            .doubleColumn("amount", 0.00044)
            .atNow();
}

UDP Transport

UDP uses LineUdpSender directly (not available via Sender.fromConfig()). It is fire-and-forget with no delivery guarantees.

import io.questdb.client.cutlass.line.LineUdpSender;
import io.questdb.client.std.Numbers;
import io.questdb.client.std.NumericException;

// Parameters: interface IPv4 address, target IPv4 address, target port, buffer capacity, TTL
int lo = Numbers.parseIPv4("127.0.0.1");
int target = Numbers.parseIPv4("127.0.0.1");
try (LineUdpSender sender = new LineUdpSender(lo, target, 9009, 1024, 2)) {
    sender.table("trades")
            .symbol("symbol", "ETH-USD")
            .doubleColumn("price", 2615.54)
            .atNow();
    sender.flush();
}

Authentication and TLS

HTTP with username/password:

try (Sender sender = Sender.fromConfig("https::addr=localhost:9000;username=admin;password=quest;")) {
    // ...
}

HTTP with bearer token:

try (Sender sender = Sender.fromConfig("http::addr=localhost:9000;token=my_bearer_token;")) {
    // ...
}

TCP with authentication:

try (Sender sender = Sender.fromConfig("tcp::addr=localhost:9009;user=admin;token=my_token;")) {
    // ...
}

TLS with certificate validation disabled (not for production):

try (Sender sender = Sender.fromConfig("https::addr=localhost:9000;tls_verify=unsafe_off;")) {
    // ...
}

Explicit Timestamps

import java.time.Instant;
import java.time.temporal.ChronoUnit;

try (Sender sender = Sender.fromConfig("http::addr=localhost:9000;")) {
    // Using an Instant
    sender.table("trades")
            .symbol("symbol", "ETH-USD")
            .doubleColumn("price", 2615.54)
            .at(Instant.now());

    // Using a long value with time unit
    sender.table("trades")
            .symbol("symbol", "BTC-USD")
            .doubleColumn("price", 39269.98)
            .at(1_000_000_000L, ChronoUnit.NANOS);
}

Configuration via Environment Variable

Instead of hardcoding the configuration string, set the QDB_CLIENT_CONF environment variable:

export QDB_CLIENT_CONF="http::addr=localhost:9000;"

Then create the sender:

try (Sender sender = Sender.fromEnv()) {
    // ...
}

Configuration Reference

The configuration string format is:

schema::key1=value1;key2=value2;

Schemas: http, https, tcp, tcps

Key	Default	Description
addr	(required)	Server address as host:port
username		HTTP basic auth username
password		HTTP basic auth password
token		Bearer token (HTTP) or private key token (TCP)
user		Username for TCP auth
tls_verify	on	TLS certificate validation (on or unsafe_off)
tls_roots		Path to custom truststore
tls_roots_password		Truststore password
auto_flush	on	Enable auto-flush (on or off)
auto_flush_rows	75000	Flush after N rows (HTTP only)
auto_flush_interval	1000	Flush interval in milliseconds (HTTP; off to disable)
request_timeout	30000	HTTP request timeout in milliseconds
request_min_throughput	102400	Min expected throughput in bytes/sec (HTTP)
retry_timeout	10000	Total retry duration in milliseconds (HTTP)
max_buf_size	104857600	Maximum buffer capacity in bytes
max_name_len	127	Maximum table/column name length
protocol_version	auto	ILP protocol version (1, 2, 3, or auto)

For the full configuration reference, see the QuestDB ILP documentation.

Requirements

• Java 11 or later
• Maven 3+ (for building from source)

Building from Source

git clone https://github.com/questdb/java-questdb-client.git
cd java-questdb-client
mvn clean package -DskipTests

Building Native Libraries

The client includes native libraries (C/C++ and assembly) for performance-critical operations. Pre-built binaries are included in the repository, but you can rebuild them locally if needed.

Prerequisites

Tool	Version	Notes
CMake	3.5+	Build system generator
NASM	2.14+	Netwide Assembler for assembly code
C/C++ Compiler	GCC, Clang, or MinGW	C++17 support required
Make	Any	Build tool
JDK	11+	For JNI headers

macOS (ARM64 or x86-64)

# Install build tools
brew install cmake nasm

# Set deployment target
export MACOSX_DEPLOYMENT_TARGET=13.0

# Build native library
cd core
cmake -B cmake-build-release -DCMAKE_BUILD_TYPE=Release
cmake --build cmake-build-release --config Release

Linux x86-64

# Install build tools (Debian/Ubuntu)
sudo apt-get install cmake nasm build-essential

# Build native library
cd core
cmake -DCMAKE_BUILD_TYPE=Release -B cmake-build-release -S.
cmake --build cmake-build-release --config Release

Linux ARM64

# Install build tools (Debian/Ubuntu)
sudo apt-get install cmake nasm build-essential

# Build using ARM64 toolchain
cd core
cmake -DCMAKE_TOOLCHAIN_FILE=./src/main/c/toolchains/linux-arm64.cmake \
      -DCMAKE_BUILD_TYPE=Release -B cmake-build-release-arm64 -S.
cmake --build cmake-build-release-arm64 --config Release

Windows x86-64 (Cross-compilation from Linux)

# Install cross-compilation tools (Debian/Ubuntu)
sudo apt-get install cmake nasm gcc-mingw-w64 g++-mingw-w64

# Build using Windows toolchain
cd core
cmake -DCMAKE_TOOLCHAIN_FILE=./src/main/c/toolchains/windows-x86_64.cmake \
      -DCMAKE_CROSSCOMPILING=True -DCMAKE_BUILD_TYPE=Release \
      -B cmake-build-release-win64
cmake --build cmake-build-release-win64 --config Release

Native Library Output Locations

Built libraries are placed in the resources directory for each platform:

core/target/classes/io/questdb/client/bin-local/
├── libquestdb.dylib  # macOS
├── libquestdb.so     # Linux
└── libquestdb.dll    # Windows

Community

• QuestDB Documentation
• QuestDB Community Forum
• QuestDB Slack
• GitHub Issues

License

This project is licensed under the Apache License 2.0.