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Java

This file is generated by https://github.com/tigerbeetledb/tigerbeetle/blob/0.13.134/src/clients/docs_generate.zig.

tigerbeetle-java

The TigerBeetle client for Java.

javadoc

maven-central

Prerequisites​

Linux >= 5.6 is the only production environment we support. But for ease of development we also support macOS and Windows.

  • Java >= 11
  • Maven >= 3.6 (not strictly necessary but it's what our guides assume)

Setup​

First, create a directory for your project and cd into the directory.

Then create pom.xml and copy this into it:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.tigerbeetle</groupId>
  <artifactId>samples</artifactId>
  <version>1.0-SNAPSHOT</version>

  <properties>
    <maven.compiler.source>11</maven.compiler.source>
    <maven.compiler.target>11</maven.compiler.target>
  </properties>

  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.8.1</version>
        <configuration>
          <compilerArgs>
            <arg>-Xlint:all,-options,-path</arg>
          </compilerArgs>
        </configuration>
      </plugin>

      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>exec-maven-plugin</artifactId>
        <version>1.6.0</version>
        <configuration>
          <mainClass>com.tigerbeetle.samples.Main</mainClass>
        </configuration>
      </plugin>
    </plugins>
  </build>

  <dependencies>
    <dependency>
      <groupId>com.tigerbeetle</groupId>
      <artifactId>tigerbeetle-java</artifactId>
      <!-- Grab the latest commit from: https://repo1.maven.org/maven2/com/tigerbeetle/tigerbeetle-java/maven-metadata.xml -->
      <version>0.0.1-3431</version>
    </dependency>
  </dependencies>
</project>

Then, install the TigerBeetle client:

mvn install

Now, create src/main/java/Main.java and copy this into it:

package com.tigerbeetle.samples;

import com.tigerbeetle.*;

public final class Main {
    public static void main(String[] args) {
        System.out.println("Import ok!");
    }
}

Finally, build and run:

mvn exec:java

Now that all prerequisites and dependencies are correctly set up, let's dig into using TigerBeetle.

Sample projects​

This document is primarily a reference guide to the client. Below are various sample projects demonstrating features of TigerBeetle.

  • Basic: Create two accounts and transfer an amount between them.
  • Two-Phase Transfer: Create two accounts and start a pending transfer between them, then post the transfer.
  • Many Two-Phase Transfers: Create two accounts and start a number of pending transfer between them, posting and voiding alternating transfers.

Creating a Client​

A client is created with a cluster ID and replica addresses for all replicas in the cluster. The cluster ID and replica addresses are both chosen by the system that starts the TigerBeetle cluster.

Clients are thread-safe and a single instance should be shared between multiple concurrent tasks.

Multiple clients are useful when connecting to more than one TigerBeetle cluster.

In this example the cluster ID is 0 and there is one replica. The address is read from the TB_ADDRESS environment variable and defaults to port 3000.

var tbAddress = System.getenv("TB_ADDRESS");
Client client = new Client(
  0,
  new String[] {tbAddress.length() > 0 ? tbAddress : "3000"}
);

If you create a Client like this, don't forget to call client.close() when you are done with it. Otherwise you can use the try-with-resources syntax:

try (var client = new Client(...)) {
  // Use client
} catch (Exception e) {
  // Handle exception
}

The following are valid addresses:

  • 3000 (interpreted as 127.0.0.1:3000)
  • 127.0.0.1:3000 (interpreted as 127.0.0.1:3000)
  • 127.0.0.1 (interpreted as 127.0.0.1:3001, 3001 is the default port)

Creating Accounts​

See details for account fields in the Accounts reference.

AccountBatch accounts = new AccountBatch(1);
accounts.add();
accounts.setId(137);
accounts.setUserData128(UInt128.asBytes(java.util.UUID.randomUUID()));
accounts.setUserData64(1234567890);
accounts.setUserData32(42);
accounts.setLedger(1);
accounts.setCode(718);
accounts.setFlags(0);

CreateAccountResultBatch accountErrors = client.createAccounts(accounts);

The 128-bit fields like id and user_data_128 have a few overrides to make it easier to integrate. You can either pass in a long, a pair of longs (least and most significant bits), or a byte[].

There is also a com.tigerbeetle.UInt128 helper with static methods for converting 128-bit little-endian unsigned integers between instances of long, java.util.UUID, java.math.BigInteger and byte[].

The fields for transfer amounts and account balances are also 128-bit, but they are always represented as a java.math.BigInteger.

Account Flags​

The account flags value is a bitfield. See details for these flags in the Accounts reference.

To toggle behavior for an account, combine enum values stored in the AccountFlags object with bitwise-or:

  • AccountFlags.LINKED
  • AccountFlags.DEBITS_MUST_NOT_EXCEED_CREDITS
  • AccountFlags.CREDITS_MUST_NOT_EXCEED_CREDITS

For example, to link two accounts where the first account additionally has the debits_must_not_exceed_credits constraint:

accounts = new AccountBatch(3);

// First account
accounts.add();
// Code to fill out fields for first account
accounts.setFlags(AccountFlags.LINKED | AccountFlags.DEBITS_MUST_NOT_EXCEED_CREDITS);

// Second account
accounts.add();
// Code to fill out fields for second account

accountErrors = client.createAccounts(accounts);

Response and Errors​

The response is an empty array if all accounts were created successfully. If the response is non-empty, each object in the response array contains error information for an account that failed. The error object contains an error code and the index of the account in the request batch.

See all error conditions in the create_accounts reference.

accounts = new AccountBatch(3);

// First account
accounts.add();
// Code to fill out fields for first account

// Second account
accounts.add();
// Code to fill out fields for second account

// Third account
accounts.add();
// Code to fill out fields for third account

accountErrors = client.createAccounts(accounts);
while (accountErrors.next()) {
    switch (accountErrors.getResult()) {
        case Exists:
            System.err.printf("Account at %d already exists.\n",
                accountErrors.getIndex());
            break;

        default:
            System.err.printf("Error creating account at %d: %s\n",
                accountErrors.getIndex(),
                accountErrors.getResult());
            break;
    }
}

Account Lookup​

Account lookup is batched, like account creation. Pass in all IDs to fetch. The account for each matched ID is returned.

If no account matches an ID, no object is returned for that account. So the order of accounts in the response is not necessarily the same as the order of IDs in the request. You can refer to the ID field in the response to distinguish accounts.

IdBatch ids = new IdBatch(2);
ids.add(137);
ids.add(138);
accounts = client.lookupAccounts(ids);

Create Transfers​

This creates a journal entry between two accounts.

See details for transfer fields in the Transfers reference.

TransferBatch transfers = new TransferBatch(1);
transfers.add();
transfers.setId(1);
transfers.setDebitAccountId(1);
transfers.setCreditAccountId(2);
transfers.setAmount(10);
transfers.setUserData128(UInt128.asBytes(java.util.UUID.randomUUID()));
transfers.setUserData64(1234567890);
transfers.setUserData32(42);
transfers.setTimeout(0);
transfers.setLedger(1);
transfers.setCode(1);
transfers.setFlags(0);

CreateTransferResultBatch transferErrors = client.createTransfers(transfers);

Response and Errors​

The response is an empty array if all transfers were created successfully. If the response is non-empty, each object in the response array contains error information for a transfer that failed. The error object contains an error code and the index of the transfer in the request batch.

See all error conditions in the create_transfers reference.

while (transferErrors.next()) {
    switch (transferErrors.getResult()) {
        case ExceedsCredits:
            System.err.printf("Transfer at %d exceeds credits.\n",
                transferErrors.getIndex());
            break;

        default:
            System.err.printf("Error creating transfer at %d: %s\n",
                transferErrors.getIndex(),
                transferErrors.getResult());
            break;
    }
}

Batching​

TigerBeetle performance is maximized when you batch API requests. The client does not do this automatically for you. So, for example, you can insert 1 million transfers one at a time like so:

var transferIds = new long[]{100, 101, 102};
var debitIds = new long[]{1, 2, 3};
var creditIds = new long[]{4, 5, 6};
var amounts = new long[]{1000, 29, 11};
for (int i = 0; i < transferIds.length; i++) {
  TransferBatch batch = new TransferBatch(1);
  batch.add();
  batch.setId(transferIds[i]);
  batch.setDebitAccountId(debitIds[i]);
  batch.setCreditAccountId(creditIds[i]);
  batch.setAmount(amounts[i]);

  CreateTransferResultBatch errors = client.createTransfers(batch);
  // error handling omitted
}

But the insert rate will be a fraction of potential. Instead, always batch what you can.

The maximum batch size is set in the TigerBeetle server. The default is 8191.

var BATCH_SIZE = 8191;
for (int i = 0; i < transferIds.length; i += BATCH_SIZE) {
  TransferBatch batch = new TransferBatch(BATCH_SIZE);

  for (int j = 0; j < BATCH_SIZE && i + j < transferIds.length; j++) {
    batch.add();
    batch.setId(transferIds[i+j]);
    batch.setDebitAccountId(debitIds[i+j]);
    batch.setCreditAccountId(creditIds[i+j]);
    batch.setAmount(amounts[i+j]);
  }

  CreateTransferResultBatch errors = client.createTransfers(batch);
  // error handling omitted
}

Queues and Workers​

If you are making requests to TigerBeetle from workers pulling jobs from a queue, you can batch requests to TigerBeetle by having the worker act on multiple jobs from the queue at once rather than one at a time. i.e. pulling multiple jobs from the queue rather than just one.

Transfer Flags​

The transfer flags value is a bitfield. See details for these flags in the Transfers reference.

To toggle behavior for an account, combine enum values stored in the TransferFlags object with bitwise-or:

  • TransferFlags.NONE
  • TransferFlags.LINKED
  • TransferFlags.PENDING
  • TransferFlags.POST_PENDING_TRANSFER
  • TransferFlags.VOID_PENDING_TRANSFER

For example, to link transfer0 and transfer1:

transfers = new TransferBatch(2);

// First transfer
transfers.add();
// Code to fill out fields for first transfer
transfers.setFlags(TransferFlags.LINKED);

// Second transfer
transfers.add();
// Code to fill out fields for second transfer
transferErrors = client.createTransfers(transfers);

Two-Phase Transfers​

Two-phase transfers are supported natively by toggling the appropriate flag. TigerBeetle will then adjust the credits_pending and debits_pending fields of the appropriate accounts. A corresponding post pending transfer then needs to be sent to post or void the transfer.

Post a Pending Transfer​

With flags set to post_pending_transfer, TigerBeetle will post the transfer. TigerBeetle will atomically roll back the changes to debits_pending and credits_pending of the appropriate accounts and apply them to the debits_posted and credits_posted balances.

transfers = new TransferBatch(1);

// First transfer
transfers.add();
// Code to fill out fields for first transfer
transfers.setFlags(TransferFlags.POST_PENDING_TRANSFER);
transferErrors = client.createTransfers(transfers);

Void a Pending Transfer​

In contrast, with flags set to void_pending_transfer, TigerBeetle will void the transfer. TigerBeetle will roll back the changes to debits_pending and credits_pending of the appropriate accounts and not apply them to the debits_posted and credits_posted balances.

transfers = new TransferBatch(1);

// First transfer
transfers.add();
// Code to fill out fields for first transfer
transfers.setFlags(TransferFlags.VOID_PENDING_TRANSFER);
transferErrors = client.createTransfers(transfers);

Transfer Lookup​

NOTE: While transfer lookup exists, it is not a flexible query API. We are developing query APIs and there will be new methods for querying transfers in the future.

Transfer lookup is batched, like transfer creation. Pass in all ids to fetch, and matched transfers are returned.

If no transfer matches an id, no object is returned for that transfer. So the order of transfers in the response is not necessarily the same as the order of ids in the request. You can refer to the id field in the response to distinguish transfers.

ids = new IdBatch(2);
ids.add(1);
ids.add(2);
transfers = client.lookupTransfers(ids);

Linked Events​

When the linked flag is specified for an account when creating accounts or a transfer when creating transfers, it links that event with the next event in the batch, to create a chain of events, of arbitrary length, which all succeed or fail together. The tail of a chain is denoted by the first event without this flag. The last event in a batch may therefore never have the linked flag set as this would leave a chain open-ended. Multiple chains or individual events may coexist within a batch to succeed or fail independently.

Events within a chain are executed within order, or are rolled back on error, so that the effect of each event in the chain is visible to the next, and so that the chain is either visible or invisible as a unit to subsequent events after the chain. The event that was the first to break the chain will have a unique error result. Other events in the chain will have their error result set to linked_event_failed.

transfers = new TransferBatch(10);

// An individual transfer (successful):
transfers.add();
transfers.setId(1);

// A chain of 4 transfers (the last transfer in the chain closes the chain with linked=false):
transfers.add();
transfers.setId(2); // Commit/rollback.
transfers.setFlags(TransferFlags.LINKED);

transfers.add();
transfers.setId(3); // Commit/rollback.
transfers.setFlags(TransferFlags.LINKED);

transfers.add();
transfers.setId(2); // Fail with exists
transfers.setFlags(TransferFlags.LINKED);

transfers.add();
transfers.setId(4); // Fail without committing

// An individual transfer (successful):
// This should not see any effect from the failed chain above.
transfers.add();
transfers.setId(2);

// A chain of 2 transfers (the first transfer fails the chain):
transfers.add();
transfers.setId(2);
transfers.setFlags(TransferFlags.LINKED);

transfers.add();
transfers.setId(3);

// A chain of 2 transfers (successful):
transfers.add();
transfers.setId(3);
transfers.setFlags(TransferFlags.LINKED);

transfers.add();
transfers.setId(4);

transferErrors = client.createTransfers(transfers);

Development Setup​

On Linux and macOS​

In a POSIX shell run:

git clone https://github.com/tigerbeetle/tigerbeetle
cd tigerbeetle
git submodule update --init --recursive
./scripts/install_zig.sh
cd src/clients/java
./scripts/install.sh
if [ "$TEST" = "true" ]; then mvn test; else echo "Skipping client unit tests"; fi

On Windows​

In PowerShell run:

git clone https://github.com/tigerbeetle/tigerbeetle
cd tigerbeetle
git submodule update --init --recursive
.\scripts\install_zig.bat
cd src/clients/java
.\scripts\install.bat
if ($env:TEST -eq 'true') { mvn test } else { echo "Skipping client unit test" }