<!-- This file is generated by [/src/scripts/client_readmes.zig](/src/scripts/client_readmes.zig). -->
# tigerbeetle-rust (Cloud Native)

A **cloud-native variant** of the TigerBeetle Rust client that supports **DNS-based service discovery**.

This client requires the fork version of TigerBeetle: [https://github.com/Krishnacore/tigerbeetle](https://github.com/Krishnacore/tigerbeetle)

For Kubernetes deployments, you can use the TigerBeetle Operator: [https://github.com/Krishnacore/tigerbeetle-operator](https://github.com/Krishnacore/tigerbeetle-operator)

[![crates.io](https://img.shields.io/crates/v/cn-tigerbeetle)](https://crates.io/crates/cn-tigerbeetle)
[![docs.rs](https://img.shields.io/docsrs/cn-tigerbeetle)](https://docs.rs/cn-tigerbeetle)

## Prerequisites

Linux >= 5.6 is the only production environment we
support. But for ease of development we also support macOS and Windows.
* Rust 1.68+

## Setup

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

Then create `Cargo.toml` and copy this into it:

```toml
[package]
name = "tigerbeetle-test"
version = "0.1.0"
edition = "2024"

[dependencies]
cn-tigerbeetle = "0.1"
futures = "0.3"
```

Now, create `src/main.rs` and copy this into it:

```rust
use cn_tigerbeetle as tb;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    futures::executor::block_on(main_async())
}

async fn main_async() -> Result<(), Box<dyn std::error::Error>> {
    println!("hello world");
}
```

Finally, build and run:

```console
cargo run
```

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](/src/clients/rust/samples/basic/): Create two accounts and transfer an amount between them.
* [Two-Phase Transfer](/src/clients/rust/samples/two-phase/): Create two accounts and start a pending transfer between
them, then post the transfer.
* [Many Two-Phase Transfers](/src/clients/rust/samples/two-phase-many/): Create two accounts and start a number of pending transfers
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. This allows events to be 
[automatically batched](https://docs.tigerbeetle.com/coding/requests/#batching-events).

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`.

```rust
let cluster_id = 0;
let replica_address = std::env::var("TB_ADDRESS")
    .ok()
    .unwrap_or_else(|| String::from("3000"));
let client = tb::Client::new(cluster_id, &replica_address)?;
```

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)
* `tigerbeetle.default.svc.cluster.local:3000` (DNS name for Kubernetes service discovery)
* `tigerbeetle-0.tigerbeetle.default.svc.cluster.local:3000` (DNS name for specific pod)

### DNS-Based Service Discovery

This cloud-native variant supports **DNS-based address resolution**, making it ideal for Kubernetes and other container orchestration platforms. Instead of hardcoding IP addresses, you can use DNS names that resolve dynamically:

```rust
let client = tb::Client::new(0, "tigerbeetle.default.svc.cluster.local:3000")?;
```

This is particularly useful when deploying with the [TigerBeetle Operator](https://github.com/Krishnacore/tigerbeetle-operator), which automatically creates the appropriate Kubernetes services.

## Creating Accounts

See details for account fields in the [Accounts
reference](https://docs.tigerbeetle.com/reference/account).

```rust
let account_errors = client
    .create_accounts(&[tb::Account {
        id: tb::id(),
        ledger: 1,
        code: 718,
        ..Default::default()
    }])
    .await?;
// Error handling omitted.
```

See details for the recommended ID scheme in
[time-based identifiers](https://docs.tigerbeetle.com/coding/data-modeling#tigerbeetle-time-based-identifiers-recommended).

### Account Flags

The account flags value is a bitfield. See details for
these flags in the [Accounts
reference](https://docs.tigerbeetle.com/reference/account#flags).

To toggle behavior for an account, use the `AccountFlags` bitflags.
You can combine multiple flags using the `|` operator. Here are a
few examples:

* `AccountFlags::Linked`
* `AccountFlags::DebitsMustNotExceedCredits`
* `AccountFlags::CreditsMustNotExceedDebits`
* `AccountFlags::History`
* `AccountFlags::Linked | AccountFlags::History`

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

```rust
let account0 = tb::Account {
    id: 100,
    ledger: 1,
    code: 718,
    flags: tb::AccountFlags::DebitsMustNotExceedCredits | tb::AccountFlags::Linked,
    ..Default::default()
};
let account1 = tb::Account {
    id: 101,
    ledger: 1,
    code: 718,
    flags: tb::AccountFlags::History,
    ..Default::default()
};

let account_errors = client.create_accounts(&[account0, account1]).await?;
// Error handling omitted.
```

### 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](https://docs.tigerbeetle.com/reference/requests/create_accounts).

```rust
let account0 = tb::Account {
    id: 102,
    ledger: 1,
    code: 718,
    ..Default::default()
};
let account1 = tb::Account {
    id: 103,
    ledger: 1,
    code: 718,
    ..Default::default()
};
let account2 = tb::Account {
    id: 104,
    ledger: 1,
    code: 718,
    ..Default::default()
};

let account_errors = client
    .create_accounts(&[account0, account1, account2])
    .await?;

assert!(account_errors.len() <= 3);

for err in account_errors {
    match err.result {
        tb::CreateAccountResult::Exists => {
            println!("Batch account at {} already exists.", err.index);
        }
        _ => {
            eprintln!(
                "Batch account at {} failed to create: {:?}",
                err.index, err.result
            );
        }
    }
}
```

To handle errors, iterate over the `Vec<CreateAccountsResult>` returned
from `client.create_accounts()`. Each result contains an `index` field
to map back to the input account and a `result` field with the
`CreateAccountResult` enum.

## 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.

```rust
let accounts = client.lookup_accounts(&[100, 101]).await?;
```

## Create Transfers

This creates a journal entry between two accounts.

See details for transfer fields in the [Transfers
reference](https://docs.tigerbeetle.com/reference/transfer).

```rust
let transfers = vec![tb::Transfer {
    id: tb::id(),
    debit_account_id: 101,
    credit_account_id: 102,
    amount: 10,
    ledger: 1,
    code: 1,
    ..Default::default()
}];

let transfer_errors = client.create_transfers(&transfers).await?;
// Error handling omitted.
```

See details for the recommended ID scheme in
[time-based identifiers](https://docs.tigerbeetle.com/coding/data-modeling#tigerbeetle-time-based-identifiers-recommended).

### 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](https://docs.tigerbeetle.com/reference/requests/create_transfers).

```rust
let transfers = vec![
    tb::Transfer {
        id: 1,
        debit_account_id: 101,
        credit_account_id: 102,
        amount: 10,
        ledger: 1,
        code: 1,
        ..Default::default()
    },
    tb::Transfer {
        id: 2,
        debit_account_id: 101,
        credit_account_id: 102,
        amount: 10,
        ledger: 1,
        code: 1,
        ..Default::default()
    },
    tb::Transfer {
        id: 3,
        debit_account_id: 101,
        credit_account_id: 102,
        amount: 10,
        ledger: 1,
        code: 1,
        ..Default::default()
    },
];

let transfer_errors = client.create_transfers(&transfers).await?;

for err in transfer_errors {
    match err.result {
        tb::CreateTransferResult::Exists => {
            println!("Batch transfer at {} already exists.", err.index);
        }
        _ => {
            eprintln!(
                "Batch transfer at {} failed to create: {:?}",
                err.index, err.result
            );
        }
    }
}
```

To handle transfer errors, iterate over the `Vec<CreateTransfersResult>`
returned from `client.create_transfers()`. Each result contains an
`index` field to map back to the input transfer and a `result` field
with the `CreateTransferResult` enum.

## Batching

TigerBeetle performance is maximized when you batch
API requests.
A client instance shared across multiple threads/tasks can automatically
batch concurrent requests, but the application must still send as many events
as possible in a single call.
For example, if you insert 1 million transfers sequentially, one at a time,
the insert rate will be a *fraction* of the potential, because the client will
wait for a reply between each one.

```rust
let batch: Vec<tb::Transfer> = vec![];
for transfer in &batch {
    let transfer_errors = client.create_transfers(&[*transfer]).await?;
    // Error handling omitted.
}
```

Instead, **always batch as much as you can**.
The maximum batch size is set in the TigerBeetle server. The default is 8189.

```rust
let transfers: Vec<tb::Transfer> = vec![];
const BATCH_SIZE: usize = 8189;
for batch in transfers.chunks(BATCH_SIZE) {
    let transfer_errors = client.create_transfers(batch).await?;
    // 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](https://docs.tigerbeetle.com/reference/transfer#flags).

To toggle behavior for a transfer, use the `TransferFlags` bitflags.
You can combine multiple flags using the `|` operator. Here are a
few examples:

* `TransferFlags::Linked`
* `TransferFlags::Pending`
* `TransferFlags::PostPendingTransfer`
* `TransferFlags::VoidPendingTransfer`
* `TransferFlags::Linked | TransferFlags::Pending`

For example, to link `transfer0` and `transfer1`:

```rust
let transfer0 = tb::Transfer {
    id: 4,
    debit_account_id: 101,
    credit_account_id: 102,
    amount: 10,
    ledger: 1,
    code: 1,
    flags: tb::TransferFlags::Linked,
    ..Default::default()
};
let transfer1 = tb::Transfer {
    id: 5,
    debit_account_id: 101,
    credit_account_id: 102,
    amount: 10,
    ledger: 1,
    code: 1,
    ..Default::default()
};

let transfer_errors = client.create_transfers(&[transfer0, transfer1]).await?;
// Error handling omitted.
```

### 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.

```rust
let transfer0 = tb::Transfer {
    id: 6,
    debit_account_id: 101,
    credit_account_id: 102,
    amount: 10,
    ledger: 1,
    code: 1,
    ..Default::default()
};

let transfer_errors = client.create_transfers(&[transfer0]).await?;
// Error handling omitted.

let transfer1 = tb::Transfer {
    id: 7,
    amount: u128::MAX,
    pending_id: 6,
    flags: tb::TransferFlags::PostPendingTransfer,
    ..Default::default()
};

let transfer_errors = client.create_transfers(&[transfer1]).await?;
// Error handling omitted.
```

#### 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.

```rust
let transfer0 = tb::Transfer {
    id: 8,
    debit_account_id: 101,
    credit_account_id: 102,
    amount: 10,
    ledger: 1,
    code: 1,
    ..Default::default()
};

let transfer_errors = client.create_transfers(&[transfer0]).await?;
// Error handling omitted.

let transfer1 = tb::Transfer {
    id: 9,
    amount: 0,
    pending_id: 8,
    flags: tb::TransferFlags::VoidPendingTransfer,
    ..Default::default()
};

let transfer_errors = client.create_transfers(&[transfer1]).await?;
// Error handling omitted.
```

## 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 `id`s 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 `id`s in the request. You can refer to the
`id` field in the response to distinguish transfers.

```rust
let transfers = client.lookup_transfers(&[1, 2]).await?;
```

## Get Account Transfers

NOTE: This is a preview API that is subject to breaking changes once we have
a stable querying API.

Fetches the transfers involving a given account, allowing basic filter and pagination
capabilities.

The transfers in the response are sorted by `timestamp` in chronological or
reverse-chronological order.

```rust
let filter = tb::AccountFilter {
    account_id: 2,
    user_data_128: 0,
    user_data_64: 0,
    user_data_32: 0,
    code: 0,
    reserved: Default::default(),
    timestamp_min: 0,
    timestamp_max: 0,
    limit: 10,
    flags: tb::AccountFilterFlags::Debits
        | tb::AccountFilterFlags::Credits
        | tb::AccountFilterFlags::Reversed,
};

let transfers = client.get_account_transfers(filter).await?;
```

## Get Account Balances

NOTE: This is a preview API that is subject to breaking changes once we have
a stable querying API.

Fetches the point-in-time balances of a given account, allowing basic filter and
pagination capabilities.

Only accounts created with the flag
[`history`](https://docs.tigerbeetle.com/reference/account#flagshistory) set retain
[historical balances](https://docs.tigerbeetle.com/reference/requests/get_account_balances).

The balances in the response are sorted by `timestamp` in chronological or
reverse-chronological order.

```rust
let filter = tb::AccountFilter {
    account_id: 2,
    user_data_128: 0,
    user_data_64: 0,
    user_data_32: 0,
    code: 0,
    reserved: Default::default(),
    timestamp_min: 0,
    timestamp_max: 0,
    limit: 10,
    flags: tb::AccountFilterFlags::Debits
        | tb::AccountFilterFlags::Credits
        | tb::AccountFilterFlags::Reversed,
};

let account_balances = client.get_account_balances(filter).await?;
```

## Query Accounts

NOTE: This is a preview API that is subject to breaking changes once we have
a stable querying API.

Query accounts by the intersection of some fields and by timestamp range.

The accounts in the response are sorted by `timestamp` in chronological or
reverse-chronological order.

```rust
let filter = tb::QueryFilter {
    user_data_128: 1000,
    user_data_64: 100,
    user_data_32: 10,
    code: 1,
    ledger: 0,
    reserved: Default::default(),
    timestamp_min: 0,
    timestamp_max: 0,
    limit: 10,
    flags: tb::QueryFilterFlags::Reversed,
};

let accounts = client.query_accounts(filter).await?;
```

## Query Transfers

NOTE: This is a preview API that is subject to breaking changes once we have
a stable querying API.

Query transfers by the intersection of some fields and by timestamp range.

The transfers in the response are sorted by `timestamp` in chronological or
reverse-chronological order.

```rust
let filter = tb::QueryFilter {
    user_data_128: 1000,
    user_data_64: 100,
    user_data_32: 10,
    code: 1,
    ledger: 0,
    reserved: Default::default(),
    timestamp_min: 0,
    timestamp_max: 0,
    limit: 10,
    flags: tb::QueryFilterFlags::Reversed,
};

let transfers = client.query_transfers(filter).await?;
```

## 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`.

```rust
let mut batch = vec![];
let linked_flag = tb::TransferFlags::Linked;

// An individual transfer (successful):
batch.push(tb::Transfer {
    id: 1,
    ..Default::default()
});

// A chain of 4 transfers (the last transfer in the chain closes the chain with linked=false):
batch.push(tb::Transfer {
    id: 2,
    flags: linked_flag,
    ..Default::default()
});
batch.push(tb::Transfer {
    id: 3,
    flags: linked_flag,
    ..Default::default()
});
batch.push(tb::Transfer {
    id: 2,
    flags: linked_flag,
    ..Default::default()
});
batch.push(tb::Transfer {
    id: 4,
    ..Default::default()
});

// An individual transfer (successful):
// This should not see any effect from the failed chain above.
batch.push(tb::Transfer {
    id: 2,
    ..Default::default()
});

// A chain of 2 transfers (the first transfer fails the chain):
batch.push(tb::Transfer {
    id: 2,
    flags: linked_flag,
    ..Default::default()
});
batch.push(tb::Transfer {
    id: 3,
    ..Default::default()
});

// A chain of 2 transfers (successful):
batch.push(tb::Transfer {
    id: 3,
    flags: linked_flag,
    ..Default::default()
});
batch.push(tb::Transfer {
    id: 4,
    ..Default::default()
});

let transfer_errors = client.create_transfers(&batch).await?;
// Error handling omitted.
```

## Imported Events

When the `imported` flag is specified for an account when creating accounts or
a transfer when creating transfers, it allows importing historical events with
a user-defined timestamp.

The entire batch of events must be set with the flag `imported`.

It's recommended to submit the whole batch as a `linked` chain of events, ensuring that
if any event fails, none of them are committed, preserving the last timestamp unchanged.
This approach gives the application a chance to correct failed imported events, re-submitting
the batch again with the same user-defined timestamps.

```rust
// External source of time.
let mut historical_timestamp: u64 = 0;
let historical_accounts: Vec<tb::Account> = vec![]; // Loaded from an external source.
let historical_transfers: Vec<tb::Transfer> = vec![]; // Loaded from an external source.

// First, load and import all accounts with their timestamps from the historical source.
let mut accounts_batch = vec![];
for (index, mut account) in historical_accounts.into_iter().enumerate() {
    // Set a unique and strictly increasing timestamp.
    historical_timestamp += 1;
    account.timestamp = historical_timestamp;

    account.flags = if index < accounts_batch.len() - 1 {
        tb::AccountFlags::Imported | tb::AccountFlags::Linked
    } else {
        tb::AccountFlags::Imported
    };

    accounts_batch.push(account);
}

let account_errors = client.create_accounts(&accounts_batch).await?;
// Error handling omitted.

// Then, load and import all transfers with their timestamps from the historical source.
let mut transfers_batch = vec![];
for (index, mut transfer) in historical_transfers.into_iter().enumerate() {
    // Set a unique and strictly increasing timestamp.
    historical_timestamp += 1;
    transfer.timestamp = historical_timestamp;

    transfer.flags = if index < transfers_batch.len() - 1 {
        tb::TransferFlags::Imported | tb::TransferFlags::Linked
    } else {
        tb::TransferFlags::Imported
    };

    transfers_batch.push(transfer);
}

let transfer_errors = client.create_transfers(&transfers_batch).await?;
// Error handling omitted.
// Since it is a linked chain, in case of any error the entire batch is rolled back and can be retried
// with the same historical timestamps without regressing the cluster timestamp.
```
