Zerobus Rust SDK

A high-performance Rust client for streaming data ingestion into Databricks Delta tables using the Zerobus service.

Disclaimer

Public Preview: This SDK is supported for production use cases and is available to all customers. Databricks is actively working on stabilizing the Zerobus Ingest SDK for Rust. Minor version updates may include backwards-incompatible changes.

We are keen to hear feedback from you on this SDK. Please file issues, and we will address them.

Overview
Features
Installation
Quick Start
Repository Structure
How It Works
Usage Guide
Configuration Options
Error Handling
Examples
Best Practices
API Reference
Building from Source
Community and Contributing
License

Overview

The Zerobus Rust SDK provides a robust, async-first interface for ingesting large volumes of data into Databricks Delta tables. It abstracts the complexity of the Zerobus service and handles authentication, retries, stream recovery, and acknowledgment tracking automatically.

What is Zerobus? Zerobus is a high-throughput streaming service for direct data ingestion into Databricks Delta tables, optimized for real-time data pipelines and high-volume workloads.

Features

Async/Await Support - Built on Tokio for efficient concurrent I/O operations
Automatic OAuth 2.0 Authentication - Seamless token management with Unity Catalog
Built-in Recovery - Automatic retry and reconnection for transient failures
High Throughput - Configurable inflight record limits for optimal performance
Batch Ingestion - Ingest multiple records at once with all-or-nothing semantics for maximum throughput
Flexible Serialization - Support for both JSON (simple) and Protocol Buffers (type-safe) data formats
Type Safety - Protocol Buffers ensure schema validation at compile time
Schema Generation - CLI tool to generate protobuf schemas from Unity Catalog tables
Flexible Configuration - Fine-tune timeouts, retries, and recovery behavior
Graceful Stream Management - Proper flushing and acknowledgment tracking
Acknowledgment Callbacks - Receive notifications when records are acknowledged or encounter errors

Installation

Add the SDK to your Cargo.toml:

cargo add databricks-zerobus-ingest-sdk
cargo add prost prost-types
cargo add tokio --features macros,rt-multi-thread

Why these dependencies?

databricks-zerobus-ingest-sdk - The SDK itself
prost and prost-types - Required for encoding your data to Protocol Buffers and loading schema descriptors
tokio - Async runtime required for running async functions (the SDK is fully async)

What's in the crates.io package? The published crate contains only the core Zerobus ingestion SDK. Tools for schema generation (tools/generate_files) and working examples (examples/) are only available in the GitHub repository. You'll need to clone the repo to generate protobuf schemas from your Unity Catalog tables.

For Local Development

Clone the repository and use a path dependency:

git clone https://github.com/databricks/zerobus-sdk-rs.git
cd your_project

Then in your Cargo.toml:

[dependencies]
databricks-zerobus-ingest-sdk = { path = "../zerobus-sdk-rs/sdk" }
prost = "0.13.3"
prost-types = "0.13.3"
tokio = { version = "1.42.0", features = ["macros", "rt-multi-thread"] }

Quick Start

The SDK supports two serialization formats and two ingestion methods:

Serialization:

JSON (Recommended for getting started): Simpler approach using JSON strings, no schema generation required
Protocol Buffers (Recommended for production): Type-safe approach with schema validation at compile time

Ingestion Methods:

Single-record (ingest_record_offset): Ingest records one at a time with per-record acknowledgment
Batch (ingest_records_offset): Ingest multiple records at once with all-or-nothing semantics for higher throughput

Note: The older ingest_record() and ingest_records() methods are deprecated as of v0.4.0. Use the _offset variants instead.

See examples/README.md for detailed setup instructions and examples for all combinations.

Repository Structure

zerobus_rust_sdk/
├── sdk/                                # Core SDK library
│   ├── src/
│   │   ├── lib.rs                      # Main SDK and stream implementation
│   │   ├── default_token_factory.rs    # OAuth 2.0 token handling
│   │   ├── errors.rs                   # Error types and retryable logic
│   │   ├── headers_provider.rs         # Trait for custom authentication headers
│   │   ├── stream_configuration.rs     # Stream options
│   │   ├── landing_zone.rs             # Inflight record buffer
│   │   └── offset_generator.rs         # Logical offset tracking
│   ├── zerobus_service.proto           # gRPC protocol definition
│   ├── build.rs                        # Build script for protobuf compilation
│   └── Cargo.toml
│
├── tools/
│   └── generate_files/                 # Schema generation CLI tool
│       ├── src/
│       │   ├── main.rs                 # CLI entry point
│       │   └── generate.rs             # Unity Catalog -> Proto conversion
│       ├── README.md                   # Tool documentation
│       └── Cargo.toml
│
├── examples/
│   ├── README.md                       # Examples documentation
│   ├── basic_example_json/             # JSON single-record example
│   │   ├── src/main.rs                 # Example usage code
│   │   └── Cargo.toml
│   ├── basic_example_json_batch/       # JSON batch ingestion example
│   │   ├── src/main.rs                 # Example usage code
│   │   └── Cargo.toml
│   ├── basic_example_proto/            # Protocol Buffers single-record example
│   │   ├── src/main.rs                 # Example usage code
│   │   ├── output/                     # Generated schema files
│   │   │   ├── orders.proto
│   │   │   ├── orders.rs
│   │   │   └── orders.descriptor
│   │   └── Cargo.toml
│   └── basic_example_proto_batch/      # Protocol Buffers batch ingestion example
│       ├── src/main.rs                 # Example usage code
│       ├── output/                     # Generated schema files
│       │   ├── orders.proto
│       │   ├── orders.rs
│       │   └── orders.descriptor
│       └── Cargo.toml
│
├── tests/                              # Integration tests crate
│   ├── src/
│   │   ├── mock_grpc.rs                # Mock Zerobus gRPC server
│   │   └── rust_tests.rs               # Test suite
│   ├── build.rs
│   └── Cargo.toml
│
├── Cargo.toml                          # Workspace configuration
└── README.md                           # This file

Key Components

sdk/ - The main library crate containing all SDK functionality
tools/ - CLI tool for generating Protocol Buffer schemas from Unity Catalog tables
examples/ - Complete working examples demonstrating SDK usage
Workspace - Root Cargo.toml defines a Cargo workspace for unified builds

How It Works

Architecture Overview

+-----------------+
|    Your App     |
+-----------------+
        | 1. create_stream()
        v
+-----------------+
|   ZerobusSdk    |
| - Manages TLS   |
| - Creates       |
|   channels      |
+-----------------+
        | 2. Opens bidirectional gRPC stream
        v
+--------------------------------------+
|            ZerobusStream             |
| +----------------------------------+ |
| |           Supervisor             | | Manages lifecycle, recovery
| +----------------------------------+ |
|                  |                   |
|      +-----------+-----------+       |
|      v                       v       |
| +----------+          +----------+   | 
| |  Sender  |          | Receiver |   | Parallel tasks
| |  Task    |          |  Task    |   |
| +----------+          +----------+   |
|      ^                       |       |
|      |                       v       |
| +----------------------------------+ |
| |          Landing Zone            | | Inflight buffer
| +----------------------------------+ |
+--------------------------------------+
            | 3. gRPC stream
            v
+-----------------------+
|      Databricks       |
|    Zerobus Service    |
+-----------------------+

Data Flow

Ingestion - Your app calls stream.ingest_record(data) or stream.ingest_records(batch)
Buffering - Records are placed in the landing zone with logical offsets
Sending - Sender task sends records over gRPC with physical offsets
Acknowledgment - Receiver task gets server ack and resolves the future
Recovery - If connection fails, supervisor reconnects and resends unacked records

Authentication Flow

The SDK uses OAuth 2.0 client credentials flow:

SDK constructs authorization request with Unity Catalog privileges
Sends request to {uc_endpoint}/oidc/v1/token with client credentials
Token includes scoped permissions for the specific table
Token is attached to gRPC metadata as Bearer token
Fresh tokens are fetched automatically on each connection

Custom Authentication

For advanced use cases, you can implement the HeadersProvider trait to supply your own authentication headers. This is useful for integrating with a different OAuth provider, using a centralized token caching service, or implementing alternative authentication mechanisms.

Note: The headers you provide must still conform to the authentication protocol expected by the Zerobus service. The default implementation, OAuthHeadersProvider, serves as the reference for the required headers (authorization and x-databricks-zerobus-table-name). This feature provides flexibility in how you source your credentials, not in changing the authentication protocol itself.

Example:

use databricks_zerobus_ingest_sdk::*;
use std::collections::HashMap;
use std::sync::Arc;
use async_trait::async_trait;

struct MyCustomAuthProvider;

#[async_trait]
impl HeadersProvider for MyCustomAuthProvider {
    async fn get_headers(&self) -> ZerobusResult<HashMap<&'static str, String>> {
        let mut headers = HashMap::new();
        // Custom logic to fetch and cache a token would go here.
        headers.insert("authorization", "Bearer <your-token>".to_string());
        headers.insert("x-databricks-zerobus-table-name", "<your-table-name>".to_string());
        Ok(headers)
    }
}

async fn example(sdk: ZerobusSdk, table_properties: TableProperties) -> ZerobusResult<()> {
    let custom_provider = Arc::new(MyCustomAuthProvider {});
    let stream = sdk.create_stream_with_headers_provider(
        table_properties,
        custom_provider,
        None,
    ).await?;
    Ok(())
}

Usage Guide

The SDK supports two approaches for data serialization:

JSON - Simpler approach that uses JSON strings. No schema generation required, making it ideal for quick prototyping. See examples/README.md for a complete example.
Protocol Buffers - Type-safe approach with schema validation at compile time. Recommended for production use cases. This guide focuses on the Protocol Buffers approach.

For JSON-based ingestion, you can skip the schema generation step and directly pass JSON strings to ingest_record().

1. Generate Protocol Buffer Schema (Protocol Buffers approach only)

Important Note: The schema generation tool and examples are only available in the GitHub repository. The crate published on crates.io contains only the core Zerobus ingestion SDK logic. To generate protobuf schemas or see working examples, clone the repository:
git clone https://github.com/databricks/zerobus-sdk-rs.git
cd zerobus-sdk-rs

Use the included tool to generate schema files from your Unity Catalog table:

cd tools/generate_files

# For AWS
cargo run -- \
  --uc-endpoint "https://<your-workspace>.cloud.databricks.com" \
  --client-id "your-client-id" \
  --client-secret "your-client-secret" \
  --table "catalog.schema.table" \
  --output-dir "../../output"

# For Azure
cargo run -- \
  --uc-endpoint "https://<your-workspace>.azuredatabricks.net" \
  --client-id "your-client-id" \
  --client-secret "your-client-secret" \
  --table "catalog.schema.table" \
  --output-dir "../../output"

This generates three files:

{table}.proto - Protocol Buffer schema definition
{table}.rs - Rust structs with serialization code
{table}.descriptor - Binary descriptor for runtime validation

See tools/generate_files/README.md for supported data types and limitations.

See examples/README.md for more information on how to get OAuth credentials.

2. Initialize the SDK

Create an SDK instance with your Databricks workspace endpoints:

// For AWS
let sdk = ZerobusSdk::new(
    "https://<your-shard-id>.zerobus.<region>.cloud.databricks.com".to_string(),  // Zerobus endpoint
    "https://<your-workspace>.cloud.databricks.com".to_string(),     // Unity Catalog endpoint
)?;

// For Azure
let sdk = ZerobusSdk::new(
    "https://<your-shard-id>.zerobus.<region>.azuredatabricks.net".to_string(),  // Zerobus endpoint
    "https://<your-workspace>.azuredatabricks.net".to_string(),     // Unity Catalog endpoint
)?;

Note: The workspace ID is automatically extracted from the Zerobus endpoint when ZerobusSdk::new() is called.

3. Configure Authentication

The SDK handles authentication automatically. You just need to provide:

Client ID - Your OAuth client ID
Client Secret - Your OAuth client secret
Unity Catalog Endpoint - Passed to SDK constructor
Table Name - Included in table properties

let client_id = "your-client-id".to_string();
let client_secret = "your-client-secret".to_string();

See examples/README.md for more information on how to get these credentials.

4. Create a Stream

Configure table properties and stream options:

use std::fs;
use prost::Message;
use prost_types::{FileDescriptorSet, DescriptorProto};

// Load descriptor from generated files
fn load_descriptor(path: &str, file: &str, msg: &str) -> DescriptorProto {
    let bytes = fs::read(path).expect("Failed to read descriptor");
    let file_set = FileDescriptorSet::decode(bytes.as_ref()).unwrap();

    let file_desc = file_set.file.into_iter()
        .find(|f| f.name.as_deref() == Some(file))
        .unwrap();

    file_desc.message_type.into_iter()
        .find(|m| m.name.as_deref() == Some(msg))
        .unwrap()
}

let descriptor_proto = load_descriptor(
    "output/orders.descriptor",
    "orders.proto",
    "table_Orders",
);

let table_properties = TableProperties {
    table_name: "catalog.schema.orders".to_string(),
    descriptor_proto,
};

let options = StreamConfigurationOptions {
    max_inflight_requests: 10000,
    recovery: true,
    recovery_timeout_ms: 15000,
    recovery_backoff_ms: 2000,
    recovery_retries: 4,
    ..Default::default()
};

let mut stream = sdk.create_stream(
    table_properties,
    client_id,
    client_secret,
    Some(options),
).await?;

5. Ingest Data

The SDK provides multiple ingestion methods:

Single Record Ingestion

Ingest records one at a time by encoding them with Protocol Buffers. Use ingest_record_offset() to get the offset directly:

use prost::Message;

let record = YourMessage {
    field1: Some("value".to_string()),
    field2: Some(42),
};

// This await queues the record for sending and returns the offset directly.
let offset_id = stream.ingest_record_offset(record.encode_to_vec()).await?;

// Later, you can explicitly wait for acknowledgment using the offset.
stream.wait_for_offset(offset_id).await?;

Alternative API: Future-Based Acknowledgment (Deprecated)

The older ingest_record() method returns a Future for acknowledgment. This method is deprecated as of v0.4.0:

use prost::Message;

let record = YourMessage {
    field1: Some("value".to_string()),
    field2: Some(42),
};

// DEPRECATED: Returns a Future that resolves to the offset
let ack_future = stream.ingest_record(record.encode_to_vec()).await?;
let offset_id = ack_future.await?;

Recommended: Use ingest_record_offset() for new code. It provides a cleaner API by returning the offset directly (after queuing), allowing you to use wait_for_offset() when you explicitly need to wait for acknowledgment

Batch Ingestion

For higher throughput and all-or-nothing semantics, use ingest_records_offset() to ingest multiple records at once:

let records: Vec<Vec<u8>> = vec![
    YourMessage { id: Some(1), /* ... */ }.encode_to_vec(),
    YourMessage { id: Some(2), /* ... */ }.encode_to_vec(),
    YourMessage { id: Some(3), /* ... */ }.encode_to_vec(),
];

// This await queues the batch for sending and returns the offset directly.
// Returns Some(offset) for non-empty batches, None for empty batches.
if let Some(offset_id) = stream.ingest_records_offset(records).await? {
    // Later, wait for this specific batch acknowledgment.
    stream.wait_for_offset(offset_id).await?;
}

Batch API Semantics:

All-or-nothing: The entire batch succeeds or fails as a unit. If any record in the batch fails, the entire batch is rejected.
Atomic acknowledgment: You receive a single acknowledgment for the entire batch, not individual records.
Better throughput: Reduces network overhead by sending multiple records in a single request.
Empty batches: Ingesting an empty batch is a no-op. The future resolves to None.
Preserved on failure: Batches are preserved as units when retrieving via get_unacked_batches() or when reingested via recreate_stream(). Note that get_unacked_records() flattens batches into individual records.

High throughput patterns:

With ingest_record_offset() and ingest_records_offset(), you can ingest many records without immediately waiting for acknowledgments. Use flush() to periodically wait for all pending acknowledgments:

let mut ingested_cnt = 0;

// Example with single-record ingestion
for i in 0..100_000 {
    let record = YourMessage {
        id: Some(i),
        timestamp: Some(chrono::Utc::now().timestamp()),
        data: Some(format!("record-{}", i)),
    };

    // This await only waits for the record to be queued.
    let _offset = stream.ingest_record_offset(record.encode_to_vec()).await?;
    ingested_cnt += 1;

    // Periodically flush and wait for acks to avoid unbounded memory growth
    if ingested_cnt >= 10_000 {
        stream.flush().await?;
        ingested_cnt = 0;
    }
}

// Flush and wait for remaining acknowledgments
stream.flush().await?;

// Same pattern works for batch ingestion
let batches = vec![/* batch1 */, /* batch2 */, /* batch3 */];
for batch in batches {
    let _offset = stream.ingest_records_offset(batch).await?;
    ingested_cnt += 1;
    // ...
}

Parallelizing with multiple streams:

Since each stream uses a single gRPC connection, opening multiple threads on the same stream doesn't improve throughput. For true parallelization, open multiple streams (e.g., partition your data):

use tokio::task::JoinSet;

let mut tasks = JoinSet::new();

// Partition data across multiple streams for parallel ingestion
for partition in 0..4 {
    let sdk_clone = sdk.clone();
    let table_properties = table_properties.clone();
    let client_id = client_id.clone();
    let client_secret = client_secret.clone();

    tasks.spawn(async move {
        let mut stream = sdk_clone.create_stream(
            table_properties,
            client_id,
            client_secret,
            None,
        ).await?;

        // Ingest partition data (using single-record or batch ingestion)
        for i in (partition * 25_000)..((partition + 1) * 25_000) {
            let record = YourMessage { id: Some(i), /* ... */ };
            let _offset = stream.ingest_record_offset(record.encode_to_vec()).await?;
        }

        // Close implicitly waits for all acknowledgments from the server.
        stream.close().await?; 
        Ok::<_, ZerobusError>(())
    });
}

// Wait for all streams to complete
while let Some(result) = tasks.join_next().await {
    result??;
}

6. Handle Acknowledgments

The recommended ingest_record_offset() and ingest_records_offset() methods return offsets directly (after queuing):

ingest_record_offset() returns OffsetId (the logical offset)
ingest_records_offset() returns Option<OffsetId> (None if the batch is empty)

// Ingest and get offset (after queuing the record)
let offset_id = stream.ingest_record_offset(data).await?;
println!("Record sent with offset Id: {}", offset_id);

// Wait for acknowledgment when needed
stream.wait_for_offset(offset_id).await?;
println!("Record committed at offset: {}", offset_id);

// For batches, the method returns Option<OffsetId>
// (None if the batch is empty)
let batch = vec![data1, data2, data3];
if let Some(offset_id) = stream.ingest_records_offset(batch).await? {
    println!("Batch sent with last offset: {}", offset_id);
    stream.wait_for_offset(offset_id).await?;
    println!("Batch committed");
} else {
    println!("Empty batch, no records ingested");
}

// High-throughput: collect offsets and wait selectively
let mut offsets = Vec::new();
for i in 0..1000 {
    let offset = stream.ingest_record_offset(record).await?;
    offsets.push(offset);
}
// Wait for specific offsets as needed
for offset in offsets {
    stream.wait_for_offset(offset).await?;
}

// Or use flush() to wait for all pending acknowledgments at once
stream.flush().await?;

Using Acknowledgment Callbacks

For scenarios where you need to track acknowledgments without explicitly waiting (e.g., for metrics or logging), you can use callbacks:

use databricks_zerobus_ingest_sdk::{AckCallback, OffsetId};
use std::sync::Arc;

// Define a callback that implements the AckCallback trait
struct MyCallback;

impl AckCallback for MyCallback {
    fn on_ack(&self, offset_id: OffsetId) {
        // Called when a record is acknowledged
        println!("✓ Acknowledged offset: {}", offset_id);
    }

    fn on_error(&self, offset_id: OffsetId, error_message: &str) {
        // Called when a record encounters an error
        eprintln!("✗ Error for offset {}: {}", offset_id, error_message);
    }
}

// Configure stream with callback
let options = StreamConfigurationOptions {
    max_inflight_requests: 10000,
    ack_callback: Some(Arc::new(MyCallback)),
    ..Default::default()
};

let mut stream = sdk.create_stream(
    table_properties,
    client_id,
    client_secret,
    Some(options),
).await?;

for i in 0..1000 {
    let record = YourMessage { id: Some(i), /* ... */ };
    stream.ingest_record_offset(record.encode_to_vec()).await?;
    // Callback fires when this record is acknowledged
}

stream.flush().await?;

Important: Callbacks run synchronously in a dedicated callback handler task. Keep them lightweight (simple logging, metrics increment) to avoid callback backlog. For heavy work like database writes or network calls, send data to a channel for processing in a separate task:

use tokio::sync::mpsc;

struct ChannelCallback {
    tx: mpsc::UnboundedSender<OffsetId>,
}

impl AckCallback for ChannelCallback {
    fn on_ack(&self, offset_id: OffsetId) {
        // Lightweight: just send to channel
        let _ = self.tx.send(offset_id);
    }

    fn on_error(&self, offset_id: OffsetId, error_message: &str) {
        eprintln!("Error: {}", error_message);
    }
}

let (tx, mut rx) = mpsc::unbounded_channel();
let callback = Arc::new(ChannelCallback { tx });

// Heavy processing in separate task
tokio::spawn(async move {
    while let Some(offset) = rx.recv().await {
        // Heavy work here (database writes, API calls, etc.)
        write_to_database(offset).await;
    }
});

7. Close the Stream

Always close streams to ensure data is flushed:

// Close gracefully (flushes automatically)
stream.close().await?;

If the stream fails, retrieve unacknowledged records:

match stream.close().await {
    Err(_) => {
        // Option 1: Get individual records (flattened)
        let unacked = stream.get_unacked_records().await?;
        let total_records = unacked.count();
        println!("Failed to ack {} records", total_records);
        
        // Option 2: Get records grouped by batch (preserves batch structure)
        let unacked_batches = stream.get_unacked_batches().await?;
        let total_records: usize = unacked_batches.iter().map(|batch| batch.get_record_count()).sum();
        println!("Failed to ack {} records in {} batches", total_records, unacked_batches.len());
        
        // Retry with a new stream
    }
    Ok(_) => println!("Stream closed successfully"),
}

Configuration Options

StreamConfigurationOptions

Field	Type	Default	Description
`max_inflight_requests`	`usize`	1,000,000	Maximum unacknowledged requests in flight
`recovery`	`bool`	true	Enable automatic stream recovery on failure
`recovery_timeout_ms`	`u64`	15,000	Timeout for recovery operations (ms)
`recovery_backoff_ms`	`u64`	2,000	Delay between recovery retry attempts (ms)
`recovery_retries`	`u32`	4	Maximum number of recovery attempts
`server_lack_of_ack_timeout_ms`	`u64`	60,000	Timeout waiting for server acks (ms)
`flush_timeout_ms`	`u64`	300,000	Timeout for flush operations (ms)
`record_type`	`RecordType`	`RecordType::Proto`	Record serialization format (Proto or Json)
`stream_paused_max_wait_time_ms`	`Option<u64>`	`None`	Max time to wait during graceful close (`None` = full server duration, `Some(0)` = immediate, `Some(x)` = min(x, server_duration))
`ack_callback`	`Option<Arc<dyn AckCallback>>`	`None`	Optional callback for acknowledgment notifications
`callback_max_wait_time_ms`	`Option<u64>`	`None`	Maximum time to wait for callback processing to complete after closing the stream (`None` = wait indefinitely, `Some(x)` = wait up to `x` ms)

Example:

let options = StreamConfigurationOptions {
    max_inflight_requests: 50000,
    recovery: true,
    recovery_timeout_ms: 20000,
    recovery_retries: 5,
    flush_timeout_ms: 600000,
    ..Default::default()
};

Error Handling

The SDK categorizes errors as retryable or non-retryable:

Retryable Errors

Auto-recovered if recovery is enabled:

Network failures
Connection timeouts
Temporary server errors
Stream closed by server

Non-Retryable Errors

Require manual intervention:

InvalidUCTokenError - Invalid OAuth credentials
InvalidTableName - Table doesn't exist or invalid format
InvalidArgument - Invalid parameters or schema mismatch
Code::Unauthenticated - Authentication failure
Code::PermissionDenied - Insufficient table permissions
ChannelCreationError - Failed to establish TLS connection

Check if an error is retryable:

match stream.ingest_record(payload).await {
    Ok(ack) => {
        let offset = ack.await?;
    }
    Err(e) if e.is_retryable() => {
        eprintln!("Retryable error, SDK will auto-recover: {}", e);
    }
    Err(e) => {
        eprintln!("Fatal error, manual intervention needed: {}", e);
        return Err(e.into());
    }
}

Examples

Complete Working Examples

The examples/ directory contains four working examples covering different serialization formats and ingestion patterns:

Example	Serialization	Ingestion	Description
`basic_example_json/`	JSON	Single-record	Simple JSON strings, no schema required
`basic_example_json_batch/`	JSON	Batch	Multiple JSON records with all-or-nothing semantics, no schema required
`basic_example_proto/`	Protocol Buffers	Single-record	Type-safe with compile-time validation
`basic_example_proto_batch/`	Protocol Buffers	Batch	High-throughput batch ingestion with Proto

Check examples/README.md for setup instructions and detailed comparisons.

Stream Recovery

let sdk = ZerobusSdk::new(endpoint, uc_endpoint);

let mut stream = sdk.create_stream(
    table_properties.clone(),
    client_id.clone(),
    client_secret.clone(),
    Some(options),
).await?;

// Ingest data...
match stream.close().await {
    Err(_) => {
        // Stream failed, recreate with unacked records
        stream = sdk.recreate_stream(stream).await?;
    }
    Ok(_) => println!("Closed successfully"),
}

Tests

Integration tests live in the tests/ crate and run against a lightweight mock Zerobus gRPC server.

Mock server: tests/src/mock_grpc.rs
Test suite: tests/src/rust_tests.rs

Run tests with logs:

cargo test -p tests -- --nocapture

Best Practices

Reuse SDK Instances - Create one ZerobusSdk per application and reuse for multiple streams
Always Close Streams - Use stream.close().await? to ensure all data is flushed
Choose the Right Ingestion Method:
- Use ingest_records_offset() for high throughput batch ingestion
- Use ingest_record_offset() when processing records individually
- Both return offsets directly; use wait_for_offset() to explicitly wait for acknowledgments
- The older ingest_record() and ingest_records() methods are deprecated
Tune Inflight Limits - Adjust max_inflight_requests based on memory and throughput needs
Enable Recovery - Always set recovery: true in production environments
Handle Ack Futures - Use tokio::spawn for fire-and-forget or batch-wait for verification
Monitor Errors - Log and alert on non-retryable errors
Validate Schemas - Use the schema generation tool to ensure type safety (for Protocol Buffers)
Secure Credentials - Never hardcode secrets; use environment variables or secret managers
Test Recovery - Simulate failures to verify your error handling logic

API Reference

`ZerobusSdk`

Main entry point for the SDK.

Constructor:

pub fn new(zerobus_endpoint: String, unity_catalog_url: String) -> ZerobusResult<Self>

Methods:

pub async fn create_stream(
    &self,
    table_properties: TableProperties,
    client_id: String,
    client_secret: String,
    options: Option<StreamConfigurationOptions>,
) -> ZerobusResult<ZerobusStream>

pub async fn recreate_stream(
    &self,
    stream: ZerobusStream
) -> ZerobusResult<ZerobusStream>

Recreates a failed stream, preserving and re-ingesting unacknowledged records.

pub async fn create_stream_with_headers_provider(
    &self,
    table_properties: TableProperties,
    headers_provider: Arc<dyn HeadersProvider>,
    options: Option<StreamConfigurationOptions>,
) -> ZerobusResult<ZerobusStream>

Creates a stream with a custom headers provider for advanced authentication.

`ZerobusStream`

Represents an active ingestion stream.

Methods:

pub async fn ingest_record_offset(
    &self,
    payload: impl Into<EncodedRecord>
) -> ZerobusResult<OffsetId>

Ingests a single encoded record (Protocol Buffers or JSON). The await queues the record for sending and returns the logical offset ID directly. Use wait_for_offset() to explicitly wait for server acknowledgment of this offset.

pub async fn ingest_records_offset(
    &self,
    payloads: Vec<impl Into<EncodedRecord>>
) -> ZerobusResult<Option<OffsetId>>

Ingests multiple encoded records as a batch with all-or-nothing semantics. The entire batch either succeeds or fails as a unit. The await queues the batch for sending and returns the logical offset ID directly (or None for empty batches). Use wait_for_offset() to explicitly wait for server acknowledgment.

pub async fn ingest_record(
    &self,
    payload: Vec<u8>
) -> ZerobusResult<impl Future<Output = ZerobusResult<OffsetId>>>>

Deprecated: Use ingest_record_offset() instead. Returns a future that resolves to the offset ID.

pub async fn ingest_records(
    &self,
    payloads: Vec<Vec<u8>>
) -> ZerobusResult<impl Future<Output = ZerobusResult<Option<OffsetId>>>>

Deprecated: Use ingest_records_offset() instead. Returns a future that resolves to Some(offset_id) for non-empty batches, or None if the batch is empty.

pub async fn wait_for_offset(&self, offset_id: OffsetId) -> ZerobusResult<()>

Waits for acknowledgment of a specific logical offset. Use this method with offsets returned from ingest_record_offset() or ingest_records_offset() to explicitly wait for server acknowledgment.

pub async fn flush(&self) -> ZerobusResult<()>

Flushes all pending records and waits for acknowledgment.

pub async fn close(&mut self) -> ZerobusResult<()>

Flushes and closes the stream gracefully.

pub async fn get_unacked_records(&self) -> ZerobusResult<impl Iterator<Item = EncodedRecord>>

Returns an iterator over all unacknowledged records as individual EncodedRecord items. This flattens batches into individual records. Only call after stream failure.

pub async fn get_unacked_batches(&self) -> ZerobusResult<Vec<EncodedBatch>>

Returns unacknowledged records grouped by batch, preserving the original batch structure. Records ingested together remain grouped:

Each ingest_record() call creates a batch containing one record
Each ingest_records() call creates a batch containing multiple records

Only call after stream failure.

`TableProperties`

Configuration for the target table.

Fields:

pub struct TableProperties {
    pub table_name: String,
    pub descriptor_proto: Option<prost_types::DescriptorProto>,
}

table_name - Full table name (e.g., "catalog.schema.table")
descriptor_proto - Optional Protocol buffer descriptor loaded from generated files (required for Proto record type, None for JSON)

`StreamConfigurationOptions`

Stream behavior configuration.

Fields:

pub struct StreamConfigurationOptions {
    pub max_inflight_requests: usize,
    pub recovery: bool,
    pub recovery_timeout_ms: u64,
    pub recovery_backoff_ms: u64,
    pub recovery_retries: u32,
    pub server_lack_of_ack_timeout_ms: u64,
    pub flush_timeout_ms: u64,
    pub record_type: RecordType,
    pub stream_paused_max_wait_time_ms: Option<u64>,
    pub ack_callback: Option<Arc<dyn AckCallback>>,
    pub callback_max_wait_time_ms: Option<u64>
}

See Configuration Options for details.

`AckCallback`

Trait for receiving acknowledgment notifications.

Methods:

pub trait AckCallback: Send + Sync {
    fn on_ack(&self, offset_id: OffsetId);
    fn on_error(&self, offset_id: OffsetId, error_message: &str);
}

on_ack() - Called when a record/batch is successfully acknowledged
on_error() - Called when a record/batch encounters an error

`HeadersProvider`

Trait for custom authentication header providers.

Methods:

#[async_trait]
pub trait HeadersProvider: Send + Sync {
    async fn get_headers(&self) -> ZerobusResult<HashMap<&'static str, String>>;
}

Implement this trait to provide custom authentication headers. The default implementation (OAuthHeadersProvider) handles OAuth 2.0 token management. Use this for:

Custom token caching strategies
Alternative authentication mechanisms
Integration with centralized credential services

See Custom Authentication section for usage examples.

`ZerobusError`

Error type for all SDK operations.

Methods:

pub fn is_retryable(&self) -> bool

Returns true if the error can be automatically recovered by the SDK.

Building from Source

For contributors or those who want to build and test the SDK:

git clone https://github.com/YOUR_USERNAME/zerobus_rust_sdk.git
cd zerobus_rust_sdk
cargo build --workspace

Build specific components:

# Build only SDK
cargo build -p databricks-zerobus-ingest-sdk

# Build only schema tool
cargo build -p generate_files

# Build and run JSON example
cargo run -p basic_example_json

# Build and run Protocol Buffers example
cargo run -p basic_example_proto

Community and Contributing

This is an open source project. We welcome contributions, feedback, and bug reports.

Contributing Guide: Learn how to contribute, including our development process and coding style.
Changelog: See the history of changes in the SDK.
Security Policy: Read about our security process and how to report vulnerabilities.
Developer Certificate of Origin (DCO): Understand the agreement for contributions.
Open Source Attributions: See a list of the open source libraries we use.

License

This SDK is licensed under the Databricks License. See the LICENSE file for the full license text. The license is also available online at https://www.databricks.com/legal/db-license.

Requirements

Rust 1.70 or higher (2021 edition)
Databricks workspace with Zerobus access enabled
OAuth 2.0 client credentials (client ID and secret)
Unity Catalog endpoint access
TLS - Uses native OS certificate store

For issues, questions, or contributions, please visit the GitHub repository.

databricks-zerobus-ingest-sdk 0.4.0

Zerobus Rust SDK

Disclaimer

Table of Contents

Overview

Features

Installation

For Local Development

Quick Start

Repository Structure

Key Components

How It Works

Architecture Overview

Data Flow

Authentication Flow

Custom Authentication

Usage Guide

1. Generate Protocol Buffer Schema (Protocol Buffers approach only)

2. Initialize the SDK

3. Configure Authentication

4. Create a Stream

5. Ingest Data

Single Record Ingestion

Alternative API: Future-Based Acknowledgment (Deprecated)

Batch Ingestion

6. Handle Acknowledgments

Using Acknowledgment Callbacks

7. Close the Stream

Configuration Options

StreamConfigurationOptions

Error Handling

Retryable Errors

Non-Retryable Errors

Examples

Complete Working Examples

Stream Recovery

Tests

Best Practices

API Reference

ZerobusSdk

ZerobusStream

TableProperties

StreamConfigurationOptions

AckCallback

HeadersProvider

ZerobusError

Building from Source

Community and Contributing

License

Requirements

`ZerobusSdk`

`ZerobusStream`

`TableProperties`

`StreamConfigurationOptions`

`AckCallback`

`HeadersProvider`

`ZerobusError`