Struct pravega_client::index::IndexWriter

pub struct IndexWriter<T: Fields + PartialOrd + PartialEq + Debug> { /* private fields */ }

Index Writer writes a fixed size Record to the stream.

Write takes a byte array as data and Fields. It hashes each Field name and construct a Record. Then it serializes the Record and writes to the stream.

Examples

use pravega_client_config::ClientConfigBuilder;
use pravega_client::client_factory::ClientFactory;
use pravega_client_shared::ScopedStream;
use pravega_client_macros::Fields;
use std::io::Write;
use tokio;

#[derive(Fields, Debug, PartialOrd, PartialEq)]
struct MyFields {
    id: u64,
    timestamp: u64,
}

#[tokio::main]
async fn main() {
    // assuming Pravega controller is running at endpoint `localhost:9090`
    let config = ClientConfigBuilder::default()
        .controller_uri("localhost:9090")
        .build()
        .expect("creating config");

    let client_factory = ClientFactory::new(config);

    // assuming scope:myscope, stream:mystream exist.
    // notice that this stream should be a fixed sized single segment stream
    let stream = ScopedStream::from("myscope/mystream");

    let mut index_writer = client_factory.create_index_writer(stream).await;

    let fields = MyFields{id: 1, timestamp: 1000};
    let data = vec!{1; 10};

    index_writer.append(fields, data).await.expect("append data with fields");
    index_writer.flush().await.expect("flush");
}

Implementations

impl<T: Fields + PartialOrd + PartialEq + Debug> IndexWriter<T>

pub async fn append( &mut self, fields: T, data: Vec<u8> ) -> Result<(), IndexWriterError>

Append data with a given Fields.

pub async fn append_conditionally( &mut self, fields: T, condition_on: T, data: Vec<u8> ) -> Result<(), IndexWriterError>

Append data with a given Fields and conditioned on a Fields. The conditional Fields should match the latest Fields in the stream, if not, this method will fail with error.

pub async fn flush(&mut self) -> Result<(), IndexWriterError>

Flush data.

pub async fn truncate(&mut self, offset: u64) -> Result<(), IndexWriterError>

Truncate data to a given offset.