Module opendal::services::hdfs

Hadoop Distributed File System (HDFS™) support.

A distributed file system that provides high-throughput access to application data.

Features

HDFS support needs to enable feature services-hdfs.

Configuration

• root: Set the work dir for backend.
• name_node: Set the name node for backend.

Refer to Builder’s public API docs for more information.

Environment

• OPENDAL_HDFS_ROOT
• OPENDAL_HDFS_NAME_NODE

HDFS also needs some environment set correctly.

• JAVA_HOME: the path to java home, could be found via java -XshowSettings:properties -version
• HADOOP_HOME: the path to hadoop home, opendal relays on this env to discover hadoop jars and set CLASSPATH automatically.

Most of the time, setting JAVA_HOME and HADOOP_HOME is enough. But there are some edge cases:

• If meeting errors like the following:

error while loading shared libraries: libjvm.so: cannot open shared object file: No such file or directory

Java’s lib are not including in pkg-config find path, please set LD_LIBRARY_PATH:

export LD_LIBRARY_PATH=${JAVA_HOME}/lib/server:${LD_LIBRARY_PATH}

The path of libjvm.so could be different, please keep an eye on it.

• If meeting errors like the following:

(unable to get stack trace for java.lang.NoClassDefFoundError exception: ExceptionUtils::getStackTrace error.)

CLASSPATH is not set correctly or your hadoop installation is incorrect.

Example

Via Environment

Set environment correctly:

export OPENDAL_HDFS_ROOT=/path/to/dir/
export OPENDAL_HDFS_NAME_NODE=hdfs://127.0.0.1:9000

use std::sync::Arc;

use anyhow::Result;
use opendal::Object;
use opendal::Operator;
use opendal::Scheme;

#[tokio::main]
async fn main() -> Result<()> {
    let op: Operator = Operator::from_env(Scheme::Hdfs)?;

    // Create an object handle to start operation on object.
    let _: Object = op.object("test_file");

    Ok(())
}

Via Builder

use std::sync::Arc;

use anyhow::Result;
use opendal::services::hdfs;
use opendal::Accessor;
use opendal::Object;
use opendal::Operator;

#[tokio::main]
async fn main() -> Result<()> {
    // Create fs backend builder.
    let mut builder = hdfs::Builder::default();
    // Set the name node for hdfs.
    builder.name_node("hdfs://127.0.0.1:9000");
    // Set the root for hdfs, all operations will happen under this root.
    //
    // NOTE: the root must be absolute path.
    builder.root("/tmp");

    // `Accessor` provides the low level APIs, we will use `Operator` normally.
    let op: Operator = Operator::new(builder.build()?);

    // Create an object handle to start operation on object.
    let _: Object = op.object("test_file");

    Ok(())
}

Structs

Backend

Backend for hdfs services.

Builder

Builder for hdfs services