HDFS2 go reader/writer example

hdfs2-example.go

package main 
/* 

To build, you need the following magic & an HDP2 install

export CGO_CFLAGS="-I/usr/include/ -I$HADOOP_HOME/include" 
export CGO_LDFLAGS="-L $HADOOP_HOME/lib/native -L $JAVA_HOME/jre/lib/amd64/server/"

Then just 

go get -u -a
go build -ldflags="-r $HADOOP_HOME/lib/native/"

This will give you a binary which will run as long as HADOOP_HOME is set up properly.

The hdf2go will set up a classpath by itself and the -r arg will bake in the libhdfs.so path into the binary
*/

import "github.com/t3rmin4t0r/hdfs2go"
import "fmt"

func main() {
	fs, err := hdfs2.Connect("localhost", 56565)
	if err != nil {
		fmt.Printf("Error on connecting to hdfs: %v\n", err)
		return
	}
	defer fs.Disconnect()
	file, err := fs.OpenFile("/a.txt", hdfs2.O_WRONLY|hdfs2.O_CREATE, 0, 0, 0)
	if err != nil {
		fmt.Printf("Error on opening file: %v\n", err)
		return
	}
	buf := []byte("hello hdfs world, from go!")
	size, err := fs.Write(file, buf, len(buf))

	if err != nil {
		fmt.Printf("Error on writing bytes to file: %v\n", err)
		return
	} else {
		fmt.Printf("Wrote %d bytes to /a.txt\n", size)
	}
	err = fs.Flush(file)
	err = fs.CloseFile(file)
	rfile, err := fs.OpenFile("/a.txt", hdfs2.O_RDONLY, 0, 0, 0)
	buffer :=  make([]byte, len(buf))
	val, err := fs.Read(rfile, buffer, len(buffer))
	if err != nil {
		fmt.Printf("Error on reading file: %v\n", err)
		return
	} else {
		fmt.Printf("Read %d bytes from /a.txt\n", val)
	}
	fs.CloseFile(rfile)
	fs.Delete("/a.txt", false)

}