go-ceph/docs/hints.md

API Hints & Quick How-Tos

Below you'll find some brief sections that show how some of the API calls in go-ceph work together. This is not meant to cover every possible use case but are recorded here as a quick way to get familiar with these calls.

rados Package

Connecting to a cluster

Connect to a Ceph cluster using a configuration file located in the default search paths.

conn, _ := rados.NewConn()
conn.ReadDefaultConfigFile()
conn.Connect()

A connection can be shutdown by calling the Shutdown method on the connection object (e.g. conn.Shutdown()). There are also other methods for configuring the connection. Specific configuration options can be set:

conn.SetConfigOption("log_file", "/dev/null")

and command line options can also be used using the ParseCmdLineArgs method.

args := []string{ "--mon-host", "1.1.1.1" }
err := conn.ParseCmdLineArgs(args)

For other configuration options see the full documentation.

Object I/O

Object in RADOS can be written to and read from with through an interface very similar to a standard file I/O interface:

// open a pool handle
ioctx, err := conn.OpenIOContext("mypool")

// write some data
bytesIn := []byte("input data")
err = ioctx.Write("obj", bytesIn, 0)

// read the data back out
bytesOut := make([]byte, len(bytesIn))
_, err := ioctx.Read("obj", bytesOut, 0)

if !bytes.Equal(bytesIn, bytesOut) {
    fmt.Println("Output is not input!")
}

Pool maintenance

The list of pools in a cluster can be retreived using the ListPools method on the connection object. On a new cluster the following code snippet:

pools, _ := conn.ListPools()
fmt.Println(pools)

will produce the output [data metadata rbd], along with any other pools that might exist in your cluster. Pools can also be created and destroyed. The following creates a new, empty pool with default settings.

conn.MakePool("new_pool")

Deleting a pool is also easy. Call DeletePool(name string) on a connection object to delete a pool with the given name. The following will delete the pool named new_pool and remove all of the pool's data.

conn.DeletePool("new_pool")