common commands: add new sub-package for common interface types

Add new common interface types for working with Ceph's "JSON commands"
to a public sub-package.

Signed-off-by: John Mulligan <[email protected]>

Author: phlogistonjohn

Diff for: common/commands/doc.go

@@ -0,0 +1,7 @@
+/*
+Package commands provides types and utility functions that are used for
+interfacing with the JSON based command infrastructure in Ceph.
+
+The *rados.Conn type implements many of the interfaces found in this package.
+*/
+package commands

Diff for: common/commands/interfaces.go

@@ -0,0 +1,20 @@
+package commands
+
+// MgrCommander in an interface for the API needed to execute JSON formatted
+// commands on the ceph mgr.
+type MgrCommander interface {
+	MgrCommand(buf [][]byte) ([]byte, string, error)
+}
+
+// MonCommander is an interface for the API needed to execute JSON formatted
+// commands on the ceph mon(s).
+type MonCommander interface {
+	MonCommand(buf []byte) ([]byte, string, error)
+}
+
+// RadosCommander provides an interface for APIs needed to execute JSON
+// formatted commands on the Ceph cluster.
+type RadosCommander interface {
+	MgrCommander
+	MonCommander
+}