rados: add wrapper to set locator key on IOContext (#651)

add wrapper to set locator key on IOContext

Signed-off-by: Alexander Pücker <alexander.puecker@hetzner.com>

* mark API as PREVIEW and update docs

Signed-off-by: Alexander Pücker <alexander.puecker@hetzner.com>

* move new API call into own file to add preview build tag

Signed-off-by: Alexander Pücker <alexander.puecker@hetzner.com>

* reset locater with nil instead of a empty string

Signed-off-by: Alexander Pücker <alexander.puecker@hetzner.com>

* rename variables for naming consistency

Signed-off-by: Alexander Pücker <alexander.puecker@hetzner.com>

* update release versions for new API call

Signed-off-by: Alexander Pücker <alexander.puecker@hetzner.com>

docs/api-status.json

@@ -1052,6 +1052,12 @@
         "comment": "WatcherFlush flushes all pending notifications of the cluster.\n PREVIEW\n\nImplements:\n int rados_watch_flush(rados_t cluster)\n",
         "added_in_version": "v0.14.0",
         "expected_stable_version": "v0.16.0"
+      },
+      {
+        "name": "IOContext.SetLocator",
+        "comment": "SetLocator sets the key for mapping objects to pgs within an io context.\nUntil a different locator key is set, all objects in this io context will be placed in the same pg.\nTo reset the locator, an empty string must be set.\n PREVIEW\n\nImplements:\n void rados_ioctx_locator_set_key(rados_ioctx_t io, const char *key);\n",
+        "added_in_version": "v0.15.0",
+        "expected_stable_version": "v0.17.0"
       }
     ]
   },

docs/api-status.md

@@ -37,6 +37,7 @@ IOContext.Notify | v0.14.0 | v0.16.0 |
 IOContext.NotifyWithTimeout | v0.14.0 | v0.16.0 | 
 NotifyEvent.Ack | v0.14.0 | v0.16.0 | 
 Conn.WatcherFlush | v0.14.0 | v0.16.0 | 
+IOContext.SetLocator | v0.15.0 | v0.17.0 | 
 
 ## Package: rbd
 

rados/rados_set_locator.go

@@ -0,0 +1,31 @@
+//go:build ceph_preview
+// +build ceph_preview
+
+package rados
+
+// #cgo LDFLAGS: -lrados
+// #include <rados/librados.h>
+// #include <stdlib.h>
+//
+import "C"
+
+import (
+	"unsafe"
+)
+
+// SetLocator sets the key for mapping objects to pgs within an io context.
+// Until a different locator key is set, all objects in this io context will be placed in the same pg.
+// To reset the locator, an empty string must be set.
+//  PREVIEW
+//
+// Implements:
+//  void rados_ioctx_locator_set_key(rados_ioctx_t io, const char *key);
+func (ioctx *IOContext) SetLocator(locator string) {
+	if locator == "" {
+		C.rados_ioctx_locator_set_key(ioctx.ioctx, nil)
+	} else {
+		var cLoc *C.char = C.CString(locator)
+		defer C.free(unsafe.Pointer(cLoc))
+		C.rados_ioctx_locator_set_key(ioctx.ioctx, cLoc)
+	}
+}

rados/rados_set_locator_test.go

@@ -0,0 +1,50 @@
+//go:build ceph_preview
+// +build ceph_preview
+
+package rados
+
+import (
+	"github.com/stretchr/testify/assert"
+)
+
+func (suite *RadosTestSuite) TestSetLocator() {
+	suite.SetupConnection()
+
+	// create normal object without locator - used later to test reset of locator
+	testDataNoLocator := []byte("no locator")
+	err := suite.ioctx.Write("default-locator", testDataNoLocator, 0)
+	assert.NoError(suite.T(), err)
+
+	// test create and read with different locator
+	testDataLocator := []byte("test data")
+	suite.ioctx.SetLocator("SomeOtherLocator")
+	err = suite.ioctx.Write("different-locator", testDataLocator, 0)
+	assert.NoError(suite.T(), err)
+
+	_, err = suite.ioctx.Stat("different-locator")
+	assert.NoError(suite.T(), err)
+
+	bytesOut := make([]byte, len(testDataLocator))
+	nOut, err := suite.ioctx.Read("different-locator", bytesOut, 0)
+	assert.NoError(suite.T(), err)
+	assert.Equal(suite.T(), nOut, len(testDataLocator))
+	assert.Equal(suite.T(), testDataLocator, bytesOut)
+
+	// test stat with wrong locator
+	suite.ioctx.SetLocator("SomeWrongLocator")
+	_, err = suite.ioctx.Stat("different-locator")
+	assert.Error(suite.T(), err)
+	_, err = suite.ioctx.Stat("default-locator")
+	assert.Error(suite.T(), err)
+
+	// test reset of locator and access to object without locator
+	suite.ioctx.SetLocator("")
+	_, err = suite.ioctx.Stat("default-locator")
+	assert.NoError(suite.T(), err)
+
+	bytesOut = make([]byte, len(testDataNoLocator))
+	nOut, err = suite.ioctx.Read("default-locator", bytesOut, 0)
+	assert.NoError(suite.T(), err)
+	assert.Equal(suite.T(), nOut, len(testDataNoLocator))
+	assert.Equal(suite.T(), testDataNoLocator, bytesOut)
+}