Support reading service bindings from VCAP_SERVICES env var (#566)

Co-authored-by: Johannes Dillmann <j.dillmann@sap.com>

servicebindings/entry.go

@@ -1,13 +1,16 @@
 package servicebindings
 
 import (
+	"bytes"
+	"io"
 	"os"
 )
 
 // Entry represents the read-only content of a binding entry.
 type Entry struct {
-	path string
-	file *os.File
+	path  string
+	file  *os.File
+	value *bytes.Reader
 }
 
 // NewEntry returns a new Entry whose content is given by the file at the provided path.
@@ -17,25 +20,50 @@ func NewEntry(path string) *Entry {
 	}
 }
 
+// NewWithValue returns a new Entry with predefined value.
+func NewWithValue(value []byte) *Entry {
+	return &Entry{
+		value: bytes.NewReader(value),
+	}
+}
+
 // ReadBytes reads the entire raw content of the entry. There is no need to call Close after calling ReadBytes.
 func (e *Entry) ReadBytes() ([]byte, error) {
+	if e.value != nil {
+		return io.ReadAll(e.value)
+	}
 	return os.ReadFile(e.path)
 }
 
 // ReadString reads the entire content of the entry as a string. There is no need to call Close after calling
 // ReadString.
 func (e *Entry) ReadString() (string, error) {
-	bytes, err := e.ReadBytes()
-	if err != nil {
-		return "", err
+	var bytes []byte
+	var err error
+
+	if e.value != nil {
+		bytes, err = io.ReadAll(e.value)
+		if err != nil {
+			return "", err
+		}
+	} else {
+		bytes, err = e.ReadBytes()
+		if err != nil {
+			return "", err
+		}
 	}
+
 	return string(bytes), nil
 }
 
 // Read reads up to len(b) bytes from the entry. It returns the number of bytes read and any error encountered. At end
 // of entry data, Read returns 0, io.EOF.
 // Close must be called when all read operations are complete.
 func (e *Entry) Read(b []byte) (int, error) {
+	if e.value != nil {
+		return e.value.Read(b)
+	}
+
 	if e.file == nil {
 		file, err := os.Open(e.path)
 		if err != nil {
@@ -49,11 +77,16 @@ func (e *Entry) Read(b []byte) (int, error) {
 // Close closes the entry and resets it for reading. After calling Close, any subsequent calls to Read will read entry
 // data from the beginning. Close may be called on a closed entry without error.
 func (e *Entry) Close() error {
-	if e.file == nil {
-		return nil
-	}
 	defer func() {
 		e.file = nil
 	}()
-	return e.file.Close()
+
+	if e.value != nil {
+		_, err := e.value.Seek(0, io.SeekStart)
+		return err
+	} else if e.file == nil {
+		return nil
+	} else {
+		return e.file.Close()
+	}
 }

servicebindings/entry_test.go

@@ -14,9 +14,10 @@ import (
 
 func testEntry(t *testing.T, context spec.G, it spec.S) {
 	var (
-		Expect = NewWithT(t).Expect
-		entry  *servicebindings.Entry
-		tmpDir string
+		Expect         = NewWithT(t).Expect
+		entry          *servicebindings.Entry
+		entryWithValue *servicebindings.Entry
+		tmpDir         string
 	)
 
 	it.Before(func() {
@@ -26,6 +27,7 @@ func testEntry(t *testing.T, context spec.G, it spec.S) {
 		entryPath := filepath.Join(tmpDir, "entry")
 		Expect(os.WriteFile(entryPath, []byte("some data"), os.ModePerm)).To(Succeed())
 		entry = servicebindings.NewEntry(entryPath)
+		entryWithValue = servicebindings.NewWithValue([]byte("value from env"))
 	})
 
 	it.After(func() {
@@ -35,12 +37,14 @@ func testEntry(t *testing.T, context spec.G, it spec.S) {
 	context("ReadBytes", func() {
 		it("returns the raw bytes of the entry", func() {
 			Expect(entry.ReadBytes()).To(Equal([]byte("some data")))
+			Expect(entryWithValue.ReadBytes()).To(Equal([]byte("value from env")))
 		})
 	})
 
 	context("ReadString", func() {
 		it("returns the string value of the entry", func() {
 			Expect(entry.ReadString()).To(Equal("some data"))
+			Expect(entryWithValue.ReadString()).To(Equal("value from env"))
 		})
 	})
 
@@ -59,17 +63,33 @@ func testEntry(t *testing.T, context spec.G, it spec.S) {
 			Expect(err).NotTo(HaveOccurred())
 			Expect(entry.Close()).To(Succeed())
 			Expect(data).To(Equal([]byte("some data")))
+
+			data, err = io.ReadAll(entryWithValue)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(entryWithValue.Close()).To(Succeed())
+			Expect(data).To(Equal([]byte("value from env")))
+
+			data, err = io.ReadAll(entryWithValue)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(entryWithValue.Close()).To(Succeed())
+			Expect(data).To(Equal([]byte("value from env")))
 		})
 
 		it("can be closed multiple times in a row", func() {
 			_, err := io.ReadAll(entry)
 			Expect(err).NotTo(HaveOccurred())
 			Expect(entry.Close()).To(Succeed())
 			Expect(entry.Close()).To(Succeed())
+
+			_, err = io.ReadAll(entryWithValue)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(entryWithValue.Close()).To(Succeed())
+			Expect(entryWithValue.Close()).To(Succeed())
 		})
 
 		it("can be closed if never read from", func() {
 			Expect(entry.Close()).To(Succeed())
+			Expect(entryWithValue.Close()).To(Succeed())
 		})
 	})
 }

servicebindings/resolver.go

@@ -1,6 +1,7 @@
 package servicebindings
 
 import (
+	"encoding/json"
 	"errors"
 	"fmt"
 	"os"
@@ -47,9 +48,9 @@ func NewResolver() *Resolver {
 //
 // The location of bindings is given by one of the following, in order of precedence:
 //
-//   1. SERVICE_BINDING_ROOT environment variable
-//   2. CNB_BINDINGS environment variable, if above is not set
-//   3. `<platformDir>/bindings`, if both above are not set
+//  1. SERVICE_BINDING_ROOT environment variable
+//  2. CNB_BINDINGS environment variable, if above is not set
+//  3. `<platformDir>/bindings`, if both above are not set
 func (r *Resolver) Resolve(typ, provider, platformDir string) ([]Binding, error) {
 	if newRoot := bindingRoot(platformDir); r.bindingRoot != newRoot {
 		r.bindingRoot = newRoot
@@ -92,6 +93,10 @@ func (r *Resolver) ResolveOne(typ, provider, platformDir string) (Binding, error
 }
 
 func loadBindings(bindingRoot string) ([]Binding, error) {
+	if vcapEnv, ok := os.LookupEnv("VCAP_SERVICES"); ok {
+		return loadvcapservicesbinding(vcapEnv)
+	}
+
 	files, err := os.ReadDir(bindingRoot)
 	if os.IsNotExist(err) {
 		return nil, nil
@@ -233,6 +238,55 @@ func loadLegacyBinding(bindingRoot, name string) (Binding, error) {
 	return binding, nil
 }
 
+func loadvcapservicesbinding(content string) ([]Binding, error) {
+	var contentTyped map[string][]vcapServicesBinding
+
+	err := json.Unmarshal([]byte(content), &contentTyped)
+	if err != nil {
+		return []Binding{}, err
+	}
+
+	bindings := []Binding{}
+	for p, bArray := range contentTyped {
+		for _, b := range bArray {
+			entries := map[string]*Entry{}
+			for k, v := range b.Credentials {
+				entries[k], err = toJSONString(v)
+				if err != nil {
+					return nil, err
+				}
+			}
+			bindings = append(bindings, Binding{
+				Name:     b.Name,
+				Type:     b.Label,
+				Provider: p,
+				Entries:  entries,
+			})
+		}
+	}
+
+	return bindings, nil
+}
+
+type vcapServicesBinding struct {
+	Name        string                 `json:"name"`
+	Label       string                 `json:"label"`
+	Credentials map[string]interface{} `json:"credentials"`
+}
+
+func toJSONString(input interface{}) (*Entry, error) {
+	switch in := input.(type) {
+	case string:
+		return NewWithValue([]byte(in)), nil
+	default:
+		jsonProperty, err := json.Marshal(in)
+		if err != nil {
+			return nil, err
+		}
+		return NewWithValue(jsonProperty), nil
+	}
+}
+
 func loadEntries(path string) (map[string]*Entry, error) {
 	entries := map[string]*Entry{}
 	files, err := os.ReadDir(path)

servicebindings/resolver_test.go

@@ -147,6 +147,43 @@ func testResolver(t *testing.T, context spec.G, it spec.S) {
 				})
 			})
 		})
+
+		context("VCAP_SERVICES env var is set", func() {
+			it.Before(func() {
+				content, err := os.ReadFile("testdata/vcap_services.json")
+				Expect(err).NotTo(HaveOccurred())
+				Expect(os.Setenv("VCAP_SERVICES", string(content))).To(Succeed())
+			})
+
+			it.After(func() {
+				Expect(os.Unsetenv("VCAP_SERVICES")).To(Succeed())
+			})
+
+			context("SERVICE_BINDING_ROOT env var is set", func() {
+				it.Before(func() {
+					Expect(os.Setenv("SERVICE_BINDING_ROOT", bindingRootK8s)).To(Succeed())
+				})
+
+				it("resolves bindings from VCAP_SERVICES", func() {
+					resolver := servicebindings.NewResolver()
+					bindings, err := resolver.Resolve("postgres", "", platformDir)
+					Expect(err).NotTo(HaveOccurred())
+					Expect(bindings).To(ConsistOf(
+						servicebindings.Binding{
+							Name:     "postgres",
+							Path:     "",
+							Type:     "postgres",
+							Provider: "postgres",
+							Entries: map[string]*servicebindings.Entry{
+								"username": servicebindings.NewWithValue([]byte("foo")),
+								"password": servicebindings.NewWithValue([]byte("bar")),
+								"urls":     servicebindings.NewWithValue([]byte("{\"example\":\"http://example.com\"}")),
+							},
+						},
+					))
+				})
+			})
+		})
 	})
 
 	context("resolving bindings", func() {

servicebindings/testdata/vcap_services.json

@@ -0,0 +1,69 @@
+{
+    "elephantsql-provider": [
+      {
+        "name": "elephantsql-binding-c6c60",
+        "binding_guid": "44ceb72f-100b-4f50-87a2-7809c8b42b8d",
+        "binding_name": "elephantsql-binding-c6c60",
+        "instance_guid": "391308e8-8586-4c42-b464-c7831aa2ad22",
+        "instance_name": "elephantsql-c6c60",
+        "label": "elephantsql-type",
+        "tags": [
+          "postgres",
+          "postgresql",
+          "relational"
+        ],
+        "plan": "turtle",
+        "credentials": {
+          "uri": "postgres://exampleuser:examplepass@postgres.example.com:5432/exampleuser",
+          "int": 1,
+          "bool": true
+        },
+        "syslog_drain_url": null,
+        "volume_mounts": []
+      }
+    ],
+    "sendgrid-provider": [
+      {
+        "name": "mysendgrid",
+        "binding_guid": "6533b1b6-7916-488d-b286-ca33d3fa0081",
+        "binding_name": null,
+        "instance_guid": "8c907d0f-ec0f-44e4-87cf-e23c9ba3925d",
+        "instance_name": "mysendgrid",
+        "label": "sendgrid-type",
+        "tags": [
+          "smtp"
+        ],
+        "plan": "free",
+        "credentials": {
+          "hostname": "smtp.example.com",
+          "username": "QvsXMbJ3rK",
+          "password": "HCHMOYluTv"
+        },
+        "syslog_drain_url": null,
+        "volume_mounts": []
+      }
+    ],
+    "postgres": [
+      {
+        "name": "postgres",
+        "label": "postgres",
+        "plan": "default",
+        "tags": [
+          "postgres"
+        ],
+        "binding_guid": "6533b1b6-7916-488d-b286-ca33d3fa0081",
+        "binding_name": null,
+        "instance_guid": "8c907d0f-ec0f-44e4-87cf-e23c9ba3925d",
+        "credentials": {
+          "username": "foo",
+          "password": "bar",
+          "urls": {
+            "example": "http://example.com"
+          }
+        },
+        "syslog_drain_url": null,
+        "volume_mounts": []
+      }
+    ]
+  }
+