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In the current implementation, weaver doesn't allow the user to
propagate context information. We recommend users to define a struct
that encapsulates the metadata information and add it as an argument to
the method. However, more and more users are asking for an option to
propagate metadata information using the context. This request comes
especially from users that are using gRPC to communicate between their
services, and gRPC provides a way to propagate metadata information
using the context.
This PR enables the users to propagate metadata information as a
map[string]string.
```main.go
// To attach metadata with key "foo" and value "bar" to the context, you can do:
ctx := context.Background()
ctx = weavermetadata.NewContext(ctx, map[string]string{"foo": "bar"})
// To read the metadata value associated with a key "foo" in the context, you can do:
meta, found := weavermetadata.FromContext(ctx)
if found {
value := meta["foo"]
}
```
[1] https://pkg.go.dev/google.golang.org/grpc/metadata- Loading branch information
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,48 @@ | ||
| // Copyright 2024 Google LLC | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
|
||
| package call | ||
|
|
||
| import ( | ||
| "strings" | ||
|
|
||
| "github.com/ServiceWeaver/weaver/runtime/codegen" | ||
| ) | ||
|
|
||
| const metadataHeaderLen = 8 // metadata length | ||
|
|
||
| // writeContextMetadata serializes the context metadata (if any). | ||
| func writeContextMetadata(meta map[string]string) []byte { | ||
| enc := codegen.NewEncoder() | ||
| enc.Len(len(meta)) | ||
| for k, v := range meta { | ||
| enc.String(strings.ToLower(k)) | ||
| enc.String(v) | ||
| } | ||
| return enc.Data() | ||
| } | ||
|
|
||
| // readContextMetadata returns the context metadata (if any). | ||
| func readContextMetadata(meta []byte) map[string]string { | ||
| dec := codegen.NewDecoder(meta) | ||
| n := dec.Len() | ||
| res := make(map[string]string, n) | ||
| var k, v string | ||
| for i := 0; i < n; i++ { | ||
| k = strings.ToLower(dec.String()) | ||
| v = dec.String() | ||
| res[k] = v | ||
| } | ||
| return res | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,67 @@ | ||
| // Copyright 2024 Google LLC | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
|
||
| // Package weavermetadata define the structure of the metadata supported by weaver. | ||
| // | ||
| // Note that we allow metadata information to propagate as a map, where the keys | ||
| // and the values are strings. It the user wants to propagate values that are | ||
| // more complicated types, it's their responsibility to encode/decode these types | ||
| // to/from string values. | ||
| // | ||
| // Note that all keys are automatically lowercase. This ensures the user avoids | ||
| // mistakes when creating and retrieving values for the same key. E.g., the user | ||
| // can create a map with the key "Foo" but try to retrieve the value for the | ||
| // key "foo". | ||
| // | ||
| // How to: | ||
| // | ||
| // To attach metadata with key "foo" and value "bar" to the context, you can do: | ||
| // | ||
| // ctx := context.Background() | ||
| // ctx = weavermetadata.NewContext(ctx, map[string]string{"foo": "bar"}) | ||
| // | ||
| // To read the metadata value associated with a key "foo" in the context, you can do: | ||
| // | ||
| // meta, found := weavermetadata.FromContext(ctx) | ||
| // if found { | ||
| // value := meta["foo"] | ||
| // } | ||
| package weavermetadata | ||
|
|
||
| import ( | ||
| "context" | ||
| "strings" | ||
| ) | ||
|
|
||
| // metaKey is an unexported type for the key that stores the metadata. | ||
| type metaKey struct{} | ||
|
|
||
| // NewContext returns a new context that carries metadata meta. | ||
| func NewContext(ctx context.Context, meta map[string]string) context.Context { | ||
| return context.WithValue(ctx, metaKey{}, meta) | ||
| } | ||
|
|
||
| // FromContext returns the metadata value stored in ctx, if any. | ||
| func FromContext(ctx context.Context) (map[string]string, bool) { | ||
| meta, ok := ctx.Value(metaKey{}).(map[string]string) | ||
| if !ok { | ||
| return nil, false | ||
| } | ||
| out := make(map[string]string, len(meta)) | ||
| for k, v := range meta { | ||
| key := strings.ToLower(k) | ||
| out[key] = v | ||
| } | ||
| return out, true | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,94 @@ | ||
| // Copyright 2024 Google LLC | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
|
||
| package weavermetadata | ||
|
|
||
| import ( | ||
| "context" | ||
| "reflect" | ||
| "testing" | ||
| ) | ||
|
|
||
| func TestContextMetadata(t *testing.T) { | ||
| type testCase struct { | ||
| name string | ||
| meta map[string]string | ||
| isMetaExpected bool | ||
| want map[string]string | ||
| } | ||
| for _, test := range []testCase{ | ||
| { | ||
| name: "no metadata", | ||
| }, | ||
| { | ||
| name: "with empty metadata", | ||
| meta: map[string]string{}, | ||
| isMetaExpected: false, | ||
| }, | ||
| { | ||
| name: "with valid metadata", | ||
| meta: map[string]string{ | ||
| "foo": "bar", | ||
| "baz": "waldo", | ||
| }, | ||
| isMetaExpected: true, | ||
| want: map[string]string{ | ||
| "foo": "bar", | ||
| "baz": "waldo", | ||
| }, | ||
| }, | ||
| { | ||
| name: "with valid metadata and uppercase keys", | ||
| meta: map[string]string{ | ||
| "Foo": "bar", | ||
| "Baz": "waldo", | ||
| }, | ||
| isMetaExpected: true, | ||
| want: map[string]string{ | ||
| "foo": "bar", | ||
| "baz": "waldo", | ||
| }, | ||
| }, | ||
| { | ||
| name: "with valid metadata and uppercase values", | ||
| meta: map[string]string{ | ||
| "Foo": "Bar", | ||
| "Baz": "Waldo", | ||
| }, | ||
| isMetaExpected: true, | ||
| want: map[string]string{ | ||
| "foo": "Bar", | ||
| "baz": "Waldo", | ||
| }, | ||
| }, | ||
| } { | ||
| t.Run(test.name, func(t *testing.T) { | ||
| ctx := context.Background() | ||
| if len(test.meta) > 0 { | ||
| ctx = NewContext(ctx, test.meta) | ||
| } | ||
|
|
||
| got, found := FromContext(ctx) | ||
| if !reflect.DeepEqual(found, test.isMetaExpected) { | ||
| t.Errorf("ExtractMetadata: expecting %v, got %v", test.isMetaExpected, found) | ||
| } | ||
| if !found { | ||
| return | ||
| } | ||
| if !reflect.DeepEqual(test.want, got) { | ||
| t.Errorf("ExtractMetadata: expecting %v, got %v", test.want, got) | ||
| } | ||
| }) | ||
| } | ||
| } |
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