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fix: minimize dependencies on 3P libraries (#101)
This keeps the functions framework as lightweight as possible, and avoids pulling in all of the Google Cloud client libraries even though only one package is needed. The new `internal/metadata` package is just a copy of [google-cloud-go/functions/metadata](https://github.com/googleapis/google-cloud-go/tree/main/functions/metadata) Minimizing what transitive dependencies the Functions Framework has is important to make them work with buildpacks, where user function code has to be bundled together with the functions framework. If a function's dependency conflicts with a Functions Framework dependency and the function is using vendor, then there can be undefined behavior at build and runtime.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,147 @@ | ||
| // Copyright 2021 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 metadata | ||
|
|
||
| import ( | ||
| "context" | ||
| "encoding/json" | ||
| "errors" | ||
| "fmt" | ||
| "time" | ||
| ) | ||
|
|
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| // Metadata holds Google Cloud Functions metadata. | ||
| type Metadata struct { | ||
| // EventID is a unique ID for the event. For example: "70172329041928". | ||
| EventID string `json:"eventId"` | ||
| // Timestamp is the date/time this event was created. | ||
| Timestamp time.Time `json:"timestamp"` | ||
| // EventType is the type of the event. For example: "google.pubsub.topic.publish". | ||
| EventType string `json:"eventType"` | ||
| // Resource is the resource that triggered the event. | ||
| Resource *Resource `json:"resource"` | ||
| } | ||
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| // Resource holds Google Cloud Functions resource metadata. | ||
| // Resource values are dependent on the event type they're from. | ||
| type Resource struct { | ||
| // Service is the service that triggered the event. | ||
| Service string `json:"service"` | ||
| // Name is the name associated with the event. | ||
| Name string `json:"name"` | ||
| // Type is the type of event. | ||
| Type string `json:"type"` | ||
| // Path is the path to the resource type (deprecated). | ||
| // This is the case for some deprecated GCS | ||
| // notifications, which populate the resource field as a string containing the topic | ||
| // rather than as the expected dictionary. | ||
| // See the Attributes section of https://cloud.google.com/storage/docs/pubsub-notifications | ||
| // for more details. | ||
| RawPath string `json:"-"` | ||
| } | ||
|
|
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| // UnmarshalJSON specializes the Resource unmarshalling to handle the case where the | ||
| // value is a string instead of a map. See the comment above on RawPath for why this | ||
| // needs to be handled. | ||
| func (r *Resource) UnmarshalJSON(data []byte) error { | ||
| // Try to unmarshal the resource into a string. | ||
| var path string | ||
| if err := json.Unmarshal(data, &path); err == nil { | ||
| r.RawPath = path | ||
| return nil | ||
| } | ||
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| // Otherwise, accept whatever the result of the normal unmarshal would be. | ||
| // Need to define a new type, otherwise it infinitely recurses and panics. | ||
| type resource Resource | ||
| var res resource | ||
| if err := json.Unmarshal(data, &res); err != nil { | ||
| return err | ||
| } | ||
|
|
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| r.Service = res.Service | ||
| r.Name = res.Name | ||
| r.Type = res.Type | ||
| return nil | ||
| } | ||
|
|
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| // MarshalJSON specializes the Resource marshalling to handle the case where the | ||
| // value is a string instead of a map. See the comment above on RawPath for why this | ||
| // needs to be handled. | ||
| func (r *Resource) MarshalJSON() ([]byte, error) { | ||
| // If RawPath is set, use that as the whole value. | ||
| if r.RawPath != "" { | ||
| return []byte(fmt.Sprintf("%q", r.RawPath)), nil | ||
| } | ||
|
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| // Otherwise, accept whatever the result of the normal marshal would be. | ||
| res := *r | ||
| b, err := json.Marshal(res) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return b, nil | ||
| } | ||
|
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| type contextKey string | ||
|
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| // GCFContextKey satisfies an interface to be able to use contextKey to read | ||
| // metadata from a Cloud Functions context.Context. | ||
| // | ||
| // Be careful making changes to this function. See FromContext. | ||
| func (k contextKey) GCFContextKey() string { | ||
| return string(k) | ||
| } | ||
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| const metadataContextKey = contextKey("metadata") | ||
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| // FromContext extracts the Metadata from the Context, if present. | ||
| func FromContext(ctx context.Context) (*Metadata, error) { | ||
| if ctx == nil { | ||
| return nil, errors.New("nil ctx") | ||
| } | ||
| // The original JSON is inserted by the Cloud Functions worker. So, the | ||
| // format must not change, or the message may fail to unmarshal. We use | ||
| // JSON as a common format between the worker and this package to ensure | ||
| // this package can be updated independently from the worker. The contextKey | ||
| // type and the metadataContextKey value use an interface to avoid using | ||
| // a built-in type as a context key (which is easy to have collisions with). | ||
| // If we need another value to be stored in the context, we can use a new | ||
| // key or interface and avoid needing to change this one. Similarly, if we | ||
| // need to change the format of the message, we should add an additional key | ||
| // to keep backward compatibility. | ||
| b, ok := ctx.Value(metadataContextKey).(json.RawMessage) | ||
| if !ok { | ||
| return nil, errors.New("unable to find metadata") | ||
| } | ||
| meta := &Metadata{} | ||
| if err := json.Unmarshal(b, meta); err != nil { | ||
| return nil, fmt.Errorf("json.Unmarshal: %v", err) | ||
| } | ||
| return meta, nil | ||
| } | ||
|
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| // NewContext returns a new Context carrying m. If m is nil, NewContext returns | ||
| // ctx. NewContext is only used for writing tests which rely on Metadata. | ||
| func NewContext(ctx context.Context, m *Metadata) context.Context { | ||
| if m == nil { | ||
| return ctx | ||
| } | ||
| b, err := json.Marshal(m) | ||
| if err != nil { | ||
| return ctx | ||
| } | ||
| return context.WithValue(ctx, metadataContextKey, json.RawMessage(b)) | ||
| } |
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