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Create a dispatcher framework for managing request lifecycle. (#1508)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,154 @@ | ||
| // Copyright 2025 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 | ||
| // | ||
| // https://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 dispatcher | ||
|
|
||
| import ( | ||
| "context" | ||
|
|
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| "github.com/datacommonsorg/mixer/internal/server/datasources" | ||
| "google.golang.org/protobuf/proto" | ||
|
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| pbv2 "github.com/datacommonsorg/mixer/internal/proto/v2" | ||
| ) | ||
|
|
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| // RequestType represents the type of request. | ||
| type RequestType string | ||
|
|
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| const ( | ||
| TypeNode RequestType = "Node" | ||
| TypeNodeSearch RequestType = "NodeSearch" | ||
| TypeObservation RequestType = "Observation" | ||
| TypeResolve RequestType = "Resolve" | ||
| ) | ||
|
|
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| // RequestContext holds the context for a given request. | ||
|
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| // NOTE: We are using the base proto.Message for requests and responses. | ||
| // Other options were using generics or going with different *RequestContext struct for each type of request. | ||
| // The downside of using a base type is that it needs casting wherever it it used. | ||
| // The upside is that we only have one context object | ||
| // and if there aren't many processors that deal with the RequestContext, casting in a small number of places is ok. | ||
| // We can revisit and use a different approach if this proves to be cumbersome. | ||
| type RequestContext struct { | ||
| context.Context | ||
| Type RequestType | ||
| OriginalRequest proto.Message | ||
| CurrentRequest proto.Message | ||
| CurrentResponse proto.Message | ||
| } | ||
|
|
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| // Processor interface defines methods for performing pre and post processing operations. | ||
| type Processor interface { | ||
| PreProcess(*RequestContext) error | ||
| PostProcess(*RequestContext) error | ||
| } | ||
|
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| // Dispatcher struct handles requests by dispatching requests to various processors and datasources as appropriate. | ||
| type Dispatcher struct { | ||
| processors []*Processor | ||
| sources *datasources.DataSources | ||
| } | ||
|
|
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| func NewDispatcher(processors []*Processor, sources *datasources.DataSources) *Dispatcher { | ||
| return &Dispatcher{ | ||
| processors: processors, | ||
| sources: sources, | ||
| } | ||
| } | ||
|
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| // handle handles a request lifecycle - pre-processing, core handling and post-processing. | ||
| func (dispatcher *Dispatcher) handle(requestContext *RequestContext, handler func(context.Context, proto.Message) (proto.Message, error)) (proto.Message, error) { | ||
| for _, processor := range dispatcher.processors { | ||
| if err := (*processor).PreProcess(requestContext); err != nil { | ||
| return nil, err | ||
| } | ||
| } | ||
|
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| response, err := handler(requestContext.Context, requestContext.CurrentRequest) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
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| requestContext.CurrentResponse = response | ||
|
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| for _, processor := range dispatcher.processors { | ||
| if err := (*processor).PostProcess(requestContext); err != nil { | ||
| return nil, err | ||
| } | ||
| } | ||
|
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| return requestContext.CurrentResponse, nil | ||
| } | ||
|
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| func (dispatcher *Dispatcher) Node(ctx context.Context, in *pbv2.NodeRequest) (*pbv2.NodeResponse, error) { | ||
| requestContext := newRequestContext(ctx, in, TypeNode) | ||
|
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| response, err := dispatcher.handle(requestContext, func(ctx context.Context, request proto.Message) (proto.Message, error) { | ||
| return dispatcher.sources.Node(ctx, request.(*pbv2.NodeRequest)) | ||
| }) | ||
|
|
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| if err != nil { | ||
| return nil, err | ||
| } | ||
| return response.(*pbv2.NodeResponse), nil | ||
| } | ||
|
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| func (dispatcher *Dispatcher) Observation(ctx context.Context, in *pbv2.ObservationRequest) (*pbv2.ObservationResponse, error) { | ||
| requestContext := newRequestContext(ctx, in, TypeObservation) | ||
|
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| response, err := dispatcher.handle(requestContext, func(ctx context.Context, request proto.Message) (proto.Message, error) { | ||
| return dispatcher.sources.Observation(ctx, request.(*pbv2.ObservationRequest)) | ||
| }) | ||
|
|
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| if err != nil { | ||
| return nil, err | ||
| } | ||
| return response.(*pbv2.ObservationResponse), nil | ||
| } | ||
|
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| func (dispatcher *Dispatcher) NodeSearch(ctx context.Context, in *pbv2.NodeSearchRequest) (*pbv2.NodeSearchResponse, error) { | ||
| requestContext := newRequestContext(ctx, in, TypeNodeSearch) | ||
|
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| response, err := dispatcher.handle(requestContext, func(ctx context.Context, request proto.Message) (proto.Message, error) { | ||
| return dispatcher.sources.NodeSearch(ctx, request.(*pbv2.NodeSearchRequest)) | ||
| }) | ||
|
|
||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return response.(*pbv2.NodeSearchResponse), nil | ||
| } | ||
|
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| func (dispatcher *Dispatcher) Resolve(ctx context.Context, in *pbv2.ResolveRequest) (*pbv2.ResolveResponse, error) { | ||
| requestContext := newRequestContext(ctx, in, TypeResolve) | ||
|
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| response, err := dispatcher.handle(requestContext, func(ctx context.Context, request proto.Message) (proto.Message, error) { | ||
| return dispatcher.sources.Resolve(ctx, request.(*pbv2.ResolveRequest)) | ||
| }) | ||
|
|
||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return response.(*pbv2.ResolveResponse), nil | ||
| } | ||
|
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| func newRequestContext(ctx context.Context, request proto.Message, requestType RequestType) *RequestContext { | ||
| return &RequestContext{ | ||
| Context: ctx, | ||
| Type: requestType, | ||
| OriginalRequest: proto.Clone(request), | ||
| CurrentRequest: request, | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,50 @@ | ||
| // Copyright 2025 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 | ||
| // | ||
| // https://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 observation | ||
|
|
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| import ( | ||
| "log" | ||
|
|
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| "github.com/datacommonsorg/mixer/internal/server/datasources" | ||
| "github.com/datacommonsorg/mixer/internal/server/dispatcher" | ||
| ) | ||
|
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| // CalculationProcessor implements the dispatcher.Processor interface for performing calculations. | ||
| type CalculationProcessor struct { | ||
| // Set and use datasources if needed. | ||
| _ *datasources.DataSources | ||
| } | ||
|
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| func (processor *CalculationProcessor) PreProcess(requestContext *dispatcher.RequestContext) error { | ||
| switch requestContext.Type { | ||
| case dispatcher.TypeObservation: | ||
| log.Printf("Pre-processing observation request.") | ||
| return nil | ||
| default: | ||
| log.Printf("NOT pre-processing request of type: %s", requestContext.Type) | ||
| return nil | ||
| } | ||
| } | ||
|
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| func (processor *CalculationProcessor) PostProcess(requestContext *dispatcher.RequestContext) error { | ||
| switch requestContext.Type { | ||
| case dispatcher.TypeObservation: | ||
| log.Printf("Post-processing observation request.") | ||
| return nil | ||
| default: | ||
| log.Printf("NOT post-processing request of type: %s", requestContext.Type) | ||
| return nil | ||
| } | ||
| } |
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