/
component.go
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/
component.go
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// Copyright The OpenTelemetry Authors
//
// 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 component // import "go.opentelemetry.io/collector/component"
import (
"context"
"errors"
"go.opentelemetry.io/collector/config"
)
var (
// ErrNilNextConsumer can be returned by receiver, or processor Start factory funcs that create the Component if the
// expected next Consumer is nil.
ErrNilNextConsumer = errors.New("nil next Consumer")
// ErrDataTypeIsNotSupported can be returned by receiver, exporter or processor factory funcs that create the
// Component if the particular telemetry data type is not supported by the receiver, exporter or processor.
ErrDataTypeIsNotSupported = errors.New("telemetry type is not supported")
)
// Component is either a receiver, exporter, processor, or an extension.
//
// A component's lifecycle has the following phases:
//
// 1. Creation: The component is created using its respective factory, via a Create* call.
// 2. Start: The component's Start method is called.
// 3. Running: The component is up and running.
// 4. Shutdown: The component's Shutdown method is called and the lifecycle is complete.
//
// Once the lifecycle is complete it may be repeated, in which case a new component
// is created, starts, runs and is shutdown again.
type Component interface {
// Start tells the component to start. Host parameter can be used for communicating
// with the host after Start() has already returned. If an error is returned by
// Start() then the collector startup will be aborted.
// If this is an exporter component it may prepare for exporting
// by connecting to the endpoint.
//
// If the component needs to perform a long-running starting operation then it is recommended
// that Start() returns quickly and the long-running operation is performed in background.
// In that case make sure that the long-running operation does not use the context passed
// to Start() function since that context will be cancelled soon and can abort the long-running
// operation. Create a new context from the context.Background() for long-running operations.
Start(ctx context.Context, host Host) error
// Shutdown is invoked during service shutdown. After Shutdown() is called, if the component
// accepted data in any way, it should not accept it anymore.
//
// If there are any background operations running by the component they must be aborted before
// this function returns. Remember that if you started any long-running background operations from
// the Start() method, those operations must be also cancelled. If there are any buffers in the
// component, they should be cleared and the data sent immediately to the next component.
//
// The component's lifecycle is completed once the Shutdown() method returns. No other
// methods of the component are called after that. If necessary a new component with
// the same or different configuration may be created and started (this may happen
// for example if we want to restart the component).
Shutdown(ctx context.Context) error
}
// StartFunc specifies the function invoked when the component.Component is being started.
type StartFunc func(context.Context, Host) error
// Start starts the component.
func (f StartFunc) Start(ctx context.Context, host Host) error {
if f == nil {
return nil
}
return f(ctx, host)
}
// ShutdownFunc specifies the function invoked when the component.Component is being shutdown.
type ShutdownFunc func(context.Context) error
// Shutdown shuts down the component.
func (f ShutdownFunc) Shutdown(ctx context.Context) error {
if f == nil {
return nil
}
return f(ctx)
}
// Kind represents component kinds.
type Kind int
const (
_ Kind = iota // skip 0, start types from 1.
KindReceiver
KindProcessor
KindExporter
KindExtension
)
// Factory is implemented by all component factories.
//
// This interface cannot be directly implemented. Implementations must
// use the factory helpers for the appropriate component type.
type Factory interface {
// Type gets the type of the component created by this factory.
Type() config.Type
unexportedFactoryFunc()
}
type baseFactory struct {
cfgType config.Type
}
func (baseFactory) unexportedFactoryFunc() {}
func (bf baseFactory) Type() config.Type {
return bf.cfgType
}