/
provider.go
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/
provider.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 confmap // import "go.opentelemetry.io/collector/confmap"
import (
"context"
"fmt"
)
// Provider is an interface that helps to retrieve a config map and watch for any
// changes to the config map. Implementations may load the config from a file,
// a database or any other source.
//
// The typical usage is the following:
//
// r, err := provider.Retrieve("file:/path/to/config")
// // Use r.Map; wait for watcher to be called.
// r.Close()
// r, err = provider.Retrieve("file:/path/to/config")
// // Use r.Map; wait for watcher to be called.
// r.Close()
// // repeat retrieve/wait/close cycle until it is time to shut down the Collector process.
// // ...
// provider.Shutdown()
type Provider interface {
// Retrieve goes to the configuration source and retrieves the selected data which
// contains the value to be injected in the configuration and the corresponding watcher that
// will be used to monitor for updates of the retrieved value.
//
// `uri` must follow the "<scheme>:<opaque_data>" format. This format is compatible
// with the URI definition (see https://datatracker.ietf.org/doc/html/rfc3986). The "<scheme>"
// must be always included in the `uri`. The "<scheme>" supported by any provider:
// - MUST consist of a sequence of characters beginning with a letter and followed by any
// combination of letters, digits, plus ("+"), period ("."), or hyphen ("-").
// See https://datatracker.ietf.org/doc/html/rfc3986#section-3.1.
// - MUST be at least 2 characters long to avoid conflicting with a driver-letter identifier as specified
// in https://tools.ietf.org/id/draft-kerwin-file-scheme-07.html#syntax.
// - For testing, all implementation MUST check that confmaptest.ValidateProviderScheme returns no error.
//
// `watcher` callback is called when the config changes. watcher may be called from
// a different go routine. After watcher is called Retrieved.Get should be called
// to get the new config. See description of Retrieved for more details.
// watcher may be nil, which indicates that the caller is not interested in
// knowing about the changes.
//
// If ctx is cancelled should return immediately with an error.
// Should never be called concurrently with itself or with Shutdown.
Retrieve(ctx context.Context, uri string, watcher WatcherFunc) (*Retrieved, error)
// Scheme returns the location scheme used by Retrieve.
Scheme() string
// Shutdown signals that the configuration for which this Provider was used to
// retrieve values is no longer in use and the Provider should close and release
// any resources that it may have created.
//
// This method must be called when the Collector service ends, either in case of
// success or error. Retrieve cannot be called after Shutdown.
//
// Should never be called concurrently with itself or with Retrieve.
// If ctx is cancelled should return immediately with an error.
Shutdown(ctx context.Context) error
}
type WatcherFunc func(*ChangeEvent)
// ChangeEvent describes the particular change event that happened with the config.
// TODO: see if this can be eliminated.
type ChangeEvent struct {
// Error is nil if the config is changed and needs to be re-fetched.
// Any non-nil error indicates that there was a problem with watching the config changes.
Error error
}
// Retrieved holds the result of a call to the Retrieve method of a Provider object.
type Retrieved struct {
rawConf interface{}
closeFunc CloseFunc
}
type retrievedSettings struct {
closeFunc CloseFunc
}
// RetrievedOption options to customize Retrieved values.
type RetrievedOption func(*retrievedSettings)
// WithRetrievedClose overrides the default Retrieved.Close function.
// The default Retrieved.Close function does nothing and always returns nil.
func WithRetrievedClose(closeFunc CloseFunc) RetrievedOption {
return func(settings *retrievedSettings) {
settings.closeFunc = closeFunc
}
}
// NewRetrieved returns a new Retrieved instance that contains the data from the raw deserialized config.
// The rawConf can be one of the following types:
// - Primitives: int, int32, int64, float32, float64, bool, string;
// - []interface{};
// - map[string]interface{};
func NewRetrieved(rawConf interface{}, opts ...RetrievedOption) (*Retrieved, error) {
if err := checkRawConfType(rawConf); err != nil {
return nil, err
}
set := retrievedSettings{}
for _, opt := range opts {
opt(&set)
}
return &Retrieved{rawConf: rawConf, closeFunc: set.closeFunc}, nil
}
// AsConf returns the retrieved configuration parsed as a Conf.
func (r *Retrieved) AsConf() (*Conf, error) {
if r.rawConf == nil {
return New(), nil
}
val, ok := r.rawConf.(map[string]interface{})
if !ok {
return nil, fmt.Errorf("retrieved value (type=%T) cannot be used as a Conf", r.rawConf)
}
return NewFromStringMap(val), nil
}
// AsRaw returns the retrieved configuration parsed as an interface{} which can be one of the following types:
// - Primitives: int, int32, int64, float32, float64, bool, string;
// - []interface{} - every member follows the same rules as the given interface{};
// - map[string]interface{} - every value follows the same rules as the given interface{};
func (r *Retrieved) AsRaw() (interface{}, error) {
return r.rawConf, nil
}
// Close and release any watchers that Provider.Retrieve may have created.
//
// Should block until all resources are closed, and guarantee that `onChange` is not
// going to be called after it returns except when `ctx` is cancelled.
//
// Should never be called concurrently with itself.
func (r *Retrieved) Close(ctx context.Context) error {
if r.closeFunc == nil {
return nil
}
return r.closeFunc(ctx)
}
// CloseFunc a function equivalent to Retrieved.Close.
type CloseFunc func(context.Context) error
func checkRawConfType(rawConf interface{}) error {
if rawConf == nil {
return nil
}
switch rawConf.(type) {
case int, int32, int64, float32, float64, bool, string, []interface{}, map[string]interface{}:
return nil
default:
return fmt.Errorf("unsupported type=%T for retrieved config", rawConf)
}
}