mirror of https://github.com/perkeep/perkeep.git
142 lines
4.8 KiB
Go
142 lines
4.8 KiB
Go
/*
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Copyright 2011 The Perkeep Authors
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package blobserver
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import (
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"errors"
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"fmt"
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"net/http"
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"sync"
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"go4.org/jsonconfig"
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)
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var ErrHandlerTypeNotFound = errors.New("requested handler type not loaded")
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type FindHandlerByTyper interface {
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// FindHandlerByType finds a handler by its handlerType and
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// returns its prefix and handler if it's loaded. If it's not
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// loaded, the error will be ErrHandlerTypeNotFound.
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//
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// This is used by handlers to find siblings (such as the "ui" type handler)
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// which might have more knowledge about the configuration for discovery, etc.
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//
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// Note that if this is called during handler construction
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// time, only the prefix may be returned with a nil handler
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// and nil err. Unlike GetHandler and GetStorage, this does
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// not cause the prefix to load immediately. At runtime (after
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// construction of all handlers), then prefix and handler will
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// both be non-nil when err is nil.
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FindHandlerByType(handlerType string) (prefix string, handler interface{}, err error)
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// AllHandlers returns a map from prefix to handler type, and
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// a map from prefix to handler.
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AllHandlers() (map[string]string, map[string]interface{})
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}
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type Loader interface {
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FindHandlerByTyper
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// MyPrefix returns the prefix of the handler currently being constructed,
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// with both leading and trailing slashes (e.g. "/ui/").
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MyPrefix() string
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// BaseURL returns the server's base URL, without trailing slash, and not including
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// the prefix (as returned by MyPrefix).
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BaseURL() string
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// GetHandlerType returns the handler's configured type, but does
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// not force it to start being loaded yet.
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GetHandlerType(prefix string) string // returns "" if unknown
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// GetHandler returns either a Storage or an http.Handler.
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// It forces the handler to be loaded and returns an error if
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// a cycle is created.
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GetHandler(prefix string) (interface{}, error)
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// GetStorage is like GetHandler but requires that the Handler be
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// a storage Handler.
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GetStorage(prefix string) (Storage, error)
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}
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// HandlerIniter is an optional interface which can be implemented
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// by Storage or http.Handlers (from StorageConstructor or HandlerConstructor)
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// to be called once all the handlers have been created.
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type HandlerIniter interface {
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InitHandler(FindHandlerByTyper) error
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}
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// A StorageConstructor returns a Storage implementation from a Loader
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// environment and a configuration.
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type StorageConstructor func(Loader, jsonconfig.Obj) (Storage, error)
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// A HandlerConstructor returns an http.Handler from a Loader
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// environment and a configuration.
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type HandlerConstructor func(Loader, jsonconfig.Obj) (http.Handler, error)
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var mapLock sync.Mutex
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var storageConstructors = make(map[string]StorageConstructor)
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var handlerConstructors = make(map[string]HandlerConstructor)
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func RegisterStorageConstructor(typ string, ctor StorageConstructor) {
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mapLock.Lock()
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defer mapLock.Unlock()
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if _, ok := storageConstructors[typ]; ok {
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panic("blobserver: StorageConstructor already registered for type: " + typ)
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}
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storageConstructors[typ] = ctor
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}
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func CreateStorage(typ string, loader Loader, config jsonconfig.Obj) (Storage, error) {
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mapLock.Lock()
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ctor, ok := storageConstructors[typ]
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mapLock.Unlock()
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if !ok {
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return nil, fmt.Errorf("Storage type %q not known or loaded", typ)
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}
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return ctor(loader, config)
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}
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// RegisterHandlerConstructor registers an http Handler constructor function
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// for a given handler type.
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//
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// It is an error to register the same handler type twice.
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func RegisterHandlerConstructor(typ string, ctor HandlerConstructor) {
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mapLock.Lock()
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defer mapLock.Unlock()
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if _, ok := handlerConstructors[typ]; ok {
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panic("blobserver: HandlerConstrutor already registered for type: " + typ)
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}
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handlerConstructors[typ] = ctor
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}
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// CreateHandler instantiates an http Handler of type 'typ' from the
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// provided JSON configuration, and finding peer handlers and
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// configuration from the environment in 'loader'.
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//
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// The handler 'typ' must have been previously registered with
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// RegisterHandlerConstructor.
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func CreateHandler(typ string, loader Loader, config jsonconfig.Obj) (http.Handler, error) {
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mapLock.Lock()
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ctor, ok := handlerConstructors[typ]
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mapLock.Unlock()
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if !ok {
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return nil, fmt.Errorf("blobserver: Handler type %q not known or loaded", typ)
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}
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return ctor(loader, config)
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}
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