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path: root/vendor/google.golang.org/grpc/naming/naming.go
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/*
 *
 * Copyright 2014, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

// Package naming defines the naming API and related data structures for gRPC.
// The interface is EXPERIMENTAL and may be suject to change.
package naming

// Operation defines the corresponding operations for a name resolution change.
type Operation uint8

const (
	// Add indicates a new address is added.
	Add Operation = iota
	// Delete indicates an exisiting address is deleted.
	Delete
)

// Update defines a name resolution update. Notice that it is not valid having both
// empty string Addr and nil Metadata in an Update.
type Update struct {
	// Op indicates the operation of the update.
	Op Operation
	// Addr is the updated address. It is empty string if there is no address update.
	Addr string
	// Metadata is the updated metadata. It is nil if there is no metadata update.
	// Metadata is not required for a custom naming implementation.
	Metadata interface{}
}

// Resolver creates a Watcher for a target to track its resolution changes.
type Resolver interface {
	// Resolve creates a Watcher for target.
	Resolve(target string) (Watcher, error)
}

// Watcher watches for the updates on the specified target.
type Watcher interface {
	// Next blocks until an update or error happens. It may return one or more
	// updates. The first call should get the full set of the results. It should
	// return an error if and only if Watcher cannot recover.
	Next() ([]*Update, error)
	// Close closes the Watcher.
	Close()
}