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<?php
/*
* Copyright 2017 MongoDB, Inc.
*
* 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.
*/
namespace MongoDB;
use MongoDB\BSON\Serializable;
use MongoDB\Driver\Cursor;
use MongoDB\Driver\Exception\ConnectionException;
use MongoDB\Driver\Exception\RuntimeException;
use MongoDB\Driver\Exception\ServerException;
use MongoDB\Exception\InvalidArgumentException;
use MongoDB\Exception\ResumeTokenException;
use IteratorIterator;
use Iterator;
/**
* Iterator for a change stream.
*
* @api
* @see \MongoDB\Collection::watch()
* @see http://docs.mongodb.org/manual/reference/command/changeStream/
*/
class ChangeStream implements Iterator
{
/**
* @deprecated 1.4
* @todo Remove this in 2.0 (see: PHPLIB-360)
*/
const CURSOR_NOT_FOUND = 43;
private static $errorCodeCappedPositionLost = 136;
private static $errorCodeInterrupted = 11601;
private static $errorCodeCursorKilled = 237;
private $resumeToken;
private $resumeCallable;
private $csIt;
private $key = 0;
private $hasAdvanced = false;
/**
* Constructor.
*
* @internal
* @param Cursor $cursor
* @param callable $resumeCallable
*/
public function __construct(Cursor $cursor, callable $resumeCallable)
{
$this->resumeCallable = $resumeCallable;
$this->csIt = new IteratorIterator($cursor);
}
/**
* @see http://php.net/iterator.current
* @return mixed
*/
public function current()
{
return $this->csIt->current();
}
/**
* @return \MongoDB\Driver\CursorId
*/
public function getCursorId()
{
return $this->csIt->getInnerIterator()->getId();
}
/**
* @see http://php.net/iterator.key
* @return mixed
*/
public function key()
{
if ($this->valid()) {
return $this->key;
}
return null;
}
/**
* @see http://php.net/iterator.next
* @return void
*/
public function next()
{
try {
$this->csIt->next();
if ($this->valid()) {
if ($this->hasAdvanced) {
$this->key++;
}
$this->hasAdvanced = true;
$this->resumeToken = $this->extractResumeToken($this->csIt->current());
}
/* If the cursorId is 0, the server has invalidated the cursor so we
* will never perform another getMore. This means that we cannot
* resume and we can therefore unset the resumeCallable, which will
* free any reference to Watch. This will also free the only
* reference to an implicit session, since any such reference
* belongs to Watch. */
if ((string) $this->getCursorId() === '0') {
$this->resumeCallable = null;
}
} catch (RuntimeException $e) {
if ($this->isResumableError($e)) {
$this->resume();
}
}
}
/**
* @see http://php.net/iterator.rewind
* @return void
*/
public function rewind()
{
try {
$this->csIt->rewind();
if ($this->valid()) {
$this->hasAdvanced = true;
$this->resumeToken = $this->extractResumeToken($this->csIt->current());
}
// As with next(), free the callable once we know it will never be used.
if ((string) $this->getCursorId() === '0') {
$this->resumeCallable = null;
}
} catch (RuntimeException $e) {
if ($this->isResumableError($e)) {
$this->resume();
}
}
}
/**
* @see http://php.net/iterator.valid
* @return boolean
*/
public function valid()
{
return $this->csIt->valid();
}
/**
* Extracts the resume token (i.e. "_id" field) from the change document.
*
* @param array|document $document Change document
* @return mixed
* @throws InvalidArgumentException
* @throws ResumeTokenException if the resume token is not found or invalid
*/
private function extractResumeToken($document)
{
if ( ! is_array($document) && ! is_object($document)) {
throw InvalidArgumentException::invalidType('$document', $document, 'array or object');
}
if ($document instanceof Serializable) {
return $this->extractResumeToken($document->bsonSerialize());
}
$resumeToken = is_array($document)
? (isset($document['_id']) ? $document['_id'] : null)
: (isset($document->_id) ? $document->_id : null);
if ( ! isset($resumeToken)) {
throw ResumeTokenException::notFound();
}
if ( ! is_array($resumeToken) && ! is_object($resumeToken)) {
throw ResumeTokenException::invalidType($resumeToken);
}
return $resumeToken;
}
/**
* Determines if an exception is a resumable error.
*
* @see https://github.com/mongodb/specifications/blob/master/source/change-streams/change-streams.rst#resumable-error
* @param RuntimeException $exception
* @return boolean
*/
private function isResumableError(RuntimeException $exception)
{
if ($exception instanceof ConnectionException) {
return true;
}
if ( ! $exception instanceof ServerException) {
return false;
}
if (in_array($exception->getCode(), [self::$errorCodeCappedPositionLost, self::$errorCodeCursorKilled, self::$errorCodeInterrupted])) {
return false;
}
return true;
}
/**
* Creates a new changeStream after a resumable server error.
*
* @return void
*/
private function resume()
{
$newChangeStream = call_user_func($this->resumeCallable, $this->resumeToken);
$this->csIt = $newChangeStream->csIt;
$this->csIt->rewind();
}
}
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