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PHPLIB-322: Add resume logic to ChangeStream::rewind() #479

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Merged
kvwalker merged 3 commits into mongodb:master from kvwalker:PHPLIB-322
Feb 5, 2018
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21 changes: 20 additions & 1 deletion src/ChangeStream.php
View file Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -117,7 +117,26 @@ public function next()
*/
public function rewind()
{
$this->csIt->rewind();
$resumable = false;
try {
$this->csIt->rewind();
if ($this->valid()) {
$this->extractResumeToken($this->csIt->current());
}
} catch (RuntimeException $e) {
if (strpos($e->getMessage(), "not master") !== false) {
$resumable = true;
}
if ($e->getCode() === self::CURSOR_NOT_FOUND) {
$resumable = true;
}
if ($e instanceof ConnectionTimeoutException) {
$resumable = true;
}
}
if ($resumable) {
$this->resume();
}
}

/**
Expand Down
119 changes: 113 additions & 6 deletions tests/Operation/WatchFunctionalTest.php
View file Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -73,9 +73,6 @@ public function testNextResumesAfterCursorNotFound()
$this->assertSameDocument($expectedResult, $changeStream->current());
}

/**
* @todo test that rewind() also resumes once PHPLIB-322 is implemented
*/
public function testNextResumesAfterConnectionException()
{
/* In order to trigger a dropped connection, we'll use a new client with
Expand Down Expand Up @@ -129,6 +126,56 @@ function(stdClass $command) use (&$commands) {
$this->assertSame($expectedCommands, $commands);
}

public function testRewindResumesAfterConnectionException()
{
/* In order to trigger a dropped connection, we'll use a new client with
* a socket timeout that is less than the change stream's maxAwaitTimeMS
* option. */
$manager = new Manager($this->getUri(), ['socketTimeoutMS' => 50]);
$primaryServer = $manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));

$operation = new Watch($manager, $this->getDatabaseName(), $this->getCollectionName(), [], ['maxAwaitTimeMS' => 100]);
$changeStream = $operation->execute($primaryServer);

$commands = [];

try {
(new CommandObserver)->observe(
function() use ($changeStream) {
$changeStream->rewind();
},
function(stdClass $command) use (&$commands) {
$commands[] = key((array) $command);
}
);
$this->fail('ConnectionTimeoutException was not thrown');
} catch (ConnectionTimeoutException $e) {}

$expectedCommands = [
/* The initial aggregate command for change streams returns a cursor
* envelope with an empty initial batch, since there are no changes
* to report at the moment the change stream is created. Therefore,
* we expect a getMore to be issued when we first advance the change
* stream (with either rewind() or next()). */
'getMore',
/* Since socketTimeoutMS is less than maxAwaitTimeMS, the previous
* getMore command encounters a client socket timeout and leaves the
* cursor open on the server. ChangeStream should catch this error
* and resume by issuing a new aggregate command. */
'aggregate',
/* When ChangeStream resumes, it overwrites its original cursor with
* the new cursor resulting from the last aggregate command. This
* removes the last reference to the old cursor, which causes the
* driver to kill it (via mongoc_cursor_destroy()). */
'killCursors',
/* Finally, ChangeStream will rewind the new cursor as the last step
* of the resume process. This results in one last getMore. */
'getMore',
];

$this->assertSame($expectedCommands, $commands);
}

public function testNoChangeAfterResumeBeforeInsert()
{
$this->insertDocument(['_id' => 1, 'x' => 'foo']);
Expand Down Expand Up @@ -260,7 +307,6 @@ public function testInitialCursorIsNotClosed()

/**
* @expectedException MongoDB\Exception\ResumeTokenException
* @todo test that rewind() also attempts to extract the resume token once PHPLIB-322 is implemented
*/
public function testNextCannotExtractResumeToken()
{
Expand All @@ -269,13 +315,28 @@ public function testNextCannotExtractResumeToken()
$operation = new Watch($this->manager, $this->getDatabaseName(), $this->getCollectionName(), $pipeline, ['maxAwaitTimeMS' => 100]);
$changeStream = $operation->execute($this->getPrimaryServer());

$changeStream->rewind();
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@jmikola jmikola Feb 5, 2018

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I assume this was removed because rewind() now throws its own exception and would prevent us from testing next()

I'd suggest replacing with:

/* Note: we intentionally do not start iteration with rewind() to ensure
 * that we test extraction functionality within next(). */

Borrowed from the socket exception test.

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@jmikola jmikola Feb 5, 2018

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Side thought: does this actually throw or does it only introduce a delay with its own getMore? Since we've yet to insert a document, I'd expect rewind() to not find any result to attempt extraction.

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@kvwalker kvwalker Feb 5, 2018

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You're right, the rewind() doesn't throw because it doesn't attempt extraction.

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@jmikola jmikola Feb 5, 2018

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This now makes for very amusing diff output.

jmikola reacted with laugh emoji

/* Note: we intentionally do not start iteration with rewind() to ensure
* that we test extraction functionality within next(). */
$this->insertDocument(['x' => 1]);

$changeStream->next();
}

/**
* @expectedException MongoDB\Exception\ResumeTokenException
*/
public function testRewindCannotExtractResumeToken()
{
$pipeline = [['$project' => ['_id' => 0 ]]];

$operation = new Watch($this->manager, $this->getDatabaseName(), $this->getCollectionName(), $pipeline, ['maxAwaitTimeMS' => 100]);
$changeStream = $operation->execute($this->getPrimaryServer());

$this->insertDocument(['x' => 1]);

$changeStream->rewind();
}

public function testMaxAwaitTimeMS()
{
/* On average, an acknowledged write takes about 20 ms to appear in a
Expand Down Expand Up @@ -320,6 +381,52 @@ public function testMaxAwaitTimeMS()
$this->assertTrue($changeStream->valid());
}

public function testRewindResumesAfterCursorNotFound()
{
$operation = new Watch($this->manager, $this->getDatabaseName(), $this->getCollectionName(), [], ['maxAwaitTimeMS' => 100]);
$changeStream = $operation->execute($this->getPrimaryServer());

$this->killChangeStreamCursor($changeStream);

$changeStream->rewind();
$this->assertFalse($changeStream->valid());
$this->assertNull($changeStream->current());
}

public function testRewindExtractsResumeTokenAndNextResumes()
{
$operation = new Watch($this->manager, $this->getDatabaseName(), $this->getCollectionName(), [], ['maxAwaitTimeMS' => 100]);
$changeStream = $operation->execute($this->getPrimaryServer());

$this->insertDocument(['_id' => 1, 'x' => 'foo']);
$this->insertDocument(['_id' => 2, 'x' => 'bar']);

$changeStream->rewind();
$this->assertTrue($changeStream->valid());
$expectedResult = [
'_id' => $changeStream->current()->_id,
'operationType' => 'insert',
'fullDocument' => ['_id' => 1, 'x' => 'foo'],
'ns' => ['db' => $this->getDatabaseName(), 'coll' => $this->getCollectionName()],
'documentKey' => ['_id' => 1],
];
$this->assertSameDocument($expectedResult, $changeStream->current());

$this->killChangeStreamCursor($changeStream);

$changeStream->next();
$this->assertTrue($changeStream->valid());

$expectedResult = [
'_id' => $changeStream->current()->_id,
'operationType' => 'insert',
'fullDocument' => ['_id' => 2, 'x' => 'bar'],
'ns' => ['db' => $this->getDatabaseName(), 'coll' => $this->getCollectionName()],
'documentKey' => ['_id' => 2],
];
$this->assertSameDocument($expectedResult, $changeStream->current());
}

private function insertDocument($document)
{
$insertOne = new InsertOne($this->getDatabaseName(), $this->getCollectionName(), $document);
Expand Down

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