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Read standard output and standard error of child process using stream_select.

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If a process filled up the buffer of the standard error pipe before closing the
standard output pipe, it would hang. As a result, the call to
stream_get_contents for the standard output pipe would not return, as the
standard error pipe needs to be read from in order for the process to continue.
This change uses stream_select to read from both pipes whenever data becomes
available.
This commit is contained in:
Tobias Kappé 2016-08-27 12:56:13 +02:00
parent 64b0f60368
commit 07c9264884
2 changed files with 61 additions and 5 deletions
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45
PHPCI/Helper/BaseCommandExecutor.php
View file

@ -92,14 +92,14 @@ abstract class BaseCommandExecutor implements CommandExecutor
$pipes = array();
$process = proc_open($command, $descriptorSpec, $pipes, $this->buildPath, null);
$this->lastOutput = '';
$this->lastError = '';
if (is_resource($process)) {
fclose($pipes[0]);
$this->lastOutput = stream_get_contents($pipes[1]);
$this->lastError = stream_get_contents($pipes[2]);
fclose($pipes[1]);
fclose($pipes[2]);
list($this->lastOutput, $this->lastError) =
$this->readAlternating([$pipes[1], $pipes[2]]);
$status = proc_close($process);
}
@ -125,6 +125,41 @@ abstract class BaseCommandExecutor implements CommandExecutor
return $rtn;
}
/**
* Reads from array of streams as data becomes available.
* @param array $descriptors
* @return string[] data read from each descriptor
*/
private function readAlternating(array $descriptors)
{
$outputs = [];
foreach ($descriptors as $key => $descriptor) {
stream_set_blocking($descriptor, false);
$outputs[$key] = '';
}
do {
$read = $descriptors;
$write = null;
$except = null;
stream_select($read, $write, $except, null);
foreach ($read as $descriptor) {
$key = array_search($descriptor, $descriptors);
if (feof($descriptor)) {
fclose($descriptor);
unset($descriptors[$key]);
} else {
$outputs[$key] .= fgets($descriptor);
}
}
} while (count($descriptors) > 0);
return $outputs;
}
/**
* Returns the output from the last command run.
*/

21
Tests/PHPCI/Helper/CommandExecutorTest.php
View file

@ -58,6 +58,27 @@ class CommandExecutorTest extends \PHPUnit_Framework_TestCase
$this->assertFalse($returnValue);
}
/**
* Runs a script that generates an output that fills the standard error
* buffer first, followed by the standard output buffer. The function
* should be able to read from both streams, thereby preventing the child
* process from blocking because one of its buffers is full.
*/
public function testExecuteCommand_AlternatesBothBuffers()
{
$length = 80000;
$script = <<<EOD
/bin/sh -c 'data="$(printf %%${length}s | tr " " "-")"; >&2 echo "\$data"; >&1 echo "\$data"'
EOD;
$data = str_repeat("-", $length);
$returnValue = $this->testedExecutor->executeCommand(array($script));
$this->assertTrue($returnValue);
$this->assertEquals($data, trim($this->testedExecutor->getLastOutput()));
$this->assertEquals($data, trim($this->testedExecutor->getLastError()));
}
public function testFindBinary_ReturnsPathInSpecifiedRoot()
{
$thisFileName = "CommandExecutorTest.php";