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libphutil/src/future/exec/ExecFuture.php
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ExecFuture.php
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<?php
/**
* Execute system commands in parallel using futures.
*
* ExecFuture is a future, which means it runs asynchronously and represents
* a value which may not exist yet. See @{article:Using Futures} for an
* explanation of futures. When an ExecFuture resolves, it returns the exit
* code, stdout and stderr of the process it executed.
*
* ExecFuture is the core command execution implementation in libphutil, but is
* exposed through a number of APIs. See @{article:Command Execution} for more
* discussion about executing system commands.
*
* @task create Creating ExecFutures
* @task resolve Resolving Execution
* @task config Configuring Execution
* @task info Command Information
* @task interact Interacting With Commands
* @task internal Internals
* @group exec
*/
final class ExecFuture extends Future {
protected $pipes = array();
protected $proc = null;
protected $start = null;
protected $timeout = null;
protected $procStatus = null;
protected $stdout = null;
protected $stderr = null;
protected $stdin = null;
protected $closePipe = true;
protected $stdoutPos = 0;
protected $stderrPos = 0;
protected $command = null;
protected $cwd;
protected $stdoutSizeLimit = PHP_INT_MAX;
protected $stderrSizeLimit = PHP_INT_MAX;
private $profilerCallID;
private $killedByTimeout;
protected static $descriptorSpec = array(
0 => array('pipe', 'r'), // stdin
1 => array('pipe', 'w'), // stdout
2 => array('pipe', 'w'), // stderr
);
/* -( Creating ExecFutures )----------------------------------------------- */
/**
* Create a new ExecFuture.
*
* $future = new ExecFuture('wc -l %s', $file_path);
*
* @param string ##sprintf()##-style command string which will be passed
* through @{function:csprintf} with the rest of the arguments.
* @param ... Zero or more additional arguments for @{function:csprintf}.
* @return ExecFuture ExecFuture for running the specified command.
* @task create
*/
public function __construct($command) {
$argv = func_get_args();
$this->command = call_user_func_array('csprintf', $argv);
}
/* -( Command Information )------------------------------------------------ */
/**
* Retrieve the raw command to be executed.
*
* @return string Raw command.
* @task info
*/
public function getCommand() {
return $this->command;
}
/**
* Retrieve the byte limit for the stderr buffer.
*
* @return int Maximum buffer size, in bytes.
* @task info
*/
public function getStderrSizeLimit() {
return $this->stderrSizeLimit;
}
/**
* Retrieve the byte limit for the stdout buffer.
*
* @return int Maximum buffer size, in bytes.
* @task info
*/
public function getStdoutSizeLimit() {
return $this->stdoutSizeLimit;
}
/**
* Get the process's pid. This only works after execution is initiated, e.g.
* by a call to start().
*
* @return int Process ID of the executing process.
* @task info
*/
public function getPID() {
$status = $this->procGetStatus();
return $status['pid'];
}
/* -( Configuring Execution )---------------------------------------------- */
/**
* Set a maximum size for the stdout read buffer. To limit stderr, see
* @{method:setStderrSizeLimit}. The major use of these methods is to use less
* memory if you are running a command which sometimes produces huge volumes
* of output that you don't really care about.
*
* NOTE: Setting this to 0 means "no buffer", not "unlimited buffer".
*
* @param int Maximum size of the stdout read buffer.
* @return this
* @task config
*/
public function setStdoutSizeLimit($limit) {
$this->stdoutSizeLimit = $limit;
return $this;
}
/**
* Set a maximum size for the stderr read buffer.
* See @{method:setStdoutSizeLimit} for discussion.
*
* @param int Maximum size of the stderr read buffer.
* @return this
* @task config
*/
public function setStderrSizeLimit($limit) {
$this->stderrSizeLimit = $limit;
return $this;
}
/**
* Set the current working directory to use when executing the command.
*
* @param string Directory to set as CWD before executing the command.
* @return this
* @task config
*/
public function setCWD($cwd) {
$this->cwd = $cwd;
return $this;
}
/* -( Interacting With Commands )------------------------------------------ */
/**
* Read and return output from stdout and stderr, if any is available. This
* method keeps a read cursor on each stream, but the entire streams are
* still returned when the future resolves. You can call read() again after
* resolving the future to retrieve only the parts of the streams you did not
* previously read:
*
* $future = new ExecFuture('...');
* // ...
* list($stdout) = $future->read(); // Returns output so far
* list($stdout) = $future->read(); // Returns new output since first call
* // ...
* list($stdout) = $future->resolvex(); // Returns ALL output
* list($stdout) = $future->read(); // Returns unread output
*
* NOTE: If you set a limit with @{method:setStdoutSizeLimit} or
* @{method:setStderrSizeLimit}, this method will not be able to read data
* past the limit.
*
* NOTE: If you call @{method:discardBuffers}, all the stdout/stderr data
* will be thrown away and the cursors will be reset.
*
* @return pair <$stdout, $stderr> pair with new output since the last call
* to this method.
* @task interact
*/
public function read() {
if ($this->start) {
$this->isReady(); // Sync
}
$result = array(
(string)substr($this->stdout, $this->stdoutPos),
(string)substr($this->stderr, $this->stderrPos),
);
$this->stdoutPos = strlen($this->stdout);
$this->stderrPos = strlen($this->stderr);
return $result;
}
/**
* Write data to stdin of the command.
*
* @param string Data to write.
* @param bool If true, keep the pipe open for writing. By default, the pipe
* will be closed as soon as possible so that commands which
* listen for EOF will execute. If you want to keep the pipe open
* past the start of command execution, do an empty write with
* `$keep_pipe = true` first.
* @return this
* @task interact
*/
public function write($data, $keep_pipe = false) {
$this->stdin .= $data;
$this->closePipe = !$keep_pipe;
return $this;
}
/**
* Permanently discard the stdout and stderr buffers and reset the read
* cursors. This is basically useful only if you are streaming a large amount
* of data from some process:
*
* $future = new ExecFuture('zcat huge_file.gz');
* do {
* $done = $future->resolve(0.1); // Every 100ms,
* list($stdout) = $future->read(); // read output...
* echo $stdout; // send it somewhere...
* $future->discardBuffers(); // and then free the buffers.
* } while ($done === null);
*
* Conceivably you might also need to do this if you're writing a client using
* ExecFuture and ##netcat##, but you probably should not do that.
*
* NOTE: This completely discards the data. It won't be available when the
* future resolves. This is almost certainly only useful if you need the
* buffer memory for some reason.
*
* @return this
* @task interact
*/
public function discardBuffers() {
$this->stdout = '';
$this->stderr = '';
$this->stdoutPos = 0;
$this->stderrPos = 0;
return $this;
}
/**
* Returns true if this future was killed by a timeout configured with
* @{method:setTimeout}.
*
* @return bool True if the future was killed for exceeding its time limit.
*/
public function getWasKilledByTimeout() {
return $this->killedByTimeout;
}
/* -( Configuring Execution )---------------------------------------------- */
/**
* Set a hard limit on execution time. If the command runs longer, it will
* be killed and the future will resolve with an error code. You can test
* if a future was killed by a timeout with @{method:getWasKilledByTimeout}.
*
* @param int Maximum number of seconds this command may execute for.
* @return this
* @task config
*/
public function setTimeout($seconds) {
$this->timeout = $seconds;
return $this;
}
/* -( Resolving Execution )------------------------------------------------ */
/**
* Resolve a command you expect to exit with return code 0. Works like
* @{method:resolve}, but throws if $err is nonempty. Returns only
* $stdout and $stderr. See also @{function:execx}.
*
* list($stdout, $stderr) = $future->resolvex();
*
* @param float Optional timeout after which resolution will pause and
* execution will return to the caller.
* @return pair <$stdout, $stderr> pair.
* @task resolve
*/
public function resolvex($timeout = null) {
list($err, $stdout, $stderr) = $this->resolve($timeout);
if ($err) {
$cmd = $this->command;
throw new CommandException(
"Command failed with error #{$err}!",
$cmd,
$err,
$stdout,
$stderr);
}
return array($stdout, $stderr);
}
/**
* Resolve a command you expect to return valid JSON. Works like
* @{method:resolvex}, but also throws if stderr is nonempty, or stdout is not
* valid JSON. Returns a PHP array, decoded from the JSON command output.
*
* @param float Optional timeout after which resolution will pause and
* execution will return to the caller.
* @return array PHP array, decoded from JSON command output.
* @task resolve
*/
public function resolveJSON($timeout = null) {
list($stdout, $stderr) = $this->resolvex($timeout);
if (strlen($stderr)) {
$cmd = $this->command;
throw new CommandException(
"JSON command '{$cmd}' emitted text to stderr when none was expected: ".
$stderr,
$cmd,
0,
$stdout,
$stderr);
}
$object = json_decode($stdout, true);
if (!is_array($object)) {
$cmd = $this->command;
throw new CommandException(
"JSON command '{$cmd}' did not produce a valid JSON object on stdout: ".
$stdout,
$cmd,
0,
$stdout,
$stderr);
}
return $object;
}
/**
* Resolve the process by abruptly terminating it.
*
* @return list List of <err, stdout, stderr> results.
* @task resolve
*/
public function resolveKill() {
if (defined('SIGKILL')) {
$signal = SIGKILL;
} else {
$signal = 9;
}
proc_terminate($this->proc, $signal);
$this->result = array(
128 + $signal,
$this->stdout,
$this->stderr);
$this->closeProcess();
return $this->result;
}
/* -( Internals )---------------------------------------------------------- */
/**
* Provides read sockets to the future core.
*
* @return list List of read sockets.
* @task internal
*/
public function getReadSockets() {
list($stdin, $stdout, $stderr) = $this->pipes;
$sockets = array();
if (isset($stdout) && !feof($stdout)) {
$sockets[] = $stdout;
}
if (isset($stderr) && !feof($stderr)) {
$sockets[] = $stderr;
}
return $sockets;
}
/**
* Provides write sockets to the future core.
*
* @return list List of write sockets.
* @task internal
*/
public function getWriteSockets() {
list($stdin, $stdout, $stderr) = $this->pipes;
$sockets = array();
if (isset($stdin) && strlen($this->stdin) && !feof($stdin)) {
$sockets[] = $stdin;
}
return $sockets;
}
/**
* Reads some bytes from a stream, discarding output once a certain amount
* has been accumulated.
*
* @param resource Stream to read from.
* @param int Maximum number of bytes to return from $stream. If
* additional bytes are available, they will be read and
* discarded.
* @param string Human-readable description of stream, for exception
* message.
* @return string The data read from the stream.
* @task internal
*/
protected function readAndDiscard($stream, $limit, $description) {
$output = '';
do {
$data = fread($stream, 4096);
if (false === $data) {
throw new Exception('Failed to read from '.$description);
}
$read_bytes = strlen($data);
if ($read_bytes > 0 && $limit > 0) {
if ($read_bytes > $limit) {
$data = substr($data, 0, $limit);
}
$output .= $data;
$limit -= strlen($data);
}
} while ($read_bytes > 0);
return $output;
}
/**
* Begin or continue command execution.
*
* @return bool True if future has resolved.
* @task internal
*/
public function isReady() {
if (!$this->pipes) {
$profiler = PhutilServiceProfiler::getInstance();
$this->profilerCallID = $profiler->beginServiceCall(
array(
'type' => 'exec',
'command' => $this->command,
));
if (!$this->start) {
// We might already have started the timer via initating resolution.
$this->start = microtime(true);
}
$pipes = array();
$proc = proc_open(
$this->command,
self::$descriptorSpec,
$pipes,
$this->cwd);
if (!is_resource($proc)) {
throw new Exception('Failed to open process.');
}
$this->pipes = $pipes;
$this->proc = $proc;
list($stdin, $stdout, $stderr) = $pipes;
if (!phutil_is_windows()) {
// On Windows, there's no such thing as nonblocking interprocess I/O.
// Just leave the sockets blocking and hope for the best. Some features
// will not work.
if ((!stream_set_blocking($stdout, false)) ||
(!stream_set_blocking($stderr, false)) ||
(!stream_set_blocking($stdin, false))) {
$this->__destruct();
throw new Exception('Failed to set streams nonblocking.');
}
}
$this->tryToCloseStdin();
return false;
}
if (!$this->proc) {
return true;
}
list($stdin, $stdout, $stderr) = $this->pipes;
if (isset($this->stdin) && strlen($this->stdin)) {
$bytes = fwrite($stdin, $this->stdin);
if ($bytes === false) {
throw new Exception('Unable to write to stdin!');
} else if ($bytes) {
$this->stdin = substr($this->stdin, $bytes);
}
}
$this->tryToCloseStdin();
// Read status before reading pipes so that we can never miss data that
// arrives between our last read and the process exiting.
$status = $this->procGetStatus();
$this->stdout .= $this->readAndDiscard(
$stdout,
$this->getStdoutSizeLimit() - strlen($this->stdout),
'stdout');
$this->stderr .= $this->readAndDiscard(
$stderr,
$this->getStderrSizeLimit() - strlen($this->stderr),
'stderr');
if (!$status['running']) {
$this->result = array(
$status['exitcode'],
$this->stdout,
$this->stderr,
);
$this->closeProcess();
return true;
}
$elapsed = (microtime(true) - $this->start);
if ($this->timeout && ($elapsed >= $this->timeout)) {
$this->killedByTimeout = true;
$this->resolveKill();
return true;
}
}
/**
* @return void
* @task internal
*/
public function __destruct() {
if (!$this->proc) {
return;
}
// NOTE: If we try to proc_close() an open process, we hang indefinitely. To
// avoid this, kill the process explicitly if it's still running.
$status = $this->procGetStatus();
if ($status['running']) {
$this->resolveKill();
} else {
$this->closeProcess();
}
}
/**
* Close and free resources if necessary.
*
* @return void
* @task internal
*/
private function closeProcess() {
foreach ($this->pipes as $pipe) {
if (isset($pipe)) {
@fclose($pipe);
}
}
$this->pipes = array(null, null, null);
if ($this->proc) {
@proc_close($this->proc);
$this->proc = null;
}
$this->stdin = null;
if ($this->profilerCallID !== null) {
$profiler = PhutilServiceProfiler::getInstance();
$profiler->endServiceCall(
$this->profilerCallID,
array(
'err' => $this->result ? idx($this->result, 0) : null,
));
$this->profilerCallID = null;
}
}
/**
* Execute proc_get_status(), but avoid pitfalls.
*
* @return dict Process status.
* @task internal
*/
private function procGetStatus() {
// After the process exits, we only get one chance to read proc_get_status()
// before it starts returning garbage. Make sure we don't throw away the
// last good read.
if ($this->procStatus) {
if (!$this->procStatus['running']) {
return $this->procStatus;
}
}
$this->procStatus = proc_get_status($this->proc);
return $this->procStatus;
}
/**
* Try to close stdin, if we're done using it. This keeps us from hanging if
* the process on the other end of the pipe is waiting for EOF.
*
* @return void
* @task internal
*/
private function tryToCloseStdin() {
if (!$this->closePipe) {
// We've been told to keep the pipe open by a call to write(..., true).
return;
}
if (strlen($this->stdin)) {
// We still have bytes to write.
return;
}
list($stdin) = $this->pipes;
if (!$stdin) {
// We've already closed stdin.
return;
}
// There's nothing stopping us from closing stdin, so close it.
@fclose($stdin);
$this->pipes[0] = null;
}
public function getDefaultWait() {
$wait = parent::getDefaultWait();
if ($this->timeout) {
if (!$this->start) {
$this->start = microtime(true);
}
$elapsed = (microtime(true) - $this->start);
$wait = max(0, min($this->timeout - $elapsed, $wait));
}
return $wait;
}
}
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