Fast CGI Client

A PHP fast CGI client to send requests (a)synchronously to PHP-FPM using the FastCGI Protocol.

This library is based on the work of Pierrick Charron's PHP-FastCGI-Client and was ported and modernized to latest PHP versions, extended with some features for handling multiple requests (in loops) and unit and integration tests as well.

This is the documentation of the latest release.

Please have a look at the backwards incompatible changes (BC breaks) in the changelog.

Please see the following links for earlier releases:

PHP >= 7.0 (EOL) v1.0.0, v1.0.1, v1.1.0, v1.2.0, v1.3.0, v1.4.0, v1.4.1, v1.4.2
PHP >= 7.1 v2.0.0, v2.0.1, v2.1.0, v2.2.0, v2.3.0, v2.4.0, v2.4.1, v2.4.2, v2.4.3, v2.5.0, v2.6.0, v2.7.0, v2.7.1, v2.7.2, v3.0.0-alpha, v3.0.0-beta, v3.0.0, v3.0.1, v3.1.0, v3.1.1, v3.1.2, v3.1.3, v3.1.4

Read more about the journey to and changes in v2.6.0 in this blog post.

You can find an experimental use-case in my related blog posts:

Experimental async PHP vol. 1
Experimental async PHP vol. 2

You can also find slides of my talks about this project on speakerdeck.com.

Installation

composer require hollodotme/fast-cgi-client:3.1.*

Usage - connections

This library supports two types of connecting to a FastCGI server:

Via network socket
Via unix domain socket

Create a network socket connection

<?php declare(strict_types=1);

namespace YourVendor\YourProject;

use hollodotme\FastCGI\SocketConnections\NetworkSocket;

$connection = new NetworkSocket(
	'127.0.0.1',    # Hostname
	9000,           # Port
	5000,           # Connect timeout in milliseconds (default: 5000)
	5000            # Read/write timeout in milliseconds (default: 5000)
);

Create a unix domain socket connection

<?php declare(strict_types=1);

namespace YourVendor\YourProject;

use hollodotme\FastCGI\SocketConnections\UnixDomainSocket;

$connection = new UnixDomainSocket(
	'/var/run/php/php7.3-fpm.sock',     # Socket path
	5000,                               # Connect timeout in milliseconds (default: 5000)
	5000                                # Read/write timeout in milliseconds (default: 5000)
);

Usage - single request

The following examples assume that the content of /path/to/target/script.php looks like this:

<?php declare(strict_types=1);

sleep((int)($_REQUEST['sleep'] ?? 0));
echo $_REQUEST['key'] ?? '';

Send request synchronously

<?php declare(strict_types=1);

namespace YourVendor\YourProject;

use hollodotme\FastCGI\Client;
use hollodotme\FastCGI\Requests\PostRequest;
use hollodotme\FastCGI\SocketConnections\NetworkSocket;

$client     = new Client();
$connection = new NetworkSocket('127.0.0.1', 9000);
$content    = http_build_query(['key' => 'value']);
$request    = new PostRequest('/path/to/target/script.php', $content);

$response = $client->sendRequest($connection, $request);

echo $response->getBody();

# prints
value

Send request asynchronously (Fire and forget)

<?php declare(strict_types=1);

namespace YourVendor\YourProject;

use hollodotme\FastCGI\Client;
use hollodotme\FastCGI\Requests\PostRequest;
use hollodotme\FastCGI\SocketConnections\NetworkSocket;

$client     = new Client();
$connection = new NetworkSocket('127.0.0.1', 9000);
$content    = http_build_query(['key' => 'value']);
$request    = new PostRequest('/path/to/target/script.php', $content);

$socketId = $client->sendAsyncRequest($connection, $request);

echo "Request sent, got ID: {$socketId}";

Read the response, after sending the async request

<?php declare(strict_types=1);

namespace YourVendor\YourProject;

use hollodotme\FastCGI\Client;
use hollodotme\FastCGI\Requests\PostRequest;
use hollodotme\FastCGI\SocketConnections\NetworkSocket;

$client     = new Client();
$connection = new NetworkSocket('127.0.0.1', 9000);
$content    = http_build_query(['key' => 'value']);
$request    = new PostRequest('/path/to/target/script.php', $content);

$socketId = $client->sendAsyncRequest($connection, $request);

echo "Request sent, got ID: {$socketId}";

# Do something else here in the meanwhile

# Blocking call until response is received or read timed out
$response = $client->readResponse( 
	$socketId,     # The socket ID 
	3000            # Optional timeout to wait for response,
					# defaults to read/write timeout in milliseconds set in connection
);

echo $response->getBody();

# prints
value

Notify a callback when async request responded

You can register response and failure callbacks for each request. In order to notify the callbacks when a response was received instead of returning it, you need to use the waitForResponse(int $socketId, ?int $timeoutMs = null) method.

<?php declare(strict_types=1);

namespace YourVendor\YourProject;

use hollodotme\FastCGI\Client;
use hollodotme\FastCGI\Requests\PostRequest;
use hollodotme\FastCGI\Interfaces\ProvidesResponseData;
use hollodotme\FastCGI\SocketConnections\NetworkSocket;
use Throwable;

$client     = new Client();
$connection = new NetworkSocket('127.0.0.1', 9000);
$content    = http_build_query(['key' => 'value']);
$request    = new PostRequest('/path/to/target/script.php', $content);

# Register a response callback, expects a `ProvidesResponseData` instance as the only paramter
$request->addResponseCallbacks(
	static function( ProvidesResponseData $response )
	{
		echo $response->getBody();	
	}
);

# Register a failure callback, expects a `\Throwable` instance as the only parameter
$request->addFailureCallbacks(
	static function ( Throwable $throwable )
	{
		echo $throwable->getMessage();	
	}
);

$socketId = $client->sendAsyncRequest($connection, $request);

echo "Request sent, got ID: {$socketId}";

# Do something else here in the meanwhile

# Blocking call until response is received or read timed out
# If response was received all registered response callbacks will be notified
$client->waitForResponse( 
	$socketId,     # The socket ID 
	3000            # Optional timeout to wait for response,
					# defaults to read/write timeout in milliseconds set in connection
);

# ... is the same as

while(true)
{
	if ($client->hasResponse($socketId))
	{
		$client->handleResponse($socketId, 3000);
		break;
	}
}

# prints
value

Usage - multiple requests

Sending multiple requests and reading their responses (order preserved)

<?php declare(strict_types=1);

namespace YourVendor\YourProject;

use hollodotme\FastCGI\Client;
use hollodotme\FastCGI\Requests\PostRequest;
use hollodotme\FastCGI\SocketConnections\NetworkSocket;

$client     = new Client();
$connection = new NetworkSocket('127.0.0.1', 9000);

$request1 = new PostRequest('/path/to/target/script.php', http_build_query(['key' => '1']));
$request2 = new PostRequest('/path/to/target/script.php', http_build_query(['key' => '2']));
$request3 = new PostRequest('/path/to/target/script.php', http_build_query(['key' => '3']));

$socketIds = [];

$socketIds[] = $client->sendAsyncRequest($connection, $request1);
$socketIds[] = $client->sendAsyncRequest($connection, $request2);
$socketIds[] = $client->sendAsyncRequest($connection, $request3);

echo 'Sent requests with IDs: ' . implode( ', ', $socketIds ) . "\n";

# Do something else here in the meanwhile

# Blocking call until all responses are received or read timed out
# Responses are read in same order the requests were sent
foreach ($client->readResponses(3000, ...$socketIds) as $response)
{
	echo $response->getBody() . "\n";	
}

# prints
1
2
3

Sending multiple requests and reading their responses (reactive)

<?php declare(strict_types=1);

namespace YourVendor\YourProject;

use hollodotme\FastCGI\Client;
use hollodotme\FastCGI\Requests\PostRequest;
use hollodotme\FastCGI\SocketConnections\NetworkSocket;

$client     = new Client();
$connection = new NetworkSocket('127.0.0.1', 9000);

$request1 = new PostRequest('/path/to/target/script.php', http_build_query(['key' => '1', 'sleep' => 3]));
$request2 = new PostRequest('/path/to/target/script.php', http_build_query(['key' => '2', 'sleep' => 2]));
$request3 = new PostRequest('/path/to/target/script.php', http_build_query(['key' => '3', 'sleep' => 1]));

$socketIds = [];

$socketIds[] = $client->sendAsyncRequest($connection, $request1);
$socketIds[] = $client->sendAsyncRequest($connection, $request2);
$socketIds[] = $client->sendAsyncRequest($connection, $request3);

echo 'Sent requests with IDs: ' . implode( ', ', $socketIds ) . "\n";

# Do something else here in the meanwhile

# Loop until all responses were received
while ( $client->hasUnhandledResponses() )
{
	# read all ready responses
	foreach ( $client->readReadyResponses( 3000 ) as $response )
	{
		echo $response->getBody() . "\n";
	}
	
	echo '.';
}

# ... is the same as

while ( $client->hasUnhandledResponses() )
{
	$readySocketIds = $client->getSocketIdsHavingResponse();
	
	# read all ready responses
	foreach ( $client->readResponses( 3000, ...$readySocketIds ) as $response )
	{
		echo $response->getBody() . "\n";
	}
	
	echo '.';
}

# ... is the same as

while ( $client->hasUnhandledResponses() )
{
	$readySocketIds = $client->getSocketIdsHavingResponse();
	
	# read all ready responses
	foreach ($readySocketIds as $socketId)
	{
		$response = $client->readResponse($socketId, 3000);
		echo $response->getBody() . "\n";
	}
	
	echo '.';
}

# prints
...............................................3
...............................................2
...............................................1

Sending multiple requests and notifying callbacks (reactive)

<?php declare(strict_types=1);

namespace YourVendor\YourProject;

use hollodotme\FastCGI\Client;
use hollodotme\FastCGI\Requests\PostRequest;
use hollodotme\FastCGI\Interfaces\ProvidesResponseData;
use hollodotme\FastCGI\SocketConnections\NetworkSocket;
use Throwable;

$client     = new Client();
$connection = new NetworkSocket('127.0.0.1', 9000);

$responseCallback = static function( ProvidesResponseData $response )
{
	echo $response->getBody();	
};

$failureCallback = static function ( Throwable $throwable )
{
	echo $throwable->getMessage();	
};

$request1 = new PostRequest('/path/to/target/script.php', http_build_query(['key' => '1', 'sleep' => 3]));
$request2 = new PostRequest('/path/to/target/script.php', http_build_query(['key' => '2', 'sleep' => 2]));
$request3 = new PostRequest('/path/to/target/script.php', http_build_query(['key' => '3', 'sleep' => 1]));

$request1->addResponseCallbacks($responseCallback);
$request1->addFailureCallbacks($failureCallback);

$request2->addResponseCallbacks($responseCallback);
$request2->addFailureCallbacks($failureCallback);

$request3->addResponseCallbacks($responseCallback);
$request3->addFailureCallbacks($failureCallback);

$socketIds = [];

$socketIds[] = $client->sendAsyncRequest($connection, $request1);
$socketIds[] = $client->sendAsyncRequest($connection, $request2);
$socketIds[] = $client->sendAsyncRequest($connection, $request3);

echo 'Sent requests with IDs: ' . implode( ', ', $socketIds ) . "\n";

# Do something else here in the meanwhile

# Blocking call until all responses were received and all callbacks notified
$client->waitForResponses(3000);

# ... is the same as

while ( $client->hasUnhandledResponses() )
{
	$client->handleReadyResponses(3000);
}

# ... is the same as

while ( $client->hasUnhandledResponses() )
{
	$readySocketIds = $client->getSocketIdsHavingResponse();
	
	# read all ready responses
	foreach ($readySocketIds as $socketId)
	{
		$client->handleResponse($socketId, 3000);
	}
}

# prints
3
2
1

Reading output buffer from worker script using pass through callbacks

It may be useful to see the progression of a requested script by having access to the flushed output of that script. The php.ini default output buffering for php-fpm is 4096 bytes and is (hard-coded) disabled for CLI mode. (See documentation) Calling ob_implicit_flush() causes every call to echo or print to immediately be flushed.

The callee script could look like this:

<?php declare(strict_types=1);

ob_implicit_flush();

function show( string $string )
{
	echo $string . str_repeat( "\r", 4096 - strlen( $string ) ) . "\n";
	sleep( 1 );
}

show( 'One' );
show( 'Two' );
show( 'Three' );

error_log("Oh oh!\n");

echo 'End';

The caller than could look like this:

<?php declare(strict_types=1);

namespace YourVendor\YourProject;

use hollodotme\FastCGI\Client;
use hollodotme\FastCGI\Requests\GetRequest;
use hollodotme\FastCGI\SocketConnections\NetworkSocket;

$client     = new Client();
$connection = new NetworkSocket('127.0.0.1', 9000);

$passThroughCallback = static function( string $outputBuffer, string $errorBuffer )
{
	echo 'Output: ' . $outputBuffer;
	echo 'Error: ' . $errorBuffer;
};

$request = new GetRequest('/path/to/target/script.php', '');
$request->addPassThroughCallbacks( $passThroughCallback );

$client->sendAsyncRequest($connection, $request);
$client->waitForResponses();

# prints immediately
Buffer: Content-type: text/html; charset=UTF-8

Output: One
# sleeps 1 sec
Output: Two
# sleeps 1 sec
Output: Three
# sleeps 1 sec
Error: Oh oh!
Output: End

Requests

Requests are defined by the following interface:

<?php declare(strict_types=1);

namespace hollodotme\FastCGI\Interfaces;

interface ProvidesRequestData
{
	public function getGatewayInterface() : string;

	public function getRequestMethod() : string;

	public function getScriptFilename() : string;

	public function getServerSoftware() : string;

	public function getRemoteAddress() : string;

	public function getRemotePort() : int;

	public function getServerAddress() : string;

	public function getServerPort() : int;

	public function getServerName() : string;

	public function getServerProtocol() : string;

	public function getContentType() : string;

	public function getContentLength() : int;

	public function getContent() : string;

	public function getCustomVars() : array;

	public function getParams() : array;
	
	public function getRequestUri() : string;
}

Alongside with this interface, this package provides an abstract request class, containing default values to make the API more handy for you and 5 request method implementations of this abstract class:

hollodotme\FastCGI\Requests\GetRequest
hollodotme\FastCGI\Requests\PostRequest
hollodotme\FastCGI\Requests\PutRequest
hollodotme\FastCGI\Requests\PatchRequest
hollodotme\FastCGI\Requests\DeleteRequest

So you can either implement the interface, inherit from the abstract class or simply use one of the 5 implementations.

Default values

The abstract request class defines several default values which you can optionally overwrite:

Key	Default value	Comment
GATEWAY_INTERFACE	FastCGI/1.0	Cannot be overwritten, because this is the only supported version of the client.
SERVER_SOFTWARE	hollodotme/fast-cgi-client
REMOTE_ADDR	192.168.0.1
REMOTE_PORT	9985
SERVER_ADDR	127.0.0.1
SERVER_PORT	80
SERVER_NAME	localhost
SERVER_PROTOCOL	HTTP/1.1	You can use the public class constants in `hollodotme\FastCGI\Constants\ServerProtocol`
CONTENT_TYPE	application/x-www-form-urlencoded
REQUEST_URI
CUSTOM_VARS	empty array	You can use the methods `setCustomVar`, `addCustomVars` to add own key-value pairs

Request contents

In order to make the composition of different request content types easier there are classes covering the typical content types:

UrlEncodedFormData
MultipartFormData
JsonData

You can create your own request content type composer by implementing the following interface:

ComposesRequestContent

interface ComposesRequestContent
{
	public function getContentType() : string;

	public function getContent() : string;
}

Request content example: URL encoded form data (application/x-www-form-urlencoded)

<?php declare(strict_types=1);

use hollodotme\FastCGI\RequestContents\UrlEncodedFormData;
use hollodotme\FastCGI\SocketConnections\NetworkSocket;
use hollodotme\FastCGI\Requests\PostRequest;
use hollodotme\FastCGI\Client;

$client = new Client();
$connection = new NetworkSocket( '127.0.0.1', 9000 );

$urlEncodedContent = new UrlEncodedFormData(
	[
		'nested' => [
			'one',
			'two'   => 'value2',
			'three' => [
				'value3',
			],
		],
	]
);

$postRequest = PostRequest::newWithRequestContent( '/path/to/target/script.php', $urlEncodedContent );

$response = $client->sendRequest( $connection, $postRequest );

This example produces the following $_POST array at the target script:

Array
(
    [nested] => Array
        (
            [0] => one
            [two] => value2
            [three] => Array
                (
                    [0] => value3
                )

        )
)

Request content example: multipart form data (multipart/form-data)

Multipart form-data can be used to transfer any binary data as files to the target script just like a file upload in a browser does.

PLEASE NOTE: Multipart form-data content type works with POST requests only.

<?php declare(strict_types=1);

use hollodotme\FastCGI\RequestContents\MultipartFormData;
use hollodotme\FastCGI\SocketConnections\NetworkSocket;
use hollodotme\FastCGI\Requests\PostRequest;
use hollodotme\FastCGI\Client;

$client = new Client();
$connection = new NetworkSocket( '127.0.0.1', 9000 );

$multipartContent = new MultipartFormData(
    # POST data
	[
        'simple'          => 'value',
		'nested[]'        => 'one',
		'nested[two]'     => 'value2',
		'nested[three][]' => 'value3',
	],
	# FILES
	[
		'file1'        => __FILE__,
		'files[1]'     => __FILE__,
		'files[three]' => __FILE__,
	]
);

$postRequest = PostRequest::newWithRequestContent( '/path/to/target/script.php', $multipartContent );

$response = $client->sendRequest( $connection, $postRequest );

This example produces the following $_POST and $_FILES array at the target script:

# $_POST
Array
(
    [simple] => value
    [nested] => Array
        (
            [0] => one
            [two] => value2
            [three] => Array
                (
                    [0] => value3
                )

        )

)

# $_FILES
Array
(
    [file1] => Array
        (
            [name] => multipart.php
            [type] => application/octet-stream
            [tmp_name] => /tmp/phpiIdCNM
            [error] => 0
            [size] => 1086
        )

    [files] => Array
        (
            [name] => Array
                (
                    [1] => multipart.php
                    [three] => multipart.php
                )

            [type] => Array
                (
                    [1] => application/octet-stream
                    [three] => application/octet-stream
                )

            [tmp_name] => Array
                (
                    [1] => /tmp/phpAjHINL
                    [three] => /tmp/phpicAmjN
                )

            [error] => Array
                (
                    [1] => 0
                    [three] => 0
                )

            [size] => Array
                (
                    [1] => 1086
                    [three] => 1086
                )

        )

)

Request content example: JSON encoded data (application/json)

<?php declare(strict_types=1);

use hollodotme\FastCGI\RequestContents\JsonData;
use hollodotme\FastCGI\SocketConnections\NetworkSocket;
use hollodotme\FastCGI\Requests\PostRequest;
use hollodotme\FastCGI\Client;

$client = new Client();
$connection = new NetworkSocket( '127.0.0.1', 9000 );

$jsonContent = new JsonData(
	[
		'nested' => [
			'one',
			'two'   => 'value2',
			'three' => [
				'value3',
			],
		],
	]
);

$postRequest = PostRequest::newWithRequestContent( '/path/to/target/script.php', $jsonContent );

$response = $client->sendRequest( $connection, $postRequest );

This example produces the following content for php://input at the target script:

{
  "nested": {
    "0": "one",
    "two": "value2",
    "three": [
      "value3"
    ]
  }
}

Responses

Responses are defined by the following interface:

<?php declare(strict_types=1);

namespace hollodotme\FastCGI\Interfaces;

interface ProvidesResponseData
{
	public function getHeaders() : array;

	public function getHeader( string $headerKey ) : array;
	
	public function getHeaderLine( string $headerKey ) : string;

	public function getBody() : string;

	public function getOutput() : string;
	
	public function getError() : string;

	public function getDuration() : float;
}

Assuming /path/to/target/script.php has the following content:

<?php declare(strict_types=1);

echo 'Hello World';
error_log('Some error');

The raw response would look like this:

Content-type: text/html; charset=UTF-8

Hello World

Please note:

All headers sent by your script will precede the response body
There won't be any HTTP specific headers like HTTP/1.1 200 OK, because there is no webserver involved.

Custom headers will also be part of the response:

<?php declare(strict_types=1);

header('X-Custom: Header');
header('Set-Cookie: yummy_cookie=choco');
header('Set-Cookie: tasty_cookie=strawberry');

echo 'Hello World';
error_log('Some error');

The raw response would look like this:

X-Custom: Header
Set-Cookie: yummy_cookie=choco
Set-Cookie: tasty_cookie=strawberry
Content-type: text/html; charset=UTF-8

Hello World

You can retrieve all of the response data separately from the response object:

# Get all values of a single response header
$response->getHeader('Set-Cookie'); 
// ['yummy_cookie=choco', 'tasty_cookie=strawberry']

# Get all values of a single response header as comma separated string
$response->getHeaderLine('Set-Cookie');
// 'yummy_cookie=choco, tasty_cookie=strawberry'

# Get all headers as grouped array
$response->getHeaders();
// [
//   'X-Custom' => [
//      'Header',
//   ],
//   'Set-Cookie' => [
//      'yummy_cookie=choco',
//      'tasty_cookie=strawberry',
//   ],
//   'Content-type' => [
//      'text/html; charset=UTF-8',
//   ],
// ]

# Get the body
$response->getBody(); 
// 'Hello World'

# Get the raw response output from STDOUT stream
$response->getOutput();
// 'X-Custom: Header
// Set-Cookie: yummy_cookie=choco
// Set-Cookie: tasty_cookie=strawberry
// Content-type: text/html; charset=UTF-8
// 
// Hello World'

# Get the raw response from SFTERR stream
$response->getError();
// Some error

# Get the duration
$response->getDuration(); 
// e.g. 0.0016319751739502

Trouble shooting

"File not found." response (php-fpm)

This response is generated by php-fpm for the preceding error Primary script unknown in case the requested script does not exists or there are path traversals in its path like /var/www/../run/script.php.

Although the given path may exist and would resolve to an absolute path in the file system, php-fpm does not do any path resolution and accepts only absolute paths to the script you want to execute.

Programatically you can handle this error like this:

if (preg_match("#^Primary script unknown\n?$#", $response->getError()))
{
    throw new Exception('Could not find or resolve path to script for execution.');
}

# OR

if ('404 Not Found' === $response->getHeaderLine('Status'))
{
    throw new Exception('Could not find or resolve path to script for execution.');
}

# OR

if ('File not found.' === trim($response->getBody()))
{
    throw new Exception('Could not find or resolve path to script for execution.');
}

Prepare local development environment

This requires docker and docker-compose installed on your machine.

make update

Run examples

make examples

Run all tests

make tests

Command line tool (for local debugging only)

Please note: bin/fcgiget is not included and linked to vendor/bin via composer anymore since version v3.1.2for security reasons. Read more.

Run a call through a network socket:

docker-compose exec php74 php bin/fcgiget localhost:9001/status

Run a call through a Unix Domain Socket

docker-compose exec php74 php bin/fcgiget unix:///var/run/php-uds.sock/status

This shows the response of the php-fpm status page.

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

README.md

README.md

Fast CGI Client

Installation

Usage - connections

Create a network socket connection

Create a unix domain socket connection

Usage - single request

Send request synchronously

Send request asynchronously (Fire and forget)

Read the response, after sending the async request

Notify a callback when async request responded

Usage - multiple requests

Sending multiple requests and reading their responses (order preserved)

Sending multiple requests and reading their responses (reactive)

Sending multiple requests and notifying callbacks (reactive)

Reading output buffer from worker script using pass through callbacks

Requests

Default values

Request contents

Request content example: URL encoded form data (application/x-www-form-urlencoded)

Request content example: multipart form data (multipart/form-data)

Request content example: JSON encoded data (application/json)

Responses

Trouble shooting

"File not found." response (php-fpm)

Prepare local development environment

Run examples

Run all tests

Command line tool (for local debugging only)

Files

README.md

Latest commit

History

README.md

File metadata and controls

Fast CGI Client

Installation

Usage - connections

Create a network socket connection

Create a unix domain socket connection

Usage - single request

Send request synchronously

Send request asynchronously (Fire and forget)

Read the response, after sending the async request

Notify a callback when async request responded

Usage - multiple requests

Sending multiple requests and reading their responses (order preserved)

Sending multiple requests and reading their responses (reactive)

Sending multiple requests and notifying callbacks (reactive)

Reading output buffer from worker script using pass through callbacks

Requests

Default values

Request contents

Request content example: URL encoded form data (application/x-www-form-urlencoded)

Request content example: multipart form data (multipart/form-data)

Request content example: JSON encoded data (application/json)

Responses

Trouble shooting

"File not found." response (php-fpm)

Prepare local development environment

Run examples

Run all tests

Command line tool (for local debugging only)