Swow is a high-performance pure coroutine network communication engine written in PHP and Cwhich is committed to using a minimal C core and most PHP code to support PHP high-performance web programming.

Project original intention

Although the PHP coroutine ecology now has a very diverse selection, all coroutine frameworks and libraries have a very fatal problem, that is, they all evolved from asynchronous frameworks, not bottom-up for coroutines. Due to some compatibility considerations, many capabilities that should be possessed are often sacrificed, or reasonable design changes cannot be made due to historical burdens.

Therefore, the Swow project is committed to creating a high-performance, highly controllable, and easily compatible engine designed for coroutines from the bottom up. Relying on the advantages of architecture design, it will fully release the true strength of coroutine technology. This is the original intention of Swow and its team members. We will continue to invest and work hard for this, and you are welcome to join us to participate in open source construction.

design concept

Swow’s minimum C core design determines that it is more about pursuing secondary development capabilities and debuggability in addition to ensuring key performance.

The seamless integration of Swow kernel and PHP code greatly improves the developer’s programming efficiency and flexibility.

Swow provides a variety of debugging mechanisms and powerful and low-threshold debugging capabilities to ensure that developers are free from bugs to the greatest extent. Ordinary developers can also have near-expert-level DEBUG capabilities through the blessing of tools.

thank you

Written before the introduction of capabilities: The development of PHP high-performance coroutine network communication engine has a long way to go. This is an open source work that is too high. I am very grateful to the following partners for their code contributions to the Swow project. Without everyone, there would be no current Swow ! Among them, we would like to thank @dixyes, the core member of the team, for his dedication, which has raised the capabilities and stability of Swow to a whole new level!


Supported OS

operating system swow Other asynchronous coroutine libraries
Win32 โœ… IOCP native support โŒ No native support
GNU/Linux (including musl) โœ… Epoll support + planned io_uring support โš ๏ธ No io_uring plan support
macOS โœ… Kqueue support; support intel and m1 chips โš ๏ธ Not Tier 1 support
FreeBSD โœ… Kqueue support โš ๏ธ Lack of official support statement
other [^other-platforms] โš ๏ธ Second class support: AIX / IBM i / z / OS / Android / MinGW / SunOS โš ๏ธ not clear

[^other-platforms]: Other system support depends on libuv support and community needs


C stack coroutine implementation

C stack coroutine implementation swow Other asynchronous coroutine libraries
boost-context โœ… First class support [^boost-context-tier-1] โœ…
ucontext โœ… Better compatibility โœ…
thread-context โœ… You can observe the status of all C stack coroutines through gdb โš ๏ธ Only Swoole supports

[^boost-context-tier-1]: First-class support means that members of the Swow development team will submit code contributions to boost-context to better support the application scenarios required by Swow.

Coroutine model

Coroutine model swow Other asynchronous coroutine libraries
main coroutine โœ… Wherever you go, there are coroutines โŒ Not supported, not perfectly compatible with traditional PHP ecology
Cross-coroutine scheduling โœ… Support nested coroutine cross-level scheduling โŒ Not supported, unable to achieve cross-level interruption
independent environment โœ… A single coroutine crash does not affect global stability โŒ Not supported, all crashed
Benchmarking Process Model โœ… Imitate the process model, the design is reasonable to follow โŒ self-made concept
Single Stack Lightning Switching โœ… The scheduler or internal coroutine only needs a single-stack switch โŒ Not supported, always dual-stack switching

Coroutine control ability

Coroutine control ability swow Other asynchronous coroutine libraries
forced wakeup โœ… Equivalent to ECANCELED or ETIMEDOUT โš ๏ธ Imperfect / no full scene support
abort โœ… Equivalent to SIGTERM โš ๏ธ Not fully supported
kill coroutine โœ… Equivalent to SIGKILL โŒ not supported

coroutine debugger

coroutine debugger swow Other asynchronous coroutine libraries
SDB โœ… Customized for the coroutine model โŒ Lack of Debugger fully oriented to coroutine design
Xdebug โœ… Supported from PHP-8.1 โœ… Supported from PHP-8.1

Coroutine debugger capability

Coroutine debugger capabilities swow Other asynchronous coroutine libraries
PHP writing & secondary development โœ… Inheritable extensions โŒ Depends on other extension capabilities
Production environment support โœ… No performance impact โš ๏ธ Not recommended to enable in production environment
list of coroutines โœ… Equivalent to the ps command to view the process โš ๏ธ Not fully supported, libraries that rely on traditional PHP debuggers have no support for coroutine granularity
View all coroutine information โœ… You can view the status of the coroutine, the information of each stack frame of the full call stack, the content of the source code executed, the variables on the stack, etc. โš ๏ธ Not fully supported, libraries that rely on traditional PHP debuggers have no support for coroutine granularity
Enter a coroutine and track debugging โœ… Equivalent to gdb attach โŒ not supported
Breakpoints, single-step debugging โœ… Only affects debugged coroutines โš ๏ธ Rely on tools such as Xdebug, and will block the entire process
Dynamically insert PHP instructions while debugging โœ… When using the debugger for breakpoint debugging to the BUG, โ€‹โ€‹you can dynamically execute PHP instructions to debug the BUG [^gdb-print] โŒ not supported
Scanning zombie coroutines โœ… Find coroutines that have been inactive for a long time โŒ not supported
kill coroutine โœ… Equivalent to kill command โŒ not supported
kill all coroutines and exit โœ… Equivalent to graceful shutdown โŒ not supported

[^gdb-print]: Equivalent to the print command of GDB, dynamically execute the expression given by the debugger, and print its return value.


The core effective code is less than 300 lines, and the unit test coverage rate is 100%.

channel capability swow Other asynchronous coroutine libraries
zero-buffered channel โœ… New Channel(0) โŒ not supported
buffered channel โœ… new Channel(n) โœ…
select โœ… Selector | CallbackSelector โŒ not supported
circular reference GC โœ… Can handle circular references in the queue โŒ not supported
read after close โœ… The remaining data in the queue can still be read after the channel is closed โŒ not supported


other abilities swow
WaitGroup โœ… Built-in high performance implementation
WaitReference โœ… Implemented by reference counting mechanism, coding is easier


coroutine library event driven
swow โœ… Self-maintained based on libcat [^libcat]libcat is a derivative project of libuv [^libuv]
Swoole โœ… Self-developed, but no Windows native support
Other asynchronous coroutine libraries โŒ Rely on event-driven extensions maintained by third parties, and some extensions are no longer maintained

[^libcat]: libcat is the coroutine version of libuv, which is independently maintained by the Swow team and can be used by all C-based projects. For example, you can use libcat to write a C++ coroutine project, or provide C stack coroutine capabilities for Python and Node.js Wait.

[^libuv]: The asynchronous event driver of libuv provides mainstream full-platform support, has passed extensive and rigorous production verification in languages โ€‹โ€‹such as Node.js and Julia, and has reached industrial-grade standards. The Swow team will submit code contributions to libuv to make it better support the application scenarios required by Swow.


signal ability swow Other asynchronous coroutine ecology
Windows signal simulation โœ… Use Linux-like signal mechanism under Windows โš ๏ธ Lack of Windows native support

network programming

Network programming ability swow Other asynchronous coroutine ecology
Buffer โœ… Accurately control the memory usage of each byte to achieve high-performance data processing โŒ Coarse-grained memory management
Buffer (copy-on-write) โœ… Copy-on-write mechanism + memory mapping mechanism โŒ php_stream needs to create an internal memory copy
Socket โœ… Can be linked with Buffer to achieve data transmission and reception accurate to every byte โŒ Coarse-grained memory management
Socket (writev support) โœ… Single system call zero copy to send multiple blocks of memory data โŒ unavoidable memory copy or multiple system calls
IpAddress โœ… Perfect high-performance IP address resolution library to help network programming โš ๏ธ Lack of relevant built-in support
HttpParser โœ… Can be controlled by PHP code to complete high-performance HTTP protocol analysis โŒ Can only receive underlying processed HTTP objects
WebSocket โœ… Can be controlled by PHP code to complete high-performance WebSocket protocol analysis โŒ Can only receive the underlying processed WebSocket object

With the help of the minimal capability provided by the underlying core of Swow, a high-performance API gateway can be realized by writing PHP code. The specific project practice content and production environment verification sharing, please look forward to the follow-up Twitter update of the official Swow team!

synchronous blocking coroutine

synchronous blocking coroutine swow Swoole Other asynchronous coroutine ecology
PHP stream (blocking mode) โœ… โœ… โŒ
PHP stream (non-blocking mode) โœ… BIO mode โœ… SSL_read/write mode โŒ
PHP stream (file IO) โœ… โœ… โŒ
PHP stream (file lock) โœ… Full scene coverage โœ… โŒ
pdo_mysql โœ… โœ… โŒ
pdo_pgsql โš ๏ธ Not supported yet [^not-supported-yet] โš ๏ธ Not supported yet [^not-supported-yet] โŒ
mysqli โœ… โœ… โŒ
phpredis โœ… โœ… โŒ
curl โœ… โœ… โŒ
proc_open โœ… โœ… โŒ
sockets extension โš ๏ธ Not supported yet [^not-supported-yet] โœ… โŒ
sleep, usleep, nanosleep… โœ… โœ… โŒ
shell_exec, exec, passthru… โœ… โœ… โŒ
Gethostbyname and other DNS related functions โœ… โœ… โŒ
stream_select โœ… โœ… โŒ
stream_poll_one โœ… Workerman special offer โœ… Swoole\\Event โŒ

[^not-supported-yet]: Not supported at the moment means that it will be supported in the future, or it is already in the implementation plan

Benefits of this technology:

Advantages of ecological reuse swow Swoole Other asynchronous coroutine ecology
Open source libraries based on file_get_contents(), cURL (such as: Guzzle, etc.) โœ… โœ… โŒ Ecological fragmentation
The cURL-based SDK provided by the cloud platform (such as the SDK of Alibaba Cloud, Tencent Cloud, AWS and other platforms) โœ… โœ… โŒ Ecological fragmentation
Open source library based on PDO, mysqli, phpredis โœ… โœ… โŒ Ecological fragmentation
Based on stream_select() or other event-driven asynchronous open source libraries (such as: workerman, reactphp, amphp) โœ… โœ… โŒ cannot work simultaneously
FileSystem related open source libraries (eg: symfony/filesystem) โœ… โœ… โŒ Unable to solve, block directly
Print directly to standard output or log libraries that need to read and write log files (such as: symfony/console, monolog) โœ… โœ… โŒ Unable to solve, block directly

CPU scheduling

Watchdog provides CPU scheduling capabilities for PHP. The core principle is that the Watchdog thread will periodically check the activity of the coroutines in other threads. If it is found that the coroutines in the worker threads are no longer active, they will be checked through the interrupt mechanism of ZendVM. Confirm that if the VM interrupt fails, it indicates that the worker thread is blocked by a system call and triggers an alarm; if the VM interrupt succeeds, it indicates that the worker thread is caught in CPU-intensive operations or an infinite loop, and immediately triggers the scheduling rules set by the user for scheduling.

CPU scheduling capability swow Swoole Other asynchronous coroutine ecology
CPU blocking alarm โœ… Contains system call blocking warnings โš ๏ธ Silent scheduling, no alarm โŒ No alarm, direct downtime
CPU blocking slowdown โœ… Dynamically adjustable โœ… Fixed scheduling time โŒ Unable to slow down, directly down
CPU blocking throttling โœ… Support killing coroutines stuck in an infinite loop โš ๏ธ Only timed transfer is supported to reduce negative impact โŒ Unable to cope, direct downtime
Dynamic Switch Scheduler โœ… API switch scheduler โš ๏ธ Only support settings via ini โŒ No CPU scheduling capability
Dynamic Programming Scheduling Behavior โœ… Programmable, dynamically determine the scheduling method when blocked โš ๏ธ Fixed scheduling rules โŒ No CPU scheduling capability


modernization capabilities swow Other asynchronous coroutine libraries
object oriented โœ… The kernel and PHP code are seamlessly integrated, all objects can be extended through inheritance, and secondary development can be easily completed โš ๏ธ Not fully object-oriented
exception mechanism โœ… Fully embrace the exception mechanism, and chain calls are easy to code โš ๏ธ Incomplete use of exception mechanism
Composer โœ… Support the whole process to install and deploy through Composer, and support All in one or sub-library pull methods โš ๏ธ The extension needs to be installed by other means
IDE assistant โœ… Composer built-in IDE assistant code in the package after installation โš ๏ธ Need to pull additional IDE assistant

Other debugging capabilities

Other debugging capabilities swow Other asynchronous coroutine libraries
class strace log โœ… In Debug mode, it supports printing the underlying coroutine scheduling, network sending and receiving, and system call information in strace format (supports multiple formats of time, module information, and PHP source code location display), and SSL network sending and receiving data supports plain text display, eliminating the need to capture packets Tool and certificate configuration troubles. โŒ No related support
debugInfo support โœ… Print internal objects through var_dump(), and you can also see rich debugging information โš ๏ธ Need to manually print the required information

build system

build capacity swow Swoole Other asynchronous coroutine ecology
Builder โœ… The project can be pulled through Composer, and the extension can be installed with one click using the built-in script, supporting independent extended version of each project โš ๏ธ Only manual compilation or PECL installation is supported โŒ You need to install third-party event-driven extensions yourself
PECL โŒ No planned support, PECL is in disrepair, lack of maintenance โœ… First class support โš ๏ธ Event-driven extensions are provided by a third party, and reliability cannot be guaranteed independently
Windows DLLs โœ… Can be downloaded directly from the release page โŒ Does not support Windows โŒ No Windows native support
CLI issue โœ… Based on lwmbs capability, it can be downloaded directly โœ… swoole-cli โŒ Need to compile it yourself or install it through the system package manager
One-click packaging of micro into binary โœ… Based on lwmbs capability, Swow is optional for PHP project binary packaging and release, once packaged and run in multiple places [^hyperf-box] โš ๏ธ Not supported yet [^not-supported-yet] โŒ Not supported, but can be achieved with the help of PHP packaging capabilities provided by the Swow team

[^hyperf-box]: Hyperf Box provides out-of-the-box one-click packaging binary tools for the Swow project, and more open source community partners are welcome to re-develop more out-of-the-box packaging tools based on micro technology to benefit the community.


The above capability enumeration is just the beginning of Swow. The Swow core also contains a lot of detailed design and some experimental functions that have not been officially disclosed.

In general, the future of Swow is full of imagination. It provides PHP with possibilities far beyond the past. We can use Swow’s ability to think and do more things that have never been thought about.

In the future, we will share with you the detailed description and best practices of each capability item in detail by “publishing a large number of short articles”, and disclose a large number of internal implementation details and production applications, so stay tuned!

#Swow #v100 #released #News Fast Delivery

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