The 4D Web Server allows you to take full advantage of multi-core computers by using preemptive web processes in your compiled applications. You can configure your web-related code, including 4D tags and web database methods, to run simultaneously on as many cores as possible.
For in-depth information on preemptive process in 4D, please refer to the Preemptive 4D processes section in the 4D Language Reference.
Disponibilidade do modo preemptivo para os processos web
The following table indicates whether the preemptive mode is used or is available, depending on the execution context:
|4D Server||Interpretado (associado ao depurador)||Interpretado (não associado ao depurador)||Compilado|
|Servidor Web||cooperativo||cooperativo||parâmetro web|
|Servidor Web Services||cooperativo||cooperativo||parâmetro web|
|4D remoto/usuário único||Interpretado||Compilado|
|Servidor Web||cooperativo||parâmetro web|
|Servidor Web Services||cooperativo||parâmetro web|
- REST Server: handles ORDA data model class functions
- Web Server: handles web templates, 4DACTION and database methods
- Servidor de serviços Web: trata dos pedidos SOAP
- web setting means that the preemptive mode depends on a setting value:
- when Scalable sessions option is selected, the preemptive mode is automatically used for web processes.
- otherwise, the Use preemptive processes option is taken into account.
- regarding Web service processes (server or client), preemptive mode is supported at method level. You just have to select "Can be run in preemptive processes" property for published SOAP server methods (see Publishing a Web Service with 4D) or proxy client methods (see Subscribing to a Web Service in 4D) and make sure they are confirmed thread-safe by the compiler.
Writing thread-safe web server code
All 4D code executed by the web server must be thread-safe if you want your web processes to be run in preemptive mode. When the Use preemptive processes option is checked in the Settings dialog box, the following parts of the application will be automatically evaluated by the 4D compiler:
Todos os métodos bases relacionados com a Web:
compiler_webproject method (regardless of its actual "Execution mode" property);
Basically any code processed by the
PROCESS 4D TAGScommand in the web context, for example through .shtml pages.
Any project method with the "Available through 4D tags and URLS (
4DACTION, etc.)" attribute
Triggers para as tabelas com o atributo "Expor como recurso REST"
ORDA data model class functions called via REST
For each of these methods and code parts, the compiler will check if the thread-safety rules are respected, and will return errors in case of issues. For more information about thread-safety rules, please refer to the Writing a thread-safe method paragraph in the Processes chapter of the 4D Language Reference manual.
Thread-safety of 4D web code
Most of the web-related 4D commands and functions, database methods and URLs are thread-safe and can be used in preemptive mode.
Comandos 4D e métodos base
All 4D web-related commands are thread-safe, i.e.:
- todos os comandos do tema Servidor Web,
- todos os comandos do tema Cliente HTTP.
The web-related database methods are thread-safe and can be used in preemptive mode (see below):
On Web Authentication,
On Web Connection,
On REST Authentication...).
Of course, the code executed by these methods must also be thread-safe.
URLs do servidor Web
The following 4D Web Server URLs are thread-safe and can be used in preemptive mode:
- 4daction/ (the called project method must also be thread-safe)
- 4dcgi/ (the called database methods must also be thread-safe)
- 4dimgfield/ (generated by
PROCESS 4D TAGSfor web request on picture fields)
- 4dimg/ (generated by
PROCESS 4D TAGSfor web request on picture variables)
Ícone de processo web preemptivo
Both the Runtime Explorer and the 4D Server administration window display a specific icon for preemptive web processes:
|Tipo de processo||Ícone|
|Método web preventivo|