The CppCMS framework consists of following parts: |
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## Long Living Classes |
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- Central `service` --- the major class that holds |
the main application loop and manages all resources. |
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All global resources are accessed via this service. |
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It also hold the main event driven execution loop |
based on `boost::asio::io_service`. |
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- `applications_pool` --- it the class that holds |
a pool of user created applications and dispatches |
them according to requested url. It is the major |
connector between URL and application. |
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Each time the page is requested an application fetched |
from it and then returned back for recycling. |
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- `thread_pool` --- is the thread pool for long running |
and time consuming jobs that can't be executed withing |
asynchronous event loop. |
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Generally, when new request arrives it is executed |
by application in the `thread_pool`. |
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- `locale::pool` --- is the gateway to i18n and l10n |
world. It holds the set of `std::locale` for each |
supported locale required by developer. It also |
adds custom facets like `gettext` in order to extend |
localization capabilities behind the strict set of |
facets provided by standard C++. |
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- The configuration of all CppCMS components is done |
via single JSON object that is loaded by `service` |
and accessible via `json::object const &settings()` |
member function of `service` class. |
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## Connection Related Classes |
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When the main loop is started all incoming connections |
are accepted and processed by `impl::cgi::connection` class. |
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This is an abstract class that various protocol connectors implement it. Currently CppCMS supports following protocols: |
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- HTTP --- very simple and limited implementation of HTTP |
protocol that is used for debug purposes or for running |
CppCMS behind http-proxy. |
- FastCGI --- connector that implements standard FastCGI |
web server API and allows running CppCMS application |
behind any web server. |
- SCGI --- connector that implements standard simple |
and very useful SCGI protocol that is simpler equivalent |
of complex FastCGI. |
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So, each time new connection is accepted it is read |
completely, including parsing headers and all POST data. |
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When the connection becomes ready it is assigned |
to user visible `http::context` object that provides |
an interface for user to lower level CGI like protocol. |
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When the `http::context` is ready, appropriate `application` |
is fetched from `applications_pool` and `http::context` |
object is assigned to it. |
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When application finishes response, it releases |
`http::context` object that sends all the pending data |
to output and releases `cgi::impl::connection` for further |
reuse --- keep-alive requests. |
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Then application is recycled to `applications_pool` for reuse. |
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