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-rw-r--r--web/apache/service189
1 files changed, 165 insertions, 24 deletions
diff --git a/web/apache/service b/web/apache/service
index 75c096c..4c0d395 100644
--- a/web/apache/service
+++ b/web/apache/service
@@ -8,6 +8,8 @@
#include <httpd.h>
#include <http_config.h> // module, ap_hook_*()
+#include <map>
+#include <memory> // unique_ptr
#include <string>
#include <cassert>
@@ -19,6 +21,22 @@ namespace web
{
namespace apache
{
+ // Apache has 3 configuration scopes: main server, virtual server, and
+ // directory (location). It provides configuration scope-aware modules
+ // with the ability to build a hierarchy of configuration contexts. Later,
+ // when processing a request, Apache passes the appropriate directory
+ // configuration context to the request handler.
+ //
+ // This Apache service implementation first makes a copy of the provided
+ // (in the constructor below) module exemplar for each directory context.
+ // It then initializes each of these "context exemplars" with the (merged)
+ // set of configuration options. Finally, when handling a request, it
+ // copies the corresponding "context exemplar" to create the "handling
+ // instance". Note that the "context exemplars" are create before the
+ // provided exemplar is initialized. As a result, it is possible to detect
+ // if the module's copy constructor is used to create a "context exemplar"
+ // or a "handling instance".
+ //
class service: ::module
{
public:
@@ -41,6 +59,41 @@ namespace web
{
init_directives ();
+ // Set configuration context management hooks.
+ //
+ // The overall process of building the configuration hierarchy for a
+ // module is as follows:
+ //
+ // 1. Apache creates directory and server configuration contexts for
+ // scopes containing module-defined directives by calling the
+ // create_{server,dir}_context() callback functions. For directives
+ // at the server scope the special directory context is created as
+ // well.
+ //
+ // 2. Apache calls parse_option() function for each module-defined
+ // directive. The function parses the directives and places the
+ // resulting options into the corresponding configuration context.
+ // It also establishes the directory-server contexts relations.
+ //
+ // 3. Apache calls merge_server_context() function for each virtual
+ // server. The function complements virtual server context options
+ // with the ones from the main server.
+ //
+ // 4. Apache calls config_finalizer() which complements the directory
+ // contexts options with the ones from the enclosing servers.
+ //
+ // 5. Apache calls worker_initializer() which creates module exemplar
+ // for each directory configuration context.
+ //
+ // References:
+ // http://www.apachetutor.org/dev/config
+ // http://httpd.apache.org/docs/2.4/developer/modguide.html
+ // http://wiki.apache.org/httpd/ModuleLife
+ //
+ create_server_config = &create_server_context;
+ create_dir_config = &create_dir_context;
+ merge_server_config = &merge_server_context<M>;
+
// instance<M> () is invented to delegate processing from apache
// request handler C function to the service non static member
// function. This appoach resticts number of service objects per
@@ -56,6 +109,7 @@ namespace web
delete [] cmds;
}
+ private:
template <typename M>
static service*&
instance () noexcept
@@ -88,16 +142,7 @@ namespace web
config_finalizer (apr_pool_t*, apr_pool_t*, apr_pool_t*, server_rec* s)
noexcept
{
- auto srv (instance<M> ());
- bool& parsed (srv->options_parsed_);
-
- if (!parsed)
- {
- log l (s, srv);
- srv->exemplar_.version (l);
- parsed = true;
- }
-
+ instance<M> ()->finalize_config (s);
return OK;
}
@@ -107,44 +152,140 @@ namespace web
{
auto srv (instance<M> ());
log l (s, srv);
- srv->init_worker (l);
+ srv->template init_worker<M> (l);
}
template <typename M>
static int
- request_handler (request_rec* r) noexcept
+ request_handler (request_rec* r) noexcept;
+
+ private:
+ // Our representation of the Apache configuration context.
+ //
+ // The lifetime of this object is under the control of the Apache API,
+ // which treats it as a raw sequence of bytes. In order not to tinker
+ // with the C-style structures and APR memory pools, we will keep it a
+ // (C++11) POD type with just the members required to maintain the
+ // context hierarchy.
+ //
+ // We will then use the pointers to these context objects as keys in
+ // maps to (1) the corresponding application-level option lists during
+ // the configuration cycle and to (2) the corresponding module exemplar
+ // during the HTTP request handling phase. We will also use the same
+ // type for both directory and server configuration contexts.
+ //
+ struct context
{
- auto srv (instance<M> ());
- if (!r->handler || srv->name_ != r->handler) return DECLINED;
+ // Outer (server) configuration context for the directory
+ // configuration context, NULL otherwise.
+ //
+ context* server;
- request req (r);
- log l (r->server, srv);
- return srv->template handle<M> (req, l);
- }
+ // If module directives appear directly in the server configuration
+ // scope, Apache creates a special directory context for them. This
+ // context appears at the same hierarchy level as the user-defined
+ // directory contexts of the same server scope.
+ //
+ bool special;
+
+ // Create the server configuration context.
+ //
+ context (): server (nullptr), special (false) {}
+
+ // Create the directory configuration context. Due to the Apache API
+ // implementation details it is not possible to detect the enclosing
+ // server configuration context at the time of directory context
+ // creation. As a result, the server member is set by the module's
+ // parse_option() function.
+ //
+ context (bool s): server (nullptr), special (s) {}
+
+ // Ensure the object is only destroyed by Apache.
+ //
+ ~context () = delete;
+ };
+
+ // Type of the key for configuration options and module exemplar maps.
+ //
+ using context_id = const context*;
+
+ static bool
+ is_null (context_id id) noexcept {return id == nullptr;}
+
+ static context_id
+ make_context_id (const context* c) noexcept {return c;}
+
+ // Convert Apache-provided configuration pointer to the context id.
+ //
+ static context_id
+ make_context_id (void* config) noexcept
+ {return make_context_id (static_cast<const context*> (config));}
private:
void
init_directives ();
- void
- init_worker (log& l) noexcept;
+ // Create the server configuration context. Called by the Apache API
+ // whenever a new object of that type is required.
+ //
+ static void*
+ create_server_context (apr_pool_t*, server_rec*) noexcept;
+
+ // Create the server directory configuration context. Called by the
+ // Apache API whenever a new object of that type is required.
+ //
+ static void*
+ create_dir_context (apr_pool_t*, char* dir) noexcept;
+
+ template <typename M>
+ static void*
+ merge_server_context (apr_pool_t*, void* enclosing, void* enclosed)
+ noexcept
+ {
+ // Complement the enclosed context with options of the enclosing one.
+ //
+ instance<M> ()->complement (
+ make_context_id (enclosed), make_context_id (enclosing));
+
+ return enclosed;
+ }
static const char*
- parse_option (cmd_parms* parms, void* mconfig, const char* args) noexcept;
+ parse_option (cmd_parms* parms, void* conf, const char* args) noexcept;
const char*
- add_option (const char* name, optional<std::string> value);
+ add_option (context_id id, const char* name, optional<std::string> value);
+
+ void
+ finalize_config (server_rec*);
+
+ void
+ clear_config ();
+
+ void
+ complement (context_id enclosed, context_id enclosing);
+
+ template <typename M>
+ void
+ init_worker (log&);
template <typename M>
int
- handle (request& r, log& l) noexcept;
+ handle (request&, context_id, log&) const;
private:
std::string name_;
module& exemplar_;
option_descriptions option_descriptions_;
- name_values options_;
+
+ using options = std::map<context_id, name_values>;
+ options options_;
+
+ using exemplars = std::map<context_id, std::unique_ptr<module>>;
+ exemplars exemplars_;
+
bool options_parsed_ = false;
+ bool version_logged_ = false;
};
}
}