Apache HTTP Server Version 2.4
Apache HTTP Server Version 2.4
Available Languages: en
This document describes changes to the Apache HTTPD API from version 2.2 to 2.4, that may be of interest to module/application developers and core hacks. As of the first GA release of the 2.4 branch API compatibility is preserved for the life of the 2.4 branch. (The VERSIONING description for the 2.4 release provides more information about API compatibility.)
API changes fall into two categories: APIs that are altogether new, and existing APIs that are expanded or changed. The latter are further divided into those where all changes are backwards-compatible (so existing modules can ignore them), and those that might require attention by maintainers. As with the transition from HTTPD 2.0 to 2.2, existing modules and applications will require recompiling and may call for some attention, but most should not require any substantial updating (although some may be able to take advantage of API changes to offer significant improvements).
For the purpose of this document, the API is split according to the public header files. These headers are themselves the reference documentation, and can be used to generate a browsable HTML reference with make docs.
Introduces a new API to parse and evaluate boolean and algebraic expressions, including provision for a standard syntax and customised variants.
Introduces a new API to enable httpd child processes to serve different purposes.
ap_mpm_run is replaced by a new mpm hook. Also ap_graceful_stop_signalled is lost, and ap_mpm__timed_callback is new.
In addition to the existing regexp wrapper, a new higher-level API ap_rxplus is now provided. This provides the capability to compile Perl-style expressions like s/regexp/replacement/flags and to execute them against arbitrary strings. for regexp backreferences is also added.
Introduces an API for modules to allocate and manage memory slots, most commonly for shared memory.
API to manage a shared object cache.
common structures for heartbeat modules
The function signature for ap_parse_htaccess has been changed. A apr_table_t of individual directives allowed for override must now be ed (override remains).
AP_DECLARE_MODULE macro to declare all modules.APLOG_USE_MODULE macro necessary for per-module loglevels in multi-file modules.check_config hookap_process_fnmatch_configs() function to process wildcardsap_configfile_t, ap_cfg_getline(), ap_cfg_getc() to return error codes, and add ap_pcfg_strerror() for retrieving an error description.AllowOverrideList directive. ap_check_cmd_context() accepts a new flag NOT_IN_HTACCESS to detect this case.ap_default_type, ap_requires, all 2.2 authnz APIap_get_server_name_for_url to IPv6 literals.ap__errorlog_handler to error log format string handlers.error_log hook have changed. Declaration has moved to http_core.h.ap_state_query to determine if the server is in the initial configuration preflight phase or not. This is both easier to use and more correct than the old method of creating a pool data entry in the process pool.ap_get_conn_socket to get the socket descriptor for a connection. This should be used instead of accessing the core connection config directly.APLOG_TRACEnCONN_STATE valuesap_escape_html updated; ap_unescape_all, ap_escape_path_segment_bufferEXEC_ON_READ config reading stage need to call ap_reserve_module_slots() or ap_reserve_module_slots_directive() in their pre_config hook.APLOG_TRACEnap_log_*error become macro wrappers (backwards-compatible if APLOG_MARK macro is used, except that is no longer possible to use #ifdef inside the argument list)module_index added to error_log hookap_log_command_lineEOR bucket typeap_process_async_requestAP_AUTH_INTERNAL_PER_CONF and AP_AUTH_INTERNAL_PER_URIaccess_checker_ex hook to apply additional access control and/or by authentication.ap_hook_check_access_ex, ap_hook_check_access, ap_hook_check_authn, ap_hook_check_authz which accept AP_AUTH_INTERNAL_PER_* flagsap_hook_access_checker, access_checker_ex, ap_hook_check__id, ap_hook_auth_checkerWhen possible, ing all access control hooks (including authentication and authorization hooks) using AP_AUTH_INTERNAL_PER_CONF is recommended. If all modules' access control hooks are ed with this flag, then whenever the server handles an internal sub-request that matches the same set of access control configuration directives as the initial request (which is the common case), it can avoid invoking the access control hooks another time.
If your module requires the old behavior and must perform access control checks on every sub-request with a different URI from the initial request, even if that URI matches the same set of access control configuration directives, then use AP_AUTH_INTERNAL_PER_URI.
Introduces the new provider framework for authn and authz
Introduces a commit_entity() function to the cache provider interface, allowing atomic writes to cache. Add a cache_status() hook to report the cache decision. All private structures and functions were removed.
This introduces low-level APIs to send arbitrary headers, and exposes functions to handle HTTP OPTIONS and TRACE.
Changes the disk format of the disk cache to atomic cache updates without locking. The device/inode pair of the body file is embedded in the header file, allowing confirmation that the header and body belong to one another.
The mod_disk_cache module has been renamed to mod_cache_disk in order to be consistent with the naming of other modules within the server.
The API for mod_request, to make input data available to multiple application/handler modules where required, and to parse HTML form data.
accept, lockfile, lock_mech, set_scoreboard (locking uses the new ap_mutex API)mpm_query, timed_callback, and get_namemonitor hook, ap_reclaim_child_processes, ap_relieve_child_processesap_get_scoreboard_worker is made non-backwards-compatible as an alternative version is introduced. Additional proxy_balancer . Child status stuff revamped.
Introduces a new API for managing HTTP Cookies.
no description available
A wrapper for APR proc and global mutexes in httpd, providing common configuration for the underlying mechanism and location of lock files.
NEW: ap_args_to_table
NEW: ap_recent_ctime_ex
In order to take advantage of per-module loglevel configuration, any source file that calls the ap_log_* functions should declare which module it belongs to. If the module's module_struct is called foo_module, the following code can be used to remain backward compatible with HTTPD 2.0 and 2.2:
#include <http_log.h>
#ifdef APLOG_USE_MODULE
APLOG_USE_MODULE(foo);
#endif
Note: This is absolutely required for C++-language modules. It can be skipped for C-language modules, though that breaks module-specific log level for files without it.
The number of parameters of the ap_log_* functions and the definition of APLOG_MARK has changed. Normally, the change is completely transparent. However, changes are required if a module uses APLOG_MARK as a parameter to its own functions or if a module calls ap_log_* without ing APLOG_MARK. A module which uses wrappers around ap_log_* typically uses both of these constructs.
The easiest way to change code which es APLOG_MARK to its own functions is to define and use a different macro that expands to the parameters required by those functions, as APLOG_MARK should only be used when calling ap_log_* directly. In this way, the code will remain compatible with HTTPD 2.0 and 2.2.
Code which calls ap_log_* without ing APLOG_MARK will necessarily differ between 2.4 and earlier releases, as 2.4 requires a new third argument, APLOG_MODULE_INDEX.
/* code for httpd 2.0/2.2 */
ap_log_perror(file, line, APLOG_ERR, 0, p, "Failed to allocate dynamic lock structure");
/* code for httpd 2.4 */
ap_log_perror(file, line, APLOG_MODULE_INDEX, APLOG_ERR, 0, p, "Failed to allocate dynamic lock structure");
ap_log_*error are now implemented as macros. This means that it is no longer possible to use #ifdef inside the argument list of ap_log_*error, as this would cause undefined behavior according to C99.
A server_rec pointer must be ed to ap_log_error() when called after startup. This was always appropriate, but there are even more limitations with a NULL server_rec in 2.4 than in previous releases. Beginning with 2.3.12, the global variable ap_server_conf can always be used as the server_rec parameter, as it will be NULL only when it is valid to NULL to ap_log_error(). ap_server_conf should be used only when a more appropriate server_rec is not available.
Consider the following changes to take advantage of the new APLOG_TRACE1..8 log levels:
APLOG_DEBUG and consider if one of the APLOG_TRACEn levels is more appropriate.APLOG_TRACEn levels. If expensive trace processing needs to be byed depending on the configured log level, use the APLOGtracen and APLOGrtracen macros to first check if tracing is enabled.Modules sometimes add process id and/or thread id to their log messages. These ids are now logged by default, so it may not be necessary for the module to log them explicitly. (s may remove them from the error log format, but they can be instructed to add it back if necessary for problem diagnosis.)
ap_default_type()
ap_get_server_name()
ap_get_server_name_for_url() instead. This new function handles the odd case where the server name is an IPv6 literal address.
ap_get_server_version()
ap_get_server_description(). When generating output, where the amount of information should be configurable by ServerTokens, use ap_get_server_banner().
ap_graceful_stop_signalled()
ap_mpm_query(AP_MPMQ_MPM_STATE) and checking for state AP_MPMQ_STOPPING.
ap_max_daemons_limit, ap_my_generation, and ap_threads_per_child
ap_mpm_query() query codes AP_MPMQ_MAX_DAEMON_USED, AP_MPMQ_GENERATION, and AP_MPMQ_MAX_THREADS, respectively.
ap_mpm_query()
ap_requires()
Require configuration. an auth provider function for each ed entity using ap__auth_provider(). The function will be called as necessary during Require processing. (Consult bundled modules for detailed examples.)
ap_server_conf->process->pool data
ap_state_query(AP_SQ_MAIN_STATE).ap_retained_data_create() and ap_retained_data_get().apr_global_mutex_create(), apr_proc_mutex_create()
ap_mutex_(), ap_global_mutex_create(), and ap_proc_mutex_create(); these allow your mutexes to be configurable with the Mutex directive; you can also remove any configuration mechanisms in your module for such mutexes
CORE_PRIVATE
dav_new_error() and dav_new_error_tag()
errno contained information describing the failure. Now, an apr_status_t parameter must be provided. 0/APR_SUCCESS if there is no such error information, or a valid apr_status_t value otherwise.
mpm_default.h, DEFAULT_LOCKFILE, DEFAULT_THREAD_LIMIT, DEFAULT_PIDLOG, etc.
DEFAULT_PIDLOG and DEFAULT_REL_RUNTIMEDIR are now universally available via ap_config.h.
unixd_config
unixd_setup_child()
conn_rec->remote_ip and conn_rec->remote_addr
request_rec->agent_ip and request_rec->agent_addr.conn_rec->client_ip and conn_rec->client_addr.ap_unixd_config.suexec_enabled is 0, also log the value of the new field suexec_disabled_reason, which contains an explanation of why it is not available.
ExtendedStatus had to be set to On, which in turn required that mod_status was loaded. In 2.4, just set ap_extended_status to 1 in a pre-config hook and the extended status data will be available.
ap_args_to_table() would be helpful.
ap_parse_form_data().
Content-Length and Transfer-Encoding to see if a body was specified
ap_request_has_body().
ap_pool_cleanup_set_null().
ap_runtime_dir_relative() so that the global configuration for the location of such files, either by the DEFAULT_REL_RUNTIMEDIR compile setting or the DefaultRuntimeDir directive, will be respected. Apache httpd 2.4.2 and above.
Available Languages: en