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{ Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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//#include "apr_thread_proc.h"
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* @package Multi-Processing Module library
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The MPM, "multi-processing model" provides an abstraction of the
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interface with the OS for distributing incoming connections to
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threads/process for processing. http_main invokes the MPM, and
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the MPM runs until a shutdown/restart has been indicated.
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The MPM calls out to the apache core via the ap_process_connection
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function when a connection arrives.
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The MPM may or may not be multithreaded. In the event that it is
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multithreaded, at any instant it guarantees a 1:1 mapping of threads
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ap_process_connection invocations.
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Note: In the future it will be possible for ap_process_connection
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to return to the MPM prior to finishing the entire connection; and
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the MPM will proceed with asynchronous handling for the connection;
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in the future the MPM may call ap_process_connection again -- but
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does not guarantee it will occur on the same thread as the first call.
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The MPM further guarantees that no asynchronous behaviour such as
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longjmps and signals will interfere with the user code that is
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invoked through ap_process_connection. The MPM may reserve some
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signals for its use (i.e. SIGUSR1), but guarantees that these signals
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are ignored when executing outside the MPM code itself. (This
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allows broken user code that does not handle EINTR to function
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The suggested server restart and stop behaviour will be "graceful".
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However the MPM may choose to terminate processes when the user
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requests a non-graceful restart/stop. When this occurs, the MPM kills
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all threads with extreme prejudice, and destroys the pchild pool.
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User cleanups registered in the pchild apr_pool_t will be invoked at
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this point. (This can pose some complications, the user cleanups
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are asynchronous behaviour not unlike longjmp/signal... but if the
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admin is asking for a non-graceful shutdown, how much effort should
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we put into doing it in a nice way?)
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- The MPM does not set a SIGALRM handler, user code may use SIGALRM.
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But the preferred method of handling timeouts is to use the
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timeouts provided by the BUFF abstraction.
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- The proper setting for SIGPIPE is SIG_IGN, if user code changes it
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for any of their own processing, it must be restored to SIG_IGN
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prior to executing or returning to any apache code.
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TODO: add SIGPIPE debugging check somewhere to make sure it's SIG_IGN
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* This is the function that MPMs must create. This function is responsible
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* for controlling the parent and child processes. It will run until a
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* restart/shutdown is indicated.
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* @param pconf the configuration pool, reset before the config file is read
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* @param plog the log pool, reset after the config file is read
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* @param server_conf the global server config.
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* @return 1 for shutdown 0 otherwise.
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* @deffunc int ap_mpm_run(apr_pool_t *pconf, apr_pool_t *plog, server_rec *server_conf)
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function ap_mpm_run(pconf, plog: Papr_pool_t; server_conf: Pserver_rec): Integer;
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{$IFDEF WINDOWS} stdcall; {$ELSE} cdecl; {$ENDIF}
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external LibHTTPD name LibNamePrefix + 'ap_mpm_run' + LibSuff12;
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* predicate indicating if a graceful stop has been requested ...
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* used by the connection loop
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* @return 1 if a graceful stop has been requested, 0 otherwise
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* @deffunc int ap_graceful_stop_signalled(*void)
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function ap_graceful_stop_signalled: Integer;
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{$IFDEF WINDOWS} stdcall; {$ELSE} cdecl; {$ENDIF}
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external LibHTTPD name LibNamePrefix + 'ap_graceful_stop_signalled' + LibSuff0;
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* Spawn a process with privileges that another module has requested
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* @param r The request_rec of the current request
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* @param newproc The resulting process handle.
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* @param progname The program to run
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* @param const_args the arguments to pass to the new program. The first
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* one should be the program name.
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* @param env The new environment apr_table_t for the new process. This
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* should be a list of NULL-terminated strings.
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* @param attr the procattr we should use to determine how to create the new
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* @param p The pool to use.
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function ap_os_create_privileged_process(
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const r: Prequest_rec;
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newproc: Papr_proc_t;
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const progname, args, env: PChar;
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attr: Papr_procattr_t; p: Papr_pool_t): apr_status_t;
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{$IFDEF WINDOWS} stdcall; {$ELSE} cdecl; {$ENDIF}
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external LibHTTPD name LibNamePrefix + 'ap_os_create_privileged_process' + LibSuff28;
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{ Subtypes/Values for AP_MPMQ_IS_THREADED and AP_MPMQ_IS_FORKED }
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AP_MPMQ_NOT_SUPPORTED = 0; { This value specifies whether }
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{ an MPM is capable of }
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{ threading or forking. }
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AP_MPMQ_STATIC = 1; { This value specifies whether }
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{ an MPM is using a static # }
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{ threads or daemons. }
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AP_MPMQ_DYNAMIC = 2; { This value specifies whether }
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{ an MPM is using a dynamic # }
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{ threads or daemons. }
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{ Values returned for AP_MPMQ_MPM_STATE }
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AP_MPMQ_STARTING = 0;
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AP_MPMQ_STOPPING = 2;
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AP_MPMQ_MAX_DAEMON_USED = 1; { Max # of daemons used so far }
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AP_MPMQ_IS_THREADED = 2; { MPM can do threading }
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AP_MPMQ_IS_FORKED = 3; { MPM can do forking }
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AP_MPMQ_HARD_LIMIT_DAEMONS = 4; { The compiled max # daemons }
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AP_MPMQ_HARD_LIMIT_THREADS = 5; { The compiled max # threads }
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AP_MPMQ_MAX_THREADS = 6; { # of threads/child by config }
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AP_MPMQ_MIN_SPARE_DAEMONS = 7; { Min # of spare daemons }
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AP_MPMQ_MIN_SPARE_THREADS = 8; { Min # of spare threads }
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AP_MPMQ_MAX_SPARE_DAEMONS = 9; { Max # of spare daemons }
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AP_MPMQ_MAX_SPARE_THREADS = 10; { Max # of spare threads }
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AP_MPMQ_MAX_REQUESTS_DAEMON = 11; { Max # of requests per daemon }
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AP_MPMQ_MAX_DAEMONS = 12; { Max # of daemons by config }
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AP_MPMQ_MPM_STATE = 13; { starting, running, stopping }
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AP_MPMQ_IS_ASYNC = 14; { MPM can process async connections }
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* Query a property of the current MPM.
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* @param query_code One of APM_MPMQ_*
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* @param result A location to place the result of the query
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* @return APR_SUCCESS or APR_ENOTIMPL
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* @deffunc int ap_mpm_query(int query_code, int *result)
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function ap_mpm_query(query_code: Integer; result: PInteger): apr_status_t;
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{$IFDEF WINDOWS} stdcall; {$ELSE} cdecl; {$ENDIF}
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external LibHTTPD name LibNamePrefix + 'ap_mpm_query' + LibSuff8;
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{ Defining GPROF when compiling uses the moncontrol() function to
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* disable gprof profiling in the parent, and enable it only for
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* request processing in children (or in one_process mode). It's
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* absolutely required to get useful gprof results under linux
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* because the profile itimers and such are disabled across a
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* fork(). It's probably useful elsewhere as well.
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extern void moncontrol(int);
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#define AP_MONCONTROL(x) moncontrol(x)
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#define AP_MONCONTROL(x)
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{$ifdef AP_ENABLE_EXCEPTION_HOOK}
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ap_exception_info_t = record
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AP_DECLARE_HOOK(int,fatal_exception,(ap_exception_info_t *ei))
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{$endif} {AP_ENABLE_EXCEPTION_HOOK}