<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html xmlns:fn="http://www.w3.org/2005/02/xpath-functions"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <link rel="stylesheet" href="../../../../doc/otp_doc.css" type="text/css"> <title>Erlang -- global</title> </head> <body bgcolor="white" text="#000000" link="#0000ff" vlink="#ff00ff" alink="#ff0000"><div id="container"> <script id="js" type="text/javascript" language="JavaScript" src="../../../../doc/js/flipmenu/flipmenu.js"></script><script id="js2" type="text/javascript" src="../../../../doc/js/erlresolvelinks.js"></script><script language="JavaScript" type="text/javascript"> <!-- function getWinHeight() { var myHeight = 0; if( typeof( window.innerHeight ) == 'number' ) { //Non-IE myHeight = window.innerHeight; } else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) { //IE 6+ in 'standards compliant mode' myHeight = 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href="../../../../doc/index.html">Top</a></small><p><strong>Kernel</strong><br><strong>Reference Manual</strong><br><small>Version 2.15.3</small></p> <br><a href="javascript:openAllFlips()">Expand All</a><br><a href="javascript:closeAllFlips()">Contract All</a><p><small><strong>Table of Contents</strong></small></p> <ul class="flipMenu"> <li title="kernel (App)"><a href="kernel_app.html">kernel (App) </a></li> <li id="no" title="application " expanded="false">application<ul> <li><a href="application.html"> Top of manual page </a></li> <li title="get_all_env-0"><a href="application.html#get_all_env-0">get_all_env/0</a></li> <li title="get_all_env-1"><a href="application.html#get_all_env-1">get_all_env/1</a></li> <li title="get_all_key-0"><a href="application.html#get_all_key-0">get_all_key/0</a></li> <li title="get_all_key-1"><a href="application.html#get_all_key-1">get_all_key/1</a></li> <li title="get_application-0"><a href="application.html#get_application-0">get_application/0</a></li> <li title="get_application-1"><a href="application.html#get_application-1">get_application/1</a></li> <li title="get_env-1"><a href="application.html#get_env-1">get_env/1</a></li> <li title="get_env-2"><a href="application.html#get_env-2">get_env/2</a></li> <li title="get_key-1"><a href="application.html#get_key-1">get_key/1</a></li> <li title="get_key-2"><a href="application.html#get_key-2">get_key/2</a></li> <li title="load-1"><a href="application.html#load-1">load/1</a></li> <li title="load-2"><a href="application.html#load-2">load/2</a></li> <li title="loaded_applications-0"><a href="application.html#loaded_applications-0">loaded_applications/0</a></li> <li title="permit-2"><a href="application.html#permit-2">permit/2</a></li> <li title="set_env-3"><a href="application.html#set_env-3">set_env/3</a></li> <li title="set_env-4"><a href="application.html#set_env-4">set_env/4</a></li> <li title="start-1"><a href="application.html#start-1">start/1</a></li> <li title="start-2"><a href="application.html#start-2">start/2</a></li> <li title="start_type-0"><a href="application.html#start_type-0">start_type/0</a></li> <li title="stop-1"><a href="application.html#stop-1">stop/1</a></li> <li title="takeover-2"><a href="application.html#takeover-2">takeover/2</a></li> <li title="unload-1"><a href="application.html#unload-1">unload/1</a></li> <li title="unset_env-2"><a href="application.html#unset_env-2">unset_env/2</a></li> <li title="unset_env-3"><a href="application.html#unset_env-3">unset_env/3</a></li> <li title="which_applications-0"><a href="application.html#which_applications-0">which_applications/0</a></li> <li title="which_applications-1"><a href="application.html#which_applications-1">which_applications/1</a></li> <li title="Module:start-2"><a href="application.html#Module:start-2">Module:start/2</a></li> <li title="Module:start_phase-3"><a href="application.html#Module:start_phase-3">Module:start_phase/3</a></li> <li title="Module:prep_stop-1"><a href="application.html#Module:prep_stop-1">Module:prep_stop/1</a></li> <li title="Module:stop-1"><a href="application.html#Module:stop-1">Module:stop/1</a></li> <li title="Module:config_change-3"><a href="application.html#Module:config_change-3">Module:config_change/3</a></li> </ul> </li> <li id="no" title="auth " expanded="false">auth<ul> <li><a href="auth.html"> Top of manual page </a></li> <li title="is_auth-1"><a href="auth.html#is_auth-1">is_auth/1</a></li> <li title="cookie-0"><a href="auth.html#cookie-0">cookie/0</a></li> <li title="cookie-1"><a href="auth.html#cookie-1">cookie/1</a></li> <li title="node_cookie-1"><a href="auth.html#node_cookie-1">node_cookie/1</a></li> <li title="node_cookie-2"><a href="auth.html#node_cookie-2">node_cookie/2</a></li> </ul> </li> <li id="no" title="code " expanded="false">code<ul> <li><a href="code.html"> Top of manual page </a></li> <li title="set_path-1"><a href="code.html#set_path-1">set_path/1</a></li> <li title="get_path-0"><a href="code.html#get_path-0">get_path/0</a></li> <li title="add_path-1"><a href="code.html#add_path-1">add_path/1</a></li> <li title="add_pathz-1"><a href="code.html#add_pathz-1">add_pathz/1</a></li> <li title="add_patha-1"><a href="code.html#add_patha-1">add_patha/1</a></li> <li title="add_paths-1"><a href="code.html#add_paths-1">add_paths/1</a></li> <li title="add_pathsz-1"><a href="code.html#add_pathsz-1">add_pathsz/1</a></li> <li title="add_pathsa-1"><a href="code.html#add_pathsa-1">add_pathsa/1</a></li> <li title="del_path-1"><a href="code.html#del_path-1">del_path/1</a></li> <li title="replace_path-2"><a href="code.html#replace_path-2">replace_path/2</a></li> <li title="load_file-1"><a href="code.html#load_file-1">load_file/1</a></li> <li title="load_abs-1"><a href="code.html#load_abs-1">load_abs/1</a></li> <li title="ensure_loaded-1"><a href="code.html#ensure_loaded-1">ensure_loaded/1</a></li> <li title="load_binary-3"><a href="code.html#load_binary-3">load_binary/3</a></li> <li title="delete-1"><a href="code.html#delete-1">delete/1</a></li> <li title="purge-1"><a href="code.html#purge-1">purge/1</a></li> <li title="soft_purge-1"><a href="code.html#soft_purge-1">soft_purge/1</a></li> <li title="is_loaded-1"><a href="code.html#is_loaded-1">is_loaded/1</a></li> <li title="all_loaded-0"><a href="code.html#all_loaded-0">all_loaded/0</a></li> <li title="which-1"><a href="code.html#which-1">which/1</a></li> <li title="get_object_code-1"><a href="code.html#get_object_code-1">get_object_code/1</a></li> <li title="root_dir-0"><a href="code.html#root_dir-0">root_dir/0</a></li> <li title="lib_dir-0"><a href="code.html#lib_dir-0">lib_dir/0</a></li> <li title="lib_dir-1"><a href="code.html#lib_dir-1">lib_dir/1</a></li> <li title="lib_dir-2"><a href="code.html#lib_dir-2">lib_dir/2</a></li> <li title="compiler_dir-0"><a href="code.html#compiler_dir-0">compiler_dir/0</a></li> <li title="priv_dir-1"><a href="code.html#priv_dir-1">priv_dir/1</a></li> <li title="objfile_extension-0"><a href="code.html#objfile_extension-0">objfile_extension/0</a></li> <li title="stick_dir-1"><a href="code.html#stick_dir-1">stick_dir/1</a></li> <li title="unstick_dir-1"><a href="code.html#unstick_dir-1">unstick_dir/1</a></li> <li title="is_sticky-1"><a href="code.html#is_sticky-1">is_sticky/1</a></li> <li title="rehash-0"><a href="code.html#rehash-0">rehash/0</a></li> <li title="where_is_file-1"><a href="code.html#where_is_file-1">where_is_file/1</a></li> <li title="clash-0"><a href="code.html#clash-0">clash/0</a></li> <li title="is_module_native-1"><a href="code.html#is_module_native-1">is_module_native/1</a></li> </ul> </li> <li id="no" title="disk_log " expanded="false">disk_log<ul> <li><a href="disk_log.html"> Top of manual page </a></li> <li title="accessible_logs-0"><a href="disk_log.html#accessible_logs-0">accessible_logs/0</a></li> <li title="alog-2"><a href="disk_log.html#alog-2">alog/2</a></li> <li title="balog-2"><a href="disk_log.html#balog-2">balog/2</a></li> <li title="alog_terms-2"><a href="disk_log.html#alog_terms-2">alog_terms/2</a></li> <li title="balog_terms-2"><a href="disk_log.html#balog_terms-2">balog_terms/2</a></li> <li title="block-1"><a href="disk_log.html#block-1">block/1</a></li> <li title="block-2"><a href="disk_log.html#block-2">block/2</a></li> <li title="change_header-2"><a href="disk_log.html#change_header-2">change_header/2</a></li> <li title="change_notify-3"><a href="disk_log.html#change_notify-3">change_notify/3</a></li> <li title="change_size-2"><a href="disk_log.html#change_size-2">change_size/2</a></li> <li title="chunk-2"><a href="disk_log.html#chunk-2">chunk/2</a></li> <li title="chunk-3"><a href="disk_log.html#chunk-3">chunk/3</a></li> <li title="bchunk-2"><a href="disk_log.html#bchunk-2">bchunk/2</a></li> <li title="bchunk-3"><a href="disk_log.html#bchunk-3">bchunk/3</a></li> <li title="chunk_info-1"><a href="disk_log.html#chunk_info-1">chunk_info/1</a></li> <li title="chunk_step-3"><a href="disk_log.html#chunk_step-3">chunk_step/3</a></li> <li title="close-1"><a href="disk_log.html#close-1">close/1</a></li> <li title="format_error-1"><a href="disk_log.html#format_error-1">format_error/1</a></li> <li title="inc_wrap_file-1"><a href="disk_log.html#inc_wrap_file-1">inc_wrap_file/1</a></li> <li title="info-1"><a href="disk_log.html#info-1">info/1</a></li> <li title="lclose-1"><a href="disk_log.html#lclose-1">lclose/1</a></li> <li title="lclose-2"><a href="disk_log.html#lclose-2">lclose/2</a></li> <li title="log-2"><a href="disk_log.html#log-2">log/2</a></li> <li title="blog-2"><a href="disk_log.html#blog-2">blog/2</a></li> <li title="log_terms-2"><a href="disk_log.html#log_terms-2">log_terms/2</a></li> <li title="blog_terms-2"><a href="disk_log.html#blog_terms-2">blog_terms/2</a></li> <li title="open-1"><a href="disk_log.html#open-1">open/1</a></li> <li title="pid2name-1"><a href="disk_log.html#pid2name-1">pid2name/1</a></li> <li title="reopen-2"><a href="disk_log.html#reopen-2">reopen/2</a></li> <li title="reopen-3"><a href="disk_log.html#reopen-3">reopen/3</a></li> <li title="breopen-3"><a href="disk_log.html#breopen-3">breopen/3</a></li> <li title="sync-1"><a href="disk_log.html#sync-1">sync/1</a></li> <li title="truncate-1"><a href="disk_log.html#truncate-1">truncate/1</a></li> <li title="truncate-2"><a href="disk_log.html#truncate-2">truncate/2</a></li> <li title="btruncate-2"><a href="disk_log.html#btruncate-2">btruncate/2</a></li> <li title="unblock-1"><a href="disk_log.html#unblock-1">unblock/1</a></li> </ul> </li> <li id="no" title="erl_boot_server " expanded="false">erl_boot_server<ul> <li><a href="erl_boot_server.html"> Top of manual page </a></li> <li title="start-1"><a href="erl_boot_server.html#start-1">start/1</a></li> <li title="start_link-1"><a href="erl_boot_server.html#start_link-1">start_link/1</a></li> <li title="add_slave-1"><a href="erl_boot_server.html#add_slave-1">add_slave/1</a></li> <li title="delete_slave-1"><a href="erl_boot_server.html#delete_slave-1">delete_slave/1</a></li> <li title="which_slaves-0"><a href="erl_boot_server.html#which_slaves-0">which_slaves/0</a></li> </ul> </li> <li id="no" title="erl_ddll " expanded="false">erl_ddll<ul> <li><a href="erl_ddll.html"> Top of manual page </a></li> <li title="demonitor-1"><a href="erl_ddll.html#demonitor-1">demonitor/1</a></li> <li title="info-0"><a href="erl_ddll.html#info-0">info/0</a></li> <li title="info-1"><a href="erl_ddll.html#info-1">info/1</a></li> <li title="info-2"><a href="erl_ddll.html#info-2">info/2</a></li> <li title="load-2"><a href="erl_ddll.html#load-2">load/2</a></li> <li title="load_driver-2"><a href="erl_ddll.html#load_driver-2">load_driver/2</a></li> <li title="monitor-2"><a href="erl_ddll.html#monitor-2">monitor/2</a></li> <li title="reload-2"><a href="erl_ddll.html#reload-2">reload/2</a></li> <li title="reload_driver-2"><a href="erl_ddll.html#reload_driver-2">reload_driver/2</a></li> <li title="try_load-3"><a href="erl_ddll.html#try_load-3">try_load/3</a></li> <li title="try_unload-2"><a href="erl_ddll.html#try_unload-2">try_unload/2</a></li> <li title="unload-1"><a href="erl_ddll.html#unload-1">unload/1</a></li> <li title="unload_driver-1"><a href="erl_ddll.html#unload_driver-1">unload_driver/1</a></li> <li title="loaded_drivers-0"><a href="erl_ddll.html#loaded_drivers-0">loaded_drivers/0</a></li> <li title="format_error-1"><a href="erl_ddll.html#format_error-1">format_error/1</a></li> </ul> </li> <li title="erl_prim_loader"><a href="erl_prim_loader.html">erl_prim_loader</a></li> <li title="erlang"><a href="erlang.html">erlang</a></li> <li id="no" title="error_handler " expanded="false">error_handler<ul> <li><a href="error_handler.html"> Top of manual page </a></li> <li title="undefined_function-3"><a href="error_handler.html#undefined_function-3">undefined_function/3</a></li> <li title="undefined_lambda-3"><a href="error_handler.html#undefined_lambda-3">undefined_lambda/3</a></li> </ul> </li> <li id="no" title="error_logger " expanded="false">error_logger<ul> <li><a href="error_logger.html"> Top of manual page </a></li> <li title="error_msg-1"><a href="error_logger.html#error_msg-1">error_msg/1</a></li> <li title="error_msg-2"><a href="error_logger.html#error_msg-2">error_msg/2</a></li> <li title="format-2"><a href="error_logger.html#format-2">format/2</a></li> <li title="error_report-1"><a href="error_logger.html#error_report-1">error_report/1</a></li> <li title="error_report-2"><a href="error_logger.html#error_report-2">error_report/2</a></li> <li title="warning_map-0"><a href="error_logger.html#warning_map-0">warning_map/0</a></li> <li title="warning_msg-1"><a href="error_logger.html#warning_msg-1">warning_msg/1</a></li> <li title="warning_msg-2"><a href="error_logger.html#warning_msg-2">warning_msg/2</a></li> <li title="warning_report-1"><a href="error_logger.html#warning_report-1">warning_report/1</a></li> <li title="warning_report-2"><a href="error_logger.html#warning_report-2">warning_report/2</a></li> <li title="info_msg-1"><a href="error_logger.html#info_msg-1">info_msg/1</a></li> <li title="info_msg-2"><a href="error_logger.html#info_msg-2">info_msg/2</a></li> <li title="info_report-1"><a href="error_logger.html#info_report-1">info_report/1</a></li> <li title="info_report-2"><a href="error_logger.html#info_report-2">info_report/2</a></li> <li title="add_report_handler-1"><a href="error_logger.html#add_report_handler-1">add_report_handler/1</a></li> <li title="add_report_handler-2"><a href="error_logger.html#add_report_handler-2">add_report_handler/2</a></li> <li title="delete_report_handler-1"><a href="error_logger.html#delete_report_handler-1">delete_report_handler/1</a></li> <li title="tty-1"><a href="error_logger.html#tty-1">tty/1</a></li> <li title="logfile-1"><a href="error_logger.html#logfile-1">logfile/1</a></li> </ul> </li> <li id="no" title="file " expanded="false">file<ul> <li><a href="file.html"> Top of manual page </a></li> <li title="advise-4"><a href="file.html#advise-4">advise/4</a></li> <li title="change_group-2"><a href="file.html#change_group-2">change_group/2</a></li> <li title="change_mode-2"><a href="file.html#change_mode-2">change_mode/2</a></li> <li title="change_owner-2"><a href="file.html#change_owner-2">change_owner/2</a></li> <li title="change_owner-3"><a href="file.html#change_owner-3">change_owner/3</a></li> <li title="change_time-2"><a href="file.html#change_time-2">change_time/2</a></li> <li title="change_time-3"><a href="file.html#change_time-3">change_time/3</a></li> <li title="close-1"><a href="file.html#close-1">close/1</a></li> <li title="consult-1"><a href="file.html#consult-1">consult/1</a></li> <li title="copy-2"><a href="file.html#copy-2">copy/2</a></li> <li title="copy-3"><a href="file.html#copy-3">copy/3</a></li> <li title="del_dir-1"><a href="file.html#del_dir-1">del_dir/1</a></li> <li title="delete-1"><a href="file.html#delete-1">delete/1</a></li> <li title="eval-1"><a href="file.html#eval-1">eval/1</a></li> <li title="eval-2"><a href="file.html#eval-2">eval/2</a></li> <li title="file_info-1"><a href="file.html#file_info-1">file_info/1</a></li> <li title="format_error-1"><a href="file.html#format_error-1">format_error/1</a></li> <li title="get_cwd-0"><a href="file.html#get_cwd-0">get_cwd/0</a></li> <li title="get_cwd-1"><a href="file.html#get_cwd-1">get_cwd/1</a></li> <li title="list_dir-1"><a href="file.html#list_dir-1">list_dir/1</a></li> <li title="make_dir-1"><a href="file.html#make_dir-1">make_dir/1</a></li> <li title="make_link-2"><a href="file.html#make_link-2">make_link/2</a></li> <li title="make_symlink-2"><a href="file.html#make_symlink-2">make_symlink/2</a></li> <li title="native_name_encoding-0"><a href="file.html#native_name_encoding-0">native_name_encoding/0</a></li> <li title="open-2"><a href="file.html#open-2">open/2</a></li> <li title="path_consult-2"><a href="file.html#path_consult-2">path_consult/2</a></li> <li title="path_eval-2"><a href="file.html#path_eval-2">path_eval/2</a></li> <li title="path_open-3"><a href="file.html#path_open-3">path_open/3</a></li> <li title="path_script-2"><a href="file.html#path_script-2">path_script/2</a></li> <li title="path_script-3"><a href="file.html#path_script-3">path_script/3</a></li> <li title="pid2name-1"><a href="file.html#pid2name-1">pid2name/1</a></li> <li title="position-2"><a href="file.html#position-2">position/2</a></li> <li title="pread-2"><a href="file.html#pread-2">pread/2</a></li> <li title="pread-3"><a href="file.html#pread-3">pread/3</a></li> <li title="pwrite-2"><a href="file.html#pwrite-2">pwrite/2</a></li> <li title="pwrite-3"><a href="file.html#pwrite-3">pwrite/3</a></li> <li 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<li id="no" title="seq_trace " expanded="false">seq_trace<ul> <li><a href="seq_trace.html"> Top of manual page </a></li> <li title="set_token-1"><a href="seq_trace.html#set_token-1">set_token/1</a></li> <li title="set_token-2"><a href="seq_trace.html#set_token-2">set_token/2</a></li> <li title="get_token-0"><a href="seq_trace.html#get_token-0">get_token/0</a></li> <li title="get_token-1"><a href="seq_trace.html#get_token-1">get_token/1</a></li> <li title="print-1"><a href="seq_trace.html#print-1">print/1</a></li> <li title="print-2"><a href="seq_trace.html#print-2">print/2</a></li> <li title="reset_trace-0"><a href="seq_trace.html#reset_trace-0">reset_trace/0</a></li> <li title="set_system_tracer-1"><a href="seq_trace.html#set_system_tracer-1">set_system_tracer/1</a></li> <li title="get_system_tracer-0"><a href="seq_trace.html#get_system_tracer-0">get_system_tracer/0</a></li> </ul> </li> <li title="user"><a href="user.html">user</a></li> <li id="no" title="wrap_log_reader " expanded="false">wrap_log_reader<ul> <li><a href="wrap_log_reader.html"> Top of manual page </a></li> <li title="chunk-1"><a href="wrap_log_reader.html#chunk-1">chunk/1</a></li> <li title="chunk-2"><a href="wrap_log_reader.html#chunk-2">chunk/2</a></li> <li title="close-1"><a href="wrap_log_reader.html#close-1">close/1</a></li> <li title="open-1"><a href="wrap_log_reader.html#open-1">open/1</a></li> <li title="open-2"><a href="wrap_log_reader.html#open-2">open/2</a></li> </ul> </li> <li title="zlib"><a href="zlib.html">zlib</a></li> <li title="app"><a href="app.html">app</a></li> <li title="config"><a href="config.html">config</a></li> <li title="packages"><a href="packages.html">packages</a></li> </ul> </div></div> <div id="content"> <div class="innertube"> <!-- refpage --><center><h1>global</h1></center> <h3>MODULE</h3> <div class="REFBODY">global</div> <h3>MODULE SUMMARY</h3> <div class="REFBODY">A Global Name Registration Facility</div> <h3>DESCRIPTION</h3> <div class="REFBODY"><p> <p>This documentation describes the Global module which consists of the following functionalities:</p> <ul> <li>registration of global names;</li> <li>global locks;</li> <li>maintenance of the fully connected network.</li> </ul> <p>These services are controlled via the process <span class="code">global_name_server</span> which exists on every node. The global name server is started automatically when a node is started. With the term <strong>global</strong> is meant over a system consisting of several Erlang nodes.</p> <p>The ability to globally register names is a central concept in the programming of distributed Erlang systems. In this module, the equivalent of the <span class="code">register/2</span> and <span class="code">whereis/1</span> BIFs (for local name registration) are implemented, but for a network of Erlang nodes. A registered name is an alias for a process identifier (pid). The global name server monitors globally registered pids. If a process terminates, the name will also be globally unregistered.</p> <p>The registered names are stored in replica global name tables on every node. There is no central storage point. Thus, the translation of a name to a pid is fast, as it is always done locally. When any action in taken which results in a change to the global name table, all tables on other nodes are automatically updated.</p> <p>Global locks have lock identities and are set on a specific resource. For instance, the specified resource could be a pid. When a global lock is set, access to the locked resource is denied for all other resources other than the lock requester.</p> <p>Both the registration and lock functionalities are atomic. All nodes involved in these actions will have the same view of the information.</p> <p>The global name server also performs the critical task of continuously monitoring changes in node configuration: if a node which runs a globally registered process goes down, the name will be globally unregistered. To this end the global name server subscribes to <span class="code">nodeup</span> and <span class="code">nodedown</span> messages sent from the <span class="code">net_kernel</span> module. Relevant Kernel application variables in this context are <span class="code">net_setuptime</span>, <span class="code">net_ticktime</span>, and <span class="code">dist_auto_connect</span>. See also <span class="bold_code"><a href="kernel_app.html#net_setuptime">kernel(6)</a></span>.</p> <p>The name server will also maintain a fully connected network. For example, if node <span class="code">N1</span> connects to node <span class="code">N2</span> (which is already connected to <span class="code">N3</span>), the global name servers on the nodes <span class="code">N1</span> and <span class="code">N3</span> will make sure that also <span class="code">N1</span> and <span class="code">N3</span> are connected. If this is not desired, the command line flag <span class="code">-connect_all false</span> can be used (see also <span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','erts','erl.html#connect_all');">erl(1)</a></span>). In this case the name registration facility cannot be used, but the lock mechanism will still work.</p> <p>If the global name server fails to connect nodes (<span class="code">N1</span> and <span class="code">N3</span> in the example above) a warning event is sent to the error logger. The presence of such an event does not exclude the possibility that the nodes will later connect--one can for example try the command <span class="code">rpc:call(N1, net_adm, ping, [N2])</span> in the Erlang shell--but it indicates some kind of problem with the network.</p> <div class="note"> <div class="label">Note</div> <div class="content"><p> <p>If the fully connected network is not set up properly, the first thing to try is to increase the value of <span class="code">net_setuptime</span>.</p> </p></div> </div> </p></div> <h3>DATA TYPES</h3> <p> <span class="bold_code"><a name="type-id">id()</a> = {ResourceId :: term(), LockRequesterId :: term()}</span><br></p> <h3>EXPORTS</h3> <p><a name="del_lock-1"></a><span class="bold_code">del_lock(Id) -> true</span><br><a name="del_lock-2"></a><span class="bold_code">del_lock(Id, Nodes) -> true</span><br><div class="REFBODY"> <p>Types:</p> <div class="REFTYPES"><span class="bold_code">Id = <span class="bold_code"><a href="#type-id">id()</a></span></span></div> <div class="REFTYPES"><span class="bold_code">Nodes = [node()]</span></div> </div></p> <div class="REFBODY"><p> <p>Deletes the lock <span class="code">Id</span> synchronously.</p> </p></div> <p><a name="notify_all_name-3"></a><span class="bold_code">notify_all_name(Name, Pid1, Pid2) -> none</span><br><div class="REFBODY"> <p>Types:</p> <div class="REFTYPES"><span class="bold_code">Name = term()</span></div> <div class="REFTYPES"><span class="bold_code">Pid1 = Pid2 = pid()</span></div> <div class="REFTYPES"><span class="bold_code"></span></div> </div></p> <div class="REFBODY"><p> <p>This function can be used as a name resolving function for <span class="code">register_name/3</span> and <span class="code">re_register_name/3</span>. It unregisters both pids, and sends the message <span class="code">{global_name_conflict, Name, OtherPid}</span> to both processes.</p> </p></div> <p><a name="random_exit_name-3"></a><span class="bold_code">random_exit_name(Name, Pid1, Pid2) -> pid()</span><br><div class="REFBODY"> <p>Types:</p> <div class="REFTYPES"><span class="bold_code">Name = term()</span></div> <div class="REFTYPES"><span class="bold_code">Pid1 = Pid2 = pid()</span></div> <div class="REFTYPES"><span class="bold_code"></span></div> </div></p> <div class="REFBODY"><p> <p>This function can be used as a name resolving function for <span class="code">register_name/3</span> and <span class="code">re_register_name/3</span>. It randomly chooses one of the pids for registration and kills the other one.</p> </p></div> <p><a name="random_notify_name-3"></a><span class="bold_code">random_notify_name(Name, Pid1, Pid2) -> pid()</span><br><div class="REFBODY"> <p>Types:</p> <div class="REFTYPES"><span class="bold_code">Name = term()</span></div> <div class="REFTYPES"><span class="bold_code">Pid1 = Pid2 = pid()</span></div> <div class="REFTYPES"><span class="bold_code"></span></div> </div></p> <div class="REFBODY"><p> <p>This function can be used as a name resolving function for <span class="code">register_name/3</span> and <span class="code">re_register_name/3</span>. It randomly chooses one of the pids for registration, and sends the message <span class="code">{global_name_conflict, Name}</span> to the other pid.</p> </p></div> <p><a name="register_name-2"></a><span class="bold_code">register_name(Name, Pid) -> yes | no</span><br><a name="register_name-3"></a><span class="bold_code">register_name(Name, Pid, Resolve) -> yes | no</span><br><div class="REFBODY"> <p>Types:</p> <div class="REFTYPES"><span class="bold_code">Name = term()</span></div> <div class="REFTYPES"><span class="bold_code">Pid = pid()</span></div> <div class="REFTYPES"><span class="bold_code">Resolve = method()</span></div> <div class="REFTYPES"> <span class="bold_code">method() = <br> fun((Name :: term(), Pid :: pid(), Pid2 :: pid()) -><br> pid() | none)</span><br> </div> <div class="REFBODY">{<span class="code">Module</span>, <span class="code">Function</span>} is also allowed </div> </div></p> <div class="REFBODY"><p> <p>Globally associates the name <span class="code">Name</span> with a pid, that is, Globally notifies all nodes of a new global name in a network of Erlang nodes.</p> <p>When new nodes are added to the network, they are informed of the globally registered names that already exist. The network is also informed of any global names in newly connected nodes. If any name clashes are discovered, the <span class="code">Resolve</span> function is called. Its purpose is to decide which pid is correct. If the function crashes, or returns anything other than one of the pids, the name is unregistered. This function is called once for each name clash.</p> <p>There are three pre-defined resolve functions: <span class="code">random_exit_name/3</span>, <span class="code">random_notify_name/3</span>, and <span class="code">notify_all_name/3</span>. If no <span class="code">Resolve</span> function is defined, <span class="code">random_exit_name</span> is used. This means that one of the two registered processes will be selected as correct while the other is killed.</p> <p>This function is completely synchronous. This means that when this function returns, the name is either registered on all nodes or none.</p> <p>The function returns <span class="code">yes</span> if successful, <span class="code">no</span> if it fails. For example, <span class="code">no</span> is returned if an attempt is made to register an already registered process or to register a process with a name that is already in use.</p> <div class="note"> <div class="label">Note</div> <div class="content"><p> <p>Releases up to and including OTP R10 did not check if the process was already registered. As a consequence the global name table could become inconsistent. The old (buggy) behavior can be chosen by giving the Kernel application variable <span class="code">global_multi_name_action</span> the value <span class="code">allow</span>.</p> </p></div> </div> <p>If a process with a registered name dies, or the node goes down, the name is unregistered on all nodes.</p> </p></div> <p><a name="registered_names-0"></a><span class="bold_code">registered_names() -> [Name]</span><br><div class="REFBODY"> <p>Types:</p> <div class="REFTYPES"><span class="bold_code">Name = term()</span></div> </div></p> <div class="REFBODY"><p> <p>Returns a lists of all globally registered names.</p> </p></div> <p><a name="re_register_name-2"></a><span class="bold_code">re_register_name(Name, Pid) -> yes</span><br><a name="re_register_name-3"></a><span class="bold_code">re_register_name(Name, Pid, Resolve) -> yes</span><br><div class="REFBODY"> <p>Types:</p> <div class="REFTYPES"><span class="bold_code">Name = term()</span></div> <div class="REFTYPES"><span class="bold_code">Pid = pid()</span></div> <div class="REFTYPES"><span class="bold_code">Resolve = method()</span></div> <div class="REFTYPES"> <span class="bold_code">method() = <br> fun((Name :: term(), Pid :: pid(), Pid2 :: pid()) -><br> pid() | none)</span><br> </div> <div class="REFBODY">{<span class="code">Module</span>, <span class="code">Function</span>} is also allowed </div> </div></p> <div class="REFBODY"><p> <p>Atomically changes the registered name <span class="code">Name</span> on all nodes to refer to <span class="code">Pid</span>.</p> <p>The <span class="code">Resolve</span> function has the same behavior as in <span class="code">register_name/2,3</span>.</p> </p></div> <p><a name="send-2"></a><span class="bold_code">send(Name, Msg) -> Pid</span><br><div class="REFBODY"> <p>Types:</p> <div class="REFTYPES"><span class="bold_code">Name = Msg = term()</span></div> <div class="REFTYPES"><span class="bold_code"></span></div> <div class="REFTYPES"><span class="bold_code">Pid = pid()</span></div> </div></p> <div class="REFBODY"><p> <p>Sends the message <span class="code">Msg</span> to the pid globally registered as <span class="code">Name</span>.</p> <p>Failure: If <span class="code">Name</span> is not a globally registered name, the calling function will exit with reason <span class="code">{badarg, {Name, Msg}}</span>.</p> </p></div> <p><a name="set_lock-1"></a><span class="bold_code">set_lock(Id) -> boolean()</span><br><a name="set_lock-2"></a><span class="bold_code">set_lock(Id, Nodes) -> boolean()</span><br><a name="set_lock-3"></a><span class="bold_code">set_lock(Id, Nodes, Retries) -> boolean()</span><br><div class="REFBODY"> <p>Types:</p> <div class="REFTYPES"><span class="bold_code">Id = <span class="bold_code"><a href="#type-id">id()</a></span></span></div> <div class="REFTYPES"><span class="bold_code">Nodes = [node()]</span></div> <div class="REFTYPES"><span class="bold_code">Retries = retries()</span></div> <div class="REFTYPES"> <span class="bold_code">id() = {ResourceId :: term(), LockRequesterId :: term()}</span><br> </div> <div class="REFTYPES"> <span class="bold_code">retries() = integer() >= 0 | infinity</span><br> </div> </div></p> <div class="REFBODY"><p> <p>Sets a lock on the specified nodes (or on all nodes if none are specified) on <span class="code">ResourceId</span> for <span class="code">LockRequesterId</span>. If a lock already exists on <span class="code">ResourceId</span> for another requester than <span class="code">LockRequesterId</span>, and <span class="code">Retries</span> is not equal to 0, the process sleeps for a while and will try to execute the action later. When <span class="code">Retries</span> attempts have been made, <span class="code">false</span> is returned, otherwise <span class="code">true</span>. If <span class="code">Retries</span> is <span class="code">infinity</span>, <span class="code">true</span> is eventually returned (unless the lock is never released).</p> <p>If no value for <span class="code">Retries</span> is given, <span class="code">infinity</span> is used.</p> <p>This function is completely synchronous.</p> <p>If a process which holds a lock dies, or the node goes down, the locks held by the process are deleted.</p> <p>The global name server keeps track of all processes sharing the same lock, that is, if two processes set the same lock, both processes must delete the lock.</p> <p>This function does not address the problem of a deadlock. A deadlock can never occur as long as processes only lock one resource at a time. But if some processes try to lock two or more resources, a deadlock may occur. It is up to the application to detect and rectify a deadlock.</p> <div class="note"> <div class="label">Note</div> <div class="content"><p> <p>Some values of <span class="code">ResourceId</span> should be avoided or Erlang/OTP will not work properly. A list of resources to avoid: <span class="code">global</span>, <span class="code">dist_ac</span>, <span class="code">mnesia_table_lock</span>, <span class="code">mnesia_adjust_log_writes</span>, <span class="code">pg2</span>.</p> </p></div> </div> </p></div> <p><a name="sync-0"></a><span class="bold_code">sync() -> ok | {error, Reason :: term()}</span><br></p> <div class="REFBODY"><p> <p>Synchronizes the global name server with all nodes known to this node. These are the nodes which are returned from <span class="code">erlang:nodes()</span>. When this function returns, the global name server will receive global information from all nodes. This function can be called when new nodes are added to the network.</p> <p>The only possible error reason <span class="code">Reason</span> is <span class="code">{"global_groups definition error", Error}</span>.</p> </p></div> <p><a name="trans-2"></a><span class="bold_code">trans(Id, Fun) -> Res | aborted</span><br><a name="trans-3"></a><span class="bold_code">trans(Id, Fun, Nodes) -> Res | aborted</span><br><a name="trans-4"></a><span class="bold_code">trans(Id, Fun, Nodes, Retries) -> Res | aborted</span><br><div class="REFBODY"> <p>Types:</p> <div class="REFTYPES"><span class="bold_code">Id = <span class="bold_code"><a href="#type-id">id()</a></span></span></div> <div class="REFTYPES"><span class="bold_code">Fun = trans_fun()</span></div> <div class="REFTYPES"><span class="bold_code">Nodes = [node()]</span></div> <div class="REFTYPES"><span class="bold_code">Retries = retries()</span></div> <div class="REFTYPES"><span class="bold_code">Res = term()</span></div> <div class="REFTYPES"> <span class="bold_code">retries() = integer() >= 0 | infinity</span><br> </div> <div class="REFTYPES"> <span class="bold_code">trans_fun() = function() | {module(), atom()}</span><br> </div> </div></p> <div class="REFBODY"><p> <p>Sets a lock on <span class="code">Id</span> (using <span class="code">set_lock/3</span>). If this succeeds, <span class="code">Fun()</span> is evaluated and the result <span class="code">Res</span> is returned. Returns <span class="code">aborted</span> if the lock attempt failed. If <span class="code">Retries</span> is set to <span class="code">infinity</span>, the transaction will not abort.</p> <p><span class="code">infinity</span> is the default setting and will be used if no value is given for <span class="code">Retries</span>.</p> </p></div> <p><a name="unregister_name-1"></a><span class="bold_code">unregister_name(Name) -> term()</span><br><div class="REFBODY"> <p>Types:</p> <div class="REFTYPES"><span class="bold_code">Name = term()</span></div> </div></p> <div class="REFBODY"><p> <p>Removes the globally registered name <span class="code">Name</span> from the network of Erlang nodes.</p> </p></div> <p><a name="whereis_name-1"></a><span class="bold_code">whereis_name(Name) -> pid() | undefined</span><br><div class="REFBODY"> <p>Types:</p> <div class="REFTYPES"><span class="bold_code">Name = term()</span></div> </div></p> <div class="REFBODY"><p> <p>Returns the pid with the globally registered name <span class="code">Name</span>. Returns <span class="code">undefined</span> if the name is not globally registered.</p> </p></div> <h3><a name="id125468">See Also</a></h3> <div class="REFBODY"> <p><span class="bold_code"><a href="global_group.html">global_group(3)</a></span>, <span class="bold_code"><a href="net_kernel.html">net_kernel(3)</a></span></p> </div> </div> <div class="footer"> <hr> <p>Copyright © 1997-2012 Ericsson AB. All Rights Reserved.</p> </div> </div> </div></body> </html>