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<img alt="Erlang logo" src="../../../../doc/erlang-logo.png"><br><small><a href="index.html">Reference Manual</a><br><a href="release_notes.html">Release Notes</a><br><a href="../pdf/kernel-2.15.3.pdf">PDF</a><br><a 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>
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<li id="no" title="auth " expanded="false">auth<ul>
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<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>
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<li id="no" title="code " expanded="false">code<ul>
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<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>
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<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>
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<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>
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<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>
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<li title="make_link-2"><a href="file.html#make_link-2">make_link/2</a></li>
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<li title="open-2"><a href="file.html#open-2">open/2</a></li>
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<!-- 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>
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