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-rw-r--r--erts/doc/src/Makefile1
-rw-r--r--erts/doc/src/alt_disco.xml93
-rw-r--r--erts/doc/src/part.xml1
-rw-r--r--erts/emulator/test/distribution_SUITE.erl7
4 files changed, 101 insertions, 1 deletions
diff --git a/erts/doc/src/Makefile b/erts/doc/src/Makefile
index 5fa8b0673a..96cc4413a9 100644
--- a/erts/doc/src/Makefile
+++ b/erts/doc/src/Makefile
@@ -74,6 +74,7 @@ XML_CHAPTER_FILES = \
match_spec.xml \
crash_dump.xml \
alt_dist.xml \
+ alt_disco.xml \
driver.xml \
absform.xml \
inet_cfg.xml \
diff --git a/erts/doc/src/alt_disco.xml b/erts/doc/src/alt_disco.xml
new file mode 100644
index 0000000000..d04221b9b3
--- /dev/null
+++ b/erts/doc/src/alt_disco.xml
@@ -0,0 +1,93 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<!DOCTYPE chapter SYSTEM "chapter.dtd">
+
+<chapter>
+ <header>
+ <copyright>
+ <year>2018</year><year>2018</year>
+ <holder>Ericsson AB. All Rights Reserved.</holder>
+ </copyright>
+ <legalnotice>
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+
+ </legalnotice>
+
+ <title>How to Implement an Alternative Service Discovery for Erlang Distribution
+ </title>
+ <prepared>Timmo Verlaan</prepared>
+ <responsible></responsible>
+ <docno></docno>
+ <approved></approved>
+ <checked></checked>
+ <date>2018-04-25</date>
+ <rev>PA1</rev>
+ <file>alt_disco.xml</file>
+ </header>
+ <p>
+ This section describes how to implement an alternative discovery mechanism
+ for Erlang distribution. Discovery is normally done using DNS and the
+ Erlang Port Mapper Daemon (EPMD) for port discovery.
+ </p>
+
+ <note><p>
+ Support for alternative service discovery mechanisms was added in Erlang/OTP
+ 21.
+ </p></note>
+
+
+ <section>
+ <title>Introduction</title>
+ <p>To implement your own service discovery module you have to write your own
+ EPMD module. The <seealso marker="kernel:erl_epmd">EPMD module</seealso> is
+ responsible for providing the location of another node. The distribution
+ modules (<c>inet_tcp_dist</c>/<c>inet_tls_dist</c>) call the EPMD module to
+ get the IP address and port of the other node. The EPMD module that is part
+ of Erlang/OTP will resolve the hostname using DNS and uses the EPMD unix
+ process to get the port of another node. The EPMD unix process does this by
+ connecting to the other node on a well-known port, port 4369.</p>
+ </section>
+
+ <section>
+ <title>Discovery module</title>
+ <p>The discovery module needs to implement the same API as the regular
+ <seealso marker="kernel:erl_epmd">EPMD module</seealso>. However, instead of
+ communicating with EPMD you can connect to any service to find out
+ connection details of other nodes. A discovery module is enabled
+ by setting <seealso marker="erts:erl#epmd_module">-epmd_module</seealso>
+ when starting erlang. The discovery module must implement the following
+ callbacks:</p>
+
+ <taglist>
+ <tag><seealso marker="kernel:erl_epmd#start_link/0">start_link/0</seealso></tag>
+ <item>Start any processes needed by the discovery module.</item>
+ <tag><seealso marker="kernel:erl_epmd#names/1">names/1</seealso></tag>
+ <item>Return node names held by the registrar for the given host.</item>
+ <tag><seealso marker="kernel:erl_epmd#register_node/2">register_node/2</seealso></tag>
+ <item>Register the given node name with the registrar.</item>
+ <tag><seealso marker="kernel:erl_epmd#port_please/3">port_please/3</seealso></tag>
+ <item>Return the distribution port used by the given node.</item>
+ </taglist>
+
+ <p>The discovery module may implement the following callback:</p>
+
+ <taglist>
+ <tag><seealso marker="kernel:erl_epmd#address_please/3">address_please/3</seealso></tag>
+ <item><p>Return the address of the given node.
+ If not implemented, <seealso marker="kernel:inet#gethostbyname/1">
+ inet:gethostbyname/1</seealso> will be used instead</p>
+ <p>This callback may also return the port of the given node. In that case
+ <seealso marker="kernel:erl_epmd#port_please/3">port_please/3</seealso>
+ may be omitted.</p></item>
+ </taglist>
+ </section>
+</chapter>
diff --git a/erts/doc/src/part.xml b/erts/doc/src/part.xml
index d583b873a0..fc39cb30e6 100644
--- a/erts/doc/src/part.xml
+++ b/erts/doc/src/part.xml
@@ -37,6 +37,7 @@
<xi:include href="match_spec.xml"/>
<xi:include href="crash_dump.xml"/>
<xi:include href="alt_dist.xml"/>
+ <xi:include href="alt_disco.xml"/>
<xi:include href="absform.xml"/>
<xi:include href="tty.xml"/>
<xi:include href="driver.xml"/>
diff --git a/erts/emulator/test/distribution_SUITE.erl b/erts/emulator/test/distribution_SUITE.erl
index 0e383ee879..45dd922ff0 100644
--- a/erts/emulator/test/distribution_SUITE.erl
+++ b/erts/emulator/test/distribution_SUITE.erl
@@ -73,7 +73,7 @@
dist_evil_parallel_receiver/0]).
%% epmd_module exports
--export([start_link/0, register_node/2, register_node/3, port_please/2]).
+-export([start_link/0, register_node/2, register_node/3, port_please/2, address_please/3]).
suite() ->
[{ct_hooks,[ts_install_cth]},
@@ -2086,6 +2086,11 @@ port_please(_Name, _Ip) ->
{port, Port, Version}
end.
+address_please(_Name, _Address, _AddressFamily) ->
+ %% Use localhost.
+ IP = {127,0,0,1},
+ {ok, IP}.
+
%%% Utilities
timestamp() ->