Skip to content

Commit

Permalink
Add documentation about upgrade
Browse files Browse the repository at this point in the history 
The example of how to create a first target system, which is located
in the System Principles document, is now extended to also include an
example of code upgrade.

A new chapter is added to System Principles explaining different
issues when upgrade includes new versions applications within
Erlang/OTP.
  • Loading branch information
@sirihansen
sirihansen committed Apr 3, 2014
1 parent 8eb20d1 commit c65821b
Show file tree
Hide file tree
Showing 5 changed files with 359 additions and 30 deletions.
16 changes: 14 additions & 2 deletions lib/sasl/examples/src/target_system.erl
View file
Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2011-2013. All Rights Reserved.
%% Copyright Ericsson AB 2011-2014. All Rights Reserved.
%%
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
Expand Down Expand Up @@ -65,7 +65,7 @@ create(RelFileName,SystoolsOpts) ->
[RelFileName, RelFileName]),
make_script(RelFileName,SystoolsOpts),

TarFileName = filename:join(Dir,RelFileName ++ ".tar.gz"),
TarFileName = RelFileName ++ ".tar.gz",
io:fwrite("Creating tar file ~tp ...~n", [TarFileName]),
make_tar(RelFileName,SystoolsOpts),

Expand Down Expand Up @@ -100,6 +100,12 @@ create(RelFileName,SystoolsOpts) ->
copy_file(filename:join([ErtsBinDir, "to_erl"]),
filename:join([TmpBinDir, "to_erl"]), [preserve]),

%% This is needed if 'start' script created from 'start.src' shall
%% be used as it points out this directory as log dir for 'run_erl'
TmpLogDir = filename:join([TmpDir, "log"]),
io:fwrite("Creating temporary directory ~tp ...~n", [TmpLogDir]),
ok = file:make_dir(TmpLogDir),

StartErlDataFile = filename:join([TmpDir, "releases", "start_erl.data"]),
io:fwrite("Creating ~tp ...~n", [StartErlDataFile]),
StartErlData = io_lib:fwrite("~s ~s~n", [ErtsVsn, RelVsn]),
Expand All @@ -115,6 +121,7 @@ create(RelFileName,SystoolsOpts) ->
erl_tar:add(Tar, filename:join(TmpDir,ErtsDir), ErtsDir, []),
erl_tar:add(Tar, filename:join(TmpDir,"releases"), "releases", []),
erl_tar:add(Tar, filename:join(TmpDir,"lib"), "lib", []),
erl_tar:add(Tar, filename:join(TmpDir,"log"), "log", []),
erl_tar:close(Tar),
%% file:set_cwd(Cwd),
io:fwrite("Removing directory ~tp ...~n",[TmpDir]),
Expand All @@ -136,6 +143,11 @@ install(RelFileName, RootDir) ->
subst_src_scripts(["erl", "start", "start_erl"], ErtsBinDir, BinDir,
[{"FINAL_ROOTDIR", RootDir}, {"EMU", "beam"}],
[preserve]),
%%! Workaround for pre OTP 17.0: start.src and start_erl.src did
%%! not have correct permissions, so the above 'preserve' option did not help
ok = file:change_mode(filename:join(BinDir,"start"),8#0755),
ok = file:change_mode(filename:join(BinDir,"start_erl"),8#0755),

io:fwrite("Creating the RELEASES file ...\n"),
create_RELEASES(RootDir, filename:join([RootDir, "releases",
filename:basename(RelFileName)])).
Expand Down
248 changes: 223 additions & 25 deletions system/doc/system_principles/create_target.xmlsrc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@
<chapter>
<header>
<copyright>
<year>2002</year><year>2013</year>
<year>2002</year><year>2014</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
Expand All @@ -21,7 +21,7 @@

</legalnotice>

<title>Creating a First Target System</title>
<title>Creating and Upgrading a Target System</title>
<prepared>Peter H&ouml;gfeldt</prepared>
<responsible></responsible>
<docno></docno>
Expand Down Expand Up @@ -71,23 +71,24 @@
</section>

<section>
<marker id="create"/>
<title>Creating a Target System</title>
<p>It is assumed that you have a working Erlang/OTP system structured
according to the OTP Design Principles.</p>
<p><em>Step 1.</em> First create a <c>.rel</c> file (see
<c>rel(4)</c>) that specifies the <c>erts</c> version
and lists all applications that should be included in the new
basic target system. An example is the following
<p><em>Step 1.</em> First create a <c>.rel</c> file (see <seealso
marker="sasl:rel">rel(4)</seealso>) that specifies the <c>erts</c>
version and lists all applications that should be included in the
new basic target system. An example is the following
<c>mysystem.rel</c> file:</p>
<code type="none">
%% mysystem.rel
{release,
{"MYSYSTEM", "FIRST"},
{erts, "5.1"},
[{kernel, "2.7"},
{stdlib, "1.10"},
{sasl, "1.9.3"},
{pea, "1.0"}]}. </code>
{erts, "5.10.4"},
[{kernel, "2.16.4"},
{stdlib, "1.19.4"},
{sasl, "2.3.4"},
{pea, "1.0"}]}.</code>
<p>The listed applications are not only original Erlang/OTP
applications but possibly also new applications that you have
written yourself (here examplified by the application
Expand Down Expand Up @@ -116,13 +117,13 @@ os> <input>erl -pa /home/user/target_system/myapps/pea-1.0/ebin</input></pre>
<c>systools:make_tar/2</c>. That file has the following
contents:</p>
<code type="none">
erts-5.1/bin/
erts-5.10.4/bin/
releases/FIRST/start.boot
releases/FIRST/mysystem.rel
releases/mysystem.rel
lib/kernel-2.7/
lib/stdlib-1.10/
lib/sasl-1.9.3/
lib/kernel-2.16.4/
lib/stdlib-1.19.4/
lib/sasl-2.3.4/
lib/pea-1.0/ </code>
<p>The file <c>releases/FIRST/start.boot</c> is a copy of our
<c>mysystem.boot</c></p>
Expand All @@ -142,16 +143,19 @@ lib/pea-1.0/ </code>
<item>Creates the temporary directory <c>tmp</c> and extracts the tar file
<c>mysystem.tar.gz</c> into that directory. </item>
<item>Deletes the <c>erl</c> and <c>start</c> files from
<c>tmp/erts-5.1/bin</c>. These files will be created again from
<c>tmp/erts-5.10.4/bin</c>. These files will be created again from
source when installing the release.</item>
<item>Creates the directory <c>tmp/bin</c>.</item>
<item>Copies the previously created file <c>plain.boot</c> to
<c>tmp/bin/start.boot</c>.</item>
<item>Copies the files <c>epmd</c>, <c>run_erl</c>, and
<c>to_erl</c> from the directory <c>tmp/erts-5.1/bin</c> to
<c>to_erl</c> from the directory <c>tmp/erts-5.10.4/bin</c> to
the directory <c>tmp/bin</c>.</item>
<item>Creates the directory <c>tmp/log</c>, which will be used
if the system is started as embedded with the <c>bin/start</c>
script.</item>
<item>Creates the file <c>tmp/releases/start_erl.data</c> with
the contents "5.1 FIRST". This file is to be passed as data
the contents "5.10.4 FIRST". This file is to be passed as data
file to the <c>start_erl</c> script.
</item>
<item>Recreates the file <c>mysystem.tar.gz</c> from the directories
Expand All @@ -171,11 +175,11 @@ lib/pea-1.0/ </code>
<item>Extracts the tar file <c>mysystem.tar.gz</c> into the target
directory <c>/usr/local/erl-target</c>.</item>
<item>In the target directory reads the file <c>releases/start_erl.data</c>
in order to find the Erlang runtime system version ("5.1").</item>
in order to find the Erlang runtime system version ("5.10.4").</item>
<item>Substitutes <c>%FINAL_ROOTDIR%</c> and <c>%EMU%</c> for
<c>/usr/local/erl-target</c> and <c>beam</c>, respectively, in
the files <c>erl.src</c>, <c>start.src</c>, and
<c>start_erl.src</c> of the target <c>erts-5.1/bin</c>
<c>start_erl.src</c> of the target <c>erts-5.10.4/bin</c>
directory, and puts the resulting files <c>erl</c>,
<c>start</c>, and <c>run_erl</c> in the target <c>bin</c>
directory.</item>
Expand All @@ -185,6 +189,7 @@ lib/pea-1.0/ </code>
</section>

<section>
<marker id="start"/>
<title>Starting a Target System</title>
<p>Now we have a target system that can be started in various ways.</p>
<p>We start it as a <em>basic target system</em> by invoking</p>
Expand All @@ -193,7 +198,7 @@ os> <input>/usr/local/erl-target/bin/erl</input></pre>
<p>where only the <c>kernel</c> and <c>stdlib</c> applications are
started, i.e. the system is started as an ordinary development
system. There are only two files needed for all this to work:
<c>bin/erl</c> file (obtained from <c>erts-5.1/bin/erl.src</c>)
<c>bin/erl</c> file (obtained from <c>erts-5.10.4/bin/erl.src</c>)
and the <c>bin/start.boot</c> file (a copy of <c>plain.boot</c>).</p>
<p>We can also start a distributed system (requires <c>bin/epmd</c>).</p>
<p>To start all applications specified in the original
Expand All @@ -208,17 +213,18 @@ os> <input>/usr/local/erl-target/bin/erl -boot /usr/local/erl-target/releases/FI
<c>bin/run_erl</c>, which in turn calls <c>bin/start_erl</c>
(roughly, <c>start_erl</c> is an embedded variant of
<c>erl</c>). </p>
<p>The shell script <c>start</c> is only an example. You should
edit it to suite your needs. Typically it is executed when the
UNIX system boots.</p>
<p>The shell script <c>start</c>, which is generated from
erts-5.10.4/bin/start.src during installation, is only an
example. You should edit it to suite your needs. Typically it is
executed when the UNIX system boots.</p>
<p><c>run_erl</c> is a wrapper that provides logging of output from
the run-time system to file. It also provides a simple mechanism
for attaching to the Erlang shell (<c>to_erl</c>).</p>
<p><c>start_erl</c> requires the root directory
(<c>"/usr/local/erl-target"</c>), the releases directory
(<c>"/usr/local/erl-target/releases"</c>), and the location of
the <c>start_erl.data</c> file. It reads the run-time system
version (<c>"5.1"</c>) and release version (<c>"FIRST"</c>) from
version (<c>"5.10.4"</c>) and release version (<c>"FIRST"</c>) from
the <c>start_erl.data</c> file, starts the run-time system of the
version found, and provides <c>-boot</c> flag specifying the boot
file of the release version found
Expand Down Expand Up @@ -257,6 +263,198 @@ os> <input>/usr/local/erl-target/bin/erl -boot /usr/local/erl-target/releases/FI
dependent files.</p>
</section>

<section>
<title>Creating the Next Version</title>

<p>
In this example the <c>pea</c> application has been changed, and
so are <c>erts</c>, <c>kernel</c>, <c>stdlib</c> and
<c>sasl</c>.
</p>

<p>
<em>Step 1.</em> Create the <c>.rel</c> file:
</p>
<code type="none">
%% mysystem2.rel
{release,
{"MYSYSTEM", "SECOND"},
{erts, "6.0"},
[{kernel, "3.0"},
{stdlib, "2.0"},
{sasl, "2.4"},
{pea, "2.0"}]}.</code>
<p>
<em>Step 2.</em> Create the application upgrade file (see
<seealso marker="sasl:appup">appup(4)</seealso>) for <c>pea</c>,
for example:
</p>
<code type="none">
%% pea.appup
{"2.0",
[{"1.0",[{load_module,pea_lib}]}],
[{"1.0",[{load_module,pea_lib}]}]}.</code>
<p>
<em>Step 3.</em> From the directory where the
<c>mysystem2.rel</c> file reside, start the Erlang/OTP system:
</p>
<pre>
os> <input>erl -pa /home/user/target_system/myapps/pea-2.0/ebin</input></pre>
<p>giving the path to the new version of <c>pea</c>. </p>

<p>
<em>Step 4.</em> Create the release upgrade file (see <seealso
marker="sasl:relup">relup(4)</seealso>):
</p>
<pre>
1> <input>systools:make_relup("mysystem2",["mysystem"],["mysystem"],[{path,["/home/user/target_system/myapps/pea-1.0/ebin","/my/old/erlang/lib/*/ebin"]}]).</input></pre>
<p>
where <c>"mysystem"</c> is the base release and
<c>"mysystem2"</c> is the release to upgrade to.
</p>
<p>
Note that the <c>path</c> option is used for pointing out the
old version of all applications. (The new versions are already
in the code path - assuming of course that the erlang node on
which this is executed is running the correct version of
Erlang/OTP.)
</p>
<p>
<em>Step 5.</em> Create the new release:
</p>
<pre>
2> <input>target_system:create("mysystem2").</input></pre>
<p>
Given that the <c>relup</c> file generated in step 4 above is
now located in the current directory, it will automatically be
included in the release package.
</p>
</section>

<section>
<title>Upgrading the Target System</title>
<p>
This part is done on the target node, and for this example we
want the node to be running as an embedded system with the
<c>-heart</c> option, allowing automatic restart of the
node. See <seealso marker="#start">Starting a Target
System</seealso> above for more information.
</p>
<p>
We add <c>-heart</c> to <c>bin/start</c>:
</p>
<code type="none">
#!/bin/sh
ROOTDIR=/usr/local/erl-target/

if [ -z "$RELDIR" ]
then
RELDIR=$ROOTDIR/releases
fi

START_ERL_DATA=${1:-$RELDIR/start_erl.data}

$ROOTDIR/bin/run_erl -daemon /tmp/ $ROOTDIR/log "exec $ROOTDIR/bin/start_erl $ROOTDIR $RELDIR $START_ERL_DATA -heart</code>
<p>
And we use the simplest possible <c>sys.config</c>, which we
store in <c>releases/FIRST</c>:
</p>
<code type="none">
%% sys.config
[].</code>
<p>
Finally, in order to prepare the upgrade, we need to put the new
release package in the <c>releases</c> directory of the first
target system:
</p>
<pre>
os> <input>cp mysystem2.tar.gz /usr/local/erl-target/releases</input></pre>
<p>
And assuming that the node has been started like this:
</p>
<pre>
os> <input>/usr/local/erl-target/bin/start</input></pre>
<p>
it can be accessed like this:
</p>
<pre>
os> <input>/usr/local/erl-target/bin/to_erl /tmp/erlang.pipe.1</input></pre>
<p>
Also note that logs can be found in
<c>/usr/local/erl-target/log</c>. This directory is specified as
an argument to <c>run_erl</c>in the start script listed above.
</p>
<p>
<em>Step 1.</em> Unpack the release:
</p>
<pre>
1> <input>{ok,Vsn} = release_handler:unpack_release("mysystem2").</input></pre>
<p>
<em>Step 2.</em> Install the release:
</p>
<pre>
2> <input>release_handler:install_release(Vsn).</input>
<output>{continue_after_restart,"FIRST",[]}
heart: Tue Apr 1 12:15:10 2014: Erlang has closed.
heart: Tue Apr 1 12:15:11 2014: Executed "/usr/local/erl-target/bin/start /usr/local/erl-target/releases/new_start_erl.data" -> 0. Terminating.
[End]</output></pre>
<p>
The above return value and output after the call to
<c>release_handler:install_release/1</c> means that the
<c>release_handler</c> has restarted the node by using
<c>heart</c>. This will always be done when the upgrade involves
a change of <c>erts</c>, <c>kernel</c>, <c>stdlib</c> or
<c>sasl</c>. See <seealso marker="upgrade">Upgrade when
Erlang/OTP has Changed</seealso> for more infomation about this.
</p>
<p>
The node will be accessable via a new pipe:
</p>
<pre>
os> <input>/usr/local/erl-target/bin/to_erl /tmp/erlang.pipe.2</input></pre>
<p>
Let's see which releases we have in our system:
</p>
<pre>
1> <input>release_handler:which_releases().</input>
<output>[{"MYSYSTEM","SECOND",
["kernel-3.0","stdlib-2.0","sasl-2.4","pea-2.0"],
current},
{"MYSYSTEM","FIRST",
["kernel-2.16.4","stdlib-1.19.4","sasl-2.3.4","pea-1.0"],
permanent}]</output></pre>
<p>
Our new release, "SECOND", is now the current release, but we
can also see that our "FIRST" release is still permanent. This
means that if the node would be restarted at this point, it
would come up running the "FIRST" release again.
</p>
<p>
<em>Step 3.</em> Make the new release permanent:
</p>
<pre>
2> <input>release_handler:make_permanent("SECOND").</input></pre>

<p>
Now look at the releases again:
</p>

<pre>
3> <input>release_handler:which_releases().</input>
<output>[{"MYSYSTEM","SECOND",
["kernel-3.0","stdlib-2.0","sasl-2.4","pea-2.0"],
permanent},
{"MYSYSTEM","FIRST",
["kernel-2.16.4","stdlib-1.19.4","sasl-2.3.4","pea-1.0"],
old}]</output></pre>

<p>
Here we see that the new release version is <c>permanent</c>, so
it would be safe to restart the node.
</p>

</section>

<section>
<title>Listing of target_system.erl</title>
<p>This module can also be found in the <c>examples</c> directory
Expand Down
Loading

0 comments on commit c65821b

Please sign in to comment.