Version 1, a dummy app with a single gen_server, and rebar config for…

… generating a release

.gitignore

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+ebin
+*.beam
+*~

Makefile

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+all:
+	(./rebar compile)

README

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+Dummy app for testing release upgrade/downgrade/packaging process with rebar.
+
+
+See blog post, linked as homepage from github repo.

apps/dummy_app/src/dummy_app.app.src

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+{application, dummy_app,
+ [
+  {description, "Dummy project to test release process"},
+  {vsn, "1"},
+  {registered, []},
+  {applications, [
+                  kernel,
+                  stdlib
+                 ]},
+  {mod, { dummy_app, []}},
+  {env, []}
+ ]}.

apps/dummy_app/src/dummy_app.erl

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+-module(dummy_app).
+
+-behaviour(application).
+
+%% Application callbacks
+-export([start/0, start/2, stop/1]).
+
+start() -> application:start(dummy_app).
+
+%% ===================================================================
+%% Application callbacks
+%% ===================================================================
+
+start(_StartType, _StartArgs) ->
+    error_logger:info_msg("Starting dummy_app application...~n"),
+    dummy_app_sup:start_link().
+
+stop(_State) ->
+    ok.

apps/dummy_app/src/dummy_app_server.erl

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+-module(dummy_app_server).
+
+-behaviour(gen_server).
+
+%% API
+-export([start_link/0, poke/0, num_pokes/0]).
+
+%% gen_server callbacks
+-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
+     terminate/2, code_change/3]).
+
+-record(state, {num_pokes = 0}).
+
+%% API
+start_link() ->
+    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
+
+poke() ->
+    gen_server:call(?MODULE, poke).
+
+num_pokes() ->
+    gen_server:call(?MODULE, num_pokes).
+
+
+%% gen_server callbacks
+init([]) ->
+    {ok, #state{}}.
+
+handle_call(num_pokes, _From, State = #state{ num_pokes = PokeCount }) ->
+    {reply, PokeCount, State};
+
+handle_call(poke, _From, State) ->
+    NewPokeCount = State#state.num_pokes + 1,
+    NewState     = State#state{num_pokes = NewPokeCount},
+    Reply        = {ok, NewPokeCount},
+    {reply, Reply, NewState}.
+
+handle_cast(_Msg, State) ->
+    {noreply, State}.
+
+handle_info(_Info, State) ->
+    {noreply, State}.
+
+terminate(_Reason, _State) ->
+    ok.
+
+code_change(_OldVsn, State, _Extra) ->
+    {ok, State}.
+
+%%% Internal functions

apps/dummy_app/src/dummy_app_sup.erl

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+-module(dummy_app_sup).
+
+-behaviour(supervisor).
+
+%% API
+-export([start_link/0]).
+
+%% Supervisor callbacks
+-export([init/1]).
+
+%% Helper macro for declaring children of supervisor
+-define(CHILD(I, Type), {I, {I, start_link, []}, permanent, 5000, Type, [I]}).
+
+%% ===================================================================
+%% API functions
+%% ===================================================================
+
+start_link() ->
+    supervisor:start_link({local, ?MODULE}, ?MODULE, []).
+
+%% ===================================================================
+%% Supervisor callbacks
+%% ===================================================================
+
+init([]) ->
+    Children = [
+                ?CHILD(dummy_app_server, worker) 
+               ],
+    {ok, { {one_for_one, 5, 10}, Children} }.
+

rebar.config

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+{sub_dirs, [
+            "apps/dummy_app",
+            "rel"
+           ]}.
+
+{erl_opts, [
+            debug_info, 
+            fail_on_warning
+           ]}.
+
+{require_otp_vsn, "R14"}.
+

rel/files/app.config

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+[
+ %% SASL config
+ {sasl, [
+         {sasl_error_logger, {file, "log/sasl-error.log"}},
+         {errlog_type, error},
+         {error_logger_mf_dir, "log/sasl"},      % Log directory
+         {error_logger_mf_maxbytes, 10485760},   % 10 MB max file size
+         {error_logger_mf_maxfiles, 5}           % 5 files max
+         ]}
+].
+

rel/files/dummy

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+#!/bin/bash
+# -*- tab-width:4;indent-tabs-mode:nil -*-
+# ex: ts=4 sw=4 et
+
+RUNNER_SCRIPT_DIR=$(cd ${0%/*} && pwd)
+
+RUNNER_BASE_DIR=${RUNNER_SCRIPT_DIR%/*}
+RUNNER_ETC_DIR=$RUNNER_BASE_DIR/etc
+RUNNER_LOG_DIR=$RUNNER_BASE_DIR/log
+# Note the trailing slash on $PIPE_DIR/
+PIPE_DIR=/tmp/$RUNNER_BASE_DIR/
+RUNNER_USER=
+
+# Make sure this script is running as the appropriate user
+if [ ! -z "$RUNNER_USER" ] && [ `whoami` != "$RUNNER_USER" ]; then
+    exec sudo -u $RUNNER_USER -i $0 $@
+fi
+
+# Make sure CWD is set to runner base dir
+cd $RUNNER_BASE_DIR
+
+# Make sure log directory exists
+mkdir -p $RUNNER_LOG_DIR
+
+# Extract the target node name from node.args
+NAME_ARG=`grep -e '-[s]*name' $RUNNER_ETC_DIR/vm.args`
+if [ -z "$NAME_ARG" ]; then
+    echo "vm.args needs to have either -name or -sname parameter."
+    exit 1
+fi
+
+# Extract the target cookie
+COOKIE_ARG=`grep -e '-setcookie' $RUNNER_ETC_DIR/vm.args`
+if [ -z "$COOKIE_ARG" ]; then
+    echo "vm.args needs to have a -setcookie parameter."
+    exit 1
+fi
+
+# Identify the script name
+SCRIPT=`basename $0`
+
+# Parse out release and erts info
+START_ERL=`cat $RUNNER_BASE_DIR/releases/start_erl.data`
+ERTS_VSN=${START_ERL% *}
+APP_VSN=${START_ERL#* }
+
+# Add ERTS bin dir to our path
+ERTS_PATH=$RUNNER_BASE_DIR/erts-$ERTS_VSN/bin
+
+# Setup command to control the node
+NODETOOL="$ERTS_PATH/escript $ERTS_PATH/nodetool $NAME_ARG $COOKIE_ARG"
+
+# Check the first argument for instructions
+case "$1" in
+    start)
+        # Make sure there is not already a node running
+        RES=`$NODETOOL ping`
+        if [ "$RES" = "pong" ]; then
+            echo "Node is already running!"
+            exit 1
+        fi
+        HEART_COMMAND="$RUNNER_BASE_DIR/bin/$SCRIPT start"
+        export HEART_COMMAND
+        mkdir -p $PIPE_DIR
+        shift # remove $1
+        $ERTS_PATH/run_erl -daemon $PIPE_DIR $RUNNER_LOG_DIR "exec $RUNNER_BASE_DIR/bin/$SCRIPT console $@" 2>&1
+        ;;
+
+    stop)
+        # Wait for the node to completely stop...
+        case `uname -s` in
+            Linux|Darwin|FreeBSD|DragonFly|NetBSD|OpenBSD)
+                # PID COMMAND
+                PID=`ps ax -o pid= -o command=|\
+                    grep "$RUNNER_BASE_DIR/.*/[b]eam"|awk '{print $1}'`
+                ;;
+            SunOS)
+                # PID COMMAND
+                PID=`ps -ef -o pid= -o args=|\
+                    grep "$RUNNER_BASE_DIR/.*/[b]eam"|awk '{print $1}'`
+                ;;
+            CYGWIN*)
+                # UID PID PPID TTY STIME COMMAND
+                PID=`ps -efW|grep "$RUNNER_BASE_DIR/.*/[b]eam"|awk '{print $2}'`
+                ;;
+        esac
+        $NODETOOL stop
+        while `kill -0 $PID 2>/dev/null`;
+        do
+            sleep 1
+        done
+        ;;
+
+    restart)
+        ## Restart the VM without exiting the process
+        $NODETOOL restart
+        ;;
+
+    reboot)
+        ## Restart the VM completely (uses heart to restart it)
+        $NODETOOL reboot
+        ;;
+
+    ping)
+        ## See if the VM is alive
+        $NODETOOL ping
+        ;;
+
+    attach)
+        # Make sure a node IS running
+        RES=`$NODETOOL ping`
+        if [ "$RES" != "pong" ]; then
+            echo "Node is not running!"
+            exit 1
+        fi
+
+        shift
+        $ERTS_PATH/to_erl $PIPE_DIR
+        ;;
+
+    console|console_clean)
+        # .boot file typically just $SCRIPT (ie, the app name)
+        # however, for debugging, sometimes start_clean.boot is useful:
+        case "$1" in
+            console)        BOOTFILE=$SCRIPT ;;
+            console_clean)  BOOTFILE=start_clean ;;
+        esac
+        # Setup beam-required vars
+        ROOTDIR=$RUNNER_BASE_DIR
+        BINDIR=$ROOTDIR/erts-$ERTS_VSN/bin
+        EMU=beam
+        PROGNAME=`echo $0 | sed 's/.*\\///'`
+        CMD="$BINDIR/erlexec -boot $RUNNER_BASE_DIR/releases/$APP_VSN/$BOOTFILE -embedded -config $RUNNER_ETC_DIR/app.config -args_file $RUNNER_ETC_DIR/vm.args -- ${1+"$@"}"
+        export EMU
+        export ROOTDIR
+        export BINDIR
+        export PROGNAME
+
+        # Dump environment info for logging purposes
+        echo "Exec: $CMD"
+        echo "Root: $ROOTDIR"
+
+        # Log the startup
+        logger -t "$SCRIPT[$$]" "Starting up"
+
+        # Start the VM
+        exec $CMD
+        ;;
+
+    *)
+        echo "Usage: $SCRIPT {start|stop|restart|reboot|ping|console|console_clean|attach}"
+        exit 1
+        ;;
+esac
+
+exit 0

rel/files/erl

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+#!/bin/bash
+
+## This script replaces the default "erl" in erts-VSN/bin. This is necessary
+## as escript depends on erl and in turn, erl depends on having access to a
+## bootscript (start.boot). Note that this script is ONLY invoked as a side-effect
+## of running escript -- the embedded node bypasses erl and uses erlexec directly
+## (as it should). 
+##
+## Note that this script makes the assumption that there is a start_clean.boot
+## file available in $ROOTDIR/release/VSN.
+
+# Determine the abspath of where this script is executing from.
+ERTS_BIN_DIR=$(cd ${0%/*} && pwd)
+
+# Now determine the root directory -- this script runs from erts-VSN/bin,
+# so we simply need to strip off two dirs from the end of the ERTS_BIN_DIR
+# path.
+ROOTDIR=${ERTS_BIN_DIR%/*/*}
+
+# Parse out release and erts info
+START_ERL=`cat $ROOTDIR/releases/start_erl.data`
+ERTS_VSN=${START_ERL% *}
+APP_VSN=${START_ERL#* }
+
+BINDIR=$ROOTDIR/erts-$ERTS_VSN/bin
+EMU=beam
+PROGNAME=`echo $0 | sed 's/.*\\///'`
+CMD="$BINDIR/erlexec"
+export EMU
+export ROOTDIR
+export BINDIR
+export PROGNAME
+
+exec $CMD -boot $ROOTDIR/releases/$APP_VSN/start_clean ${1+"$@"}