Add support for new relx directive that provides start/stop script hooks

New 'extended_start_script_hooks' directive that allows the
developer to define four different hook scripts to be invoked
at pre/post start/stop phases.
The hook scripts are invoked with the 'source' command, therefore
they have access to all the variables in the start script.

priv/templates/extended_bin

@@ -16,6 +16,12 @@ REL_DIR="$RELEASE_ROOT_DIR/releases/$REL_VSN"
 ERL_OPTS="{{ erl_opts }}"
 RUNNER_LOG_DIR="${RUNNER_LOG_DIR:-$RELEASE_ROOT_DIR/log}"
 
+# start/stop pre/post hooks
+PRE_START_HOOK="{{ pre_start_hook }}"
+POST_START_HOOK="{{ post_start_hook }}"
+PRE_STOP_HOOK="{{ pre_stop_hook }}"
+POST_STOP_HOOK="{{ post_stop_hook }}"
+
 find_erts_dir() {
     __erts_dir="$RELEASE_ROOT_DIR/erts-$ERTS_VSN"
     if [ -d "$__erts_dir" ]; then
@@ -234,11 +240,15 @@ case "$1" in
 
         mkdir -p "$PIPE_DIR"
 
+        [ "$PRE_START_HOOK" ] && . "$PRE_START_HOOK"
         "$BINDIR/run_erl" -daemon "$PIPE_DIR" "$RUNNER_LOG_DIR" \
-                          "$(relx_start_command)"
+                          "$(relx_start_command)" &
+        [ "$POST_START_HOOK" ] && . "$POST_START_HOOK"
+        wait $!
         ;;
 
     stop)
+        [ "$PRE_STOP_HOOK" ] && . "$PRE_STOP_HOOK"
         # Wait for the node to completely stop...
         PID="$(relx_get_pid)"
         if ! relx_nodetool "stop"; then
@@ -248,6 +258,7 @@ case "$1" in
         do
             sleep 1
         done
+        [ "$POST_STOP_HOOK" ] && . "$POST_STOP_HOOK"
         ;;
 
     restart)
@@ -389,8 +400,11 @@ case "$1" in
         echo "$RELEASE_ROOT_DIR"
         logger -t "$REL_NAME[$$]" "Starting up"
 
-        # Start the VM
-        exec "$@" -- ${1+$ARGS}
+        # Start the VM, invoke pre/post hooks
+        [ "$PRE_START_HOOK" ] && . "$PRE_START_HOOK"
+        exec "$@" -- ${1+$ARGS} &
+        [ "$POST_START_HOOK" ] && . "$POST_START_HOOK"
+        wait $!
         ;;
 
     foreground)
@@ -421,8 +435,11 @@ case "$1" in
         echo "Exec: $@" -- ${1+$ARGS}
         echo "Root: $ROOTDIR"
 
-        # Start the VM
-        exec "$@" -- ${1+$ARGS}
+        # Start the VM, invoke pre/post hooks
+        [ "$PRE_START_HOOK" ] && . "$PRE_START_HOOK"
+        exec "$@" -- ${1+$ARGS} &
+        [ "$POST_START_HOOK" ] && . "$POST_START_HOOK"
+        wait $!
         ;;
     rpc)
         # Make sure a node IS running

src/rlx_prv_assembler.erl

@@ -355,7 +355,10 @@ write_bin_file(State, Release, OutputDir, RelDir) ->
                             false ->
                                 ok
                         end,
-                        extended_bin_file_contents(OsFamily, RelName, RelVsn, rlx_release:erts(Release), ErlOpts)
+                        Hooks = rlx_state:get(State, extended_start_script_hooks, []),
+                        extended_bin_file_contents(OsFamily, RelName, RelVsn,
+                                                   rlx_release:erts(Release), ErlOpts,
+                                                   Hooks)
                 end,
     %% We generate the start script by default, unless the user
     %% tells us not too
@@ -613,13 +616,19 @@ bin_file_contents(OsFamily, RelName, RelVsn, ErtsVsn, ErlOpts) ->
     render(Template, [{rel_name, RelName}, {rel_vsn, RelVsn},
                       {erts_vsn, ErtsVsn}, {erl_opts, ErlOpts}]).
 
-extended_bin_file_contents(OsFamily, RelName, RelVsn, ErtsVsn, ErlOpts) ->
+extended_bin_file_contents(OsFamily, RelName, RelVsn, ErtsVsn, ErlOpts, Hooks) ->
     Template = case OsFamily of
         unix -> extended_bin;
         win32 -> extended_bin_windows
     end,
+    PreStartHook = proplists:get_value(pre_start, Hooks, ""),
+    PostStartHook = proplists:get_value(post_start, Hooks, ""),
+    PreStopHook = proplists:get_value(pre_stop, Hooks, ""),
+    PostStopHook = proplists:get_value(post_stop, Hooks, ""),
     render(Template, [{rel_name, RelName}, {rel_vsn, RelVsn},
-                      {erts_vsn, ErtsVsn}, {erl_opts, ErlOpts}]).
+                      {erts_vsn, ErtsVsn}, {erl_opts, ErlOpts},
+                      {pre_start_hook, PreStartHook}, {post_start_hook, PostStartHook},
+                      {pre_stop_hook, PreStopHook}, {post_stop_hook, PostStopHook}]).
 
 erl_ini(OutputDir, ErtsVsn) ->
     ErtsDirName = string:concat("erts-", ErtsVsn),

test/rlx_release_SUITE.erl

@@ -45,7 +45,8 @@
          make_dev_mode_release/1,
          make_config_script_release/1,
          make_release_twice/1,
-         make_release_twice_dev_mode/1]).
+         make_release_twice_dev_mode/1,
+         make_release_start_script_hooks/1]).
 
 -include_lib("common_test/include/ct.hrl").
 -include_lib("eunit/include/eunit.hrl").
@@ -1036,6 +1037,57 @@ make_release_twice_dev_mode(Config) ->
     ?assert(lists:member({goal_app_2, "0.0.1"}, AppSpecs1)),
     ?assert(lists:member({lib_dep_1, "0.0.1", load}, AppSpecs1)).
 
+make_release_start_script_hooks(Config) ->
+    LibDir1 = proplists:get_value(lib1, Config),
+
+    rlx_test_utils:create_app(LibDir1, "goal_app", "0.0.1", [stdlib,kernel], []),
+
+    ConfigFile = filename:join([LibDir1, "relx.config"]),
+    rlx_test_utils:write_config(ConfigFile,
+                 [{release, {foo, "0.0.1"},
+                   [goal_app]},
+                  {lib_dirs, [filename:join(LibDir1, "*")]},
+                  {generate_start_script, true},
+                  {extended_start_script, true},
+                  {extended_start_script_hooks, [
+                        {pre_start, "./scripts/pre_start"},
+                        {post_start, "./scripts/post_start"},
+                        {pre_stop, "./scripts/pre_stop"},
+                        {post_stop, "./scripts/post_stop"}
+                    ]},
+                  {mkdir, "scripts"},
+                  {overlay, [{copy, "./pre_start", "scripts/pre_start"},
+                             {copy, "./post_start", "scripts/post_start"},
+                             {copy, "./pre_stop", "scripts/pre_stop"},
+                             {copy, "./post_stop", "scripts/post_stop"}]}
+                 ]),
+
+    %% write the hook scripts, each of them will write an erlang term to a file
+    %% that will later be consulted
+    ok = file:write_file(filename:join([LibDir1, "./pre_start"]),
+                         "#!/bin/bash\n# $*\necho \\{pre_start, $REL_NAME, \\'$NAME\\', $COOKIE\\}. >> test"),
+    ok = file:write_file(filename:join([LibDir1, "./post_start"]),
+                         "#!/bin/bash\n# $*\necho \\{post_start, $REL_NAME, \\'$NAME\\', $COOKIE\\}. >> test"),
+    ok = file:write_file(filename:join([LibDir1, "./pre_stop"]),
+                         "#!/bin/bash\n# $*\necho \\{pre_stop, $REL_NAME, \\'$NAME\\', $COOKIE\\}. >> test"),
+    ok = file:write_file(filename:join([LibDir1, "./post_stop"]),
+                         "#!/bin/bash\n# $*\necho \\{post_stop, $REL_NAME, \\'$NAME\\', $COOKIE\\}. >> test"),
+
+    OutputDir = filename:join([proplists:get_value(priv_dir, Config),
+                               rlx_test_utils:create_random_name("relx-output")]),
+    {ok, _State} = relx:do(foo, undefined, [], [LibDir1], 3,
+                           OutputDir, ConfigFile),
+    %% now start/stop the release to make sure the script hooks are really getting
+    %% executed
+    os:cmd(filename:join([OutputDir, "foo", "bin", "foo start"])),
+    timer:sleep(2000),
+    os:cmd(filename:join([OutputDir, "foo", "bin", "foo stop"])),
+    %% now check that the output file contains the expected format
+    {ok,[{pre_start, foo, _, foo},
+         {post_start, foo, _, foo},
+         {pre_stop, foo, _, foo},
+         {post_stop, foo, _, foo}]} = file:consult(filename:join([OutputDir, "foo", "test"])).
+
 %%%===================================================================
 %%% Helper Functions
 %%%===================================================================