wrapper recipe: add hash-existing-files option

hash-existing-files list all the files used for hash that are not
handled by buildout. For those files, the hash is calculated as soon as
the __init__ function so that if there is a change in those files,
buildout will remove the existing wrapper (it will uninstall the
section) and replace it with the new wrapper.

slapos/recipe/wrapper.py

@@ -25,27 +25,54 @@
 #
 ##############################################################################
 
-import shlex
-
+import os, shlex
+from six.moves import filter
 from slapos.recipe.librecipe import GenericBaseRecipe, generateHashFromFiles
+from zc.buildout import UserError
 
 class Recipe(GenericBaseRecipe):
     """Recipe to create a script from given command and options.
 
     :param str command-line: shell command which launches the intended process
     :param str wrapper-path: absolute path to file's destination
-
     :param lines wait-for-files: list of files to wait for
-    :param lines hash-files: list of files to be checked by hash
+    :param lines hash-files: list of buildout-generated files to be checked by hash
+    :param lines hash-existing-files: list of existing files to be checked by hash
     :param str pidfile: path to pidfile ensure exclusivity for the process
     :param str private-dev-shm: size of private /dev/shm, using user namespaces
     :param bool reserve-cpu: command will ask for an exclusive CPU core
     """
+
+    _existing = ()
+
+    def __init__(self, buildout, name, options):
+        self.buildout = buildout
+        self.options = options
+        hash_files = options.get('hash-files')
+        if hash_files:
+          self.hash_files = hash_files.split()
+          self._existing = list(filter(os.path.exists, self.hash_files))
+        else:
+          self.hash_files = []
+        hash_files = options.get('hash-existing-files')
+        if hash_files:
+          hash_files = hash_files.split()
+          options['__hash_files__'] = generateHashFromFiles(hash_files)
+          self.hash_files += hash_files
+
+    def getWrapperPath(self):
+        wrapper_path = self.options['wrapper-path']
+        if self.hash_files:
+          wrapper_path += '-' + generateHashFromFiles(self.hash_files)
+        return wrapper_path
+
     def install(self):
+        if self._existing:
+          raise UserError(
+            "hash-files must only list files that are generated by buildout:"
+            "\n  " + "\n  ".join(self._existing))
         args = shlex.split(self.options['command-line'])
-        wrapper_path = self.options['wrapper-path']
         wait_files = self.options.get('wait-for-files')
-        hash_files = self.options.get('hash-files')
         pidfile = self.options.get('pidfile')
         private_dev_shm = self.options.get('private-dev-shm')
 
@@ -65,10 +92,10 @@ class Recipe(GenericBaseRecipe):
           kw['private_dev_shm'] = private_dev_shm
         if self.isTrueValue(self.options.get('reserve-cpu')):
           kw['reserve_cpu'] = True
-        if hash_files:
-          hash_file_list = hash_files.split()
-          hash = generateHashFromFiles(hash_file_list)
-          wrapper_path = "%s-%s" % (wrapper_path, hash)
-
-        return self.createWrapper(wrapper_path, args, environment, **kw)
+        return self.createWrapper(self.getWrapperPath(),
+                                  args, environment, **kw)
 
+    def update(self):
+        wrapper_path = self.getWrapperPath()
+        if not os.path.isfile(wrapper_path):
+          raise UserError("unstable wrapper path (%r)" % wrapper_path)