Function caller was incorrect when called from Parallel block

Current instruction is tracked as a value in yaql context.
But in Parallel block individual instructions executed in separate
threads. As a result when those threads get scheduled current
instruction in caller context already changes to the last one
(which is a synchronization point for the Parallel block).

To solve this all spawned threads need to work in their own
dedicated child contexts. Then each of those contexts will have
its own "current instruction". However this also brings a side effect:
all local variable modifications made by spawned threads will
be go to those new contexts and will be lost upon exit from Parallel.
To solve this context that local variable need to be in is marked with
special flag. When executing "$var: value" expressions DSL will scan
context chain up to the context with that flag. Currently the only
context with the flag is a method context that defines local variable scope.

Change-Id: I0647915c104dfe4e00dd86c17726245d1bbc3beb
Closes-Bug: #1497772

murano/dsl/constants.py

@@ -31,6 +31,7 @@ CTX_PACKAGE_LOADER = '$?packageLoader'
 CTX_SKIP_FRAME = '$?skipFrame'
 CTX_THIS = '$?this'
 CTX_TYPE = '$?type'
+CTX_VARIABLE_SCOPE = '$?variableScope'
 CTX_YAQL_ENGINE = '$?yaqlEngine'
 
 DM_OBJECTS = 'Objects'

murano/dsl/lhs_expression.py

@@ -15,14 +15,13 @@
 import itertools
 import types
 
-from yaql.language import expressions
 from yaql.language import specs
 from yaql.language import utils
 from yaql.language import yaqltypes
 
+from murano.dsl import constants
 from murano.dsl import dsl_types
 from murano.dsl import exceptions
-from murano.dsl import yaql_expression
 from murano.dsl import yaql_integration
 
 
@@ -39,24 +38,22 @@ class LhsExpression(object):
             self._setter(value)
 
     def __init__(self, expression):
-        if isinstance(expression, (yaql_expression.YaqlExpression,
-                                   expressions.Statement)):
-            self._expression = expression
-        else:
-            self._expression = yaql_integration.parse(str(expression))
+        self._expression = expression
 
     def _create_context(self, root_context):
-        @specs.parameter('path', yaqltypes.Lambda(with_context=True))
-        def get_context_data(path):
-            path = path(root_context)
+        @specs.parameter('name', yaqltypes.StringConstant())
+        def get_context_data(name):
 
             def set_data(value):
-                if not path or path == '$' or path == '$this':
-                    raise ValueError()
-                root_context[path] = value
+                if not name or name == '$' or name == '$this':
+                    raise ValueError('Cannot assign to {0}'.format(name))
+                ctx = root_context
+                while constants.CTX_VARIABLE_SCOPE not in ctx:
+                    ctx = ctx.parent
+                ctx[name] = value
 
             return LhsExpression.Property(
-                lambda: root_context[path], set_data)
+                lambda: root_context[name], set_data)
 
         @specs.parameter('this', LhsExpression.Property)
         @specs.parameter('key', yaqltypes.Keyword())

murano/dsl/macros.py

@@ -51,6 +51,7 @@ class MethodBlock(CodeBlock):
 
     def execute(self, context):
         new_context = context.create_child_context()
+        new_context[constants.CTX_VARIABLE_SCOPE] = True
         try:
             super(MethodBlock, self).execute(new_context)
         except exceptions.ReturnException as e:
@@ -102,7 +103,9 @@ class ParallelMacro(CodeBlock):
             return
         limit = helpers.evaluate(self._limit, context)
         helpers.parallel_select(
-            self.code_block, lambda expr: expr.execute(context), limit)
+            self.code_block,
+            lambda expr: expr.execute(context.create_child_context()),
+            limit)
 
 
 class IfMacro(expressions.DslExpression):