[config] Implements "Exclusive" context processor allowing to ask for an exclusive usage of a service while in a transformation.

bonobo/_api.py

@@ -1,5 +1,3 @@
-import warnings
-
 from bonobo.structs import Bag, Graph, Token
 from bonobo.nodes import CsvReader, CsvWriter, FileReader, FileWriter, Filter, JsonReader, JsonWriter, Limit, \
     PrettyPrint, Tee, count, identity, noop, pprint

bonobo/config/__init__.py

@@ -1,13 +1,15 @@
 from bonobo.config.configurables import Configurable
 from bonobo.config.options import Option, Method
 from bonobo.config.processors import ContextProcessor
-from bonobo.config.services import Container, Service
+from bonobo.config.services import Container, Service, Exclusive
 
+# bonobo.config public programming interface
 __all__ = [
     'Configurable',
     'Container',
     'ContextProcessor',
-    'Option',
+    'Exclusive',
     'Method',
+    'Option',
     'Service',
 ]

bonobo/config/services.py

@@ -1,5 +1,7 @@
 import re
+import threading
 import types
+from contextlib import ContextDecorator
 
 from bonobo.config.options import Option
 from bonobo.errors import MissingServiceImplementationError
@@ -87,3 +89,40 @@ class Container(dict):
         if isinstance(value, types.LambdaType):
             value = value(self)
         return value
+
+
+class Exclusive(ContextDecorator):
+    """
+    Decorator and context manager used to require exclusive usage of an object, most probably a service. It's usefull
+    for example if call order matters on a service implementation (think of an http api that requires a nonce or version
+    parameter ...).
+
+    Usage:
+
+        >>> def handler(some_service):
+        ...     with Exclusive(some_service):
+        ...         some_service.call_1()
+        ...         some_service.call_2()
+        ...         some_service.call_3()
+
+    This will ensure that nobody else is using the same service while in the "with" block, using a lock primitive to
+    ensure that.
+
+    """
+    _locks = {}
+
+    def __init__(self, wrapped):
+        self._wrapped = wrapped
+
+    def get_lock(self):
+        _id = id(self._wrapped)
+        if not _id in Exclusive._locks:
+            Exclusive._locks[_id] = threading.RLock()
+        return Exclusive._locks[_id]
+
+    def __enter__(self):
+        self.get_lock().acquire()
+        return self._wrapped
+
+    def __exit__(self, *exc):
+        self.get_lock().release()

tests/config/test_configurables.py

@@ -2,7 +2,6 @@ import pytest
 
 from bonobo.config.configurables import Configurable
 from bonobo.config.options import Option
-from bonobo.config.services import Container, Service, validate_service_name
 
 
 class MyConfigurable(Configurable):
@@ -25,28 +24,6 @@ class MyConfigurableUsingPositionalOptions(MyConfigurable):
     third = Option(str, required=False, positional=True)
 
 
-class PrinterInterface():
-    def print(self, *args):
-        raise NotImplementedError()
-
-
-class ConcretePrinter(PrinterInterface):
-    def __init__(self, prefix):
-        self.prefix = prefix
-
-    def print(self, *args):
-        return ';'.join((self.prefix, *args))
-
-
-class MyServiceDependantConfigurable(Configurable):
-    printer = Service(
-        PrinterInterface,
-    )
-
-    def __call__(self, printer: PrinterInterface, *args):
-        return printer.print(*args)
-
-
 def test_missing_required_option_error():
     with pytest.raises(TypeError) as exc:
         MyConfigurable()
@@ -107,39 +84,5 @@ def test_option_resolution_order():
     assert o.integer == None
 
 
-def test_service_name_validator():
-    assert validate_service_name('foo') == 'foo'
-    assert validate_service_name('foo.bar') == 'foo.bar'
-    assert validate_service_name('Foo') == 'Foo'
-    assert validate_service_name('Foo.Bar') == 'Foo.Bar'
-    assert validate_service_name('Foo.a0') == 'Foo.a0'
-
-    with pytest.raises(ValueError):
-        validate_service_name('foo.0')
-
-    with pytest.raises(ValueError):
-        validate_service_name('0.foo')
-
-
-SERVICES = Container(
-    printer0=ConcretePrinter(prefix='0'),
-    printer1=ConcretePrinter(prefix='1'),
-)
-
-
-def test_service_dependency():
-    o = MyServiceDependantConfigurable(printer='printer0')
-
-    assert o(SERVICES.get('printer0'), 'foo', 'bar') == '0;foo;bar'
-    assert o(SERVICES.get('printer1'), 'bar', 'baz') == '1;bar;baz'
-    assert o(*SERVICES.args_for(o), 'foo', 'bar') == '0;foo;bar'
-
-
-def test_service_dependency_unavailable():
-    o = MyServiceDependantConfigurable(printer='printer2')
-    with pytest.raises(KeyError):
-        SERVICES.args_for(o)
-
-
 def test_option_positional():
     o = MyConfigurableUsingPositionalOptions('1', '2', '3', required_str='hello')

tests/config/test_services.py

@@ -0,0 +1,96 @@
+import threading
+import time
+
+import pytest
+
+from bonobo.config import Configurable, Container, Exclusive, Service
+from bonobo.config.services import validate_service_name
+
+
+class PrinterInterface():
+    def print(self, *args):
+        raise NotImplementedError()
+
+
+class ConcretePrinter(PrinterInterface):
+    def __init__(self, prefix):
+        self.prefix = prefix
+
+    def print(self, *args):
+        return ';'.join((self.prefix, *args))
+
+
+SERVICES = Container(
+    printer0=ConcretePrinter(prefix='0'),
+    printer1=ConcretePrinter(prefix='1'),
+)
+
+
+class MyServiceDependantConfigurable(Configurable):
+    printer = Service(
+        PrinterInterface,
+    )
+
+    def __call__(self, printer: PrinterInterface, *args):
+        return printer.print(*args)
+
+
+def test_service_name_validator():
+    assert validate_service_name('foo') == 'foo'
+    assert validate_service_name('foo.bar') == 'foo.bar'
+    assert validate_service_name('Foo') == 'Foo'
+    assert validate_service_name('Foo.Bar') == 'Foo.Bar'
+    assert validate_service_name('Foo.a0') == 'Foo.a0'
+
+    with pytest.raises(ValueError):
+        validate_service_name('foo.0')
+
+    with pytest.raises(ValueError):
+        validate_service_name('0.foo')
+
+
+def test_service_dependency():
+    o = MyServiceDependantConfigurable(printer='printer0')
+
+    assert o(SERVICES.get('printer0'), 'foo', 'bar') == '0;foo;bar'
+    assert o(SERVICES.get('printer1'), 'bar', 'baz') == '1;bar;baz'
+    assert o(*SERVICES.args_for(o), 'foo', 'bar') == '0;foo;bar'
+
+
+def test_service_dependency_unavailable():
+    o = MyServiceDependantConfigurable(printer='printer2')
+    with pytest.raises(KeyError):
+        SERVICES.args_for(o)
+
+
+class VCR:
+    def __init__(self):
+        self.tape = []
+
+    def append(self, x):
+        return self.tape.append(x)
+
+
+def test_exclusive():
+    vcr = VCR()
+    vcr.append('hello')
+
+    def record(prefix, vcr=vcr):
+        with Exclusive(vcr):
+            for i in range(5):
+                vcr.append(' '.join((prefix, str(i))))
+                time.sleep(0.05)
+
+    threads = [threading.Thread(target=record, args=(str(i), )) for i in range(5)]
+
+    for thread in threads:
+        thread.start()
+        time.sleep(0.01)  # this is not good practice, how to test this without sleeping ?? XXX
+
+    for thread in threads:
+        thread.join()
+
+    assert vcr.tape == [
+        'hello', '0 0', '0 1', '0 2', '0 3', '0 4', '1 0', '1 1', '1 2', '1 3', '1 4', '2 0', '2 1', '2 2', '2 3',
+        '2 4', '3 0', '3 1', '3 2', '3 3', '3 4', '4 0', '4 1', '4 2', '4 3', '4 4'
+    ]