Controlling Opaque-Component Effects with Semisolates and Try

Many developers and systems today rely on opaque software components. When executing, these components affect each other and the broader environment in which they execute. Some of these effects are expected and desired; others not so. This paper introduces semisolates, an abstraction and corresponding subsystem for controlling and manipulating the effects of opaque components. Available as an unprivileged, higher-order, language-agnostic command, try interposes on a component’s execution to automatically capture and control its effects. Effect control includes introspection, optional application, effect stacking, and further manipulation—all driven by several real-world case studies. Today try is used in research and production applications across several organizations, mediating potentially undesired effects, maintaining full compatibility with real-world components, and incurring a modest performance overhead well within each case’s acceptable levels.