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+Modules gating using Greenwave
+==============================
+
+Every successfully built module is moved to ``done`` state. Modules in this state cannot
+be used as a build-dependency for other modules. They need to be moved to ``ready`` state.
+
+By default, MBS moves the module from ``done`` state to ``ready`` state automatically,
+but MBS can also be configured to gate move from ``done`` to ``ready`` state according
+to Greenwave service.
+
+When Greenwave integration is configured, then following additional MBS features are enabled:
+
+- When the module is moved to ``done`` state, Greenwave is queried to find out whether to module
+  can be moved to ``ready`` state instantly.
+- If the module cannot be moved to ``ready`` state yet, MBS keeps the module build in the
+  ``done`` state and waits for a message from Greenwave. If this message says that all the
+  tests defined by Greenwave policy have passed, then the module build is moved to ``ready``
+  state.
+- MBS also queries Greenwave periodically to find out the current gating status for modules
+  in the ``done`` state. This is useful in case when message from Greenwave has been lost.