PYTHON-2554 Support $merge and $out executing on secondaries #774
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ShaneHarvey
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| selection = Selection.from_topology_description(self) | ||
| # Ignore read preference for sharded clusters. | ||
| if self.topology_type != TOPOLOGY_TYPE.Sharded: | ||
| selection = selector(selection) |
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This bit is just a small cleanup with no functional change.
| @@ -263,21 +263,24 @@ def apply_selector(self, selector, address=None, custom_selector=None): | |||
| selector.min_wire_version, | |||
| common_wv)) | |||
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| if isinstance(selector, _AggWritePref): | |||
| selector.selection_hook(self) | |||
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Initially I was expecting to place the "selection_hook" logic inside _AggWritePref.__call__ but it turns out that we skip calling the selector in many cases. In fact the only time we actually do call the selector is for replica sets. I attempted to refactor this code to actually call the selector in all cases but that doesn't work either because read preference selectors are written to only work with replica sets.
So "selection_hook" is what I came up with instead.
| @@ -1161,7 +1161,7 @@ def _secondaryok_for_server(self, read_preference, server, session): | |||
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| with self._get_socket(server, session) as sock_info: | |||
| secondary_ok = (single and not sock_info.is_mongos) or ( | |||
| read_preference != ReadPreference.PRIMARY) | |||
| read_preference.mode != ReadPreference.PRIMARY.mode) | |||
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This change is required because read_preference might be a _AggWritePref.
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I'll wait for @juliusgeo to review as well. |
Implementation of https://github.com/mongodb/specifications/blob/master/source/crud/crud.rst#read-preferences-and-server-selection including the changes in DRIVERS-823 and DRIVERS-1969.