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Update CONSISTENCY.md

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Philip O'Toole 4 years ago committed by GitHub
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@ -13,7 +13,7 @@ With _none_, the node simply queries its local SQLite database, and does not eve
### Limiting read staleness ### Limiting read staleness
You can tell the node not return results (effectively) older than a certain time, however. If a read request sets the query parameter `freshness` to a [Go duration string](https://golang.org/pkg/time/#Duration), the node serving the read will check that less time has passed since it was last in contact with the leader, than that specified via freshness. If more time has passed the node will return an error. `freshness` is ignored for all consistency levels except `none`, and is also ignored if set to zero. You can tell the node not return results (effectively) older than a certain time, however. If a read request sets the query parameter `freshness` to a [Go duration string](https://golang.org/pkg/time/#Duration), the node serving the read will check that less time has passed since it was last in contact with the leader, than that specified via freshness. If more time has passed the node will return an error. `freshness` is ignored for all consistency levels except `none`, and is also ignored if set to zero.
If you decide to deploy [read-only nodes](https://github.com/rqlite/rqlite/blob/master/DOC/READ_ONLY_NODES.md) however, _none_ combined with `freshness` can be quite effective at adding read scalability to your system. If you decide to deploy [read-only nodes](https://github.com/rqlite/rqlite/blob/master/DOC/READ_ONLY_NODES.md) however, _none_ combined with `freshness` can be a particularly effective at adding read scalability to your system. You can use lots of read-only nodes, yet be sure that a given node serving a request has not fallen too far behind the leader (or even become disconnected from the cluster).
## Weak ## Weak
_Weak_ instructs the node to check that it is the leader, before querying the local SQLite file. Checking leader state only involves checking local state, so is still very fast. There is, however, a very small window of time (milliseconds by default) during which the node may return stale data. This is because after the leader check, but before the local SQLite database is read, another node could be elected leader and make changes to the cluster. As result the node may not be quite up-to-date with the rest of cluster. _Weak_ instructs the node to check that it is the leader, before querying the local SQLite file. Checking leader state only involves checking local state, so is still very fast. There is, however, a very small window of time (milliseconds by default) during which the node may return stale data. This is because after the leader check, but before the local SQLite database is read, another node could be elected leader and make changes to the cluster. As result the node may not be quite up-to-date with the rest of cluster.

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