techdocsmith commented on a change in pull request #11584:
URL: https://github.com/apache/druid/pull/11584#discussion_r832742802
##########
File path: docs/design/historical.md
##########
@@ -39,17 +39,31 @@ org.apache.druid.cli.Main server historical
### Loading and serving segments
-Each Historical process maintains a constant connection to Zookeeper and
watches a configurable set of Zookeeper paths for new segment information.
Historical processes do not communicate directly with each other or with the
Coordinator processes but instead rely on Zookeeper for coordination.
+Each Historical process copies or "pulls" segment files from Deep Storage to
local disk in an area called the *segment cache*. Set the
`druid.segmentCache.locations` to configure the size and location of the
segment cache on each Historical process. See [Historical general
configuration](../configuration/index.html#historical-general-configuration).
-The [Coordinator](../design/coordinator.md) process is responsible for
assigning new segments to Historical processes. Assignment is done by creating
an ephemeral Zookeeper entry under a load queue path associated with a
Historical process. For more information on how the Coordinator assigns
segments to Historical processes, please see
[Coordinator](../design/coordinator.md).
+See the [Tuning
Guide](../operations/basic-cluster-tuning.html#segment-cache-size) for more
information.
-When a Historical process notices a new load queue entry in its load queue
path, it will first check a local disk directory (cache) for the information
about segment. If no information about the segment exists in the cache, the
Historical process will download metadata about the new segment to serve from
Zookeeper. This metadata includes specifications about where the segment is
located in deep storage and about how to decompress and process the segment.
For more information about segment metadata and Druid segments in general,
please see [Segments](../design/segments.md). Once a Historical process
completes processing a segment, the segment is announced in Zookeeper under a
served segments path associated with the process. At this point, the segment is
available for querying.
+The [Coordinator](../design/coordinator.html) controls the assignment of
segments to Historicals and the balance of segments between Historicals.
Historical processes do not communicate directly with each other, nor do they
communicate directly with the Coordinator. Instead, the Coordinator creates
ephemeral entries in Zookeeper in a [load queue
path](../configuration/index.html#path-configuration). Each Historical process
maintains a connection to Zookeeper, watching those paths for segment
information.
+
+For more information about how the Coordinator assigns segments to Historical
processes, please see [Coordinator](../design/coordinator.html).
Review comment:
```suggestion
For more information about how the Coordinator assigns segments to
Historical processes, see [Coordinator](../design/coordinator.html).
```
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
