docs/clarify propeller scaling (#4741)

Signed-off-by: Yee Hing Tong <[email protected]>

docs/deployment/configuration/performance.rst

@@ -189,15 +189,15 @@ Manual scale-out
 ----------------
 FlytePropeller can be run manually per namespace. This is not a recommended solution as it is harder to deploy, but if your organization can deploy and maintain multiple copies of FlytePropeller, you can use this.
 
-Automatic scale-out
+Sharded scale-out
 -------------------
 FlytePropeller Manager is a new component introduced as part of `this RFC <https://github.com/flyteorg/flyte/blob/master/rfc/system/1483-flytepropeller-horizontal-scaling.md>`_ to facilitate horizontal scaling of FlytePropeller through sharding. Effectively, the Manager is responsible for maintaining liveness and proper configuration over a collection of FlytePropeller instances. This scheme uses k8s label selectors to deterministically assign FlyteWorkflow CRD responsibilities to FlytePropeller instances, effectively distributing processing load over the shards.
 
 Deployment of FlytePropeller Manager requires k8s configuration updates including a modified FlytePropeller Deployment and a new PodTemplate defining managed FlytePropeller instances. The easiest way to apply these updates is by setting the "flytepropeller.manager" value to "true" in the `helm deployment <https://docs.flyte.org/en/latest/deployment/overview.html#usage-of-helm>`_ and setting the manager config at "configmap.core.manager".
 
 Flyte provides a variety of Shard Strategies to configure how FlyteWorkflows are sharded among managed FlytePropeller instances. These include hash, which uses consistent hashing to load-balance evaluation over shards, and project / domain, which map the respective IDs to specific managed FlytePropeller instances. Below we include examples of helm configurations for each of the existing Shard Strategies.
 
-The Hash Shard Strategy, denoted by "type: hash" in the configuration below, uses consistent hashing to evenly distribute FlyteWorkflows over managed FlytePropeller instances. This configuration requires a "shard-count" variable which defines the number of managed FlytePropeller instances.
+The Hash Shard Strategy, denoted by "type: Hash" in the configuration below, uses consistent hashing to evenly distribute FlyteWorkflows over managed FlytePropeller instances. This configuration requires a "shard-count" variable which defines the number of managed FlytePropeller instances. You may change the shard count without impacting existing workflows. Note that changing the shard-count is a manual step, it is not auto-scaling.
 
 .. code-block:: yaml
 
@@ -208,7 +208,7 @@ The Hash Shard Strategy, denoted by "type: hash" in the configuration below, use
           # pod and scanning configuration redacted
           # ...
           shard:
-            type: hash     # use the "hash" shard strategy
+            type: Hash     # use the "hash" shard strategy
             shard-count: 4 # the total number of shards
  
 The Project and Domain Shard Strategies, denoted by "type: project" and "type: domain" respectively, use the FlyteWorkflow project and domain metadata to shard FlyteWorkflows. These Shard Strategies are configured using a "per-shard-mapping" option, which is a list of ID lists. Each element in the "per-shard-mapping" list defines a new shard and the ID list assigns responsibility for the specified IDs to that shard. A shard configured as a single wildcard ID (i.e. "*") is responsible for all IDs that are not covered by other shards. Only a single shard may be configured with a wildcard ID and on that shard their must be only one ID, namely the wildcard.