1. When `GenerateSecret` is called, the `SecretManager` is expected to return a new certificate. This can occur in a few ways.
   1. The most common method (pictured above) is to sign a new certificate by calling the configured CA. Typically, this is Istiod.
   1. If the certificate is not yet expired, the `SecretManager` also can return a cache response. In practice, this would

* It should not be client-specific.
  * In Istio sidecars, historically we had a lot of client-specific xDS. For example, putting the xDS-client's IP back into the xDS response. This makes efficient control plane implementation (most notably, caching), extremely challenging.
  * In practice, this largely means that references are fully qualified in the API. IP Addresses (generally) have a network associated with them, node names have a cluster associated with them, etc.

  // diskName is the Name of the data disk in the blob storage
  optional string diskName = 1;

  // diskURI is the URI of data disk in the blob storage
  optional string diskURI = 2;

  // cachingMode is the Host Caching mode: None, Read Only, Read Write.
  // +optional
  optional string cachingMode = 3;

  // fsType is Filesystem type to mount.
  // Must be a filesystem type supported by the host operating system.

#### Caching

Config translation typically takes the overwhelming majority of Istiod's resource usage. In particular, protobuf encoding. As a result, caching has been introduced, storing the already encoded `protobuf.Any` for a given resource.

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Copyright (c) 2012-2016 Dave Collins <******@****.***>

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