Merge pull request #12 from rdner/timer-interval

Add `polling_interval` parameter to `PersistedIndexRequest`

api/messages/persisted_index.proto

@@ -7,10 +7,18 @@ syntax = "proto3";
 option go_package = "github.com/elastic/elastic-agent-shipper-client/pkg/proto/messages";
 package elastic.agent.shipper.v1.messages;
 
+import "google/protobuf/duration.proto";
+
 // A request for latest sequential event index that has been persisted to the
 // disk or the outputs. This is only needed for inputs that must maintain their
 // position in some persistent data sequence between restarts.
 message PersistedIndexRequest {
+ // The interval for checking the persisted index value during the subscription.
+ // An update is not sent if the value is unchanged, so it's not guaranteed to receive
+ // an update after each interval but rather to receive an update on the changed value
+ // in `polling_interval` time at most.
+ // When the value is zero the response is sent only once and the stream is closed right after.
+ google.protobuf.Duration polling_interval = 1;
 }
 
 message PersistedIndexReply {