feat(replication): define replication RPC API

Defines the rough outline of an replication RPC API. More details/docs
to follow.

generated_types/build.rs

@@ -58,6 +58,7 @@ fn generate_grpc_types(root: &Path) -> Result<()> {
         ingester_path.join("query.proto"),
         ingester_path.join("write_info.proto"),
         ingester_path.join("write.proto"),
+        ingester_path.join("replication.proto"),
         namespace_path.join("service.proto"),
         object_store_path.join("service.proto"),
         predicate_path.join("predicate.proto"),

generated_types/protos/influxdata/iox/ingester/v1/replication.proto

@@ -0,0 +1,80 @@
+syntax = "proto3";
+package influxdata.iox.ingester.v1;
+option go_package = "github.com/influxdata/iox/ingester/v1";
+
+import "influxdata/pbdata/v1/influxdb_pb_data_protocol.proto";
+
+// A service provided by Ingester2 instances, called by Ingester Replicas.
+service PartitionBufferService {
+  // Acquire the full in-memory state of the recipient ingester, returning the
+  // data of all known partitions.
+  //
+  // This is NOT an atomic snapshot of the global in-memory state, but MUST be
+  // an atomic snapshot of a single partition's buffer state.
+  rpc GetPartitionBuffers(GetPartitionBuffersRequest) returns (stream GetPartitionBuffersResponse);
+}
+
+message GetPartitionBuffersRequest {}
+
+message GetPartitionBuffersResponse {
+  // The unique, per-instance UUID of the ingester pushing this operation.
+  string ingester_uuid = 1;
+
+  // The catalog ID of this partition.
+  int64 partition_id = 2;
+
+  // The serialised roaring bitmap of Sequence Number values buffered in this
+  // data payload.
+  //
+  // Generated by calling croaring::Bitmap::serialize().
+  bytes croaring_sequence_number_bitmap = 3;
+
+  // The complete set of data buffered for this partition at the time this
+  // message was generated.
+  influxdata.pbdata.v1.DatabaseBatch payload = 4;
+}
+
+// A service provided by Ingester Replica instances to accept pushed events from
+// an Ingester2 instance.
+service ReplicationService {
+  // Push the provided write request to the replica.
+  rpc Replicate(ReplicateRequest) returns (ReplicateResponse);
+
+  // Notify the replica that a given range of sequence numbers within a
+  // partition has been persisted.
+  rpc PersistComplete(PersistCompleteRequest) returns (PersistCompleteResponse);
+}
+
+message ReplicateRequest {
+  // The unique, per-instance UUID of the ingester pushing this operation.
+  string ingester_uuid = 1;
+
+  // The catalog ID of this partition.
+  int64 partition_id = 2;
+
+  // The Sequence Number assigned to this operation.
+  //
+  // A tuple of (ingester_uuid, sequence_number) is always guaranteed to
+  // uniquely identify this operation.
+  int64 sequence_number = 3;
+
+  // The operation payload data.
+  influxdata.pbdata.v1.DatabaseBatch payload = 4;
+}
+
+message ReplicateResponse {}
+
+message PersistCompleteRequest {
+  // The unique, per-instance UUID of the ingester pushing this operation.
+  string ingester_uuid = 1;
+
+  // The catalog ID of the partition that has had data persisted.
+  int64 partition_id = 2;
+
+  // The serialised roaring bitmap of Sequence Number values persisted.
+  //
+  // Generated by calling croaring::Bitmap::serialize().
+  bytes croaring_sequence_number_bitmap = 3;
+}
+
+message PersistCompleteResponse {}