Added gRPC interface definition for data cache

proto/controls/service/data_cache/data_cache.proto

@@ -0,0 +1,75 @@
+syntax = "proto3";
+
+package services.data_cache;
+
+service DataCacheService {
+  // Create a topic with partitions and replication factor
+  rpc CreateMQ(CreateMQRequest) returns (CreateMQResponse);
+
+  // Create many topics with identical partitions and replication factor
+  rpc CreateNMQs(CreateMQsRequest) returns (CreateMQResponse);
+
+  // Send a single message to a topic
+  rpc PushMQ(PushMQRequest) returns (ProducersResponse);
+
+  // Send a single message to many topic
+  rpc PushMQs(PushMQsRequest) returns (ProducersResponse);
+
+  // Get message from a topic 
+  rpc PullMQ(PullMQRequest) returns (ConsumersResponse);
+
+  // Get messages from many topics 
+  rpc PullMQs(PullMQsRequest) returns (ConsumersResponse);
+}
+
+message CreateMQRequest {
+  string mq_name = 1;			// topic name 
+  int32 partitions = 2;			// Each topic can be devided into multiple partitions 	
+  int32 replication_factor = 3;		// replication for high availibility 
+}
+
+message CreateMQsRequest {
+  string mq_names = 1;                  // topic names separed with ',' e.g. topic1, topic2, topic3
+  int32 partitions = 2;                 // Each topic can be devided into multiple partitions
+  int32 replication_factor = 3;         // replication for high availibility
+}
+
+message CreateMQResponse {
+  bool success = 1;			// success or failure 
+  string message = 2;			// response (error message if failure) 
+}
+
+message PushMQRequest {
+  string mq_name = 1;			// topic name
+  string key = 2;    			// optional
+  bytes value = 3;			// message
+}
+
+message PushMQsRequest {
+  string mq_names = 1;                  // list of topics 
+  string key = 2;                       // optional
+  bytes value = 3;                      // message
+}
+
+message ProducersResponse {
+  bool success = 1;			// success or failure
+  string messages_with_offsets = 2;	// response offset / error message if failure
+}
+
+message PullMQRequest {
+  string mq_name = 1;			// topic name
+  int32 timeout_seconds = 2; 		// optional, stop after secs (0 = no timeout)
+}
+
+message PullMQsRequest {
+  string mq_names = 1;                  // list of topics
+  int32 timeout_seconds = 2;            // optional, stop after secs (0 = no timeout)
+}
+
+message ConsumersResponse {
+  string keys = 1;			// associated key or keys 
+  bytes values = 2;			// response 
+  string offsets = 3;			// offset or many offsets 
+  string partitions = 4;		// partition or many partitions 
+}
+