remove redundant data on node join

Author: hacksdump

http-handlers.go

@@ -12,6 +12,7 @@ func homePageHandler(w http.ResponseWriter, r *http.Request) {
 		http.NotFound(w, r)
 		return
 	}
+	w.Header().Set("Content-Type", "application/json")
 
 	if r.Method == http.MethodGet {
 		var requestBody KeyValuePair
@@ -30,7 +31,6 @@ func homePageHandler(w http.ResponseWriter, r *http.Request) {
 		log.Printf("Trying to find the key %s in node %+v", requestKey, readFromNode)
 		keyValuePair, err := readDataFromSpecificNode(readFromNode, requestKey)
 
-		w.Header().Set("Content-Type", "application/json")
 		if err == nil {
 			w.WriteHeader(http.StatusOK)
 			err = json.NewEncoder(w).Encode(keyValuePair)
@@ -51,7 +51,6 @@ func homePageHandler(w http.ResponseWriter, r *http.Request) {
 
 		if body.Key == "" || body.Value == "" {
 			responseMessage := ResponseMessage{false,"Key or value missing. No write or update performed"}
-			w.Header().Set("Content-Type", "application/json")
 			w.WriteHeader(http.StatusBadRequest)
 			err = json.NewEncoder(w).Encode(responseMessage)
 			return
@@ -77,20 +76,46 @@ func homePageHandler(w http.ResponseWriter, r *http.Request) {
 		} else {
 			log.Fatal(err)
 		}
+	} else if r.Method == http.MethodDelete {
+		var requestBody KeyValuePair
+		err := json.NewDecoder(r.Body).Decode(&requestBody)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusBadRequest)
+			return
+		}
+		requestKey := requestBody.Key
+		log.Println("Received request to delete key", requestKey)
+		baseNode, err := addrToNode(CompleteBaseAddress())
+		if err != nil {
+			log.Fatal("Base node not found while searching for a key")
+		}
+		deleteFromNode := findNode(baseNode, requestKey)
+		log.Printf("Trying to delete the key %s from node %+v", requestKey, deleteFromNode)
+		respMessage, err := deleteDataFromSpecificNode(deleteFromNode, requestKey)
+
+		if err == nil {
+			w.WriteHeader(http.StatusOK)
+			err = json.NewEncoder(w).Encode(respMessage)
+			if err != nil {
+				log.Fatal(err)
+			}
+		} else {
+			log.Fatal(err)
+		}
 	} else {
 		http.Error(w, "Only use GET or PUT", http.StatusMethodNotAllowed)
 	}
 }
 
 func directDataLevelCommunicationHandler(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json")
 	if r.Method == http.MethodGet {
 		var requestBody KeyValuePair
 		err := json.NewDecoder(r.Body).Decode(&requestBody)
 		if err != nil {
 			http.Error(w, err.Error(), http.StatusBadRequest)
 			return
 		}
-		w.Header().Set("Content-Type", "application/json")
 		requestKey := requestBody.Key
 		log.Printf("Checking if key %s is present in local store", requestKey)
 		if val, ok := keyValueStore[requestKey]; ok {
@@ -116,7 +141,6 @@ func directDataLevelCommunicationHandler(w http.ResponseWriter, r *http.Request)
 
 		if body.Key == "" || body.Value == "" {
 			responseMessage := ResponseMessage{false,"Key or value missing. No write or update performed"}
-			w.Header().Set("Content-Type", "application/json")
 			w.WriteHeader(http.StatusBadRequest)
 			err = json.NewEncoder(w).Encode(responseMessage)
 			return
@@ -130,6 +154,21 @@ func directDataLevelCommunicationHandler(w http.ResponseWriter, r *http.Request)
 		if err != nil {
 			log.Fatal(err)
 		}
+	} else if r.Method == http.MethodDelete {
+		var requestBody KeyValuePair
+		err := json.NewDecoder(r.Body).Decode(&requestBody)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusBadRequest)
+			return
+		}
+		requestKey := requestBody.Key
+		log.Printf("Attempting to delete key %s if present", requestKey)
+		delete(keyValueStore, requestKey)
+		w.WriteHeader(http.StatusOK)
+		err = json.NewEncoder(w).Encode(ResponseMessage{true, fmt.Sprintf("Key %s deleted", requestKey)})
+		if err != nil {
+			log.Fatal(err)
+		}
 	} else {
 		http.Error(w, "Only use GET or PUT", http.StatusMethodNotAllowed)
 	}

http-requests.go

@@ -73,6 +73,22 @@ func writeDataToSpecificNode(node Node, keyValuePair KeyValuePair) (ResponseMess
 	return ResponseMessage{true, "Written"}, nil
 }
 
+func deleteDataFromSpecificNode(node Node, key string) (ResponseMessage, error) {
+	url := fmt.Sprintf("http://%s/server-data", node.Address)
+	jsonData, _ := json.Marshal(KeyValuePair{key, ""})
+	req, err := http.NewRequest(http.MethodDelete, url, bytes.NewBuffer(jsonData))
+	req.Header.Set("Content-Type", "application/json")
+	client := &http.Client{}
+	resp, err := client.Do(req)
+	if err != nil {
+		log.Fatal(err)
+	}
+	if resp.StatusCode == http.StatusOK {
+		return ResponseMessage{true, "Successfully deleted"}, nil
+	}
+	return ResponseMessage{false, "Delete failure"}, errors.New("delete failure")
+}
+
 func getAllDataFromNode(node Node) []KeyValuePair {
 	resp, err := http.Get(fmt.Sprintf("http://%s/data", node.Address))
 	if err == nil {

main.go

@@ -44,6 +44,7 @@ func insertSelfAfter(oldNodeAddr string) {
 		if util.RingDistance(node.ID, itemKeyHash, K) <
 			util.RingDistance(prevNode.ID, itemKeyHash, K) {
 			log.Printf("Copying %+v with hash %d from predecessor %d to self", item, itemKeyHash, prevNode.ID)
+			deleteDataFromSpecificNode(prevNode, item.Key)
 			keyValueStore[item.Key] = item.Value
 		}
 	}