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How-To: Save and get state
Introduction
State management is one of the most common needs of any application: new or legacy, monolith or microservice. Dealing with different databases libraries, testing them, handling retries and faults can be time consuming and hard.
Dapr provides state management capabilities that include consistency and concurrency options. In this guide we’ll start of with the basics: Using the key/value state API to allow an application to save, get and delete state.
Pre-requisites
- Dapr CLI
- Initialized Dapr environment
Example:
The below code examples loosely describe an application that processes orders. In the examples, there is an order processing service which has a Dapr sidecar. The order processing service uses Dapr to store state in a Redis state store.
Step 1: Setup a state store
A state store component represents a resource that Dapr uses to communicate with a database.
For the purpose of this guide we’ll use a Redis state store, but any state store from the supported list will work.
When using dapr init in Standalone mode, the Dapr CLI automatically provisions a state store (Redis) and creates the relevant YAML in a components directory, which for Linux/MacOS is $HOME/.dapr/components and for Windows is %USERPROFILE%\.dapr\components
To optionally change the state store being used, replace the YAML file statestore.yaml under /components with the file of your choice.
To deploy this into a Kubernetes cluster, fill in the metadata connection details of your desired statestore component in the yaml below, save as statestore.yaml, and run kubectl apply -f statestore.yaml.
apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
name: statestore
namespace: default
spec:
type: state.redis
version: v1
metadata:
- name: redisHost
value: localhost:6379
- name: redisPassword
value: ""
See the instructions here on how to setup different state stores on Kubernetes.
Step 2: Save and retrieve a single state
The following example shows how to save and retrieve a single key/value pair using the Dapr state building block.
Note
It is important to set an app-id, as the state keys are prefixed with this value. If you don’t set it one is generated for you at runtime, and the next time you run the command a new one will be generated and you will no longer be able to access previously saved state.Below are code examples that leverage Dapr SDKs for saving and retrieving a single state.
//dependencies
using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;
using Dapr.Client;
using Microsoft.AspNetCore.Mvc;
using System.Threading;
using System.Text.Json;
//code
namespace EventService
{
class Program
{
static async Task Main(string[] args)
{
string DAPR_STORE_NAME = "statestore";
while(true) {
System.Threading.Thread.Sleep(5000);
using var client = new DaprClientBuilder().Build();
Random random = new Random();
int orderId = random.Next(1,1000);
//Using Dapr SDK to save and get state
await client.SaveStateAsync(DAPR_STORE_NAME, "order_1", orderId.ToString());
await client.SaveStateAsync(DAPR_STORE_NAME, "order_2", orderId.ToString());
var result = await client.GetStateAsync<string>(DAPR_STORE_NAME, orderId.ToString());
Console.WriteLine("Result after get: " + result);
}
}
}
}
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 dotnet run
//dependencies
import io.dapr.client.DaprClient;
import io.dapr.client.DaprClientBuilder;
import io.dapr.client.domain.State;
import io.dapr.client.domain.TransactionalStateOperation;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import reactor.core.publisher.Mono;
import java.util.Random;
import java.util.concurrent.TimeUnit;
//code
@SpringBootApplication
public class OrderProcessingServiceApplication {
private static final Logger log = LoggerFactory.getLogger(OrderProcessingServiceApplication.class);
private static final String STATE_STORE_NAME = "statestore";
public static void main(String[] args) throws InterruptedException{
while(true) {
TimeUnit.MILLISECONDS.sleep(5000);
Random random = new Random();
int orderId = random.nextInt(1000-1) + 1;
DaprClient client = new DaprClientBuilder().build();
//Using Dapr SDK to save and get state
client.saveState(STATE_STORE_NAME, "order_1", Integer.toString(orderId)).block();
client.saveState(STATE_STORE_NAME, "order_2", Integer.toString(orderId)).block();
Mono<State<String>> result = client.getState(STATE_STORE_NAME, "order_1", String.class);
log.info("Result after get" + result);
}
}
}
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 mvn spring-boot:run
#dependencies
import random
from time import sleep
import requests
import logging
from dapr.clients import DaprClient
from dapr.clients.grpc._state import StateItem
from dapr.clients.grpc._request import TransactionalStateOperation, TransactionOperationType
#code
logging.basicConfig(level = logging.INFO)
DAPR_STORE_NAME = "statestore"
while True:
sleep(random.randrange(50, 5000) / 1000)
orderId = random.randint(1, 1000)
with DaprClient() as client:
#Using Dapr SDK to save and get state
client.save_state(DAPR_STORE_NAME, "order_1", str(orderId))
result = client.get_state(DAPR_STORE_NAME, "order_1")
logging.info('Result after get: ' + result.data.decode('utf-8'))
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 -- python3 OrderProcessingService.py
//dependencies
import (
"context"
"log"
"math/rand"
"time"
"strconv"
dapr "github.com/dapr/go-sdk/client"
)
//code
func main() {
for i := 0; i < 10; i++ {
time.Sleep(5000)
orderId := rand.Intn(1000-1) + 1
client, err := dapr.NewClient()
STATE_STORE_NAME := "statestore"
if err != nil {
panic(err)
}
defer client.Close()
ctx := context.Background()
//Using Dapr SDK to save and get state
if err := client.SaveState(ctx, STATE_STORE_NAME, "order_1", []byte(strconv.Itoa(orderId))); err != nil {
panic(err)
}
result, err := client.GetState(ctx, STATE_STORE_NAME, "order_2")
if err != nil {
panic(err)
}
log.Println("Result after get: ")
log.Println(result)
}
}
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 go run OrderProcessingService.go
//dependencies
import { DaprClient, HttpMethod, CommunicationProtocolEnum } from 'dapr-client';
//code
const daprHost = "127.0.0.1";
var main = function() {
for(var i=0;i<10;i++) {
sleep(5000);
var orderId = Math.floor(Math.random() * (1000 - 1) + 1);
start(orderId).catch((e) => {
console.error(e);
process.exit(1);
});
}
}
async function start(orderId) {
const client = new DaprClient(daprHost, process.env.DAPR_HTTP_PORT, CommunicationProtocolEnum.HTTP);
const STATE_STORE_NAME = "statestore";
//Using Dapr SDK to save and get state
await client.state.save(STATE_STORE_NAME, [
{
key: "order_1",
value: orderId.toString()
},
{
key: "order_2",
value: orderId.toString()
}
]);
var result = await client.state.get(STATE_STORE_NAME, "order_1");
console.log("Result after get: " + result);
}
function sleep(ms) {
return new Promise(resolve => setTimeout(resolve, ms));
}
main();
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 npm start
Begin by launching a Dapr sidecar:
dapr run --app-id orderprocessing --dapr-http-port 3601
Then in a separate terminal save a key/value pair into your statestore:
curl -X POST -H "Content-Type: application/json" -d '[{ "key": "order_1", "value": "250"}]' http://localhost:3601/v1.0/state/statestore
Now get the state you just saved:
curl http://localhost:3601/v1.0/state/statestore/order_1
Restart your sidecar and try retrieving state again to observe that state persists separately from the app.
Begin by launching a Dapr sidecar:
dapr --app-id orderprocessing --port 3601 run
Then in a separate terminal save a key/value pair into your statestore:
Invoke-RestMethod -Method Post -ContentType 'application/json' -Body '[{"key": "order_1", "value": "250"}]' -Uri 'http://localhost:3601/v1.0/state/statestore'
Now get the state you just saved:
Invoke-RestMethod -Uri 'http://localhost:3601/v1.0/state/statestore/order_1'
Restart your sidecar and try retrieving state again to observe that state persists separately from the app.
Step 3: Delete state
Below are code examples that leverage Dapr SDKs for deleting the state.
//dependencies
using Dapr.Client;
//code
namespace EventService
{
class Program
{
static async Task Main(string[] args)
{
string DAPR_STORE_NAME = "statestore";
//Using Dapr SDK to delete the state
using var client = new DaprClientBuilder().Build();
await client.DeleteStateAsync(DAPR_STORE_NAME, "order_1", cancellationToken: cancellationToken);
}
}
}
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 dotnet run
//dependencies
import io.dapr.client.DaprClient;
import io.dapr.client.DaprClientBuilder;
import org.springframework.boot.autoconfigure.SpringBootApplication;
//code
@SpringBootApplication
public class OrderProcessingServiceApplication {
public static void main(String[] args) throws InterruptedException{
String STATE_STORE_NAME = "statestore";
//Using Dapr SDK to delete the state
DaprClient client = new DaprClientBuilder().build();
String storedEtag = client.getState(STATE_STORE_NAME, "order_1", String.class).block().getEtag();
client.deleteState(STATE_STORE_NAME, "order_1", storedEtag, null).block();
}
}
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 mvn spring-boot:run
#dependencies
from dapr.clients.grpc._request import TransactionalStateOperation, TransactionOperationType
#code
logging.basicConfig(level = logging.INFO)
DAPR_STORE_NAME = "statestore"
#Using Dapr SDK to delete the state
with DaprClient() as client:
client.delete_state(store_name=DAPR_STORE_NAME, key="order_1")
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 -- python3 OrderProcessingService.py
//dependencies
import (
"context"
dapr "github.com/dapr/go-sdk/client"
)
//code
func main() {
STATE_STORE_NAME := "statestore"
//Using Dapr SDK to delete the state
client, err := dapr.NewClient()
if err != nil {
panic(err)
}
defer client.Close()
ctx := context.Background()
if err := client.DeleteState(ctx, STATE_STORE_NAME, "order_1"); err != nil {
panic(err)
}
}
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 go run OrderProcessingService.go
//dependencies
import { DaprClient, HttpMethod, CommunicationProtocolEnum } from 'dapr-client';
//code
const daprHost = "127.0.0.1";
var main = function() {
const STATE_STORE_NAME = "statestore";
//Using Dapr SDK to save and get state
const client = new DaprClient(daprHost, process.env.DAPR_HTTP_PORT, CommunicationProtocolEnum.HTTP);
await client.state.delete(STATE_STORE_NAME, "order_1");
}
main();
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 npm start
With the same Dapr instance running from above run:
curl -X DELETE 'http://localhost:3601/v1.0/state/statestore/order_1'
Try getting state again and note that no value is returned.
With the same Dapr instance running from above run:
Invoke-RestMethod -Method Delete -Uri 'http://localhost:3601/v1.0/state/statestore/order_1'
Try getting state again and note that no value is returned.
Step 4: Save and retrieve multiple states
Below are code examples that leverage Dapr SDKs for saving and retrieving multiple states.
//dependencies
import io.dapr.client.DaprClient;
import io.dapr.client.DaprClientBuilder;
import io.dapr.client.domain.State;
import java.util.Arrays;
//code
@SpringBootApplication
public class OrderProcessingServiceApplication {
private static final Logger log = LoggerFactory.getLogger(OrderProcessingServiceApplication.class);
public static void main(String[] args) throws InterruptedException{
String STATE_STORE_NAME = "statestore";
//Using Dapr SDK to retrieve multiple states
DaprClient client = new DaprClientBuilder().build();
Mono<List<State<String>>> resultBulk = client.getBulkState(STATE_STORE_NAME,
Arrays.asList("order_1", "order_2"), String.class);
}
}
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 mvn spring-boot:run
#dependencies
from dapr.clients import DaprClient
from dapr.clients.grpc._state import StateItem
#code
logging.basicConfig(level = logging.INFO)
DAPR_STORE_NAME = "statestore"
orderId = 100
#Using Dapr SDK to save and retrieve multiple states
with DaprClient() as client:
client.save_bulk_state(store_name=DAPR_STORE_NAME, states=[StateItem(key="order_2", value=str(orderId))])
result = client.get_bulk_state(store_name=DAPR_STORE_NAME, keys=["order_1", "order_2"], states_metadata={"metakey": "metavalue"}).items
logging.info('Result after get bulk: ' + str(result))
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 -- python3 OrderProcessingService.py
//dependencies
import { DaprClient, HttpMethod, CommunicationProtocolEnum } from 'dapr-client';
//code
const daprHost = "127.0.0.1";
var main = function() {
const STATE_STORE_NAME = "statestore";
var orderId = 100;
//Using Dapr SDK to save and retrieve multiple states
const client = new DaprClient(daprHost, process.env.DAPR_HTTP_PORT, CommunicationProtocolEnum.HTTP);
await client.state.save(STATE_STORE_NAME, [
{
key: "order_1",
value: orderId.toString()
},
{
key: "order_2",
value: orderId.toString()
}
]);
result = await client.state.getBulk(STATE_STORE_NAME, ["order_1", "order_2"]);
}
main();
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 npm start
With the same Dapr instance running from above save two key/value pairs into your statestore:
curl -X POST -H "Content-Type: application/json" -d '[{ "key": "order_1", "value": "250"}, { "key": "order_2", "value": "550"}]' http://localhost:3601/v1.0/state/statestore
Now get the states you just saved:
curl -X POST -H "Content-Type: application/json" -d '{"keys":["order_1", "order_2"]}' http://localhost:3601/v1.0/state/statestore/bulk
With the same Dapr instance running from above save two key/value pairs into your statestore:
Invoke-RestMethod -Method Post -ContentType 'application/json' -Body '[{ "key": "order_1", "value": "250"}, { "key": "order_2", "value": "550"}]' -Uri 'http://localhost:3601/v1.0/state/statestore'
Now get the states you just saved:
Invoke-RestMethod -Method Post -ContentType 'application/json' -Body '{"keys":["order_1", "order_2"]}' -Uri 'http://localhost:3601/v1.0/state/statestore/bulk'
Step 5: Perform state transactions
Note
State transactions require a state store that supports multi-item transactions. Visit the supported state stores page page for a full list. Note that the default Redis container created in a self-hosted environment supports them.Below are code examples that leverage Dapr SDKs for performing state transactions.
//dependencies
using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;
using Dapr.Client;
using Microsoft.AspNetCore.Mvc;
using System.Threading;
using System.Text.Json;
//code
namespace EventService
{
class Program
{
static async Task Main(string[] args)
{
string DAPR_STORE_NAME = "statestore";
while(true) {
System.Threading.Thread.Sleep(5000);
Random random = new Random();
int orderId = random.Next(1,1000);
using var client = new DaprClientBuilder().Build();
var requests = new List<StateTransactionRequest>()
{
new StateTransactionRequest("order_3", JsonSerializer.SerializeToUtf8Bytes(orderId.ToString()), StateOperationType.Upsert),
new StateTransactionRequest("order_2", null, StateOperationType.Delete)
};
CancellationTokenSource source = new CancellationTokenSource();
CancellationToken cancellationToken = source.Token;
//Using Dapr SDK to perform the state transactions
await client.ExecuteStateTransactionAsync(DAPR_STORE_NAME, requests, cancellationToken: cancellationToken);
Console.WriteLine("Order requested: " + orderId);
Console.WriteLine("Result: " + result);
}
}
}
}
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 dotnet run
//dependencies
import io.dapr.client.DaprClient;
import io.dapr.client.DaprClientBuilder;
import io.dapr.client.domain.State;
import io.dapr.client.domain.TransactionalStateOperation;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import reactor.core.publisher.Mono;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.TimeUnit;
//code
@SpringBootApplication
public class OrderProcessingServiceApplication {
private static final Logger log = LoggerFactory.getLogger(OrderProcessingServiceApplication.class);
private static final String STATE_STORE_NAME = "statestore";
public static void main(String[] args) throws InterruptedException{
while(true) {
TimeUnit.MILLISECONDS.sleep(5000);
Random random = new Random();
int orderId = random.nextInt(1000-1) + 1;
DaprClient client = new DaprClientBuilder().build();
List<TransactionalStateOperation<?>> operationList = new ArrayList<>();
operationList.add(new TransactionalStateOperation<>(TransactionalStateOperation.OperationType.UPSERT,
new State<>("order_3", Integer.toString(orderId), "")));
operationList.add(new TransactionalStateOperation<>(TransactionalStateOperation.OperationType.DELETE,
new State<>("order_2")));
//Using Dapr SDK to perform the state transactions
client.executeStateTransaction(STATE_STORE_NAME, operationList).block();
log.info("Order requested: " + orderId);
}
}
}
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 mvn spring-boot:run
#dependencies
import random
from time import sleep
import requests
import logging
from dapr.clients import DaprClient
from dapr.clients.grpc._state import StateItem
from dapr.clients.grpc._request import TransactionalStateOperation, TransactionOperationType
#code
logging.basicConfig(level = logging.INFO)
DAPR_STORE_NAME = "statestore"
while True:
sleep(random.randrange(50, 5000) / 1000)
orderId = random.randint(1, 1000)
with DaprClient() as client:
#Using Dapr SDK to perform the state transactions
client.execute_state_transaction(store_name=DAPR_STORE_NAME, operations=[
TransactionalStateOperation(
operation_type=TransactionOperationType.upsert,
key="order_3",
data=str(orderId)),
TransactionalStateOperation(key="order_3", data=str(orderId)),
TransactionalStateOperation(
operation_type=TransactionOperationType.delete,
key="order_2",
data=str(orderId)),
TransactionalStateOperation(key="order_2", data=str(orderId))
])
client.delete_state(store_name=DAPR_STORE_NAME, key="order_1")
logging.basicConfig(level = logging.INFO)
logging.info('Order requested: ' + str(orderId))
logging.info('Result: ' + str(result))
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 -- python3 OrderProcessingService.py
//dependencies
import { DaprClient, HttpMethod, CommunicationProtocolEnum } from 'dapr-client';
//code
const daprHost = "127.0.0.1";
var main = function() {
for(var i=0;i<10;i++) {
sleep(5000);
var orderId = Math.floor(Math.random() * (1000 - 1) + 1);
start(orderId).catch((e) => {
console.error(e);
process.exit(1);
});
}
}
async function start(orderId) {
const client = new DaprClient(daprHost, process.env.DAPR_HTTP_PORT, CommunicationProtocolEnum.HTTP);
const STATE_STORE_NAME = "statestore";
//Using Dapr SDK to save and retrieve multiple states
await client.state.transaction(STATE_STORE_NAME, [
{
operation: "upsert",
request: {
key: "order_3",
value: orderId.toString()
}
},
{
operation: "delete",
request: {
key: "order_2"
}
}
]);
}
function sleep(ms) {
return new Promise(resolve => setTimeout(resolve, ms));
}
main();
Navigate to the directory containing the above code, then run the following command to launch a Dapr sidecar and run the application:
dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 npm start
With the same Dapr instance running from above perform two state transactions:
curl -X POST -H "Content-Type: application/json" -d '{"operations": [{"operation":"upsert", "request": {"key": "order_1", "value": "250"}}, {"operation":"delete", "request": {"key": "order_2"}}]}' http://localhost:3601/v1.0/state/statestore/transaction
Now see the results of your state transactions:
curl -X POST -H "Content-Type: application/json" -d '{"keys":["order_1", "order_2"]}' http://localhost:3601/v1.0/state/statestore/bulk
With the same Dapr instance running from above save two key/value pairs into your statestore:
Invoke-RestMethod -Method Post -ContentType 'application/json' -Body '{"operations": [{"operation":"upsert", "request": {"key": "order_1", "value": "250"}}, {"operation":"delete", "request": {"key": "order_2"}}]}' -Uri 'http://localhost:3601/v1.0/state/statestore'
Now see the results of your state transactions:
Invoke-RestMethod -Method Post -ContentType 'application/json' -Body '{"keys":["order_1", "order_2"]}' -Uri 'http://localhost:3601/v1.0/state/statestore/bulk'
Next steps
- Read the full State API reference
- Try one of the Dapr SDKs
- Build a stateful service
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