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How-To: Save and get state

Use key value pairs to persist a 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

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.

Diagram showing state management of example service

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.

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

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


Last modified March 18, 2022: update translation in zh_hans (#2267) (0e346f1)