开始使用 Dapr 客户端 Python SDK

如何使用 Dapr Python SDK 启动和运行

Dapr 客户端包允许您从 Python 应用程序中与其他 Dapr 应用程序进行交互。

前期准备

在开始之前，请安装 Dapr Python 包。

导入客户端包

dapr 包包含 DaprClient，该工具包将用于创建和使用客户端。

from dapr.clients import DaprClient

初始化客户端

您可以以多种方式初始化 Dapr 客户端：

默认值:

当您在不带任何参数的情况下初始化客户端时，它将使用默认值作为 Dapr sidecar 实例（127.0.0.1:50001）。

from dapr.clients import DaprClient

with DaprClient() as d:
    # use the client

在初始化时指定一个端点：

当作为构造函数的参数传递时，gRPC端点优先于任何配置或环境变量。

from dapr.clients import DaprClient

with DaprClient("mydomain:50051?tls=true") as d:
    # use the client

环境变量:

Dapr Sidecar 终端点

您可以使用标准化的DAPR_GRPC_ENDPOINT环境变量来指定gRPC端点。 当设置了这个变量时，客户端可以在没有任何参数的情况下进行初始化：

export DAPR_GRPC_ENDPOINT="mydomain:50051?tls=true"

from dapr.clients import DaprClient

with DaprClient() as d:
    # the client will use the endpoint specified in the environment variables

遗留的环境变量 DAPR_RUNTIME_HOST、DAPR_HTTP_PORT 和 DAPR_GRPC_PORT 也被支持，但是 DAPR_GRPC_ENDPOINT 优先级更高。

Dapr API 令牌

如果您的 Dapr 实例配置需要 DAPR_API_TOKEN 环境变量，您可以在环境中设置它，客户端将自动使用它。
您可以在此处阅读有关 Dapr API 令牌身份验证的更多信息（链接）。

健康超时

在客户端初始化时，会对Dapr sidecar（/healthz/outboud）进行健康检查。 客户端将在 sidecar 启动并运行后继续进行。

默认超时时间为60秒，但可以通过设置DAPR_HEALTH_TIMEOUT环境变量来覆盖。

错误处理

最初，Dapr中的错误遵循了标准的gRPC错误模型。 然而，为了提供更详细和信息丰富的错误消息，在版本1.13中引入了一个增强的错误模型，与gRPC的更丰富的错误模型保持一致。 作为回应，Python SDK 实现了 DaprGrpcError，一个专门设计用于改善开发者体验的自定义异常类。
需要注意的是，将所有gRPC状态异常转换为DaprGrpcError仍在进行中。 目前，SDK中并非每个API调用都已更新以利用此自定义异常。 我们正在积极推进这项改进，并欢迎社区的贡献。

使用 Dapr python-SDK 时处理 DaprGrpcError 异常的示例：

try:
    d.save_state(store_name=storeName, key=key, value=value)
except DaprGrpcError as err:
    print(f'Status code: {err.code()}')
    print(f"Message: {err.message()}")
    print(f"Error code: {err.error_code()}")
    print(f"Error info(reason): {err.error_info.reason}")
    print(f"Resource info (resource type): {err.resource_info.resource_type}")
    print(f"Resource info (resource name): {err.resource_info.resource_name}")
    print(f"Bad request (field): {err.bad_request.field_violations[0].field}")
    print(f"Bad request (description): {err.bad_request.field_violations[0].description}")

构建块

Python SDK 允许您与所有的Dapr构建块}进行接口交互。

调用服务

Dapr Python SDK 提供了一个简单的 API，用于通过 HTTP 或 gRPC（已弃用）调用服务。 可以通过设置 DAPR_API_METHOD_INVOCATION_PROTOCOL 环境变量来选择协议，默认情况下未设置时为HTTP。 在 Dapr 中，GRPC 服务调用已被弃用，推荐使用 GRPC 代理作为替代方案。

from dapr.clients import DaprClient

with DaprClient() as d:
    # invoke a method (gRPC or HTTP GET)    
    resp = d.invoke_method('service-to-invoke', 'method-to-invoke', data='{"message":"Hello World"}')

    # for other HTTP verbs the verb must be specified
    # invoke a 'POST' method (HTTP only)    
    resp = d.invoke_method('service-to-invoke', 'method-to-invoke', data='{"id":"100", "FirstName":"Value", "LastName":"Value"}', http_verb='post')

HTTP api调用的基本终结点在DAPR_HTTP_ENDPOINT环境变量中指定。 如果未设置此变量，则端点值将从DAPR_RUNTIME_HOST和DAPR_HTTP_PORT变量中派生，其默认值分别为127.0.0.1和3500。

gRPC调用的基本终端点是用于客户端初始化的终端点（上面解释了）。

保存和获取应用程序状态

from dapr.clients import DaprClient

with DaprClient() as d:
    # Save state
    d.save_state(store_name="statestore", key="key1", value="value1")

    # Get state
    data = d.get_state(store_name="statestore", key="key1").data

    # Delete state
    d.delete_state(store_name="statestore", key="key1")

查询应用程序状态（Alpha）

    from dapr import DaprClient

    query = '''
    {
        "filter": {
            "EQ": { "state": "CA" }
        },
        "sort": [
            {
                "key": "person.id",
                "order": "DESC"
            }
        ]
    }
    '''

    with DaprClient() as d:
        resp = d.query_state(
            store_name='state_store',
            query=query,
            states_metadata={"metakey": "metavalue"},  # optional
        )

发布和订阅消息

发布消息

from dapr.clients import DaprClient

with DaprClient() as d:
    resp = d.publish_event(pubsub_name='pubsub', topic_name='TOPIC_A', data='{"message":"Hello World"}')

订阅消息

from cloudevents.sdk.event import v1
from dapr.ext.grpc import App
import json

app = App()

# Default subscription for a topic
@app.subscribe(pubsub_name='pubsub', topic='TOPIC_A')
def mytopic(event: v1.Event) -> None:
    data = json.loads(event.Data())
    print(f'Received: id={data["id"]}, message="{data ["message"]}"' 
          ' content_type="{event.content_type}"',flush=True)

# Specific handler using Pub/Sub routing
@app.subscribe(pubsub_name='pubsub', topic='TOPIC_A',
               rule=Rule("event.type == \"important\"", 1))
def mytopic_important(event: v1.Event) -> None:
    data = json.loads(event.Data())
    print(f'Received: id={data["id"]}, message="{data ["message"]}"' 
          ' content_type="{event.content_type}"',flush=True)

与输出绑定交互

from dapr.clients import DaprClient

with DaprClient() as d:
    resp = d.invoke_binding(binding_name='kafkaBinding', operation='create', data='{"message":"Hello World"}')

检索密钥

from dapr.clients import DaprClient

with DaprClient() as d:
    resp = d.get_secret(store_name='localsecretstore', key='secretKey')

Configuration

获取配置

from dapr.clients import DaprClient

with DaprClient() as d:
    # Get Configuration
    configuration = d.get_configuration(store_name='configurationstore', keys=['orderId'], config_metadata={})

订阅配置

import asyncio
from time import sleep
from dapr.clients import DaprClient

async def executeConfiguration():
    with DaprClient() as d:
        storeName = 'configurationstore'

        key = 'orderId'

        # Wait for sidecar to be up within 20 seconds.
        d.wait(20)

        # Subscribe to configuration by key.
        configuration = await d.subscribe_configuration(store_name=storeName, keys=[key], config_metadata={})
        while True:
            if configuration != None:
                items = configuration.get_items()
                for key, item in items:
                    print(f"Subscribe key={key} value={item.value} version={item.version}", flush=True)
            else:
                print("Nothing yet")
        sleep(5)

asyncio.run(executeConfiguration())

分布式锁

from dapr.clients import DaprClient

def main():
    # Lock parameters
    store_name = 'lockstore'  # as defined in components/lockstore.yaml
    resource_id = 'example-lock-resource'
    client_id = 'example-client-id'
    expiry_in_seconds = 60

    with DaprClient() as dapr:
        print('Will try to acquire a lock from lock store named [%s]' % store_name)
        print('The lock is for a resource named [%s]' % resource_id)
        print('The client identifier is [%s]' % client_id)
        print('The lock will will expire in %s seconds.' % expiry_in_seconds)

        with dapr.try_lock(store_name, resource_id, client_id, expiry_in_seconds) as lock_result:
            assert lock_result.success, 'Failed to acquire the lock. Aborting.'
            print('Lock acquired successfully!!!')

        # At this point the lock was released - by magic of the `with` clause ;)
        unlock_result = dapr.unlock(store_name, resource_id, client_id)
        print('We already released the lock so unlocking will not work.')
        print('We tried to unlock it anyway and got back [%s]' % unlock_result.status)

Workflow

from dapr.ext.workflow import WorkflowRuntime, DaprWorkflowContext, WorkflowActivityContext
from dapr.clients import DaprClient

instanceId = "exampleInstanceID"
workflowComponent = "dapr"
workflowName = "hello_world_wf"
eventName = "event1"
eventData = "eventData"

def main():
    with DaprClient() as d:
        host = settings.DAPR_RUNTIME_HOST
        port = settings.DAPR_GRPC_PORT
        workflowRuntime = WorkflowRuntime(host, port)
        workflowRuntime = WorkflowRuntime()
        workflowRuntime.register_workflow(hello_world_wf)
        workflowRuntime.register_activity(hello_act)
        workflowRuntime.start()

        # Start the workflow
        start_resp = d.start_workflow(instance_id=instanceId, workflow_component=workflowComponent,
                        workflow_name=workflowName, input=inputData, workflow_options=workflowOptions)
        print(f"start_resp {start_resp.instance_id}")

        # ...

        # Pause Test
        d.pause_workflow(instance_id=instanceId, workflow_component=workflowComponent)
        getResponse = d.get_workflow(instance_id=instanceId, workflow_component=workflowComponent)
        print(f"Get response from {workflowName} after pause call: {getResponse.runtime_status}")

        # Resume Test
        d.resume_workflow(instance_id=instanceId, workflow_component=workflowComponent)
        getResponse = d.get_workflow(instance_id=instanceId, workflow_component=workflowComponent)
        print(f"Get response from {workflowName} after resume call: {getResponse.runtime_status}")
        
        sleep(1)
        # Raise event
        d.raise_workflow_event(instance_id=instanceId, workflow_component=workflowComponent,
                    event_name=eventName, event_data=eventData)

        sleep(5)
        # Purge Test
        d.purge_workflow(instance_id=instanceId, workflow_component=workflowComponent)
        try:
            getResponse = d.get_workflow(instance_id=instanceId, workflow_component=workflowComponent)
        except DaprInternalError as err:
            if nonExistentIDError in err._message:
                print("Instance Successfully Purged")

        
        # Kick off another workflow for termination purposes 
        # This will also test using the same instance ID on a new workflow after
        # the old instance was purged
        start_resp = d.start_workflow(instance_id=instanceId, workflow_component=workflowComponent,
                        workflow_name=workflowName, input=inputData, workflow_options=workflowOptions)
        print(f"start_resp {start_resp.instance_id}")

        # Terminate Test
        d.terminate_workflow(instance_id=instanceId, workflow_component=workflowComponent)
        sleep(1)
        getResponse = d.get_workflow(instance_id=instanceId, workflow_component=workflowComponent)
        print(f"Get response from {workflowName} after terminate call: {getResponse.runtime_status}")

        # Purge Test
        d.purge_workflow(instance_id=instanceId, workflow_component=workflowComponent)
        try:
            getResponse = d.get_workflow(instance_id=instanceId, workflow_component=workflowComponent)
        except DaprInternalError as err:
            if nonExistentIDError in err._message:
                print("Instance Successfully Purged")

        workflowRuntime.shutdown()

相关链接

Python SDK示例