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# 使用 DAG 在 CloudWatch 中寫入自訂指標
您可以使用下列程式碼範例來撰寫執行 的導向無環圖 (DAG)，`PythonOperator`以擷取 Amazon MWAA 環境的作業系統層級指標。然後，DAG 會將資料作為自訂指標發佈至 Amazon CloudWatch。
自訂作業系統層級指標可讓您進一步了解環境工作者如何利用虛擬記憶體和 CPU 等資源。您可以使用此資訊來選取最適合工作負載[的環境類別](environment-class.md)。
**Topics**
+ [版本](#samples-custom-metrics-version)
+ [先決條件](#samples-custom-metrics-prereqs)
+ [權限](#samples-custom-metrics-permissions)
+ [相依性](#samples-custom-metrics-dependencies)
+ [程式碼範例](#samples-custom-metrics-code)
## 版本
您可以在 Python 3.10 中使用 **Apache Airflow v2** 和 Python 3.1[1](https://peps.python.org/pep-0664/) ****中使用此頁面的程式碼範例。 [https://peps.python.org/pep-0619/](https://peps.python.org/pep-0619/)
## 先決條件
若要使用此頁面上的程式碼範例，您需要下列項目：
+ [Amazon MWAA 環境](get-started.md)。
## 權限
使用此頁面上的程式碼範例不需要額外的許可。
## 相依性
+ 使用此頁面上的程式碼範例不需要額外的相依性。
## 程式碼範例
1. 在命令提示中，導覽至存放 DAG 程式碼的資料夾。例如：
```
cd dags
```
1. 複製下列程式碼範例的內容，並將其儲存為 `dag-custom-metrics.py`。將 取代`MWAA-ENV-NAME`為您的環境名稱。
```
from airflow import DAG
from airflow.operators.python_operator import PythonOperator
from airflow.utils.dates import days_ago
from datetime import datetime
import os,json,boto3,psutil,socket
def publish_metric(client,name,value,cat,unit='None'):
environment_name = os.getenv("MWAA_ENV_NAME")
value_number=float(value)
hostname = socket.gethostname()
ip_address = socket.gethostbyname(hostname)
print('writing value',value_number,'to metric',name)
response = client.put_metric_data(
Namespace='MWAA-Custom',
MetricData=[
{
'MetricName': name,
'Dimensions': [
{
'Name': 'Environment',
'Value': environment_name
},
{
'Name': 'Category',
'Value': cat
},
{
'Name': 'Host',
'Value': ip_address
},
],
'Timestamp': datetime.now(),
'Value': value_number,
'Unit': unit
},
]
)
print(response)
return response
def python_fn(**kwargs):
client = boto3.client('cloudwatch')
cpu_stats = psutil.cpu_stats()
print('cpu_stats', cpu_stats)
virtual = psutil.virtual_memory()
cpu_times_percent = psutil.cpu_times_percent(interval=0)
publish_metric(client=client, name='virtual_memory_total', cat='virtual_memory', value=virtual.total, unit='Bytes')
publish_metric(client=client, name='virtual_memory_available', cat='virtual_memory', value=virtual.available, unit='Bytes')
publish_metric(client=client, name='virtual_memory_used', cat='virtual_memory', value=virtual.used, unit='Bytes')
publish_metric(client=client, name='virtual_memory_free', cat='virtual_memory', value=virtual.free, unit='Bytes')
publish_metric(client=client, name='virtual_memory_active', cat='virtual_memory', value=virtual.active, unit='Bytes')
publish_metric(client=client, name='virtual_memory_inactive', cat='virtual_memory', value=virtual.inactive, unit='Bytes')
publish_metric(client=client, name='virtual_memory_percent', cat='virtual_memory', value=virtual.percent, unit='Percent')
publish_metric(client=client, name='cpu_times_percent_user', cat='cpu_times_percent', value=cpu_times_percent.user, unit='Percent')
publish_metric(client=client, name='cpu_times_percent_system', cat='cpu_times_percent', value=cpu_times_percent.system, unit='Percent')
publish_metric(client=client, name='cpu_times_percent_idle', cat='cpu_times_percent', value=cpu_times_percent.idle, unit='Percent')
return "OK"
with DAG(dag_id=os.path.basename(__file__).replace(".py", ""), schedule_interval='*/5 * * * *', catchup=False, start_date=days_ago(1)) as dag:
t = PythonOperator(task_id="memory_test", python_callable=python_fn, provide_context=True)
```
1. 執行下列 AWS CLI 命令，將 DAG 複製到您環境的儲存貯體，然後使用 Apache Airflow UI 觸發 DAG。
```
aws s3 cp your-dag.py s3://your-environment-bucket/dags/
```
1. 如果 DAG 執行成功，您會在 Apache Airflow 日誌中取得類似以下內容的內容：
```
[2022-08-16, 10:54:46 UTC] {{logging_mixin.py:109}} INFO - cpu_stats scpustats(ctx_switches=3253992384, interrupts=1964237163, soft_interrupts=492328209, syscalls=0)
[2022-08-16, 10:54:46 UTC] {{logging_mixin.py:109}} INFO - writing value 16024199168.0 to metric virtual_memory_total
[2022-08-16, 10:54:46 UTC] {{logging_mixin.py:109}} INFO - {'ResponseMetadata': {'RequestId': 'fad289ac-aa51-46a9-8b18-24e4e4063f4d', 'HTTPStatusCode': 200, 'HTTPHeaders': {'x-amzn-requestid': 'fad289ac-aa51-46a9-8b18-24e4e4063f4d', 'content-type': 'text/xml', 'content-length': '212', 'date': 'Tue, 16 Aug 2022 17:54:45 GMT'}, 'RetryAttempts': 0}}
[2022-08-16, 10:54:46 UTC] {{logging_mixin.py:109}} INFO - writing value 14356287488.0 to metric virtual_memory_available
[2022-08-16, 10:54:46 UTC] {{logging_mixin.py:109}} INFO - {'ResponseMetadata': {'RequestId': '6ef60085-07ab-4865-8abf-dc94f90cab46', 'HTTPStatusCode': 200, 'HTTPHeaders': {'x-amzn-requestid': '6ef60085-07ab-4865-8abf-dc94f90cab46', 'content-type': 'text/xml', 'content-length': '212', 'date': 'Tue, 16 Aug 2022 17:54:45 GMT'}, 'RetryAttempts': 0}}
[2022-08-16, 10:54:46 UTC] {{logging_mixin.py:109}} INFO - writing value 1342296064.0 to metric virtual_memory_used
[2022-08-16, 10:54:46 UTC] {{logging_mixin.py:109}} INFO - {'ResponseMetadata': {'RequestId': 'd5331438-5d3c-4df2-bc42-52dcf8d60a00', 'HTTPStatusCode': 200, 'HTTPHeaders': {'x-amzn-requestid': 'd5331438-5d3c-4df2-bc42-52dcf8d60a00', 'content-type': 'text/xml', 'content-length': '212', 'date': 'Tue, 16 Aug 2022 17:54:45 GMT'}, 'RetryAttempts': 0}}
...
[2022-08-16, 10:54:46 UTC] {{python.py:152}} INFO - Done. Returned value was: OK
[2022-08-16, 10:54:46 UTC] {{taskinstance.py:1280}} INFO - Marking task as SUCCESS. dag_id=dag-custom-metrics, task_id=memory_test, execution_date=20220816T175444, start_date=20220816T175445, end_date=20220816T175446
[2022-08-16, 10:54:46 UTC] {{local_task_job.py:154}} INFO - Task exited with return code 0
```