python - 使用 cassandra-python-driver 记录所有查询

Question

我正在尝试找到一种方法来记录从 python 代码在 Cassandra 上完成的所有查询。使用 BatchStatement

是否有任何钩子或回调我可以用来记录这个？

Answer 1

2个选项：

1. 依照session.add_request_init_listener

   从源代码：

   一个）BoundStatement

   https://github.com/datastax/python-driver/blob/3.11.0/cassandra/query.py#L560

   传入的值存储在 中raw_values，您可以尝试提取它

   b)BatchStatement

   https://github.com/datastax/python-driver/blob/3.11.0/cassandra/query.py#L676

   它将用于构造此对象的所有语句和参数存储在_statements_and_parameters. 虽然不是公共财产，但似乎可以获取

   c）只调用了这个钩子，我没有找到任何其他钩子 https://github.com/datastax/python-driver/blob/master/cassandra/cluster.py#L2097

   但它与查询的实际执行无关 - 它只是一种检查已构造的查询类型并可能添加额外的回调/错误返回的方法

2. 从不同的角度接近它并使用痕迹

   https://datastax.github.io/python-driver/faq.html#how-do-i-trace-a-request https://datastax.github.io/python-driver/api/cassandra/cluster.html #cassandra.cluster.ResponseFuture.get_all_query_traces

   通过在 Session.execute_async() 中设置 trace=True，可以为任何请求打开请求跟踪。通过等待未来来查看结果，然后 ResponseFuture.get_query_trace()

BatchStatement这是使用选项 2 进行跟踪的示例：

bs = BatchStatement()                                                        
bs.add_all(['insert into test.test(test_type, test_desc) values (%s, %s)',   
            'insert into test.test(test_type, test_desc) values (%s, %s)',   
            'delete from test.test where test_type=%s',
            'update test.test set test_desc=%s where test_type=%s'],
           [['hello1', 'hello1'],                                            
            ['hello2', 'hello2'],                                            
            ['hello2'],
            ['hello100', 'hello1']])     
res = session.execute(bs, trace=True)                                        
trace = res.get_query_trace()                                                
for event in trace.events:                                                   
    if event.description.startswith('Parsing'):                              
        print event.description 

它产生以下输出：

Parsing insert into test.test(test_type, test_desc) values ('hello1', 'hello1')
Parsing insert into test.test(test_type, test_desc) values ('hello2', 'hello2')
Parsing delete from test.test where test_type='hello2'
Parsing update test.test set test_desc='hello100' where test_type='hello1'

Answer 2

add_request_init_listener(fn, *args, **kwargs)

Adds a callback with arguments to be called when any request is created.

It will be invoked as fn(response_future, *args, **kwargs) after each client request is created, and before the request is sent*

Using the callback you can easily log all query made by that session.

Example :

from cassandra.cluster import Cluster
from cassandra.auth import PlainTextAuthProvider


class RequestHandler:

    def on_request(self, rf):
        # This callback is invoked each time a request is created, on the thread creating the request.
        # We can use this to count events, or add callbacks
        print(rf.query)


auth_provider = PlainTextAuthProvider(
    username='cassandra',
    password='cassandra'
)

cluster = Cluster(['192.168.65.199'],auth_provider=auth_provider)
session = cluster.connect('test')

handler = RequestHandler()
# each instance will be registered with a session, and receive a callback for each request generated
session.add_request_init_listener(handler.on_request)

from time import sleep

for count in range(1, 10):
    print(count)
    for row in session.execute("select * from kv WHERE key = %s", ["ed1e49e0-266f-11e7-9d76-fd55504093c1"]):
        print row
    sleep(1)

Answer 3

您是否考虑为您的execute或等效的（例如execute_concurrent）创建一个装饰器来记录用于您的语句或准备好的语句的 CQL 查询？

您可以以仅在成功执行查询时才记录 CQL 查询的方式编写此代码。