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

完成执行时专门记录

有没有我可以用来记录这个的挂钩或回调？

Answer 1

您是否考虑过为您的 execute 或等效项（例如 execute_concurrent）创建装饰器来记录用于您的语句或准备语句的 CQL 查询？

您可以采用仅在查询成功执行后才记录 CQL 查询的方式编写。

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*

使用回调，您可以轻松记录该会话进行的所有查询。

示例：

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

2 个选项：

坚持session.add_request_init_listener

来自源代码：

a) BoundStatement

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

传递的值存储在raw_values中，你可以尝试提取它

b) BatchStatement

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

它存储了在_statements_and_parameters中用于构造该对象的所有语句和参数。虽然不是 public 属性
，但似乎可以获取
c) 只调用了这个hook，没找到其他hook 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建何种查询并可能添加额外的方法 callbacks/errbacks
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

Request tracing can be turned on for any request by setting trace=True in Session.execute_async(). View the results by waiting on the future, then ResponseFuture.get_query_trace()

这是使用选项 2 的 BatchStatement 跟踪示例：

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'

使用 cassandra-python-driver 记录所有查询

Logging all queries with cassandra-python-driver

python

cassandra

cassandra-python-driver