Dlq t #12
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Dlq t #12
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shibd
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Jan 13, 2023
Fixes apache#167 ### Motivation Here are some debugging info when the segfault happened in `testCloseClient`. The outputs have been trimmed to make them clear. An example crash at `async_write`: ``` #12 0x00007ffff7496dad in basic_stream_socket<...>::boost::asio::async_write /usr/include/boost/asio/impl/write.hpp:512 #13 0x00007ffff748e003 in ClientConnection::asyncWrite lib/ClientConnection.h:245 #14 0x00007ffff746e0b6 in ClientConnection::handleHandshake (this=0x555555e689d0) lib/ClientConnection.cc:502 ``` Another example crash at `async_receive`: ``` #6 0x00007ffff7497247 in basic_stream_socket<...>::async_receive /usr/include/boost/asio/basic_stream_socket.hpp:677 #7 0x00007ffff748e647 in ClientConnection::asyncReceive lib/ClientConnection.h:258 #8 0x00007ffff746fa5d in ClientConnection::readNextCommand lib/ClientConnection.cc:606 ``` The frame where it crashed: ``` 245 if (descriptor_data->shutdown_) (gdb) p descriptor_data $2 = (boost::asio::detail::epoll_reactor::per_descriptor_data &) @0x555555e4a780: 0x0 ``` We can see the socket descriptor is `nullptr`. The root cause is when `async_receive` or `async_write` is called, the `io_service` object might be closed. This case happened when `createProducerAsync` is called, the actual producer creation continues in another thread, while the `client.close()` happens in the current thread. ### Modifications Check if the `ClientConnection` is closed before `async_receive` or `async_write`. To avoid the use of lock, changing the `state_` field to atomic. ### Verifications ```bash ./tests/pulsar-tests --gtest_filter='ClientTest.testCloseClient' --gtest_repeat=20 ``` It never crashed after applying this patch.
shibd
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Feb 18, 2024
### Motivation We observed server null `ClientConnection` accesses in test environment. See the `this=0x0` outputs in the following two typical stacks. ``` #8 bytesWritten (this=0xb8, size=371) at lib/SharedBuffer.h:166 #9 pulsar::ClientConnection::handleRead (this=0x0, err=..., bytesTransferred=371, minReadSize=4) at lib/ClientConnection.cc:609 ``` ``` #12 0x00007f33202933d2 in unique_lock (__m=..., this=0x7f3311c82800) at /opt/rh/devtoolset-7/root/usr/include/c++/7/bits/std_mutex.h:197 #13 pulsar::ClientConnection::sendPendingCommands (this=0x0) at lib/ClientConnection.cc:1071 #14 0x00007f3320293d2d in pulsar::ClientConnection::handleSendPair (this=0x0, err=...) at lib/ClientConnection.cc:1066 ``` Though `shared_from_this()` is always passed to the `std::bind` function, when the method of `ClientConnection` is called, the pointer is still `null`. ### Modifications First, replace all `std::bind` calls with the lambda expression that catches `std::weak_ptr<ClientConnection>` and perform null checks explicitly on the value returned by the `lock()` method. Since now all asio callbacks don't hold a `shared_ptr`, the owner of the `ClientConnection` object should be `ConnectionPool`, i.e. the pool maintains some connections, while all asio callbacks use `weak_ptr` to test if the connection is present. Second, make `ClientConnection::getConnection` return `shared_ptr` rather than `weak_ptr` so that the caller side does not need to check if `lock()` returns null in the callback of this future. We cannot make `ConnectionPool::getConnectionAsync` return `shared_ptr` because it could return the future of `connectPromise_`, which is hold by `ClientConnection` itself. We should avoid holding a `shared_ptr` of `ClientConnection` because its owner is `ConnectionPool`.
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