8c3c5777da
The connection's `cpu_concurrency_t` struct tracks the state of a connection to manage the admission of new requests and prevent CPU overload during connection storms. When a connection holds units (allowed only 0 or 1), it is considered to be in the "CPU state" and contributes to the concurrency limits used when accepting new connections. The bug stems from the fact that `counted_data_source_impl::get` and `counted_data_sink_impl::put` calls can interleave during execution. This occurs because of `should_parallelize` and `_ready_to_respond`, the latter being a future chain that can run in the background while requests are being read. Consequently, while reading request (N), the system may concurrently be writing the response for request (N-1) on the same connection. This interleaving allows `return_all()` to be called twice before the subsequent `consume_units()` is invoked. While the second `return_all()` call correctly returns 0 units, the matching `consume_units()` call would mistakenly take an extra unit from the semaphore. Over time, a connection blocked on a read operation could end up holding an unreturned semaphore unit. If this pattern repeats across multiple connections, the semaphore units are eventually depleted, preventing the server from accepting any new connections. The fix ensures that we always consume the exact number of units that were previously returned. With this change, interleaved operations behave as follows: get() return_all — returns 1 unit put() return_all — returns 0 units get() consume_units — takes back 1 unit put() consume_units — takes back 0 units Logically, the networking phase ends when the first network operation concludes. But more importantly, when a network operation starts, we no longer hold any units. Other solutions are possible but the chosen one seems to be the simplest and safest to backport. Fixes SCYLLADB-485 Backport: all supported affected versions, bug introduced with initial feature implementation in:ed3e4f33fd- (cherry picked from commit0376d16ad3) - (cherry picked from commit3b98451776) Parent PR: #28530 Closes scylladb/scylladb#28716 * github.com:scylladb/scylladb: test: auth_cluster: add test for hanged AUTHENTICATING connections transport: fix connection code to consume only initially taken semaphore units
Scylla in-source tests.
For details on how to run the tests, see docs/dev/testing.md
Shared C++ utils, libraries are in lib/, for Python - pylib/
alternator - Python tests which connect to a single server and use the DynamoDB API unit, boost, raft - unit tests in C++ cqlpy - Python tests which connect to a single server and use CQL topology* - tests that set up clusters and add/remove nodes cql - approval tests that use CQL and pre-recorded output rest_api - tests for Scylla REST API Port 9000 scylla-gdb - tests for scylla-gdb.py helper script nodetool - tests for C++ implementation of nodetool
If you can use an existing folder, consider adding your test to it. New folders should be used for new large categories/subsystems, or when the test environment is significantly different from some existing suite, e.g. you plan to start scylladb with different configuration, and you intend to add many tests and would like them to reuse an existing Scylla cluster (clusters can be reused for tests within the same folder).
To add a new folder, create a new directory, and then
copy & edit its suite.ini.