suharev7 / clickhouse-rs / 53
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Ran 18 Jan 2019 04:03PM UTC

Jobs 1

Files 39

Run time 5s

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pending completion

Build # 53

Build Type

travis-ci-com

Committed by

Commit Message

For new connections handling, hold lock over len check and iteration

When checking whether new connections are ready, there's a lock on the
new connections at two points in time:
- checking the len of the connections Vec
- iterating over the connections Vec and swapping out ones that are
ready.

A race condition (and subsequent panic) may occur when:
- two handles try to get a new handle, which calls `poll`, which calls
`handle_futures` which checks if new connections are ready.
- handle 1 gains lock, checks len of `new` connections, gets result of
1, and releases lock.
- handle 2 does the same.
- handle 1 iterates over `0..len`, where len is 1. Because the client
is ready, handle 1 gets lock, removes it from `new` and puts it in `idle`,
and releases lock.
- handle 2 iterates over `0..len`, where len is 1. Because handle 1
already removed the connection, in `new`, the len of `new` is actually
0. After handle 2 acquires the lock, it tries to access `new[i]` but
panics because `new` is empty.

The solution is to hold the lock between the time the length of `new` is
checked, and the time that `new` is iterated over using that len.

Addresses the following error:

```
thread 'arbiter:3c5ae82c-8c17-442d-9b94-4285fed8c742:actix-net-worker-7' panicked at 'index out of bounds: the len is 0 but the index is 0', /rustc/ec194646f/src/libcore/slice/mod.rs:2461:14
stack backtrace:
0: <unknown>
1: <unknown>
2: <unknown>
3: <unknown>
4: std::panicking::rust_panic_with_hook
5: <unknown>
6: rust_begin_unwind
7: core::panicking::panic_fmt
8: core::panicking::panic_bounds_check
9: <unknown>
10:
<clickhouse_rs::pool::futures::get_handle::GetHandle as futures::future::Future>::poll
...
```

Pull Request Pull Request #24: For new connections handling, hold lock over len check and iteration

Run Details

2312 of 2752 relevant lines covered (84.01%)

0.84 hits per line

Jobs

ID	Job ID	Ran	Files	Coverage
3	53.3	18 Jan 2019 04:03PM UTC	0	84.01	Travis Job 53.3

Source Files on build 53

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