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connection_pool glitches

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This commit is contained in:
Ruben Perez
2025-01-31 14:48:30 +01:00
parent 736c1d009a
commit 67e12918ae
1 changed files with 53 additions and 55 deletions
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108
include/boost/mysql/connection_pool.hpp
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@@ -44,7 +44,7 @@ namespace mysql {
* automatically. It's safe to destroy the `connection_pool` object before `*this`.
*
* \par Thread safety
* This object and the \ref any_connection object it may point to are **not thread safe**,
* This object and the \ref any_connection object it may point to are *not thread safe*,
* even if the connection pool used to obtain them was constructed with
* \ref pool_params::thread_safe set to true.
*
@@ -56,9 +56,9 @@ namespace mysql {
* In other words, individual connections can't be shared between threads. Pools can
* be shared only if they're constructed with \ref pool_params::thread_safe set to true.
*
* - Distinct objects: safe if the \ref connection_pool that was used to obtain the objects
* was created with \ref pool_params::thread_safe set to true. Otherwise, unsafe.
* - Shared objects: always unsafe.
* \li Distinct objects: safe if the \ref connection_pool that was used to obtain the objects
* was created with \ref pool_params::thread_safe set to true. Otherwise, unsafe.
* \li Shared objects: always unsafe.
*/
class pooled_connection
{
@@ -79,7 +79,7 @@ class pooled_connection
public:
/**
* \brief Constructs an invalid pooled connection.
* \brief Default constructor.
* \details
* The resulting object is invalid (`this->valid() == false`).
*
@@ -101,6 +101,8 @@ public:
*/
pooled_connection(pooled_connection&& other) noexcept : impl_(std::move(other.impl_)) {}
pooled_connection(const pooled_connection&) = delete;
/**
* \brief Move assignment.
* \details
@@ -129,7 +131,6 @@ public:
return *this;
}
pooled_connection(const pooled_connection&) = delete;
pooled_connection& operator=(const pooled_connection&) = delete;
/**
@@ -249,7 +250,7 @@ public:
* Pools are composed of an internal state object, plus a handle to such state.
* Each component has different thread-safety rules.
*
* Regarding **internal state**, connection pools are **not thread-safe by default**,
* Regarding *internal state*, connection pools are *not thread-safe by default*,
* but can be made safe by constructing them with
* \ref pool_params::thread_safe set to `true`.
* Internal state is also mutated by some functions outside `connection_pool`, like
@@ -258,16 +259,16 @@ public:
* The following actions imply a pool state mutation, and are protected by a strand
* when thread-safety is enabled:
*
* - Calling \ref connection_pool::async_run.
* - Calling \ref connection_pool::async_get_connection.
* - Cancelling \ref async_get_connection by emitting a cancellation signal.
* - Returning a connection by destroying a \ref pooled_connection or
* calling \ref pooled_connection::return_without_reset.
* - Cancelling the pool by calling \ref connection_pool::cancel,
* emitting a cancellation signal for \ref async_run, or destroying the
* `connection_pool` object.
* \li Calling \ref connection_pool::async_run.
* \li Calling \ref connection_pool::async_get_connection.
* \li Cancelling \ref async_get_connection by emitting a cancellation signal.
* \li Returning a connection by destroying a \ref pooled_connection or
* calling \ref pooled_connection::return_without_reset.
* \li Cancelling the pool by calling \ref connection_pool::cancel,
* emitting a cancellation signal for \ref async_run, or destroying the
* `connection_pool` object.
*
* The **handle to the pool state** is **never thread-safe**, even for
* The *handle to the pool state* is *never thread-safe*, even for
* pools with thread-safety enabled. Functions like assignments
* modify the handle, and cause race conditions if called
* concurrently with other functions. Other objects,
@@ -276,9 +277,9 @@ public:
*
* In summary:
*
* - Distinct objects: safe.
* - Shared objects: unsafe. Setting \ref pool_params::thread_safe
* to `true` makes some functions safe.
* \li Distinct objects: safe.
* \li Shared objects: unsafe. Setting \ref pool_params::thread_safe
* to `true` makes some functions safe.
*
* \par Object lifetimes
* Connection pool objects create an internal state object that is referenced
@@ -363,12 +364,12 @@ public:
* The passed executor becomes the pool executor, available through \ref get_executor.
* `ex` is used as follows:
*
* - If `params.thread_safe == true`, `ex` is used to build a strand. The strand is used
* to build internal I/O objects, like timers.
* - If `params.thread_safe == false`, `ex` is used directly to build internal I/O objects.
* - If `params.connection_executor` is empty, `ex` is used to build individual connections,
* regardless of the chosen thread-safety mode. Otherwise, `params.connection_executor`
* is used.
* \li If `params.thread_safe == true`, `ex` is used to build a strand. The strand is used
* to build internal I/O objects, like timers.
* \li If `params.thread_safe == false`, `ex` is used directly to build internal I/O objects.
* \li If `params.connection_executor` is empty, `ex` is used to build individual connections,
* regardless of the chosen thread-safety mode. Otherwise, `params.connection_executor`
* is used.
*
* \par Exception safety
* Strong guarantee. Exceptions may be thrown by memory allocations.
@@ -394,22 +395,15 @@ public:
* pool_params.
*/
template <
class ExecutionContext
#ifndef BOOST_MYSQL_DOXYGEN
,
class ExecutionContext,
class = typename std::enable_if<std::is_convertible<
decltype(std::declval<ExecutionContext&>().get_executor()),
asio::any_io_executor>::value>::type
#endif
>
asio::any_io_executor>::value>::type>
connection_pool(ExecutionContext& ctx, pool_params params)
: connection_pool(ctx.get_executor(), std::move(params), 0)
{
}
connection_pool(const connection_pool&) = delete;
connection_pool& operator=(const connection_pool&) = delete;
/**
* \brief Move-constructor.
* \details
@@ -426,9 +420,9 @@ public:
*
* \par Thread-safety
* Mutates `other`'s internal state handle. Does not access the pool state.
* This function **can never be called concurrently with other functions
* that read the internal state handle**, even for pools created
* with \ref pool_params::thread_safe set to true.
* This function
* *can never be called concurrently with other functions that read the internal state handle*,
* even for pools created with \ref pool_params::thread_safe set to true.
*
* The internal pool state is not accessed, so this function can be called
* concurrently with functions that only access the pool's internal state,
@@ -436,6 +430,8 @@ public:
*/
connection_pool(connection_pool&& other) = default;
connection_pool(const connection_pool&) = delete;
/**
* \brief Move assignment.
* \details
@@ -452,9 +448,9 @@ public:
*
* \par Thread-safety
* Mutates `*this` and `other`'s internal state handle. Does not access the pool state.
* This function **can never be called concurrently with other functions
* that read the internal state handle**, even for pools created
* with \ref pool_params::thread_safe set to true.
* This function
* *can never be called concurrently with other functions that read the internal state handle*,
* even for pools created with \ref pool_params::thread_safe set to true.
*
* The internal pool state is not accessed, so this function can be called
* concurrently with functions that only access the pool's internal state,
@@ -462,6 +458,8 @@ public:
*/
connection_pool& operator=(connection_pool&& other) = default;
connection_pool& operator=(const connection_pool&) = delete;
/**
* \brief Destructor.
* \details
@@ -469,9 +467,9 @@ public:
*
* \par Thread-safety
* Mutates the internal state handle. Mutates the pool state.
* This function **can never be called concurrently with other functions
* that read the internal state handle**, even for pools created
* with \ref pool_params::thread_safe set to true.
* This function
* *can never be called concurrently with other functions that read the internal state handle*,
* even for pools created with \ref pool_params::thread_safe set to true.
*
* The internal pool state is modified as per \ref cancel.
* If thread-safety is enabled, it's safe to call the destructor concurrently
@@ -569,8 +567,8 @@ public:
* is equivalent to calling \ref connection_pool::cancel.
* The following `asio::cancellation_type_t` values are supported:
*
* - `asio::cancellation_type_t::terminal`
* - `asio::cancellation_type_t::partial`
* \li `asio::cancellation_type_t::terminal`
* \li `asio::cancellation_type_t::partial`
*
* Note that `asio::cancellation_type_t::total` is not supported because invoking
* `async_run` always has observable side effects.
@@ -659,18 +657,18 @@ public:
* Cancelling `async_get_connection` has no observable side effects.
* The following `asio::cancellation_type_t` values are supported:
*
* - `asio::cancellation_type_t::terminal`
* - `asio::cancellation_type_t::partial`
* - `asio::cancellation_type_t::total`
* \li `asio::cancellation_type_t::terminal`
* \li `asio::cancellation_type_t::partial`
* \li `asio::cancellation_type_t::total`
*
* \par Errors
* - \ref client_errc::no_connection_available, if the `async_get_connection`
* operation is cancelled before a connection becomes available.
* - \ref client_errc::pool_not_running, if the `async_get_connection`
* operation is cancelled before async_run is called.
* - \ref client_errc::pool_cancelled, if the pool is cancelled before
* the operation completes, or `async_get_connection` is called
* on a pool that has been cancelled.
* \li \ref client_errc::no_connection_available, if the `async_get_connection`
* operation is cancelled before a connection becomes available.
* \li \ref client_errc::pool_not_running, if the `async_get_connection`
* operation is cancelled before async_run is called.
* \li \ref client_errc::pool_cancelled, if the pool is cancelled before
* the operation completes, or `async_get_connection` is called
* on a pool that has been cancelled.
*
* \par Thread-safety
* Reads the internal state handle. Mutates the pool state.