When a double close is detected in a debug build, a debug assertion is
triggered. This will generate a core dump which should help investigate
the double close.
Since there is a concept called "listener" it is confusing that the
dcb "this" argument in some dcb functions is called 'listener' instead
of 'dcb' as it is called everywhere else.
The internal header directory conflicted with in-source builds causing a
build failure. This is fixed by renaming the internal header directory to
something other than maxscale.
The renaming pointed out a few problems in a couple of source files that
appeared to include internal headers when the headers were in fact public
headers.
Fixed maxctrl in-source builds by making the copying of the sources
optional.
Only used in conjunction with queued connections, which are not
enabled anyway. Once that comes on the table again, better to use
some standard data structures.
Apart from listeners, all DCBs will be assigned to the current
thread. This simplifies the addition of DCBs to worker threads.
Also performed a small cleanup of poll_add_dcb to make it more readable.
Now it is also possible to ensure that a DCB stays alive while
a task referring to it is posted from one worker to another.
That will be implemented in a subsequent commit.
The polling mechanism can now optionally be used for managing
the lifetime of an object placed into the poll set.
If a MXS_POLL_DATA has a non-null 'free', then the reference count
of the data will be increased before calling the handler and
decreased after. In that case, if the reference count reaches 0,
the free function will be called.
Note that the reference counts of *all* MXS_POLL_DATAs returned
by 'epoll_wait' will be increased before the events are delivered
to the handlers individually for each MXS_POLL_DATA, and then once
all events have been delivered, the reference count of each
MXS_POLL_DATA will be decreased.
This ensure that if there are interdependencies between different
MXS_POLL_DATAs returned by one call to 'epoll_wait', the case that
an MXS_POLL_DATA is deleted before its events have been delivered
can be avoided by using the reference count for lifetime management.
In subsequent commits, the reference count will be taken into use
in the lifetime management of DCBs.
When something fails inside dcb_connect we rewind the situation
properly, without calling any of the close functions intended for
shutting down a properly created DCB. That way they can be simplified
and once the reference counting is taken into use it is sufficient to
call dcb_dec_ref(dcb) instead of dcb_free_all_memory().
If a fake event is added to the current dcb, we arrange things so
that it is delivered immediately when the handling of the event(s)
during which the fake event was added, has been performed.
Otherwise the event is delivered via the event loop.
The adminusers test did not properly initialize all subsystems in
MaxScale. The polling and DCB tests weren't updated with the changes to
the DCB closing.
dcb_readq_append()
dcb_readq_prepend()
dcb_readq_set()
dcb_readq_has()
dcb_readq_release()
dcb_readq_get()
dcb_readq_length()
No code but for DCB code itself should directly manipulate the
internals of a DCB. Thesse functions will be taken into use in
protocol modules.
Before each event handler is called, it is checked whether the
dcb has been closed. If it has been, then the event handler is
not called.
The check has to be made before each event handler, because any
event handler can close the dcb.
If the current worker id is -1, we do not insist that the dcb
is closed by the owning thread. That will happen only for dcbs
that are created before the workers have been started and hence
it is also ok to close them after the workers have exited.
If a dcb being closed is the dcb for which events are currently being
processed, the dcb is not closed immediately but only after all events
have been delivered.
This will be used by a subsequent `session_get_current()` and
`session_get_current_id()` for obtaining the current SESSION and
session id, respectively. The latter of those will be used by the
logging mechanism for logging the session id in conjunction with
messages.
When dcb_close() is called, the DCB is only marked for closing
and the actual closing takes place only after all event handlers
have been called. That way, the state of the DCB will not change
during event processing but only after.
From a handler perspective this should now be just like it was
when the zombie queue was present.
TODO: There are far too many state variables or variables akin to
state variables - dcb_role, state, persistentstart, n_close -
in DCB. A cleanup is warranted.
As each client/server connection will be handled by a specific
thread, all closing activity can take place directly when the
connection is closed and not later when the zombie queue is
processed.
In a subsequent commit the zombie queue will be removed.
The example in the epoll(7) manpage only sets the EPOLLIN event flag.
Although it is not explicitly stated that only EPOLLIN events arrive for
sockets that are listening, any other types of events should not be
relevant for listeners.
If a connection has not been fully established (i.e. authentication has
been completed) then it should not be considered as a connection pool
candidate.
The server internal session id may be larger than 4 bytes (MariaDB uses 8)
but only 4 are sent in the handshake. The full value can be queried
from the server, but this query is not supported by MaxScale yet. In any
case, both the protocol and MXS_SESSION now have 64 bit counters. Only the
low 32 bits are sent in the handshake, similar to server.
