Reproduce #217 by connecting with telnet to debug client interface and execute command:
fail accept 23
and try to execute read query, for example, with
mysql -h 127.0.0.1 -P 4008 -u maxuser -pmaxpwd -e 'select current_user(), @@server_id'
dcb_final_free: Router session is not closed anymore when dcb is closed. Router session is shared among all dcbs and is closed and freed with session.
dcb_connect: dcb's state must be switched fro DCB_STATE_ALLOC to DCB_STATE_DISCONNECTED before dcb_final_free can be called for it.
dcb_close: poll_remove_dcb encapsulates dcb's state transition in the same way as poll_add_dcb. Removed state modification from dcb_close. Read return value of poll_remove_dcb and log accordingly.
dcb_set state: remove dassert if dcb_set_state_nomutex returned false. False can be returned indicating that intented change didn't occur but the end state, for example, may be acceptable. Failures in state transitions are asserted in dcb_Set_state_nomutex.
poll.c
poll_add_dcb: dcb state is now set here to either DCB_STATE_LISTENING or to DCB_STATE_POLLING according to dcb's role. Failures in state setting and in epoll_ctl are detected, logged and handled.
poll_remove_dcb: Failures in state setting and epoll_ctl are detected, logged, and handled.
mysql_client_server_protocol.h
Removed macros MYSQL_FAILED_AUTHENTICATION & MYSQL_SUCCESFUL_AUTHENTICATION as they were not necessary and used with constant values 0 and 1 depending on the case.
Renamed variable 'conn' to 'protocol' in cases where it meant protocol.
mysql_backend.c
gw_read_backend_event: In case when there was nothing to read or read failed, backend dcb is closed because situation is assumed to be such that backend server closed its side of the socket. Removed macros MYSQL_FAILED/SUCCESFUL_AUTHENTICATION
gw_create_backend_connection: Assigned protocol with fd which is connected to backend.
backend_write_delayqueue: In case where dcb_write fails to write anything, close backend dcb to avoid it getting hanging.
mysql_client.c
gw_read_client_event: Read return value of routeQuery and if it isn't == 1, call mysql_send_custom_error with client dcb and set client's protocol state to MYSQL_IDLE instead of MYSQL_ROUTING.
gw_MySQLAccept: Static reply counter was erroneously used as a criteria for jumping to return point where return value was constantly 'success' (=0). Replaced static reply counter with private. Fixed return value in different cases.
mysql_common.c
gw_receive_backend_auth: Changed to return boolean values indicating of success or failue. Used integers which were assigned to macroed values on the caller side. Added length check before accessing buffer.
readconnroute.c
Cut too long lines and removed statements with side effects.
skygw_debug.h
Added macro STRPROTOCOLSTATE(s) to produce string representation of a given protocol state.
If backend connection can't be created, backend_dcb is not create, router client session is not created and what already is created in session_alloc, is freed.
mysql_client.c : gw_read_client_event
If session creation failed, then - instead of sending ok to client, "failed to create new session" is sent and client dcb is closed.
: gw_MySQLAccept
removed loop where accept was called again and again. With single thread looping forever is not possible because there's no one to free previously allocated resources.
If accept fails ten times in a row, then return without new client dcb.
: dcb_alloc switched malloc to calloc, dcb->fd is initialized to -1.
: dcb_process_zombies return value of close(fd) is checked. Closed fds are stored to conn_open array.
: dcb_connect assigns new fd only if backend connection succeeds. Dcb is added to poll set in the same way, only if connect succeed.
gateway.c : conn_open array is initialized in main. For each created socket, a true is set to corresponding slot. Max. number of slots is 1024.
mysql_client_server_protocol.h : gw_do_connect_to declaration
mysql_backend.c : gw_create_backend_connection returns rv >= 0 and a protocol which is assigned to backend_dcb. In error, -1 is returned and fd is not set.
mysql_client.c : conn_open array is kept up-to-date and protocol pointer is assigned also to dcb outside mysql_protocol_init.
mysql_common.c : gw_do_connect_to_backend 3rd argument is pointer to fd, not protocol. dcb is added to poll set later in dcb_connect.
skygw_debug.h : define conn_open[1024] array where open connections can be marked in debug build.
-------
Removed DCB states DCB_STATE_IDLE, and DCB_STATE_PROCESSING.
Added DCB_STATE_UNDEFINED for initial content for state variable which doesn't have any specific value set, and DCB_STATE_NOPOLLING to indicate that dcb has been removed from poll set.
Added following dcb roles: DCB_ROLE_SERVICE_LISTENER for listeners of services, and DCB_ROLE_REQUEST_HANDLER for client/backend dcbs. Listeners may have state DCB_STATE_LISTENING, but not DCB_STATE_POLLING. Request handlers may have DCB_STATE_POLLING but not DCB_STATE_LISTENING. Role is passed as an argument to dcb.c:dcb_alloc.
From now on, struct check numbers of DCB are included and checked in DEBUG build only.
Added dcb_role_t dcb_role-member to DCB as well as SPINLOCK dcb_initlock, which protects state changes.
Removed extern keyword from function declarations because functions are by default externally visible if they are declared in header.
dcb.b
------
Function dcb_set_state, and dcb_set_state_nomutex provide functions for changing dcb states. Latter implements a state machine for dcb.
Function dcb_add_to_zombieslist replaces dcb_free. It adds in atomic step dcb to zombieslist and changes state to DCB_STATE_ZOMBIE.
Function dcb_final_free removes dcb from allDCBs list, terminates router and client sessions, and frees dcb and related memory.
Function dcb_process_zombies removes executing thread from dcb's bitmask, and it there are no further thread bits, moves dcb to a victim list, and finally, for each dcb on victim list, closes fd and sets state to DCB_STATE_DISCONNECTED.
Function dcb_close sets dcb state to DCB_STATE_NOPOLLIN, removes dcb from poll set and sets bit to bitmask for each server thread in an atomic step.
poll.c
------
Function poll_add_dcb sets either DCB_STATE_LISTENING or DCB_STATE_POLLING state for newly created dcb, depending whether the role of dcb is DCB_ROLE_SERVICE_LISTENER, or DCB_ROLE_REQUEST_HANDLER, respectively. Then dcb is set to poll set.
poll_waitevents : commented out code which skipped event if dcb was added to zombieslist or if fd was closed. Added state checks.
service.c : Minor changes.
httpd.c : Removed dcb state changes. They are done in core.
mysql_backend.c : Added checks, removed dcb state changes.
mysql_client.c : Removed dcb state changes. Added checks.
mysql_common.c : Minor changes
telnetd.c : Removed state changes. Replaced some typecasts and pointer references with local variable reads.
skygw_debug.h : Removed two states, and added two to state printing macro.
reworked the reference count mechanism on the session. Introduced a
FREE state for the session and alter the session destruction flow so
that we only remove the session when all the DCB's have singled they
have finished processing events for the DCB rather than when the first
thread decides to clsoe the DCB.
routeQuery()
(dcb->func).close(dcb);
This will prevent setting again dcb->sate = DCB_STATE_POLLING in return_rc label.
The log entry for
[gw_read_client_event] ioctl FIONREAD for fd 21 failed. errno 9, Bad file descriptor. dcb->state = 3
now is not present anymore.
