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alert.c
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#include "postgres.h"
#include "access/xact.h"
#include "executor/spi.h"
#include "access/htup_details.h"
#include "catalog/pg_type.h"
#include "commands/trigger.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "storage/lwlock.h"
#include "storage/proc.h"
#include "storage/procarray.h"
#include "utils/builtins.h"
#include "utils/timestamp.h"
#if PG_VERSION_NUM >= 140000
#include "utils/wait_event.h"
#elif PG_VERSION_NUM >= 130000
#include "pgstat.h"
#endif
#include "orafce.h"
#include "builtins.h"
#include "pipe.h"
#include "shmmc.h"
#include "utils/rel.h"
PG_FUNCTION_INFO_V1(dbms_alert_register);
PG_FUNCTION_INFO_V1(dbms_alert_remove);
PG_FUNCTION_INFO_V1(dbms_alert_removeall);
PG_FUNCTION_INFO_V1(dbms_alert_set_defaults);
PG_FUNCTION_INFO_V1(dbms_alert_signal);
PG_FUNCTION_INFO_V1(dbms_alert_waitany);
PG_FUNCTION_INFO_V1(dbms_alert_waitone);
PG_FUNCTION_INFO_V1(dbms_alert_waitany_maxwait);
PG_FUNCTION_INFO_V1(dbms_alert_waitone_maxwait);
#if PG_VERSION_NUM >= 130000
extern ConditionVariable *alert_cv;
#endif
typedef struct alert_signal_data
{
text *event;
text *message;
struct alert_signal_data *next;
} alert_signal_data;
static MemoryContext local_buf_cxt;
static LocalTransactionId local_buf_lxid = InvalidTransactionId;
static alert_signal_data *signals;
#ifndef _GetCurrentTimestamp
#define _GetCurrentTimestamp() GetCurrentTimestamp()
#endif
#ifndef GetNowFloat
#ifdef HAVE_INT64_TIMESTAMP
#define GetNowFloat() ((float8) _GetCurrentTimestamp() / 1000000.0)
#else
#define GetNowFloat() _GetCurrentTimestamp()
#endif
#endif
/* in sec 1000 days */
#define MAXWAIT 86400000
#if PG_VERSION_NUM >= 170000
#define CURRENT_LXID (MyProc->vxid.lxid)
#else
#define CURRENT_LXID (MyProc->lxid)
#endif
static void unregister_event(int event_id, int sid);
static char* find_and_remove_message_item(int message_id, int sid,
bool all, bool remove_all,
bool filter_message,
int *sleep, char **event_name);
/*
* There are maximum 30 events and 255 collaborating sessions
*
*/
static alert_lock *session_lock = NULL;
#define NOT_FOUND -1
#define NOT_USED -1
/*
* Compare text and cstr
*/
static int
textcmpm(text *txt, char *str)
{
char *p;
int len;
len = VARSIZE(txt) - VARHDRSZ;
p = VARDATA(txt);
while (len-- && *p != '\0')
{
int retval;
if (0 != (retval = *p++ - *str++))
return retval;
}
if (len > 0)
return 1;
if (*str != '\0')
return -1;
return 0;
}
/*
* this function is called when we know so session with sid is not valid
* anymore.
*/
static void
purge_shared_alert_mem()
{
int i;
LWLockAcquire(ProcArrayLock, LW_SHARED);
for (i = 0; i < MAX_LOCKS; i++)
{
PGPROC *proc;
if (locks[i].sid == NOT_USED)
continue;
proc = BackendPidGetProcWithLock(locks[i].pid);
if (proc == NULL)
{
int j;
int invalid_sid = locks[i].sid;
for (j = 0; j < MAX_EVENTS; j++)
{
if (events[j].event_name != NULL)
{
find_and_remove_message_item(j, invalid_sid,
false, true, true, NULL, NULL);
unregister_event(j, invalid_sid);
}
}
locks[i].sid = NOT_USED;
}
}
LWLockRelease(ProcArrayLock);
}
/*
* find or create event rec
*
*/
static alert_lock*
find_lock(int sid, bool create)
{
int i;
int first_free = NOT_FOUND;
if (session_lock != NULL)
return session_lock;
for (i = 0; i < MAX_LOCKS; i++)
{
if (locks[i].sid == sid)
return &locks[i];
else if (locks[i].sid == NOT_USED && first_free == NOT_FOUND)
first_free = i;
}
if (create)
{
if (first_free == NOT_FOUND)
{
purge_shared_alert_mem();
for (i = 0; i < MAX_LOCKS; i++)
{
if (locks[i].sid == NOT_USED)
{
first_free = i;
break;
}
}
}
if (first_free != NOT_FOUND)
{
locks[first_free].sid = sid;
locks[first_free].echo = NULL;
locks[first_free].pid = MyProcPid;
session_lock = &locks[first_free];
return &locks[first_free];
}
else
ereport(ERROR,
(errcode(ERRCODE_ORA_PACKAGES_LOCK_REQUEST_ERROR),
errmsg("lock request error"),
errdetail("Failed to create session lock."),
errhint("There are too many collaborating sessions. Increase MAX_LOCKS in 'pipe.h'.")));
}
return NULL;
}
static alert_event*
find_event(text *event_name, bool create, int *event_id)
{
int i;
for (i = 0; i < MAX_EVENTS;i++)
{
if (events[i].event_name != NULL && textcmpm(event_name,events[i].event_name) == 0)
{
if (event_id != NULL)
*event_id = i;
return &events[i];
}
}
if (create)
{
for (i=0; i < MAX_EVENTS; i++)
{
if (events[i].event_name == NULL)
{
events[i].event_name = ora_scstring(event_name);
events[i].max_receivers = 0;
events[i].receivers = NULL;
events[i].messages = NULL;
events[i].receivers_number = 0;
if (event_id != NULL)
*event_id = i;
return &events[i];
}
}
ereport(ERROR,
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
errmsg("event registration error"),
errdetail("Too many registered events."),
errhint("There are too many collaborating sessions. Increase MAX_EVENTS in 'pipe.h'.")));
}
return NULL;
}
static void
register_event(text *event_name)
{
alert_event *ev;
int *new_receivers;
int first_free;
int i;
find_lock(sid, true);
ev = find_event(event_name, true, NULL);
first_free = NOT_FOUND;
for (i = 0; i < ev->max_receivers; i++)
{
if (ev->receivers[i] == sid)
return; /* event is registered */
if (ev->receivers[i] == NOT_USED && first_free == NOT_FOUND)
first_free = i;
}
/*
* I can have a maximum of MAX_LOCKS receivers for one event.
* Array receivers is increased for 16 fields
*/
if (first_free == NOT_FOUND)
{
if (ev->max_receivers + 16 > MAX_LOCKS)
ereport(ERROR,
(errcode(ERRCODE_ORA_PACKAGES_LOCK_REQUEST_ERROR),
errmsg("lock request error"),
errdetail("Failed to create session lock."),
errhint("There are too many collaborating sessions. Increase MAX_LOCKS in 'pipe.h'.")));
/* increase receiver's array */
new_receivers = (int*)salloc((ev->max_receivers + 16)*sizeof(int));
for (i = 0; i < ev->max_receivers + 16; i++)
{
if (i < ev->max_receivers)
new_receivers[i] = ev->receivers[i];
else
new_receivers[i] = NOT_USED;
}
ev->max_receivers += 16;
if (ev->receivers)
ora_sfree(ev->receivers);
ev->receivers = new_receivers;
first_free = ev->max_receivers - 16;
}
ev->receivers_number += 1;
ev->receivers[first_free] = sid;
}
/*
* Remove receiver from default receivers of message,
* I expect clean all message_items
*/
static void
unregister_event(int event_id, int sid)
{
alert_event *ev;
ev = &events[event_id];
if (ev->receivers_number > 0)
{
int i;
for (i = 0; i < ev->max_receivers; i++)
{
if (ev->receivers[i] == sid)
{
ev->receivers[i] = NOT_USED;
ev->receivers_number -= 1;
break;
}
}
if (ev->receivers_number == 0)
{
ora_sfree(ev->receivers);
ora_sfree(ev->event_name);
ev->receivers = NULL;
ev->event_name = NULL;
}
}
}
/*
* remove receiver from list of receivers.
* Message has always minimal one receiver
* Return true, if exist other receiver
*/
static bool
remove_receiver(message_item *msg, int sid)
{
int i;
bool find_other = false;
bool found = false;
for (i = 0; i < msg->receivers_number; i++)
{
if (msg->receivers[i] == sid)
{
msg->receivers[i] = NOT_USED;
found = true;
}
else if (msg->receivers[i] != NOT_USED)
{
find_other = true;
}
if (found && find_other)
break;
}
return find_other;
}
/*
*
* Reads message message_id for user sid. If arg:all is true,
* then get any message. If arg:remove_all then remove all
* signaled messages for sid. If arg:filter_message then
* skip other messages than message_id, else read and remove
* all others messages than message_id.
*
*/
static char*
find_and_remove_message_item(int message_id, int sid,
bool all, bool remove_all,
bool filter_message,
int *sleep, char **event_name)
{
alert_lock *alck;
char *result = NULL;
if (sleep != NULL)
*sleep = 0;
alck = find_lock(sid, false);
if (event_name)
*event_name = NULL;
if (alck != NULL && alck->echo != NULL)
{
/* if I have registered and created item */
struct _message_echo *echo, *last_echo;
echo = alck->echo;
last_echo = NULL;
while (echo != NULL)
{
char *message_text;
int _message_id;
bool destroy_msg_item = false;
if (filter_message && echo->message_id != message_id)
{
last_echo = echo;
echo = echo->next_echo;
continue;
}
message_text = echo->message->message;
_message_id = echo->message_id;
if (!remove_receiver(echo->message, sid))
{
destroy_msg_item = true;
if (echo->message->prev_message != NULL)
echo->message->prev_message->next_message =
echo->message->next_message;
else
events[echo->message_id].messages =
echo->message->next_message;
if (echo->message->next_message != NULL)
echo->message->next_message->prev_message =
echo->message->prev_message;
ora_sfree(echo->message->receivers);
ora_sfree(echo->message);
}
if (last_echo == NULL)
{
alck->echo = echo->next_echo;
ora_sfree(echo);
echo = alck->echo;
}
else
{
last_echo->next_echo = echo->next_echo;
ora_sfree(echo);
echo = last_echo;
}
if (remove_all)
{
if (message_text != NULL && destroy_msg_item)
ora_sfree(message_text);
continue;
}
else if (_message_id == message_id || all)
{
/* I have to do local copy */
if (message_text)
{
result = pstrdup(message_text);
if (destroy_msg_item)
ora_sfree(message_text);
}
if (event_name != NULL)
*event_name = pstrdup(events[_message_id].event_name);
break;
}
}
}
return result;
}
/*
* Queue mustn't to contain duplicate messages
*/
static void
create_message(text *event_name, text *message)
{
int event_id;
alert_event *ev;
message_item *msg_item = NULL;
find_event(event_name, false, &event_id);
/* process event only when any recipient exitsts */
if (NULL != (ev = find_event(event_name, false, &event_id)))
{
if (ev->receivers_number > 0)
{
int i,j,k;
msg_item = ev->messages;
while (msg_item != NULL)
{
if (msg_item->message == NULL && message == NULL)
return;
if (msg_item->message != NULL && message != NULL)
if (0 == textcmpm(message,msg_item->message))
return;
msg_item = msg_item->next_message;
}
msg_item = salloc(sizeof(message_item));
msg_item->receivers = salloc(ev->receivers_number*sizeof(int));
msg_item->receivers_number = ev->receivers_number;
if (message != NULL)
msg_item->message = ora_scstring(message);
else
msg_item->message = NULL;
msg_item->message_id = event_id;
for (i = j = 0; j < ev->max_receivers; j++)
{
if (ev->receivers[j] != NOT_USED)
{
msg_item->receivers[i++] = ev->receivers[j];
for (k = 0; k < MAX_LOCKS; k++)
if (locks[k].sid == ev->receivers[j])
{
/* create echo */
message_echo *echo = salloc(sizeof(message_echo));
echo->message = msg_item;
echo->message_id = event_id;
echo->next_echo = NULL;
if (locks[k].echo == NULL)
locks[k].echo = echo;
else
{
message_echo *p;
p = locks[k].echo;
while (p->next_echo != NULL)
p = p->next_echo;
p->next_echo = echo;
}
}
}
}
msg_item->next_message = NULL;
if (ev->messages == NULL)
{
msg_item->prev_message = NULL;
ev->messages = msg_item;
}
else
{
message_item *p;
p = ev->messages;
while (p->next_message != NULL)
p = p->next_message;
p->next_message = msg_item;
msg_item->prev_message = p;
}
}
}
}
#define WATCH_PRE(t, et, c) \
et = GetNowFloat() + (float8)t; c = 0; \
do \
{ \
#define WATCH_POST(t,et,c) \
if (GetNowFloat() >= et) \
break; \
if (cycle++ % 100 == 0) \
CHECK_FOR_INTERRUPTS(); \
pg_usleep(10000L); \
} while(t != 0);
/*
*
* PROCEDURE DBMS_ALERT.REGISTER (name IN VARCHAR2);
*
* Registers the calling session to receive notification of alert name.
*
*/
Datum
dbms_alert_register(PG_FUNCTION_ARGS)
{
text *name = PG_GETARG_TEXT_P(0);
int cycle = 0;
float8 endtime;
float8 timeout = 2;
WATCH_PRE(timeout, endtime, cycle);
if (ora_lock_shmem(SHMEMMSGSZ, MAX_PIPES, MAX_EVENTS, MAX_LOCKS, false))
{
register_event(name);
LWLockRelease(shmem_lockid);
PG_RETURN_VOID();
}
WATCH_POST(timeout, endtime, cycle);
LOCK_ERROR();
PG_RETURN_VOID();
}
/*
*
* PROCEDURE DBMS_ALERT.REMOVE(name IN VARCHAR2);
*
* Unregisters the calling session from receiving notification of alert name.
* Don't raise any exceptions.
*
*/
Datum
dbms_alert_remove(PG_FUNCTION_ARGS)
{
text *name = PG_GETARG_TEXT_P(0);
int ev_id;
int cycle = 0;
float8 endtime;
float8 timeout = 2;
WATCH_PRE(timeout, endtime, cycle);
if (ora_lock_shmem(SHMEMMSGSZ, MAX_PIPES,MAX_EVENTS,MAX_LOCKS,false))
{
alert_event *ev;
ev = find_event(name, false, &ev_id);
if (NULL != ev)
{
find_and_remove_message_item(ev_id, sid,
false, true, true, NULL, NULL);
unregister_event(ev_id, sid);
}
LWLockRelease(shmem_lockid);
PG_RETURN_VOID();
}
WATCH_POST(timeout, endtime, cycle);
LOCK_ERROR();
PG_RETURN_VOID();
}
/*
*
* PROCEDURE DBMS_ALERT.REMOVEALL;
*
* Unregisters the calling session from notification of all alerts.
*
*/
Datum
dbms_alert_removeall(PG_FUNCTION_ARGS)
{
int cycle = 0;
float8 endtime;
float8 timeout = 2;
WATCH_PRE(timeout, endtime, cycle);
if (ora_lock_shmem(SHMEMMSGSZ, MAX_PIPES,MAX_EVENTS,MAX_LOCKS,false))
{
alert_lock *alck;
int i;
for (i = 0; i < MAX_EVENTS; i++)
{
if (events[i].event_name != NULL)
{
find_and_remove_message_item(i, sid,
false, true, true, NULL, NULL);
unregister_event(i, sid);
}
}
alck = find_lock(sid, false);
if (alck)
{
/* After all events unregistration, an echo field should NULL */
Assert(alck->echo == NULL);
alck->sid = NOT_USED;
session_lock = NULL;
}
LWLockRelease(shmem_lockid);
PG_RETURN_VOID();
}
WATCH_POST(timeout, endtime, cycle);
LOCK_ERROR();
PG_RETURN_VOID();
}
/*
* workhorse for dbms_alert_waitany and dbms_alert_waitany_maxwait
*/
static Datum
_dbms_alert_waitany(int timeout, FunctionCallInfo fcinfo)
{
TupleDesc tupdesc;
AttInMetadata *attinmeta;
HeapTuple tuple;
Datum result;
char *str[3] = {NULL, NULL, "1"};
instr_time start_time;
TupleDesc btupdesc;
#if PG_VERSION_NUM < 130000
long cycle = 0;
#endif
INSTR_TIME_SET_CURRENT(start_time);
for (;;)
{
if (ora_lock_shmem(SHMEMMSGSZ, MAX_PIPES, MAX_EVENTS, MAX_LOCKS, false))
{
str[1] = find_and_remove_message_item(-1, sid,
true, false, false, NULL, &str[0]);
if (str[0])
{
str[2] = "0";
LWLockRelease(shmem_lockid);
break;
}
LWLockRelease(shmem_lockid);
}
if (timeout > 0)
{
instr_time cur_time;
long cur_timeout;
INSTR_TIME_SET_CURRENT(cur_time);
INSTR_TIME_SUBTRACT(cur_time, start_time);
cur_timeout = timeout * 1000L - (long) INSTR_TIME_GET_MILLISEC(cur_time);
if (cur_timeout <= 0)
break;
#if PG_VERSION_NUM >= 130000
if (cur_timeout > 1000)
cur_timeout = 1000;
if (ConditionVariableTimedSleep(alert_cv, cur_timeout, PG_WAIT_EXTENSION))
{
/* exit on timeout */
INSTR_TIME_SET_CURRENT(cur_time);
INSTR_TIME_SUBTRACT(cur_time, start_time);
cur_timeout = timeout * 1000L - (long) INSTR_TIME_GET_MILLISEC(cur_time);
if (cur_timeout <= 0)
break;
}
#else
if (cycle++ % 10)
CHECK_FOR_INTERRUPTS();
pg_usleep(10000L);
/* exit on timeout */
INSTR_TIME_SET_CURRENT(cur_time);
INSTR_TIME_SUBTRACT(cur_time, start_time);
cur_timeout = timeout * 1000L - (long) INSTR_TIME_GET_MILLISEC(cur_time);
if (cur_timeout <= 0)
break;
#endif
}
else
break;
}
#if PG_VERSION_NUM >= 130000
ConditionVariableCancelSleep();
#endif
get_call_result_type(fcinfo, NULL, &tupdesc);
btupdesc = BlessTupleDesc(tupdesc);
attinmeta = TupleDescGetAttInMetadata(btupdesc);
tuple = BuildTupleFromCStrings(attinmeta, str);
result = HeapTupleGetDatum(tuple);
if (str[0])
pfree(str[0]);
if (str[1])
pfree(str[1]);
return result;
}
/*
*
* PROCEDURE DBMS_ALERT.WAITANY(name OUT VARCHAR2 ,message OUT VARCHAR2
* ,status OUT INTEGER
* ,timeout IN NUMBER DEFAULT MAXWAIT);
*
* Waits for up to timeout seconds to be notified of any alerts for which
* the session is registered. If status = 0 then name and message contain
* alert information. If status = 1 then timeout seconds elapsed without
* notification of any alert.
*
*/
Datum
dbms_alert_waitany(PG_FUNCTION_ARGS)
{
int timeout;
if (!PG_ARGISNULL(0))
{
/*
* cannot to change SQL API now, so use not well choosed
* float.
*/
timeout = (int) PG_GETARG_FLOAT8(0);
if (timeout < 0)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("negative timeout is not allowed")));
if (timeout > MAXWAIT)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("timeout is too large (maximum: %d)", MAXWAIT)));
}
else
timeout = MAXWAIT;
return _dbms_alert_waitany(timeout, fcinfo);
}
Datum
dbms_alert_waitany_maxwait(PG_FUNCTION_ARGS)
{
return _dbms_alert_waitany(MAXWAIT, fcinfo);
}
/*
* common part of dbms_alert_waitone and dbms_alert_waitone_maxwait
*/
static Datum
_dbms_alert_waitone(text *name, int timeout, FunctionCallInfo fcinfo)
{
TupleDesc tupdesc;
AttInMetadata *attinmeta;
HeapTuple tuple;
Datum result;
int message_id;
char *str[2] = {NULL,"1"};
char *event_name;
instr_time start_time;
TupleDesc btupdesc;
#if PG_VERSION_NUM < 130000
long cycle = 0;
#endif
INSTR_TIME_SET_CURRENT(start_time);
for (;;)
{
if (ora_lock_shmem(SHMEMMSGSZ, MAX_PIPES, MAX_EVENTS, MAX_LOCKS, false))
{
if (NULL != find_event(name, false, &message_id))
{
str[0] = find_and_remove_message_item(message_id, sid,
false, false, false, NULL, &event_name);
if (event_name != NULL)
{
str[1] = "0";
pfree(event_name);
LWLockRelease(shmem_lockid);
break;
}
}
LWLockRelease(shmem_lockid);
}
if (timeout > 0)
{
instr_time cur_time;
long cur_timeout;
INSTR_TIME_SET_CURRENT(cur_time);
INSTR_TIME_SUBTRACT(cur_time, start_time);
cur_timeout = timeout * 1000L - (long) INSTR_TIME_GET_MILLISEC(cur_time);
if (cur_timeout <= 0)
break;
#if PG_VERSION_NUM >= 130000
if (cur_timeout > 1000)
cur_timeout = 1000;
if (ConditionVariableTimedSleep(alert_cv, cur_timeout, PG_WAIT_EXTENSION))
{
/* exit on timeout */
INSTR_TIME_SET_CURRENT(cur_time);
INSTR_TIME_SUBTRACT(cur_time, start_time);
cur_timeout = timeout * 1000L - (long) INSTR_TIME_GET_MILLISEC(cur_time);
if (cur_timeout <= 0)
break;
}
#else
if (cycle++ % 10)
CHECK_FOR_INTERRUPTS();
pg_usleep(10000L);
/* exit on timeout */
INSTR_TIME_SET_CURRENT(cur_time);
INSTR_TIME_SUBTRACT(cur_time, start_time);
cur_timeout = timeout * 1000L - (long) INSTR_TIME_GET_MILLISEC(cur_time);
if (cur_timeout <= 0)
break;
#endif
}
else
break;
}
#if PG_VERSION_NUM >= 130000
ConditionVariableCancelSleep();
#endif
get_call_result_type(fcinfo, NULL, &tupdesc);
btupdesc = BlessTupleDesc(tupdesc);
attinmeta = TupleDescGetAttInMetadata(btupdesc);
tuple = BuildTupleFromCStrings(attinmeta, str);
result = HeapTupleGetDatum(tuple);
if (str[0])
pfree(str[0]);
return result;
}
/*
*
* PROCEDURE DBMS_ALERT.WAITONE(name IN VARCHAR2, message OUT VARCHAR2