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pg_query_state.c
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/*
* pg_query_state.c
* Extract information about query state from other backend
*
* Copyright (c) 2016-2016, Postgres Professional
*
* contrib/pg_query_state/pg_query_state.c
* IDENTIFICATION
*/
#include "pg_query_state.h"
#include "access/htup_details.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "executor/execParallel.h"
#include "executor/executor.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "nodes/print.h"
#include "pgstat.h"
#include "postmaster/bgworker.h"
#include "storage/ipc.h"
#include "storage/s_lock.h"
#include "storage/spin.h"
#include "storage/procarray.h"
#include "storage/procsignal.h"
#include "storage/shm_toc.h"
#include "utils/guc.h"
#include "utils/timestamp.h"
#ifdef PG_MODULE_MAGIC
PG_MODULE_MAGIC;
#endif
#define TEXT_CSTR_CMP(text, cstr) \
(memcmp(VARDATA(text), (cstr), VARSIZE(text) - VARHDRSZ))
/* GUC variables */
bool pg_qs_enable = true;
bool pg_qs_timing = false;
bool pg_qs_buffers = false;
/* Saved hook values in case of unload */
static ExecutorStart_hook_type prev_ExecutorStart = NULL;
static ExecutorRun_hook_type prev_ExecutorRun = NULL;
static ExecutorFinish_hook_type prev_ExecutorFinish = NULL;
static shmem_startup_hook_type prev_shmem_startup_hook = NULL;
void _PG_init(void);
void _PG_fini(void);
/* hooks defined in this module */
static void qs_ExecutorStart(QueryDesc *queryDesc, int eflags);
#if PG_VERSION_NUM < 100000
static void qs_ExecutorRun(QueryDesc *queryDesc, ScanDirection direction, uint64 count);
#else
static void qs_ExecutorRun(QueryDesc *queryDesc, ScanDirection direction,
uint64 count, bool execute_once);
#endif
static void qs_ExecutorFinish(QueryDesc *queryDesc);
static shm_mq_result receive_msg_by_parts(shm_mq_handle *mqh, Size *total,
void **datap, bool nowait);
/* Global variables */
List *QueryDescStack = NIL;
static ProcSignalReason UserIdPollReason = INVALID_PROCSIGNAL;
static ProcSignalReason QueryStatePollReason = INVALID_PROCSIGNAL;
static ProcSignalReason WorkerPollReason = INVALID_PROCSIGNAL;
static bool module_initialized = false;
static const char *be_state_str[] = { /* BackendState -> string repr */
"undefined", /* STATE_UNDEFINED */
"idle", /* STATE_IDLE */
"active", /* STATE_RUNNING */
"idle in transaction", /* STATE_IDLEINTRANSACTION */
"fastpath function call", /* STATE_FASTPATH */
"idle in transaction (aborted)", /* STATE_IDLEINTRANSACTION_ABORTED */
"disabled", /* STATE_DISABLED */
};
static int reqid = 0;
typedef struct
{
slock_t mutex; /* protect concurrent access to `userid` */
Oid userid;
Latch *caller;
pg_atomic_uint32 n_peers;
} RemoteUserIdResult;
static void SendCurrentUserId(void);
static void SendBgWorkerPids(void);
static Oid GetRemoteBackendUserId(PGPROC *proc);
static List *GetRemoteBackendWorkers(PGPROC *proc);
static List *GetRemoteBackendQueryStates(PGPROC *leader,
List *pworkers,
bool verbose,
bool costs,
bool timing,
bool buffers,
bool triggers,
ExplainFormat format);
/* Shared memory variables */
shm_toc *toc = NULL;
RemoteUserIdResult *counterpart_userid = NULL;
pg_qs_params *params = NULL;
shm_mq *mq = NULL;
/*
* Estimate amount of shared memory needed.
*/
static Size
pg_qs_shmem_size()
{
shm_toc_estimator e;
Size size;
int nkeys;
shm_toc_initialize_estimator(&e);
nkeys = 3;
shm_toc_estimate_chunk(&e, sizeof(RemoteUserIdResult));
shm_toc_estimate_chunk(&e, sizeof(pg_qs_params));
shm_toc_estimate_chunk(&e, (Size) QUEUE_SIZE);
shm_toc_estimate_keys(&e, nkeys);
size = shm_toc_estimate(&e);
return size;
}
/*
* Distribute shared memory.
*/
static void
pg_qs_shmem_startup(void)
{
bool found;
Size shmem_size = pg_qs_shmem_size();
void *shmem;
int num_toc = 0;
shmem = ShmemInitStruct("pg_query_state", shmem_size, &found);
if (!found)
{
toc = shm_toc_create(PG_QS_MODULE_KEY, shmem, shmem_size);
counterpart_userid = shm_toc_allocate(toc, sizeof(RemoteUserIdResult));
shm_toc_insert(toc, num_toc++, counterpart_userid);
SpinLockInit(&counterpart_userid->mutex);
pg_atomic_init_u32(&counterpart_userid->n_peers, 0);
params = shm_toc_allocate(toc, sizeof(pg_qs_params));
shm_toc_insert(toc, num_toc++, params);
mq = shm_toc_allocate(toc, QUEUE_SIZE);
shm_toc_insert(toc, num_toc++, mq);
}
else
{
toc = shm_toc_attach(PG_QS_MODULE_KEY, shmem);
#if PG_VERSION_NUM < 100000
counterpart_userid = shm_toc_lookup(toc, num_toc++);
params = shm_toc_lookup(toc, num_toc++);
mq = shm_toc_lookup(toc, num_toc++);
#else
counterpart_userid = shm_toc_lookup(toc, num_toc++, false);
params = shm_toc_lookup(toc, num_toc++, false);
mq = shm_toc_lookup(toc, num_toc++, false);
#endif
}
if (prev_shmem_startup_hook)
prev_shmem_startup_hook();
module_initialized = true;
}
/*
* Module load callback
*/
void
_PG_init(void)
{
if (!process_shared_preload_libraries_in_progress)
return;
/*
* Request additional shared resources. (These are no-ops if we're not in
* the postmaster process.) We'll allocate or attach to the shared
* resources in qs_shmem_startup().
*/
RequestAddinShmemSpace(pg_qs_shmem_size());
/* Register interrupt on custom signal of polling query state */
UserIdPollReason = RegisterCustomProcSignalHandler(SendCurrentUserId);
QueryStatePollReason = RegisterCustomProcSignalHandler(SendQueryState);
WorkerPollReason = RegisterCustomProcSignalHandler(SendBgWorkerPids);
if (QueryStatePollReason == INVALID_PROCSIGNAL
|| WorkerPollReason == INVALID_PROCSIGNAL
|| UserIdPollReason == INVALID_PROCSIGNAL)
{
ereport(WARNING, (errcode(ERRCODE_INSUFFICIENT_RESOURCES),
errmsg("pg_query_state isn't loaded: insufficient custom ProcSignal slots")));
return;
}
/* Define custom GUC variables */
DefineCustomBoolVariable("pg_query_state.enable",
"Enable module.",
NULL,
&pg_qs_enable,
true,
PGC_SUSET,
0,
NULL,
NULL,
NULL);
DefineCustomBoolVariable("pg_query_state.enable_timing",
"Collect timing data, not just row counts.",
NULL,
&pg_qs_timing,
false,
PGC_SUSET,
0,
NULL,
NULL,
NULL);
DefineCustomBoolVariable("pg_query_state.enable_buffers",
"Collect buffer usage.",
NULL,
&pg_qs_buffers,
false,
PGC_SUSET,
0,
NULL,
NULL,
NULL);
EmitWarningsOnPlaceholders("pg_query_state");
/* Install hooks */
prev_ExecutorStart = ExecutorStart_hook;
ExecutorStart_hook = qs_ExecutorStart;
prev_ExecutorRun = ExecutorRun_hook;
ExecutorRun_hook = qs_ExecutorRun;
prev_ExecutorFinish = ExecutorFinish_hook;
ExecutorFinish_hook = qs_ExecutorFinish;
prev_shmem_startup_hook = shmem_startup_hook;
shmem_startup_hook = pg_qs_shmem_startup;
}
/*
* Module unload callback
*/
void
_PG_fini(void)
{
module_initialized = false;
/* clear global state */
list_free(QueryDescStack);
/* Uninstall hooks. */
ExecutorStart_hook = prev_ExecutorStart;
ExecutorRun_hook = prev_ExecutorRun;
ExecutorFinish_hook = prev_ExecutorFinish;
shmem_startup_hook = prev_shmem_startup_hook;
}
/*
* ExecutorStart hook:
* set up flags to store runtime statistics,
* push current query description in global stack
*/
static void
qs_ExecutorStart(QueryDesc *queryDesc, int eflags)
{
/* Enable per-node instrumentation */
if (pg_qs_enable && ((eflags & EXEC_FLAG_EXPLAIN_ONLY) == 0))
{
queryDesc->instrument_options |= INSTRUMENT_ROWS;
if (pg_qs_timing)
queryDesc->instrument_options |= INSTRUMENT_TIMER;
if (pg_qs_buffers)
queryDesc->instrument_options |= INSTRUMENT_BUFFERS;
}
if (prev_ExecutorStart)
prev_ExecutorStart(queryDesc, eflags);
else
standard_ExecutorStart(queryDesc, eflags);
}
/*
* ExecutorRun:
* Catch any fatal signals
*/
static void
#if PG_VERSION_NUM < 100000
qs_ExecutorRun(QueryDesc *queryDesc, ScanDirection direction, uint64 count)
#else
qs_ExecutorRun(QueryDesc *queryDesc, ScanDirection direction, uint64 count,
bool execute_once)
#endif
{
QueryDescStack = lcons(queryDesc, QueryDescStack);
PG_TRY();
{
if (prev_ExecutorRun)
#if PG_VERSION_NUM < 100000
prev_ExecutorRun(queryDesc, direction, count);
else
standard_ExecutorRun(queryDesc, direction, count);
#else
prev_ExecutorRun(queryDesc, direction, count, execute_once);
else
standard_ExecutorRun(queryDesc, direction, count, execute_once);
#endif
QueryDescStack = list_delete_first(QueryDescStack);
}
PG_CATCH();
{
QueryDescStack = list_delete_first(QueryDescStack);
PG_RE_THROW();
}
PG_END_TRY();
}
/*
* ExecutorFinish:
* Catch any fatal signals
*/
static void
qs_ExecutorFinish(QueryDesc *queryDesc)
{
QueryDescStack = lcons(queryDesc, QueryDescStack);
PG_TRY();
{
if (prev_ExecutorFinish)
prev_ExecutorFinish(queryDesc);
else
standard_ExecutorFinish(queryDesc);
QueryDescStack = list_delete_first(QueryDescStack);
}
PG_CATCH();
{
QueryDescStack = list_delete_first(QueryDescStack);
PG_RE_THROW();
}
PG_END_TRY();
}
/*
* Find PgBackendStatus entry
*/
static PgBackendStatus *
search_be_status(int pid)
{
int beid;
if (pid <= 0)
return NULL;
for (beid = 1; beid <= pgstat_fetch_stat_numbackends(); beid++)
{
PgBackendStatus *be_status = pgstat_fetch_stat_beentry(beid);
if (be_status && be_status->st_procpid == pid)
return be_status;
}
return NULL;
}
void
UnlockShmem(LOCKTAG *tag)
{
LockRelease(tag, ExclusiveLock, false);
}
void
LockShmem(LOCKTAG *tag, uint32 key)
{
LockAcquireResult result;
tag->locktag_field1 = PG_QS_MODULE_KEY;
tag->locktag_field2 = key;
tag->locktag_field3 = 0;
tag->locktag_field4 = 0;
tag->locktag_type = LOCKTAG_USERLOCK;
tag->locktag_lockmethodid = USER_LOCKMETHOD;
result = LockAcquire(tag, ExclusiveLock, false, false);
Assert(result == LOCKACQUIRE_OK);
elog(DEBUG1, "LockAcquireResult is not OK %d", result);
}
/*
* Structure of stack frame of fucntion call which transfers through message queue
*/
typedef struct
{
text *query;
text *plan;
} stack_frame;
/*
* Convert serialized stack frame into stack_frame record
* Increment '*src' pointer to the next serialized stack frame
*/
static stack_frame *
deserialize_stack_frame(char **src)
{
stack_frame *result = palloc(sizeof(stack_frame));
text *query = (text *) *src,
*plan = (text *) (*src + INTALIGN(VARSIZE(query)));
result->query = palloc(VARSIZE(query));
memcpy(result->query, query, VARSIZE(query));
result->plan = palloc(VARSIZE(plan));
memcpy(result->plan, plan, VARSIZE(plan));
*src = (char *) plan + INTALIGN(VARSIZE(plan));
return result;
}
/*
* Convert serialized stack frames into List of stack_frame records
*/
static List *
deserialize_stack(char *src, int stack_depth)
{
List *result = NIL;
char *curr_ptr = src;
int i;
for (i = 0; i < stack_depth; i++)
{
stack_frame *frame = deserialize_stack_frame(&curr_ptr);
result = lappend(result, frame);
}
return result;
}
/*
* Implementation of pg_query_state function
*/
PG_FUNCTION_INFO_V1(pg_query_state);
Datum
pg_query_state(PG_FUNCTION_ARGS)
{
typedef struct
{
PGPROC *proc;
ListCell *frame_cursor;
int frame_index;
List *stack;
} proc_state;
/* multicall context type */
typedef struct
{
ListCell *proc_cursor;
List *procs;
} pg_qs_fctx;
FuncCallContext *funcctx;
MemoryContext oldcontext;
pg_qs_fctx *fctx;
#define N_ATTRS 5
pid_t pid = PG_GETARG_INT32(0);
if (SRF_IS_FIRSTCALL())
{
LOCKTAG tag;
bool verbose = PG_GETARG_BOOL(1),
costs = PG_GETARG_BOOL(2),
timing = PG_GETARG_BOOL(3),
buffers = PG_GETARG_BOOL(4),
triggers = PG_GETARG_BOOL(5);
text *format_text = PG_GETARG_TEXT_P(6);
ExplainFormat format;
PGPROC *proc;
Oid counterpart_user_id;
shm_mq_msg *msg;
List *bg_worker_procs = NIL;
List *msgs;
instr_time start_time;
instr_time cur_time;
if (!module_initialized)
ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("pg_query_state wasn't initialized yet")));
if (pid == MyProcPid)
ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("attempt to extract state of current process")));
proc = BackendPidGetProc(pid);
if (!proc || proc->backendId == InvalidBackendId || proc->databaseId == InvalidOid || proc->roleId == InvalidOid)
ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("backend with pid=%d not found", pid)));
if (TEXT_CSTR_CMP(format_text, "text") == 0)
format = EXPLAIN_FORMAT_TEXT;
else if (TEXT_CSTR_CMP(format_text, "xml") == 0)
format = EXPLAIN_FORMAT_XML;
else if (TEXT_CSTR_CMP(format_text, "json") == 0)
format = EXPLAIN_FORMAT_JSON;
else if (TEXT_CSTR_CMP(format_text, "yaml") == 0)
format = EXPLAIN_FORMAT_YAML;
else
ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("unrecognized 'format' argument")));
/*
* init and acquire lock so that any other concurrent calls of this fuction
* can not occupy shared queue for transfering query state
*/
LockShmem(&tag, PG_QS_RCV_KEY);
INSTR_TIME_SET_CURRENT(start_time);
while (pg_atomic_read_u32(&counterpart_userid->n_peers) != 0)
{
pg_usleep(1000000); /* wait one second */
CHECK_FOR_INTERRUPTS();
INSTR_TIME_SET_CURRENT(cur_time);
INSTR_TIME_SUBTRACT(cur_time, start_time);
if (INSTR_TIME_GET_MILLISEC(cur_time) > MAX_RCV_TIMEOUT)
{
elog(WARNING, "pg_query_state: last request was interrupted");
break;
}
}
pg_atomic_write_u32(&counterpart_userid->n_peers, 1);
params->reqid = ++reqid;
pg_write_barrier();
counterpart_user_id = GetRemoteBackendUserId(proc);
if (!(superuser() || GetUserId() == counterpart_user_id))
ereport(ERROR, (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("permission denied")));
bg_worker_procs = GetRemoteBackendWorkers(proc);
msgs = GetRemoteBackendQueryStates(proc,
bg_worker_procs,
verbose,
costs,
timing,
buffers,
triggers,
format);
funcctx = SRF_FIRSTCALL_INIT();
if (list_length(msgs) == 0)
{
elog(WARNING, "backend does not reply");
UnlockShmem(&tag);
SRF_RETURN_DONE(funcctx);
}
msg = (shm_mq_msg *) linitial(msgs);
switch (msg->result_code)
{
case QUERY_NOT_RUNNING:
{
PgBackendStatus *be_status = search_be_status(pid);
if (be_status)
elog(INFO, "state of backend is %s",
be_state_str[be_status->st_state - STATE_UNDEFINED]);
else
elog(INFO, "backend is not running query");
UnlockShmem(&tag);
SRF_RETURN_DONE(funcctx);
}
case STAT_DISABLED:
elog(INFO, "query execution statistics disabled");
UnlockShmem(&tag);
SRF_RETURN_DONE(funcctx);
case QS_RETURNED:
{
TupleDesc tupdesc;
ListCell *i;
int64 max_calls = 0;
/* print warnings if exist */
if (msg->warnings & TIMINIG_OFF_WARNING)
ereport(WARNING, (errcode(ERRCODE_WARNING),
errmsg("timing statistics disabled")));
if (msg->warnings & BUFFERS_OFF_WARNING)
ereport(WARNING, (errcode(ERRCODE_WARNING),
errmsg("buffers statistics disabled")));
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
/* save stack of calls and current cursor in multicall context */
fctx = (pg_qs_fctx *) palloc(sizeof(pg_qs_fctx));
fctx->procs = NIL;
foreach(i, msgs)
{
List *qs_stack;
shm_mq_msg *msg = (shm_mq_msg *) lfirst(i);
proc_state *p_state = (proc_state *) palloc(sizeof(proc_state));
if (msg->result_code != QS_RETURNED)
continue;
AssertState(msg->result_code == QS_RETURNED);
qs_stack = deserialize_stack(msg->stack, msg->stack_depth);
p_state->proc = msg->proc;
p_state->stack = qs_stack;
p_state->frame_index = 0;
p_state->frame_cursor = list_head(qs_stack);
fctx->procs = lappend(fctx->procs, p_state);
max_calls += list_length(qs_stack);
}
fctx->proc_cursor = list_head(fctx->procs);
funcctx->user_fctx = fctx;
funcctx->max_calls = max_calls;
/* Make tuple descriptor */
#if PG_VERSION_NUM < 120000
tupdesc = CreateTemplateTupleDesc(N_ATTRS, false);
#else
tupdesc = CreateTemplateTupleDesc(N_ATTRS);
#endif
TupleDescInitEntry(tupdesc, (AttrNumber) 1, "pid", INT4OID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 2, "frame_number", INT4OID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 3, "query_text", TEXTOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 4, "plan", TEXTOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 5, "leader_pid", INT4OID, -1, 0);
funcctx->tuple_desc = BlessTupleDesc(tupdesc);
UnlockShmem(&tag);
MemoryContextSwitchTo(oldcontext);
}
break;
}
}
/* restore function multicall context */
funcctx = SRF_PERCALL_SETUP();
fctx = funcctx->user_fctx;
if (funcctx->call_cntr < funcctx->max_calls)
{
HeapTuple tuple;
Datum values[N_ATTRS];
bool nulls[N_ATTRS];
proc_state *p_state = (proc_state *) lfirst(fctx->proc_cursor);
stack_frame *frame = (stack_frame *) lfirst(p_state->frame_cursor);
/* Make and return next tuple to caller */
MemSet(values, 0, sizeof(values));
MemSet(nulls, 0, sizeof(nulls));
values[0] = Int32GetDatum(p_state->proc->pid);
values[1] = Int32GetDatum(p_state->frame_index);
values[2] = PointerGetDatum(frame->query);
values[3] = PointerGetDatum(frame->plan);
if (p_state->proc->pid == pid)
nulls[4] = true;
else
values[4] = Int32GetDatum(pid);
tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
/* increment cursor */
#if PG_VERSION_NUM >= 130000
p_state->frame_cursor = lnext(p_state->stack, p_state->frame_cursor);
#else
p_state->frame_cursor = lnext(p_state->frame_cursor);
#endif
p_state->frame_index++;
if (p_state->frame_cursor == NULL)
#if PG_VERSION_NUM >= 130000
fctx->proc_cursor = lnext(fctx->procs, fctx->proc_cursor);
#else
fctx->proc_cursor = lnext(fctx->proc_cursor);
#endif
SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
}
else
SRF_RETURN_DONE(funcctx);
}
static void
SendCurrentUserId(void)
{
SpinLockAcquire(&counterpart_userid->mutex);
counterpart_userid->userid = GetUserId();
SpinLockRelease(&counterpart_userid->mutex);
SetLatch(counterpart_userid->caller);
}
/*
* Extract effective user id from backend on which `proc` points.
*
* Assume the `proc` points on valid backend and it's not current process.
*
* This fuction must be called after registration of `UserIdPollReason` and
* initialization `RemoteUserIdResult` object in shared memory.
*/
static Oid
GetRemoteBackendUserId(PGPROC *proc)
{
Oid result;
Assert(proc && proc->backendId != InvalidBackendId);
Assert(UserIdPollReason != INVALID_PROCSIGNAL);
Assert(counterpart_userid);
counterpart_userid->userid = InvalidOid;
counterpart_userid->caller = MyLatch;
pg_write_barrier();
SendProcSignal(proc->pid, UserIdPollReason, proc->backendId);
for (;;)
{
SpinLockAcquire(&counterpart_userid->mutex);
result = counterpart_userid->userid;
SpinLockRelease(&counterpart_userid->mutex);
if (result != InvalidOid)
break;
#if PG_VERSION_NUM < 100000
WaitLatch(MyLatch, WL_LATCH_SET, 0);
#elif PG_VERSION_NUM < 120000
WaitLatch(MyLatch, WL_LATCH_SET, 0, PG_WAIT_EXTENSION);
#else
WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, 0,
PG_WAIT_EXTENSION);
#endif
CHECK_FOR_INTERRUPTS();
ResetLatch(MyLatch);
}
return result;
}
/*
* Receive a message from a shared message queue until timeout is exceeded.
*
* Parameter `*nbytes` is set to the message length and *data to point to the
* message payload. If timeout is exceeded SHM_MQ_WOULD_BLOCK is returned.
*/
static shm_mq_result
shm_mq_receive_with_timeout(shm_mq_handle *mqh,
Size *nbytesp,
void **datap,
int64 timeout)
{
int rc = 0;
int64 delay = timeout;
instr_time start_time;
instr_time cur_time;
INSTR_TIME_SET_CURRENT(start_time);
for (;;)
{
shm_mq_result mq_receive_result;
mq_receive_result = receive_msg_by_parts(mqh, nbytesp, datap, true);
if (mq_receive_result != SHM_MQ_WOULD_BLOCK)
return mq_receive_result;
if (rc & WL_TIMEOUT || delay <= 0)
return SHM_MQ_WOULD_BLOCK;
#if PG_VERSION_NUM < 100000
rc = WaitLatch(MyLatch, WL_LATCH_SET | WL_TIMEOUT, delay);
#elif PG_VERSION_NUM < 120000
rc = WaitLatch(MyLatch,
WL_LATCH_SET | WL_TIMEOUT,
delay, PG_WAIT_EXTENSION);
#else
rc = WaitLatch(MyLatch,
WL_LATCH_SET | WL_EXIT_ON_PM_DEATH | WL_TIMEOUT,
delay, PG_WAIT_EXTENSION);
#endif
INSTR_TIME_SET_CURRENT(cur_time);
INSTR_TIME_SUBTRACT(cur_time, start_time);
delay = timeout - (int64) INSTR_TIME_GET_MILLISEC(cur_time);
if (delay <= 0)
return SHM_MQ_WOULD_BLOCK;
CHECK_FOR_INTERRUPTS();
ResetLatch(MyLatch);
}
}
/*
* Extract to *result pids of all parallel workers running from leader process
* that executes plan tree whose state root is `node`.
*/
static bool
extract_running_bgworkers(PlanState *node, List **result)
{
if (node == NULL)
return false;
if (IsA(node, GatherState))
{
GatherState *gather_node = (GatherState *) node;
int i;
if (gather_node->pei)
{
for (i = 0; i < gather_node->pei->pcxt->nworkers_launched; i++)
{
pid_t pid;
BackgroundWorkerHandle *bgwh;
BgwHandleStatus status;
bgwh = gather_node->pei->pcxt->worker[i].bgwhandle;
if (!bgwh)
continue;
status = GetBackgroundWorkerPid(bgwh, &pid);
if (status == BGWH_STARTED)
*result = lcons_int(pid, *result);
}
}
}
return planstate_tree_walker(node, extract_running_bgworkers, (void *) result);
}
typedef struct
{
int reqid;
int number;
pid_t pids[FLEXIBLE_ARRAY_MEMBER];
} BgWorkerPids;
static void
SendBgWorkerPids(void)
{
ListCell *iter;
List *all_workers = NIL;
BgWorkerPids *msg;
int msg_len;
int i;
shm_mq_handle *mqh;
LOCKTAG tag;
LockShmem(&tag, PG_QS_SND_KEY);
mqh = shm_mq_attach(mq, NULL, NULL);
foreach(iter, QueryDescStack)
{
QueryDesc *curQueryDesc = (QueryDesc *) lfirst(iter);
List *bgworker_pids = NIL;
extract_running_bgworkers(curQueryDesc->planstate, &bgworker_pids);
all_workers = list_concat(all_workers, bgworker_pids);
}
msg_len = offsetof(BgWorkerPids, pids)
+ sizeof(pid_t) * list_length(all_workers);
msg = palloc(msg_len);
msg->reqid = params->reqid;
msg->number = list_length(all_workers);
i = 0;
foreach(iter, all_workers)
{
pid_t current_pid = lfirst_int(iter);
AssertState(current_pid > 0);
msg->pids[i++] = current_pid;
}
shm_mq_send(mqh, msg_len, msg, false);
UnlockShmem(&tag);
}
/*
* Extracts all parallel worker `proc`s running by process `proc`
*/
static List *
GetRemoteBackendWorkers(PGPROC *proc)
{
int sig_result;
shm_mq_handle *mqh;
shm_mq_result mq_receive_result;
BgWorkerPids *msg;
Size msg_len;
int i;
List *result = NIL;
LOCKTAG tag;
Assert(proc && proc->backendId != InvalidBackendId);
Assert(WorkerPollReason != INVALID_PROCSIGNAL);
Assert(mq);
LockShmem(&tag, PG_QS_SND_KEY);
mq = shm_mq_create(mq, QUEUE_SIZE);
shm_mq_set_sender(mq, proc);
shm_mq_set_receiver(mq, MyProc);
UnlockShmem(&tag);
sig_result = SendProcSignal(proc->pid, WorkerPollReason, proc->backendId);
if (sig_result == -1)
goto signal_error;
mqh = shm_mq_attach(mq, NULL, NULL);
mq_receive_result = shm_mq_receive(mqh, &msg_len, (void **) &msg, false);
if (mq_receive_result != SHM_MQ_SUCCESS || msg == NULL || msg->reqid != reqid || msg_len != offsetof(BgWorkerPids, pids) + msg->number*sizeof(pid_t))
goto mq_error;
for (i = 0; i < msg->number; i++)
{
pid_t pid = msg->pids[i];
PGPROC *proc = BackendPidGetProc(pid);
if (!proc || !proc->pid)
continue;
result = lcons(proc, result);
}
#if PG_VERSION_NUM < 100000
shm_mq_detach(mq);
#else
shm_mq_detach(mqh);
#endif
return result;
signal_error:
ereport(ERROR, (errcode(ERRCODE_INTERNAL_ERROR),
errmsg("invalid send signal")));
mq_error:
ereport(ERROR, (errcode(ERRCODE_INTERNAL_ERROR),
errmsg("error in message queue data transmitting")));
}
static shm_mq_msg *
copy_msg(shm_mq_msg *msg)
{
shm_mq_msg *result = palloc(msg->length);
memcpy(result, msg, msg->length);
return result;
}
static shm_mq_result
receive_msg_by_parts(shm_mq_handle *mqh, Size *total, void **datap,
bool nowait)
{
shm_mq_result mq_receive_result;
shm_mq_msg *buff;
int offset;
int *expected;
Size len;
/* Get the expected number of bytes in message */
mq_receive_result = shm_mq_receive(mqh, &len, (void **) &expected, nowait);
if (mq_receive_result != SHM_MQ_SUCCESS)
return mq_receive_result;
Assert(len == sizeof(int));
*datap = palloc0(*expected);
/* Get the message itself */
for (offset = 0; offset < *expected; )
{
/* Keep receiving new messages until we assemble the full message */
mq_receive_result = shm_mq_receive(mqh, &len, ((void **) &buff), nowait);
memcpy((char *) *datap + offset, buff, len);
offset += len;
if (mq_receive_result != SHM_MQ_SUCCESS)
return mq_receive_result;
}
*total = offset;
return mq_receive_result;
}
static List *