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MDEV-29676 refactored and documented spider_get_share() and friends
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Extracted out common subroutines, gave more meaningful names etc,
added comments etc.

Also:
- Documented active servers load balancing reads, and other fields in
  SPIDER_SHARE etc.
- Removed commented out code
- Documented and refactored self-reference check
- Removed some unnecessary functions
- Renamed unhelpful roop_count
- Refactored spider_get_{sts,crd}, where we turn get_type into an enum
- Cleaned up spider_mbase_handler::show_table_status() and
  spider_mbase_handler::show_index()
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@mariadb-YuchenPei
mariadb-YuchenPei committed Apr 28, 2023
1 parent a8dac17 commit b5d3171
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Showing 15 changed files with 1,305 additions and 1,961 deletions.
16 changes: 3 additions & 13 deletions storage/spider/ha_spider.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -309,10 +309,10 @@ int ha_spider::open(
no_bytes_in_map(table->read_set));
wide_handler_alloc = TRUE;

if (!share && !spider_get_share(name, table, thd, this, &error_num))
goto error_get_share;
if (!share && !spider_get_share(name, table, thd, this, &error_num))
goto error_get_share;

wide_share = share->wide_share;
wide_share = share->wide_share;

DBUG_PRINT("info",("spider create partition_handler"));
DBUG_PRINT("info",("spider table=%p", table));
Expand Down Expand Up @@ -6559,13 +6559,6 @@ int ha_spider::info(
auto_inc_temporary = FALSE;
#endif
wide_handler->sql_command = thd_sql_command(thd);
/*
if (
sql_command == SQLCOM_DROP_TABLE ||
sql_command == SQLCOM_ALTER_TABLE ||
sql_command == SQLCOM_SHOW_CREATE
) {
*/
if (flag & HA_STATUS_AUTO)
{
if (share->lgtm_tblhnd_share->auto_increment_value)
Expand All @@ -6583,9 +6576,6 @@ int ha_spider::info(
wide_handler->sql_command == SQLCOM_ALTER_TABLE
)
DBUG_RETURN(0);
/*
}
*/

if (flag &
(HA_STATUS_TIME | HA_STATUS_CONST | HA_STATUS_VARIABLE | HA_STATUS_AUTO))
Expand Down
4 changes: 3 additions & 1 deletion storage/spider/ha_spider.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -63,8 +63,10 @@ class ha_spider final : public handler
char *conn_keys_first_ptr;
char **conn_keys;
SPIDER_CONN **conns;
/* for active-standby mode */
/* array of indexes of active servers */
uint *conn_link_idx;
/* A bitmap indicating whether each active server have some higher
numbered server in the same "group" left to try (can fail over) */
uchar *conn_can_fo;
void **quick_targets;
int *need_mons;
Expand Down
148 changes: 60 additions & 88 deletions storage/spider/spd_conn.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2992,12 +2992,6 @@ void *spider_bg_sts_action(
if (spider.search_link_idx < 0)
{
spider_trx_set_link_idx_for_all(&spider);
/*
spider.search_link_idx = spider_conn_next_link_idx(
thd, share->link_statuses, share->access_balances,
spider.conn_link_idx, spider.search_link_idx, share->link_count,
SPIDER_LINK_STATUS_OK);
*/
spider.search_link_idx = spider_conn_first_link_idx(thd,
share->link_statuses, share->access_balances, spider.conn_link_idx,
share->link_count, SPIDER_LINK_STATUS_OK);
Expand All @@ -3013,32 +3007,6 @@ void *spider_bg_sts_action(
share->conn_keys[spider.search_link_idx], trx,
&spider, FALSE, FALSE, &error_num);
conns[spider.search_link_idx]->error_mode = 0;
/*
if (
error_num &&
share->monitoring_kind[spider.search_link_idx] &&
need_mons[spider.search_link_idx]
) {
lex_start(thd);
error_num = spider_ping_table_mon_from_table(
trx,
thd,
share,
spider.search_link_idx,
(uint32) share->monitoring_sid[spider.search_link_idx],
share->table_name,
share->table_name_length,
spider.conn_link_idx[spider.search_link_idx],
NULL,
0,
share->monitoring_kind[spider.search_link_idx],
share->monitoring_limit[spider.search_link_idx],
share->monitoring_flag[spider.search_link_idx],
TRUE
);
lex_end(thd->lex);
}
*/
spider.search_link_idx = -1;
}
if (spider.search_link_idx != -1 && conns[spider.search_link_idx])
Expand All @@ -3049,31 +3017,6 @@ void *spider_bg_sts_action(
share->bg_sts_sync,
2, HA_STATUS_CONST | HA_STATUS_VARIABLE))
{
/*
if (
share->monitoring_kind[spider.search_link_idx] &&
need_mons[spider.search_link_idx]
) {
lex_start(thd);
error_num = spider_ping_table_mon_from_table(
trx,
thd,
share,
spider.search_link_idx,
(uint32) share->monitoring_sid[spider.search_link_idx],
share->table_name,
share->table_name_length,
spider.conn_link_idx[spider.search_link_idx],
NULL,
0,
share->monitoring_kind[spider.search_link_idx],
share->monitoring_limit[spider.search_link_idx],
share->monitoring_flag[spider.search_link_idx],
TRUE
);
lex_end(thd->lex);
}
*/
spider.search_link_idx = -1;
}
}
Expand Down Expand Up @@ -3316,12 +3259,6 @@ void *spider_bg_crd_action(
if (spider.search_link_idx < 0)
{
spider_trx_set_link_idx_for_all(&spider);
/*
spider.search_link_idx = spider_conn_next_link_idx(
thd, share->link_statuses, share->access_balances,
spider.conn_link_idx, spider.search_link_idx, share->link_count,
SPIDER_LINK_STATUS_OK);
*/
spider.search_link_idx = spider_conn_first_link_idx(thd,
share->link_statuses, share->access_balances, spider.conn_link_idx,
share->link_count, SPIDER_LINK_STATUS_OK);
Expand Down Expand Up @@ -3747,6 +3684,24 @@ void *spider_bg_mon_action(
}
}

/**
Returns a random (active) server with a maximum required link status
Calculate the sum of balances of all servers whose link status is at
most the specified status ("eligible"), generate a random number
less than this balance, then find the first server cumulatively
exceeding this balance
@param thd Connection used for generating a random number
@param link_statuses The link statuses of servers
@param access_balances The access balances of servers
@param conn_link_idx Array of indexes to servers
@param link_count Number of servers
@param link_status The maximum required link status
@retval Index to the found server
@retval -1 if no eligible servers
@retval -2 if out of memory
*/
int spider_conn_first_link_idx(
THD *thd,
long *link_statuses,
Expand All @@ -3755,35 +3710,35 @@ int spider_conn_first_link_idx(
int link_count,
int link_status
) {
int roop_count, active_links = 0;
longlong balance_total = 0, balance_val;
int eligible_link_idx, eligible_links = 0;
longlong balance_total = 0, balance_threshold;
double rand_val;
int *link_idxs, link_idx;
long *balances;
int *link_idxs, result;
DBUG_ENTER("spider_conn_first_link_idx");
char *ptr;
ptr = (char *) my_alloca((sizeof(int) * link_count) + (sizeof(long) * link_count));
/* Allocate memory for link_idxs */
ptr = (char *) my_alloca((sizeof(int) * link_count));
if (!ptr)
{
DBUG_PRINT("info",("spider out of memory"));
DBUG_RETURN(-2);
}
link_idxs = (int *) ptr;
ptr += sizeof(int) * link_count;
balances = (long *) ptr;
for (roop_count = 0; roop_count < link_count; roop_count++)

/* Filter for eligible servers, store their indexes and calculate
the total balances */
for (int link_idx = 0; link_idx < link_count; link_idx++)
{
DBUG_ASSERT((conn_link_idx[roop_count] - roop_count) % link_count == 0);
if (link_statuses[conn_link_idx[roop_count]] <= link_status)
DBUG_ASSERT((conn_link_idx[link_idx] - link_idx) % link_count == 0);
if (link_statuses[conn_link_idx[link_idx]] <= link_status)
{
link_idxs[active_links] = roop_count;
balances[active_links] = access_balances[roop_count];
balance_total += access_balances[roop_count];
active_links++;
link_idxs[eligible_links] = link_idx;
balance_total += access_balances[link_idx];
eligible_links++;
}
}

if (active_links == 0)
if (eligible_links == 0)
{
DBUG_PRINT("info",("spider all links are failed"));
my_afree(link_idxs);
Expand All @@ -3793,21 +3748,25 @@ int spider_conn_first_link_idx(
DBUG_PRINT("info",("spider thread_id=%lu", thd_get_thread_id(thd)));
rand_val = spider_rand(thd->variables.server_id + thd_get_thread_id(thd));
DBUG_PRINT("info",("spider rand_val=%f", rand_val));
balance_val = (longlong) (rand_val * balance_total);
DBUG_PRINT("info",("spider balance_val=%lld", balance_val));
for (roop_count = 0; roop_count < active_links - 1; roop_count++)
{
balance_threshold = (longlong) (rand_val * balance_total);
DBUG_PRINT("info",("spider balance_threshold=%lld", balance_threshold));
/* Since balance_threshold < total balance, this loop WILL break */
for (eligible_link_idx = 0;
eligible_link_idx < eligible_links;
eligible_link_idx++)
{
result = link_idxs[eligible_link_idx];
const long balance = access_balances[result];
DBUG_PRINT("info",("spider balances[%d]=%ld",
roop_count, balances[roop_count]));
if (balance_val < balances[roop_count])
link_idxs[eligible_link_idx], balance));
if (balance_threshold < balance)
break;
balance_val -= balances[roop_count];
balance_threshold -= balance;
}

DBUG_PRINT("info",("spider first link_idx=%d", link_idxs[roop_count]));
link_idx = link_idxs[roop_count];
DBUG_PRINT("info",("spider first link_idx=%d", result));
my_afree(link_idxs);
DBUG_RETURN(link_idx);
DBUG_RETURN(result);
}

int spider_conn_next_link_idx(
Expand Down Expand Up @@ -3842,6 +3801,17 @@ int spider_conn_next_link_idx(
DBUG_RETURN(tmp_link_idx);
}

/**
Finds the next active server with a maximum required link status
@param link_statuses The statuses of servers
@param conn_link_idx The array of active servers
@param link_idx The index of the current active server
@param link_count The number of active servers
@param link_status The required maximum link status
@return The next active server whose link status is
at most the required one.
*/
int spider_conn_link_idx_next(
long *link_statuses,
uint *conn_link_idx,
Expand All @@ -3854,6 +3824,8 @@ int spider_conn_link_idx_next(
link_idx++;
if (link_idx >= link_count)
break;
/* Asserts that the `link_idx`th active server is in the correct
"group" */
DBUG_ASSERT((conn_link_idx[link_idx] - link_idx) % link_count == 0);
} while (link_statuses[conn_link_idx[link_idx]] > link_status);
DBUG_PRINT("info",("spider link_idx=%d", link_idx));
Expand Down
2 changes: 1 addition & 1 deletion storage/spider/spd_copy_tables.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -398,7 +398,7 @@ int spider_udf_get_copy_tgt_tables(
(error_num = spider_get_sys_tables_connect_info(
table_tables, tmp_share, 0, mem_root)) ||
(error_num = spider_get_sys_tables_link_status(
table_tables, tmp_share, 0, mem_root)) ||
table_tables, tmp_share->link_statuses, mem_root)) ||
(error_num = spider_get_sys_tables_link_idx(
table_tables, &table_conn->link_idx, mem_root))
) {
Expand Down
12 changes: 12 additions & 0 deletions storage/spider/spd_db_include.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -19,12 +19,19 @@
#define SPD_INIT_ALLOC_ROOT(A, B, C, D) \
init_alloc_root(PSI_INSTRUMENT_ME, A, B, C, D)

/** Maximum possible number of `SPIDER_DBTON`s available to use */
#define SPIDER_DBTON_SIZE 15

#ifndef SIZEOF_STORED_DOUBLE
#define SIZEOF_STORED_DOUBLE 8
#endif

/**
Possible wrapper values, e.g. for `SPIDER_DBTON::wrapper` and
`SPIDER_SHARE::tgt_wrappers`.
fixme: change this to enum
*/
#define SPIDER_DB_WRAPPER_MYSQL "mysql"
#define SPIDER_DB_WRAPPER_MARIADB "mariadb"

Expand Down Expand Up @@ -683,6 +690,8 @@ struct st_spider_db_request_key
class spider_db_util
{
public:
/** Same as the `SPIDER_DBTON::dbton_id` of the `SPIDER_DBTON`
containing this `spider_db_util` */
uint dbton_id;
spider_db_util() = default;
virtual ~spider_db_util() = default;
Expand Down Expand Up @@ -1683,7 +1692,10 @@ static const LEX_CSTRING maturity_name[] =

typedef struct st_spider_dbton
{
/** The index of this dbton in `spider_dbton` */
uint dbton_id;
/** The wrapper of this dbton, same possible values as each element
of `SPIDER_SHARE::tgt_wrappers` */
const char *wrapper;
enum spider_db_access_type db_access_type;
int (*init)();
Expand Down
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