PS-2033, proof of concept (#540)

bin/pt-stalk

@@ -979,7 +979,7 @@ collect_mysql_data_loop() {
    (echo $ts; $CMD_MYSQL $EXT_ARGV -e "SHOW FULL PROCESSLIST\G") \
       >> "$d/$p-processlist" &
    if [ "$have_lock_waits_table" ]; then
-      (echo $ts; lock_waits)   >>"$d/$p-lock-waits" &
+      (echo $ts; lock_waits "$d/lock_waits.running")   >>"$d/$p-lock-waits" &
       (echo $ts; transactions) >>"$d/$p-transactions" &
    fi
 
@@ -988,7 +988,7 @@ collect_mysql_data_loop() {
    fi
 
    if [ "${mysql_version}" '>' "5.6" ]; then
-      (echo $ts; ps_prepared_statements) >> "$d/$p-prepared-statements" &
+      (echo $ts; ps_prepared_statements "$d/prepared_statements.isrunnning") >> "$d/$p-prepared-statements" &
    fi
 
    slave_status "$d/$p-slave-status" "${mysql_version}" 
@@ -1089,6 +1089,11 @@ open_tables() {
 }
 
 lock_waits() {
+   local flag_file=$1
+   if test -f "$flag_file"; then
+      echo "Lock collection already running, skipping this iteration"
+   else
+      touch "$flag_file"
       local sql1="SELECT SQL_NO_CACHE
          CONCAT('thread ', b.trx_mysql_thread_id, ' from ', p.host) AS who_blocks,
          IF(p.command = \"Sleep\", p.time, 0) AS idle_in_trx,
@@ -1119,6 +1124,8 @@ lock_waits() {
       LEFT JOIN INFORMATION_SCHEMA.PROCESSLIST AS p ON p.id = b.trx_mysql_thread_id
       ORDER BY wait_time DESC\G"
       $CMD_MYSQL $EXT_ARGV -e "$sql2"
+      rm "$flag_file"
+   fi
 } 
 
 transactions() {
@@ -1200,10 +1207,17 @@ ps_locks_transactions() {
 }
 
 ps_prepared_statements() {
+   local flag_file=$1
+   if test -f "$flag_file"; then
+      echo "Prepared statements collection already running, skipping this iteration"
+   else
+      touch "$flag_file"
       $CMD_MYSQL $EXT_ARGV -e "SELECT t.processlist_id, pse.* \
                                FROM performance_schema.prepared_statements_instances pse \
                                JOIN performance_schema.threads t \
                                ON (pse.OWNER_THREAD_ID=t.thread_id)\G"
+      rm "$flag_file"
+   fi
 }
 
 slave_status() {

lib/bash/collect.sh

@@ -266,7 +266,7 @@ collect_mysql_data_loop() {
    (echo $ts; $CMD_MYSQL $EXT_ARGV -e "SHOW FULL PROCESSLIST\G") \
       >> "$d/$p-processlist" &
    if [ "$have_lock_waits_table" ]; then
-      (echo $ts; lock_waits)   >>"$d/$p-lock-waits" &
+      (echo $ts; lock_waits "$d/lock_waits.running")   >>"$d/$p-lock-waits" &
       (echo $ts; transactions) >>"$d/$p-transactions" &
    fi
 
@@ -275,7 +275,7 @@ collect_mysql_data_loop() {
    fi
 
    if [ "${mysql_version}" '>' "5.6" ]; then
-      (echo $ts; ps_prepared_statements) >> "$d/$p-prepared-statements" &
+      (echo $ts; ps_prepared_statements "$d/prepared_statements.isrunnning") >> "$d/$p-prepared-statements" &
    fi
 
    slave_status "$d/$p-slave-status" "${mysql_version}" 
@@ -387,6 +387,11 @@ open_tables() {
 }
 
 lock_waits() {
+   local flag_file=$1
+   if test -f "$flag_file"; then
+      echo "Lock collection already running, skipping this iteration"
+   else
+      touch "$flag_file"
       local sql1="SELECT SQL_NO_CACHE
          CONCAT('thread ', b.trx_mysql_thread_id, ' from ', p.host) AS who_blocks,
          IF(p.command = \"Sleep\", p.time, 0) AS idle_in_trx,
@@ -417,6 +422,8 @@ lock_waits() {
       LEFT JOIN INFORMATION_SCHEMA.PROCESSLIST AS p ON p.id = b.trx_mysql_thread_id
       ORDER BY wait_time DESC\G"
       $CMD_MYSQL $EXT_ARGV -e "$sql2"
+      rm "$flag_file"
+   fi
 } 
 
 transactions() {
@@ -498,10 +505,21 @@ ps_locks_transactions() {
 }
 
 ps_prepared_statements() {
+# PS-2033:
+# If no flag file exists, create it, then collect data
+# After data collected, remove the file
+# If flag file exists, skip current iteration
+   local flag_file=$1
+   if test -f "$flag_file"; then
+      echo "Prepared statements collection already running, skipping this iteration"
+   else
+      touch "$flag_file"
       $CMD_MYSQL $EXT_ARGV -e "SELECT t.processlist_id, pse.* \
                                FROM performance_schema.prepared_statements_instances pse \
                                JOIN performance_schema.threads t \
                                ON (pse.OWNER_THREAD_ID=t.thread_id)\G"
+      rm "$flag_file"
+   fi
 }
 
 slave_status() {