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#!/usr/bin/python
#
# dbslower Trace MySQL and PostgreSQL queries slower than a threshold.
#
# USAGE: dbslower [-v] [-p PID [PID ...]] [-b PATH_TO_BINARY] [-m THRESHOLD]
# {mysql,postgres}
#
# By default, a threshold of 1ms is used. Set the threshold to 0 to trace all
# queries (verbose).
#
# Script works in two different modes:
# 1) USDT probes, which means it needs MySQL and PostgreSQL built with
# USDT (DTrace) support.
# 2) uprobe and uretprobe on exported function of binary specified by
# PATH_TO_BINARY parameter. (At the moment only MySQL support)
#
# If no PID or PATH_TO_BINARY is provided, the script attempts to discover
# all MySQL or PostgreSQL database processes and uses USDT probes.
#
# Strongly inspired by Brendan Gregg's work on the mysqld_qslower script.
#
# Copyright 2017, Sasha Goldshtein
# Licensed under the Apache License, Version 2.0
#
# 15-Feb-2017 Sasha Goldshtein Created this.
from bcc import BPF, USDT
import argparse
import re
import subprocess
examples = """examples:
dbslower postgres # trace PostgreSQL queries slower than 1ms
dbslower postgres -p 188 322 # trace specific PostgreSQL processes
dbslower mysql -p 480 -m 30 # trace MySQL queries slower than 30ms
dbslower mysql -p 480 -v # trace MySQL queries & print the BPF program
dbslower mysql -x $(which mysqld) # trace MySQL queries with uprobes
"""
parser = argparse.ArgumentParser(
description="",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=examples)
parser.add_argument("-v", "--verbose", action="store_true",
help="print the BPF program")
parser.add_argument("db", choices=["mysql", "postgres"],
help="the database engine to use")
parser.add_argument("-p", "--pid", type=int, nargs='*',
dest="pids", metavar="PID", help="the pid(s) to trace")
parser.add_argument("-x", "--exe", type=str,
dest="path", metavar="PATH", help="path to binary")
parser.add_argument("-m", "--threshold", type=int, default=1,
help="trace queries slower than this threshold (ms)")
parser.add_argument("--ebpf", action="store_true",
help=argparse.SUPPRESS)
args = parser.parse_args()
threshold_ns = args.threshold * 1000000
mode = "USDT"
if args.path and not args.pids:
if args.db == "mysql":
regex = "\\w+dispatch_command\\w+"
symbols = BPF.get_user_functions_and_addresses(args.path, regex)
if len(symbols) == 0:
print("Can't find function 'dispatch_command' in %s" % (args.path))
exit(1)
(mysql_func_name, addr) = symbols[0]
if mysql_func_name.find(b'COM_DATA') >= 0:
mode = "MYSQL57"
else:
mode = "MYSQL56"
else:
# Placeholder for PostrgeSQL
# Look on functions initStringInfo, pgstat_report_activity, EndCommand,
# NullCommand
print("Sorry at the moment PostgreSQL supports only USDT")
exit(1)
program = """
#include <uapi/linux/ptrace.h>
DEFINE_THRESHOLD
DEFINE_USDT
DEFINE_MYSQL56
DEFINE_MYSQL57
struct temp_t {
u64 timestamp;
#ifdef USDT
char *query;
#else
/*
MySQL clears query packet before uretprobe call - so copy query in advance
*/
char query[256];
#endif //USDT
};
struct data_t {
u64 pid;
u64 timestamp;
u64 duration;
char query[256];
};
BPF_HASH(temp, u64, struct temp_t);
BPF_PERF_OUTPUT(events);
int query_start(struct pt_regs *ctx) {
#if defined(MYSQL56) || defined(MYSQL57)
/*
Trace only packets with enum_server_command == COM_QUERY
*/
#ifdef MYSQL56
u64 command = (u64) PT_REGS_PARM1(ctx);
#else //MYSQL57
u64 command = (u64) PT_REGS_PARM3(ctx);
#endif
if (command != 3) return 0;
#endif
struct temp_t tmp = {};
tmp.timestamp = bpf_ktime_get_ns();
#if defined(MYSQL56)
bpf_probe_read(&tmp.query, sizeof(tmp.query), (void*) PT_REGS_PARM3(ctx));
#elif defined(MYSQL57)
void* st = (void*) PT_REGS_PARM2(ctx);
char* query;
bpf_probe_read(&query, sizeof(query), st);
bpf_probe_read(&tmp.query, sizeof(tmp.query), query);
#else //USDT
bpf_usdt_readarg(1, ctx, &tmp.query);
#endif
u64 pid = bpf_get_current_pid_tgid();
temp.update(&pid, &tmp);
return 0;
}
int query_end(struct pt_regs *ctx) {
struct temp_t *tempp;
u64 pid = bpf_get_current_pid_tgid();
tempp = temp.lookup(&pid);
if (!tempp)
return 0;
u64 delta = bpf_ktime_get_ns() - tempp->timestamp;
#ifdef THRESHOLD
if (delta >= THRESHOLD) {
#endif //THRESHOLD
struct data_t data = {};
data.pid = pid >> 32; // only process id
data.timestamp = tempp->timestamp;
data.duration = delta;
bpf_probe_read(&data.query, sizeof(data.query), tempp->query);
events.perf_submit(ctx, &data, sizeof(data));
#ifdef THRESHOLD
}
#endif //THRESHOLD
temp.delete(&pid);
return 0;
};
""".replace("DEFINE_USDT", "#define USDT" if mode == "USDT" else "") \
.replace("DEFINE_MYSQL56", "#define MYSQL56" if mode == "MYSQL56" else "") \
.replace("DEFINE_MYSQL57", "#define MYSQL57" if mode == "MYSQL57" else "") \
.replace("DEFINE_THRESHOLD",
"#define THRESHOLD %d" % threshold_ns if threshold_ns > 0 else "")
if mode.startswith("MYSQL"):
# Uprobes mode
bpf = BPF(text=program)
bpf.attach_uprobe(name=args.path, sym=mysql_func_name,
fn_name="query_start")
bpf.attach_uretprobe(name=args.path, sym=mysql_func_name,
fn_name="query_end")
else:
# USDT mode
if not args.pids or len(args.pids) == 0:
if args.db == "mysql":
args.pids = map(int, subprocess.check_output(
"pidof mysqld".split()).split())
elif args.db == "postgres":
args.pids = map(int, subprocess.check_output(
"pidof postgres".split()).split())
usdts = map(lambda pid: USDT(pid=pid), args.pids)
for usdt in usdts:
usdt.enable_probe("query__start", "query_start")
usdt.enable_probe("query__done", "query_end")
if args.verbose:
print('\n'.join(map(lambda u: u.get_text(), usdts)))
bpf = BPF(text=program, usdt_contexts=usdts)
if args.verbose or args.ebpf:
print(program)
if args.ebpf:
exit()
start = BPF.monotonic_time()
def print_event(cpu, data, size):
event = bpf["events"].event(data)
print("%-14.6f %-6d %8.3f %s" % (
float(event.timestamp - start) / 1000000000,
event.pid, float(event.delta) / 1000000, event.query))
if mode.startswith("MYSQL"):
print("Tracing database queries for application %s slower than %d ms..." %
(args.path, args.threshold))
else:
print("Tracing database queries for pids %s slower than %d ms..." %
(', '.join(map(str, args.pids)), args.threshold))
print("%-14s %-6s %8s %s" % ("TIME(s)", "PID", "MS", "QUERY"))
bpf["events"].open_perf_buffer(print_event, page_cnt=64)
while True:
try:
bpf.perf_buffer_poll()
except KeyboardInterrupt:
exit()
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