https://yq.aliyun.com/articles/117042

Redis提供了list、hash、zset等复杂类型的数据结构，业务在使用的时候可能由于key设计不合理导致某个key过大，由于redis简单的单线程模型，业务在获取或者删除大key的时候都会有一定的影响，另外在集群模式下由于大key的产生还很容易导致某个子节点的内存满，综上所述我们需要提供大key的搜索工具。

初始化环境

安装python客户端

下载python客户端
wget “https://pypi.python.org/packages/68/44/5efe9e98ad83ef5b742ce62a15bea609ed5a0d1caf35b79257ddb324031a/redis-2.10.5.tar.gz#md5=3b26c2b9703b4b56b30a1ad508e31083”

解压安装

tar -xvf redis-2.10.5.tar.gz
cd redis-2.10.5
sudo python setup.py install

扫描脚本

遍历key

对于Redis主从版本可以通过scan命令进行扫描，对于集群版本提供了ISCAN命令进行扫描，命令规则如下, 其中节点个数node可以通过info命令来获取到

 

ISCAN idx cursor [MATCH pattern] [COUNT count]（idx为节点的id，从0开始，16到64gb的集群实例为8个节点故idx为0到7，128g 256gb的为16个节点）

扫描脚本

import sys
import redis

f = open('bigKey.txt', 'a')
f2 = open('ttl.txt', 'a')
def check_big_key(r, k):
  bigKey = False
  length = 0
  try:
    type = r.type(k)
    if type == "string":
      length = r.strlen(k)
    elif type == "hash":
      length = r.hlen(k)
    elif type == "list":
      length = r.llen(k)
    elif type == "set":
      length = r.scard(k)
    elif type == "zset":
      length = r.zcard(k)
  except:
    return
  if length > 10240:
    bigKey = True
  if bigKey :
    print db,k,type,length
    f.write("%s\n" % (k))
    f.flush()
  ttl = r.ttl(k)
  if ttl < 0:
    print "ttl-----:",k,ttl
    f2.write("%s\n" % (k))
    f2.flush()
def find_big_key_normal(db_host, db_port, db_password, db_num):
  r = redis.StrictRedis(host=db_host, port=db_port, password=db_password, db=db_num)
  for k in r.scan_iter(count=1000):
    check_big_key(r, k)

def find_big_key_sharding(db_host, db_port, db_password, db_num, nodecount):
  r = redis.StrictRedis(host=db_host, port=db_port, password=db_password, db=db_num)
  cursor = 0
  for node in range(0, nodecount) :
    while True:
      iscan = r.execute_command("iscan",str(node), str(cursor), "count", "1000")
      for k in iscan[1]:
        check_big_key(r, k)
      cursor = iscan[0]
      print cursor, db, node, len(iscan[1])
      if cursor == "0":
        break;

if __name__ == '__main__':
  if len(sys.argv) != 4:
     print 'Usage: python ', sys.argv[0], ' host port password '
     exit(1)
  db_host = sys.argv[1]
  db_port = sys.argv[2]
  db_password = sys.argv[3]
  r = redis.StrictRedis(host=db_host, port=int(db_port), password=db_password)
  nodecount = r.info()['nodecount']
  #nodecount = 1
  keyspace_info = r.info("keyspace")
  for db in keyspace_info:
    print 'check ', db, ' ', keyspace_info[db]
    if nodecount > 1:
      find_big_key_sharding(db_host, db_port, db_password, db.replace("db",""), nodecount)
    else:
      find_big_key_normal(db_host, db_port, db_password, db.replace("db", ""))
  f.close()
  f2.close()

可以通过python find_bigkey host 6379 password来执行，支持阿里云Redis的主从版本和集群版本的大key查找，默认大key的阈值为10240，也就是对于string类型的value大于10240的认为是大key，对于list的话如果list长度大于10240认为是大key，对于hash的话如果field的数目大于10240认为是大key。另外默认该脚本每次搜索1000个key，对业务的影响比较低，不过最好在业务低峰期进行操作，避免scan命令对业务的影响。