laravel5框架下报错Class 'Predis\Client' not found

故障报错：

2015/12/25 11:16:36 [error] 15155#0: *43 FastCGI sent in stderr:
 "PHP message: PHP Fatal error:  Class 'Predis\Client' not found in
  /var/www/xxxxx/vendor/laravel/framework/src/Illuminate/Redis/Database.php 
  on line 62" while reading response header from upstream, 
  client: 127.0.0.1, server: localhost, request: "POST /xxx/v2/task/cr HTTP/1.1",
   upstream: "fastcgi://127.0.0.1:9000", host: "127.0.0.1:7500"

环境描述：

系统环境：

CentOS release 6.5 (Final)

php版本：

PHP 5.5.28 (cli) (built: Nov 19 2015 12:08:01) 
Copyright (c) 1997-2015 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2015 Zend Technologies

laravel框架和predis版本

  "require": {
    "php": ">=5.5.9",
    "laravel/framework": "5.1.*",
    "predis/predis": "^1.0",
},

存储：redis实现

redis-cli 2.8.3

supervisor来实现队列

[program:zhuima]
process_name=%(program_name)s_%(process_num)02d
command= php artisan queue:work --sleep=3 --tries=1 --daemon
autostart=true
autorestart=true
user=www
numprocs=8
redirect_stderr=true
stdout_logfile=/tmp/xxx.log

症状出现频率：

刚开始是正常的，使用一会就会出现Class 'Predis\Client' not found的报错，
临时解决方式：重装predis模块解决，但是过一会，时间间隔半个小时左右又会报错

求助php大神帮忙定位下是什么问题？