详解PHP使用Redis存储session时的一个Warning定位

[Session]
session.save_handler = redis
session.save_path = "tcp://x.x.x.x:6379?auth=yyyy"
session.use_cookies = 1

static void php_session_save_current_state(TSRMLS_D) /* {{{ */
{
  int ret = FAILURE;

  //是否session数组
  IF_SESSION_VARS() {
    if (PS(mod_data) || PS(mod_user_implemented)) {
      char *val;
      int vallen;

     //变量编码
      val = php_session_encode(&vallen TSRMLS_CC);
      if (val) {
        //保存session数据
        ret = PS(mod)->s_write(&PS(mod_data), PS(id), val, vallen TSRMLS_CC);
        efree(val);
      } else {
        //清空session
        ret = PS(mod)->s_write(&PS(mod_data), PS(id), "", 0 TSRMLS_CC);
      }
    }


    //看出错提示语在这里
    if (ret == FAILURE) {
      php_error_docref(NULL TSRMLS_CC, E_WARNING, "Failed to write session data (%s). Please "
          "verify that the current setting of session.save_path "
          "is correct (%s)",
          PS(mod)->s_name,
          PS(save_path));
    }
  }

  if (PS(mod_data) || PS(mod_user_implemented)) {
    PS(mod)->s_close(&PS(mod_data) TSRMLS_CC);
  }
}




static void php_session_flush(TSRMLS_D){
  如果 (PS(session_status) == php_session_active)
    session_status = none

    这里调用...
    php_session_save_current_state
}

static PHP_FUNCTION(session_write_close)
{
  php_session_flush(TSRMLS_C);
}


static PHP_FUNCTION(session_register_shutdown){

}

[16723] 04 Jul 15:15:01.987 # Server started, Redis version 2.8.9
[16723] 04 Jul 15:15:01.987 # WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
[16723] 04 Jul 15:15:01.996 * DB loaded from disk: 0.008 seconds
[16723] 04 Jul 15:15:01.996 * The server is now ready to accept connections on port 6379

$ free -m
       total    used    free   shared  buffers   cached
Mem:     3516    3171    345     0    684    1680
-/+ buffers/cache:    806    2709
Swap:     2055    724    1330

used_memory:2841648
used_memory_human:2.71M
used_memory_rss:3710976
used_memory_peak:2877576
used_memory_peak_human:2.74M
used_memory_lua:33792
mem_fragmentation_ratio:1.31
mem_allocator:jemalloc-3.2.0

/5 * * * /data/scripts/check_redis.sh >/dev/null 2>&1 ##check_redis.tag.1

PORT='6379'
ETH1_ADDR=`/sbin/ifconfig eth1 | awk -F ':' '/inet addr/{print $2}' | sed 's/[a-zA-Z ]//g'`

retval=`nmap --system-dns -sT -p ${PORT} ${ETH1_ADDR} | grep open`
if [ "${retval}X" = "X" ]; then
    /sbin/service redis restart >/dev/null 2>&1
fi