SNMP學習筆記之Python的netsnmp和pysnmp的性能對比

 

0x00 概覽

用python獲取snmp信息有多個現成的庫可以使用，其中比較常用的是netsnmp和pysnmp兩個庫。網上有較多的關於兩個庫的例子。

本文重點在於如何並發的獲取snmp的數據，即同時獲取多台機器的snmp信息。

 

0x01 netsnmp多線程測試

先說netsnmp。python的netsnmp，其實是來自於net-snmp包。

python通過一個c文件調用net-snmp的接口獲取數據。

因此，在並發獲取多台機器的時候，不能夠使用協程獲取。因為使用協程，在get數據的時候，協程會一直等待net-snmp接口返回數據，而不會像socket使用時那樣在等待數據時把CPU切換給其他協程使用。從這點上來說，使用協程和串行獲取沒有區別。

那么如何解決並發獲取的問題呢？可以使用線程，多線程獲取(當然也可以使用多進程)。多個線程同時調用net-snmp的接口獲取數據，然后cpu在多個線程之間不停切換。當一個線程獲取一個結果后，可以繼續調用接口獲取下一個snmp數據。

這里我寫了一個樣例程序。首先把所有的host和oid做成任務放到隊列里，然后啟動多個線程，去執行獲取任務。程序樣例如下：

import threading
import time
import netsnmp
import Queue

start_time = time.time()
hosts = ["192.20.150.109", "192.20.150.110", "192.20.150.111", "192.20.150.112", "192.20.150.113", "192.20.150.114",
     "192.20.150.115", "192.20.150.116", "192.20.150.117", "192.20.150.118", "192.20.150.119", "192.20.150.120",
     "192.20.150.121", "192.20.80.148", "192.20.80.149", "192.20.96.59", "192.20.82.14", "192.20.82.15",
     "192.20.82.17", "192.20.82.19", "192.20.82.12", "192.20.80.139", "192.20.80.137", "192.20.80.136",
     "192.20.80.134", "192.20.80.133", "192.20.80.131", "192.20.80.130", "192.20.81.141", "192.20.81.140",
     "192.20.82.26", "192.20.82.28", "192.20.82.23", "192.20.82.21", "192.20.80.128", "192.20.80.127",
     "192.20.80.122", "192.20.81.159", "192.20.80.121", "192.20.80.124", "192.20.81.151", "192.20.80.118",
     "192.20.80.119", "192.20.80.113", "192.20.80.112", "192.20.80.116", "192.20.80.115", "192.20.78.62",
     "192.20.81.124", "192.20.81.125", "192.20.81.122", "192.20.81.121", "192.20.82.33", "192.20.82.31",
     "192.20.82.32", "192.20.82.30", "192.20.81.128", "192.20.82.39", "192.20.82.37", "192.20.82.35",
     "192.20.81.130", "192.20.80.200", "192.20.81.136", "192.20.81.137", "192.20.81.131", "192.20.81.133",
     "192.20.81.134", "192.20.82.43", "192.20.82.45", "192.20.82.41", "192.20.79.152", "192.20.79.155",
     "192.20.79.154", "192.25.76.235", "192.25.76.234", "192.25.76.233", "192.25.76.232", "192.25.76.231",
     "192.25.76.228", "192.25.20.96", "192.25.20.95", "192.25.20.94", "192.25.20.93", "192.24.163.14",
     "192.24.163.21", "192.24.163.29", "192.24.163.6", "192.18.136.22", "192.18.136.23", "192.24.193.2",
     "192.24.193.19", "192.24.193.18", "192.24.193.11", "192.20.157.132", "192.20.157.133", "192.24.212.232",
     "192.24.212.231", "192.24.212.230"]
oids = [".1.3.6.1.4.1.2021.11.9.0",".1.3.6.1.4.1.2021.11.10.0",".1.3.6.1.4.1.2021.11.11.0",".1.3.6.1.4.1.2021.10.1.3.1",
    ".1.3.6.1.4.1.2021.10.1.3.2",".1.3.6.1.4.1.2021.10.1.3.3",".1.3.6.1.4.1.2021.4.6.0",".1.3.6.1.4.1.2021.4.14.0",
    ".1.3.6.1.4.1.2021.4.15.0"]
myq = Queue.Queue()
rq = Queue.Queue()

#把host和oid組成任務
for host in hosts:
  for oid in oids:
    myq.put((host,oid))

def poll_one_host():
  while True:
    try:
      #死循環從隊列中獲取任務，直到隊列任務為空
      host, oid = myq.get(block=False)
      session = netsnmp.Session(Version=2, DestHost=host, Community="cluster",Timeout=3000000,Retries=0)
      var_list = netsnmp.VarList()
      var_list.append(netsnmp.Varbind(oid))
      ret = session.get(var_list)
      rq.put((host, oid, ret, (time.time() - start_time)))
    except Queue.Empty:
      break

thread_arr = []

#開啟多線程
num_thread = 50
for i in range(num_thread):
  t = threading.Thread(target=poll_one_host, kwargs={})
  t.setDaemon(True)
  t.start()
  thread_arr.append(t)

#等待任務執行完畢
for i in range(num_thread):
  thread_arr[i].join()

while True:
  try:
    info = rq.get(block=False)
    print info
  except Queue.Empty:
    print time.time() - start_time
    break

netsnmp除了支持get操作之外，還支持walk操作，即遍歷某個oid。

但是walk使用的時候需要謹慎，以免導致高延時等問題。

 

0x02 pysnmp測試

pysnmp是用python實現的一套snmp協議的庫。其自身提供了對於異步的支持。

pysnmp常用操作

import time
import Queue
from pysnmp.hlapi.asyncore import *
t = time.time()
myq = Queue.Queue()

#回調函數。在有數據返回時觸發
def cbFun(snmpEngine, sendRequestHandle, errorIndication, errorStatus, errorIndex, varBinds, cbCtx):
   myq.put((time.time()-t, varBinds))
hosts = ["192.20.150.109", "192.20.150.110", "192.20.150.111", "192.20.150.112", "192.20.150.113", "192.20.150.114",
     "192.20.150.115", "192.20.150.116", "192.20.150.117", "192.20.150.118", "192.20.150.119", "192.20.150.120",
     "192.20.150.121", "192.20.80.148", "192.20.80.149", "192.20.96.59", "192.20.82.14", "192.20.82.15",
     "192.20.82.17", "192.20.82.19", "192.20.82.12", "192.20.80.139", "192.20.80.137", "192.20.80.136",
     "192.20.80.134", "192.20.80.133", "192.20.80.131", "192.20.80.130", "192.20.81.141", "192.20.81.140",
     "192.20.82.26", "192.20.82.28", "192.20.82.23", "192.20.82.21", "192.20.80.128", "192.20.80.127",
     "192.20.80.122", "192.20.81.159", "192.20.80.121", "192.20.80.124", "192.20.81.151", "192.20.80.118",
     "192.20.80.119", "192.20.80.113", "192.20.80.112", "192.20.80.116", "192.20.80.115", "192.20.78.62",
     "192.20.81.124", "192.20.81.125", "192.20.81.122", "192.20.81.121", "192.20.82.33", "192.20.82.31",
     "192.20.82.32", "192.20.82.30", "192.20.81.128", "192.20.82.39", "192.20.82.37", "192.20.82.35",
     "192.20.81.130", "192.20.80.200", "192.20.81.136", "192.20.81.137", "192.20.81.131", "192.20.81.133",
     "192.20.81.134", "192.20.82.43", "192.20.82.45", "192.20.82.41", "192.20.79.152", "192.20.79.155",
     "192.20.79.154", "192.25.76.235", "192.25.76.234", "192.25.76.233", "192.25.76.232", "192.25.76.231",
     "192.25.76.228", "192.25.20.96", "192.25.20.95", "192.25.20.94", "192.25.20.93", "192.24.163.14",
     "192.24.163.21", "192.24.163.29", "192.24.163.6", "192.18.136.22", "192.18.136.23", "192.24.193.2",
     "192.24.193.19", "192.24.193.18", "192.24.193.11", "192.20.157.132", "192.20.157.133", "192.24.212.232",
     "192.24.212.231", "192.24.212.230"]

oids = [".1.3.6.1.4.1.2021.11.9.0",".1.3.6.1.4.1.2021.11.10.0",".1.3.6.1.4.1.2021.11.11.0",".1.3.6.1.4.1.2021.10.1.3.1",
    ".1.3.6.1.4.1.2021.10.1.3.2",".1.3.6.1.4.1.2021.10.1.3.3",".1.3.6.1.4.1.2021.4.6.0",".1.3.6.1.4.1.2021.4.14.0",
    ".1.3.6.1.4.1.2021.4.15.0"]
    
snmpEngine = SnmpEngine()

#添加任務
for oid in oids:
  for h in hosts:
    getCmd(snmpEngine,
      CommunityData('cluster'),
      UdpTransportTarget((h, 161), timeout=3, retries=0,),
      ContextData(),
      ObjectType(ObjectIdentity(oid)),
      cbFun=cbFun)
time1 = time.time() - t

#執行異步獲取snmp
snmpEngine.transportDispatcher.runDispatcher()

#打印結果
while True:
  try:
    info = myq.get(block=False)
    print info
  except Queue.Empty:
    print time1
    print time.time() - t
    break

pysnmp本身只支持最基礎的get和getnext命令，因此如果想使用walk，需要自己進行實現。

 

0x03 兩者性能測試

在同一個環境下，對兩者進行了性能測試。兩者對198個host，10個oid進行采集。

可以看到netsnmp的采集速度跟線程數有關。當線程數增大到一定程度，采集時間不再縮短。因為開辟線程同樣會消耗時間。而已有的線程已經足夠處理。

pysnmp性能較之略差一下。詳細分析pysnmp在添加任務(執行getCmd時)消耗了約1.2s，之后的采集約消耗3.3秒。

在增加了oid數，在進行實驗。host仍然是198個，oid是42個。

 

0x04 總結

可以看到差距被進一步拉大。在線程足夠多的情況下，netsnmp的效率要明顯強於pysnmp。

因為二者都支持可以並行采集多個host，從易用性來說，netsnmp更為簡單一些，且netsnmp支持walk功能。本文更加推薦netsnmp。

安裝netsnmp需要安裝net-snmp。如果centos，則使用yum會較為方便。