{"id":3407,"date":"2015-08-01T23:16:32","date_gmt":"2015-08-02T05:16:32","guid":{"rendered":"http:\/\/benincosa.com\/?p=3407"},"modified":"2015-08-01T23:36:07","modified_gmt":"2015-08-02T05:36:07","slug":"go-with-nx-api","status":"publish","type":"post","link":"https:\/\/benincosa.com\/?p=3407","title":{"rendered":"Go with NX-API"},"content":{"rendered":"

I’ve been working on a project<\/a> to collect data from Cisco Nexus switches. \u00a0I first tackled making SNMP calls to collect counter statistics but then I thought, why not try it with the NX-API that came with the Nexus 9ks?<\/p>\n

The documentation for the APIs<\/a> I hoped would be better, but the samples on github<\/a> were enough to get anybody going… as long as you do it in Python. \u00a0But these days the cool systems programmers are moving to Go for several reasons:<\/p>\n

    \n
  1. The concurrency capabilities will take your breath away. \u00a0Yes, I go crazy with all the go routines<\/a> and channels. \u00a0Its a really cool feature in the language and great for when you want to run a lot of tasks in parallel. \u00a0(Like logging into a bunch of switches and capturing data maybe? )<\/li>\n
  2. The binaries can be distributed without any hassle of dependencies. \u00a0Why does this matter? \u00a0Well, for example, if I want to run the python-novaclient commands on my machine, I have to first install python and its dependencies, then run pip to install the packages and those dependencies. \u00a0I’m always looking for more lube to make trying new things out easier. \u00a0Static binaries ease the friction.<\/li>\n<\/ol>\n

    After playing around with the switch I finally got something working so I thought I’d share it. \u00a0The code I developed is on my sticky pipe project<\/a>. \u00a0For the TL;DR version of this post check out the function getNXAPIData for the working stuff. \u00a0The rest of this will walk through making a call to the switch.<\/p>\n

    1. \u00a0Get the parameters.<\/h3>\n

    You’ll have to figure out a way to get the username and password from the user. \u00a0In my program I used environment variables, but you may also want to take command line variables. \u00a0There are lots of places on the internet you can find that so I’m not going into that with much detail other than something simple like:<\/p>\n

    func main() {\r\n  \/\/ some stuff above here...\r\n\r\n  \/\/ Get all the parameters the user entered.  os.Args[0] is the program\r\n  \/\/ name, so get everything from os.Args[1] to the end.  \r\n  argArray := os.Args[1:]\r\n\r\n  \/\/ make sure there are at least 3 arguments\r\n  if len(argArray) < 3 { \r\n    fmt.Println(\"please enter the switch, username, and password\")\r\n    return\r\n  }\r\n  \/\/ more stuff\r\n}<\/pre>\n
    2. Create the message to send to the Nexus<\/h3>\n
    The NX-API isn’t a\u00a0RESTful API. \u00a0Instead, you just enter Nexus commands like you would if you were on the command line. \u00a0The \u00a0NX-API then responds with output back in JSON notation. \u00a0You can also get XML, but why in the world would you do that to yourself? \u00a0XML was cool like 10 years ago, but let’s\u00a0move on people! \u00a0There’s a JSON RPC format, but I don’t get what this gives you that JSON doesn’t other than order by adding flags to order things. \u00a0Stick with JSON and your life will not suck.<\/p>\n
    Here’s how we do that:<\/p>\n
    command := \"show interface brief\"\r\nvar jsonStr = []byte(`{\r\n  \"ins_api\": {\r\n    \"version\":       \"1.0\",\r\n    \"type\":          \"cli_show\",\r\n    \"chunk\":         \"0\",\r\n    \"sid\":           \"1\",\r\n    \"input\":         \"` + command + `\", \r\n    \"output_format\": \"json\",\r\n  }\r\n}`)<\/pre>\n
    This format of a message seems to handle any JSON that we want to throw at the Nexus. \u00a0This is really all you need to send your go robots forth to manage your world.<\/p>\n
    3. \u00a0Connect to the Nexus Switch<\/h3>\n
    I start by creating an http.NewRequest. \u00a0The parameters are<\/p>\n