Node.js MtrExt

Node.js wrapper for the mtr command / tool.

This project is based heavily on https://github.com/Kami/node-mtr I was going to fork that project but I've realised that my fork would contain breaking changes when compared to the results from the original package (node-mtr), hence 'MtrExt' -> "Mtr Extended"

Table of contents

1. Installation
2. Using
   • Example
   • Results
3. Understanding the example
4. Understanding the results
5. Troubleshooting
   • Bad parameters for mtr
   • mtr missing or can not be located
6. References
   • -o FIELDS
7. Documentation

1. Installation

npm install mtrext

2. Using

Example

server.js

var mtrClient = require('mtrext').MtrExt;
var mtr = new mtrClient('192.168.0.1', { resolveDns: true, packetLen: 60 });
mtr.traceroute();
mtr.on('end', function(results) {
    console.log(JSON.stringify(results));
});
mtr.on('error', function(err) {
    console.error(err);
});

Results

{
    "args": [
        "-4",
        "-o LSDR NBAW JMXI",
        "-r",
        "-w",
        "--psize",
        60,
        "192.168.100.1"
    ],
    "code": 0,
    "status": "success",
    "timetaken": [
        14,
        258393002
    ],
    "data": {
        "raw": "Start: Wed Jun 19 08:55:05 2019\nHOST: server2                         Loss%   Snt Drop   Rcv   Last  Best   Avg  Wrst  Jttr Javg Jmax Jint\n  1.|-- router1           0.0%    10    0    10    1.4   0.4   1.1   3.1   0.9  0.9  2.7  7.3\n  2.|-- server1        0.0%    10    0    10    1.1   0.6   1.3   2.8   1.2  0.9  2.1  7.4\n",
        "hops": [
            {
                "hop": "1",
                "host": "router1",
                "loss": "0.0",
                "snt": "10",
                "drop": "0",
                "rcv": "10",
                "last": "1.4",
                "best": "0.4",
                "avg": "1.1",
                "wrst": "3.1",
                "jttr": "0.9",
                "javg": "0.9",
                "jmax": "2.7",
                "jint": "7.3"
            },
            {
                "hop": "2",
                "host": "server1",
                "loss": "0.0",
                "snt": "10",
                "drop": "0",
                "rcv": "10",
                "last": "1.1",
                "best": "0.6",
                "avg": "1.3",
                "wrst": "2.8",
                "jttr": "1.2",
                "javg": "0.9",
                "jmax": "2.1",
                "jint": "7.4"
            }
        ]
    }
}

3. Understanding the example

var mtr = new mtrClient('127.0.0.1', { resolveDns: true, packetLen: 60 });

This sets up mtrext to use the following parameters "resolveDns" and "packetlen" which are both optional. From "man mtr" for "packetlen"

If set to a negative number, every iteration will use a different, random packet size up to that number.

4. Understanding the results

"args" - This shows the end-user exactly what parameters were passed on to the mtr command. This is shown in case you want to manually re-run the mtr command.

"code" - The return code from the mtr command.

"status" - This is internally generated to indicate if there were any problems.

"timetaken" - This is based on the values coming back from "hrtime" [seconds, nanoseconds] https://nodejs.org/api/process.html#process_process_hrtime_time

"data" - This contains the "raw" output from mtr and the parsed data ("hops") based upon that. The "raw" output is useful if there is a parsing issue.

5. Troubleshooting

From time to time things may go wrong. To that end, I've tried to pad out the err messages as much as possible. Using the following code block we can view the error(s):

mtr.on('error', function(err) {
    console.log(err);
});

Bad parameters for mtr

Because of the different flavors of mtr, there could be an issue with the parameters that get sent to mtr. The following result set shows how that would look like. "data.results.raw" has the error.

{ Error
    at ChildProcess.<anonymous> (/data/projects/node/mtr_test/node_modules/mtrext/lib/mtrext.js:113:19)
    at ChildProcess.emit (events.js:198:13)
    at Process.ChildProcess._handle.onexit (internal/child_process.js:248:12)
  data:
   { args:
      [ '-4',
        '-o LSDR NBAW JMXI CCCC',
        '-r',
        '-w',
        '--psize',
        60,
        '192.168.100.1' ],
     code: 1,
     status: 'failed',
     timetaken: [ 0, 175462135 ],
     results: { raw: 'Unknown field identifier: C\n' } } }

mtr missing or can not be located

Looking at https://nodejs.org/api/errors.html#errors_common_system_errors one can get a better idea of what the system error means. In this case, 'mtr' is not found.

Please note that so far, the Windows platform is not supported as I can't find a CLI version of mtr.

{ Error: spawn mtr ENOENT
    at Process.ChildProcess._handle.onexit (internal/child_process.js:240:19)
    at onErrorNT (internal/child_process.js:415:16)
    at process._tickCallback (internal/process/next_tick.js:63:19)
    at Function.Module.runMain (internal/modules/cjs/loader.js:832:11)
    at startup (internal/bootstrap/node.js:283:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:622:3)
  errno: 'ENOENT',
  code: 'ENOENT',
  syscall: 'spawn mtr',
  path: 'mtr',
  spawnargs:
   [ '-4',
     '-o LSDR NBAW JMXI',
     '-r',
     '-w',
     '--psize',
     60,
     '192.168.100.1' ] }

6. References

mtr man page https://linux.die.net/man/8/mtr

-o FIELDS

7. Documentation

There is now dynamically generated documentation that is built when npm install is run. Those files will be located under the 'documentation' folder. The reasoning for adding dynamically generated documentation is that if there was anyone else who wanted to fork this project or get a better understanding of how this all works, then they would have a starting point.