https://github.com/pd/srvaddr

Simple SRV record querying from the CLI
https://github.com/pd/srvaddr

command-line dns docker-image golang srv-record

Last synced: about 2 months ago
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Simple SRV record querying from the CLI

• Host: GitHub
• URL: https://github.com/pd/srvaddr
• Owner: pd
• License: mit
• Created: 2016-05-20T16:26:20.000Z (about 10 years ago)
• Default Branch: master
• Last Pushed: 2016-05-23T18:36:22.000Z (about 10 years ago)
• Last Synced: 2025-06-27T21:37:56.788Z (12 months ago)
• Topics: command-line, dns, docker-image, golang, srv-record
• Language: Go
• Homepage:
• Size: 8.79 KB
• Stars: 3
• Watchers: 1
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: MIT-LICENSE

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README

          
# srvaddr

Small command-line utility for querying SRV DNS records and rendering the results into a template

or an easily manipulated JSON structure.

## Installation

The usual:

    $ go get -u github.com/pd/srvaddr

    $ go install github.com/pd/srvaddr

    

You can download binaries from the [Github Releases][]:

    $ curl -o srvaddr https://github.com/pd/srvaddr/releases/download/v0.1/srvaddr_linux_amd64 && \

        chmod +x ./srvaddr && \

        ./srvaddr -h

Alternatively, it's available as a [docker image][]:

    $ docker run philodespotos/srvaddr _xmpp-server._tcp.google.com

    xmpp-server.l.google.com:5269

    alt1.xmpp-server.l.google.com:5269

    alt2.xmpp-server.l.google.com:5269

    alt3.xmpp-server.l.google.com:5269

    alt4.xmpp-server.l.google.com:5269

## Examples

The default template simply lists the hostname(s) and port(s) returned for the given query:

    $ srvaddr _frontend._tcp.tld

    box2.example.com:1234

    box3.example.com:7654

    box1.example.com:9876

The results are displayed in no particular order.

> NB: Nothing I use in practice actually populates the priority or weight values in SRV

> records, but the results should _probably_ be sorted based on those.

To lookup multiple services at once, the default unlabeled output is ambiguous. You can label

each service and use the "env-style" template:

    $ srvaddr ZK=_zookeeper._tcp.service.consul MQ=_rabbit._tcp.service.consul

    ZK_ADDR0=spof.node.dc1.consul:2181

    ZK_HOST0=spof.node.dc1.consul

    ZK_PORT0=2181

    ZK_ADDR1=spof.node.dc1.consul:2181

    ZK_HOST1=spof.node.dc1.consul

    ZK_PORT1=2181

    MQ_ADDR0=spof.node.dc1.consul:5672

    MQ_HOST0=spof.node.dc1.consul

    MQ_PORT0=5672

Under the hood, the output formats are all just defined with [text/template][]. You can use

a custom template with `-t filename` (with `-` representing stdin, as usual):

    $ echo '{{with index .db 0}}database port is {{.Port}}{{end}}' | \

        srvaddr -t - db=_postgres._tcp.internal

    database port is 16273

Go's templating can be unwieldy at times. You can just emit JSON, maybe pipe it into [jq][]:

    $ srvaddr -json zk=_zookeeper._tcp.service.consul | jq .

    {

      "zk": [

        {

          "Host": "deadbeef.node.dc1.consul.",

          "IP": "10.2.2.2",

          "Port": 2181

        },

        {

          "Host": "beadfeed.node.dc1.consul.",

          "IP": "10.1.1.1",

          "Port": 2181

        }

      ]

    }

Not all DNS servers will return the additional `A` records necessary for the IP

to be known; favor using the hostname, which is part of the SRV record itself,

whenever possible.

By default, `srvaddr` uses a nameserver from `resolv.conf`; to use a different nameserver:

    $ srvaddr -ns 127.0.0.1:8600 _kafka._tcp.service.consul

## Development

I'll probably write tests at some point. Setting up the mocks was too distracting early on.

Meanwhile, a fairly low friction way of serving up some SRV records is to run consul locally.

Here's a minimal example config:

~~~json

{

  "server": true,

  "bootstrap_expect": 1,

  "log_level": "debug",

  "services": [

    { "id": "zk1", "name": "zk", "address": "10.1.1.1", "port": 2181 },

    { "id": "zk2", "name": "zk", "address": "10.2.2.2", "port": 2181 },

    { "name": "api", "address": "10.3.3.3", "port": 443 },

    { "name": "mq", "address": "127.0.0.1", "port": 5672 }

  ]

}

~~~

[Github Releases]: https://github.com/pd/srvaddr/releases

[docker image]: https://hub.docker.com/r/philodespotos/srvaddr/

[text/template]: https://godoc.org/pkg/text/template

[jq]: https://stedolan.github.io/jq/