Teach logStash to accept static key/values from the config file

[cjthompson]

This PR gives the logstash writer the ability to write a static list of key-value pairs to each log entry. This allows for custom configuration file to be written on different servers/environments that will contain static data to log, such as the server name, ip address, or other important server-specific information.

One way to leverage this change is to use the npm config module with a default bucker configuration section and override that using a separate config per environment and server.

• Example:

{
    "logstash": {
        "static_keys": {
            "hostname": "host.domain.com",
        }
    }
}

[nlf]

Working on a major refactor/rewrite of all the code right now, but I feel like we could use tags for this rather than adding a transport specific config item.. Just a quick check for if tags is an object in the logstash transport should be plenty, no?

[cjthompson]

Perhaps, if you define tags in the configuration so that certain tags will always be outputted.

[nlf]

As is, you can do

var logger = require('bucker').createLogger(/* opts */).tags(/* tags */);

and you'll get the same effect

[nlf]

I am working on the rewrite though, so if you have other ideas, now is a good time to bring them up

[glock47]

https://github.com/nlf/bucker/pull/30#issuecomment-46035928