# APID

Apid is a container for publishing APIs that provides core services to its plugins including configuration, 
API publishing, data access, and a local pub/sub event system.

## To build and run standalone

    cd cmd/apid
    glide install
    go build
    ./apid

For command line options:

    ./apid -help

# Configuration

Configuration can be done via yaml file or environment variables. Keys are case-insensitive. 
By default, apid will look for a file called apid_config.yaml in the current working directory. 

#### Environment variables

Config will pick up env vars automatically. Use "apid_" as a prefix for settings. For example, for apid's "log_level" 
configuration setting, set env var "apid_log_level". 

### Defaults

    api_port: 9000
    api_expvar_path: nil  # not exposed
    data_path: /var/tmp
    events_buffer_size: 5
    log_level: debug    # valid values: Debug, Info, Warning, Error, Fatal, Panic
 
# Services

apid provides the following services:

* apid.API()
* apid.Config()
* apid.Data()
* apid.Events()
* apid.Log()
 
### Initialization of services and plugins

A driver process must initialize apid and its plugins like this:

    apid.Initialize(factory.DefaultServicesFactory()) // when done, all services are available
    apid.InitializePlugins() // when done, all plugins are running
    api := apid.API() // access the API service
    err := api.Listen() // start the listener


Once apid.Initialize() has been called, all services are accessible via the apid package functions as details above. 

# Plugins

The only requirement of an apid plugin is to register itself upon init(). However, generally plugins will access
the Log service and some kind of driver (via API or Events), so it's common practice to see something like this:
 
    var log apid.LogService
     
    func init() {
      apid.RegisterPlugin(initPlugin)
    }
    
    func initPlugin(services apid.Services) error {
    
      log = services.Log().ForModule("myPluginName") // note: could also access via `apid.Log().ForModule()`
      
      services.API().HandleFunc("/verifyAPIKey", handleRequest)
    }
    
    func handleRequest(w http.ResponseWriter, r *http.Request) {
      // respond to request
    }

# Helpful Hints

* Use `export APID_DATA_TRACE_LOG_LEVEL=debug` to see DB Tracing