Clients / Go¶

The lenses-go is a Go client enabling Gophers to take advantage of the Rest and WebSocket endpoints Lenses exposes. Users of this library can:

Manage topics
Manage schemas
Manage processors
Manage connectors
Browse topic data via SQL
Subscribe to live continuous SQL queries via SQL

Installation¶

The only requirement is the Go Programming Language.

$ go get -u github.com/landoop/lenses-go

Getting started¶

import "github.com/landoop/lenses-go"

Authentication¶

// Prepare authentication using raw Username and Password.
auth := lenses.BasicAuthentication{Username: "user", Password: "pass"}

auth := lenses.KerberosAuthentication{
    ConfFile: "/etc/krb5.conf",
    Method:   lenses.KerberosWithPassword{
        Realm: "my.realm or default if empty",
        Username: "user",
        Password: "pass",
    },
}

auth := lenses.KerberosAuthentication{
    ConfFile: "/etc/krb5.conf",
    Method:   lenses.KerberosWithKeytab{KeytabFile: "/home/me/krb5_my_keytab.txt"},
}

auth := lenses.KerberosAuthentication{
    ConfFile: "/etc/krb5.conf",
    Method:   lenses.KerberosFromCCache{CCacheFile: "/tmp/krb5_my_cache_file.conf"},
}

Configuration¶

// Prepare the client's configuration based on the host and the authentication above.
currentConfig := lenses.ClientConfig{Host: "domain.com", Authentication: auth, Timeout: "15s", Debug: true}

// Creating the client using the configuration.
client, err := lenses.OpenConnection(currentConfig)
if err != nil {
    // handle error.
}

Read `Config` from any `io.Reader` or file¶

// ReadConfig reads and decodes Config from an io.Reader based on a custom unmarshaler.
// This can be useful to read configuration via network or files (see `ReadConfigFromFile`).
// Sets the `outPtr`. Retruns a non-nil error on any unmarshaler's errors.
ReadConfig(r io.Reader, unmarshaler UnmarshalFunc, outPtr *Config) error

// ReadConfigFromFile reads and decodes Config from a file based on a custom unmarshaler,
// `ReadConfigFromJSON` and `ReadConfigFromYAML` are the internal users,
// but the end-developer can use any custom type of decoder to read a configuration file
// with ease using this function, but keep note that the default behavior of the fields
// depend on the existing unmarshalers, use these tag names to map your decoder's properties.
//
// Accepts the absolute or the relative path of the configuration file.
// Sets the `outPtr`. Retruns a non-nil error if parsing or decoding the file failed or file doesn't exist.
ReadConfigFromFile(filename string, unmarshaler UnmarshalFunc, outPtr *Config) error

// TryReadConfigFromFile will try to read a specific file and unmarshal to `Config`.
// It will try to read it with one of these built'n formats:
// 1. JSON
// 2. YAML
TryReadConfigFromFile(filename string, outPtr *Config) error

// TryReadConfigFromHome will try to read the `Config`
// from the current user's home directory/.lenses, the lookup is based on
// the common configuration filename pattern:
// lenses-cli.json, lenses-cli.yml or lenses.json and lenses.yml.
TryReadConfigFromHome(outPtr *Config) bool

// TryReadConfigFromExecutable will try to read the `Config`
// from the (client's caller's) executable path that started the current process.
// The lookup is based on the common configuration filename pattern:
// lenses-cli.json, lenses-cli.yml or lenses.json and lenses.yml.
TryReadConfigFromExecutable(outPtr *Config) bool

// TryReadConfigFromCurrentWorkingDir will try to read the `Config`
// from the current working directory, note that it may differs from the executable path.
// The lookup is based on the common configuration filename pattern:
// lenses-cli.json, lenses-cli.yml or lenses.json and lenses.yml.
TryReadConfigFromCurrentWorkingDir(outPtr *Config) bool

// ReadConfigFromJSON reads and decodes Config from a json file, i.e `configuration.json`.
//
// Accepts the absolute or the relative path of the configuration file.
// Error may occur when the file doesn't exists or is not formatted correctly.
ReadConfigFromJSON(filename string, outPtr *Config) error

// ReadConfigFromYAML reads and decodes Config from a yaml file, i.e `configuration.yml`.
//
// Accepts the absolute or the relative path of the configuration file.
// Error may occur when the file doesn't exists or is not formatted correctly.
ReadConfigFromYAML(filename string, outPtr *Config) error

Example Code:

# file: ./lenses.yml
CurrentContext: main
Contexts:
  main:
    Host: https://landoop.com
    Kerberos:
      ConfFile: /etc/krb5.conf
      WithPassword:
        Username: the_username
        Password: the_password
        Realm: empty_for_default

Usage¶

var config lenses.Config
err := lenses.ReadConfigFromYAML("./lenses.yml", &config)
if err != nil {
    // handle error.
}

client, err := lenses.OpenConnection(*config.GetCurrent())

Note

Config contains tons of capabilities and helpers, you can quickly check them by navigating to the config.go source file.

API Calls¶

All lenses-go#Client methods return a typed value based on the call and an error as second output to catch any errors coming from backend or client, forget panics.

Go types are first class citizens here, we will not confuse you or let you work based on luck!

topics, err := client.GetTopics()
if err != nil {
    // handle error.
}

// Print the length of the topics we've just received from our Lenses Box.
print(len(topics))

Detailed documentation for each one of the available API calls can be found at godocs.

TroubleShooting¶

For troubleshooting or additional information and join our slack channel