Lenses Client (Go)

The Landoop's Lenses REST API client written in Go.

Installation

The only requirement is the Go Programming Language version 1.10+ and a Lenses Box of version 2.0 at least.

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

This command will install both the client library for development usage and the CLI in $PATH (setup your $GOPATH/bin if you didn't already).

CLI

Lenses offers a powerful CLI (command-line tool) built in Go that utilizes the REST and WebSocket APIs of Lenses, to communicate with Apache Kafka and exposes a straight forward way to perform common data engineering and site reliability engineering tasks, such as:

• Automate your CI/CD (continuous-integration and continuous-delivery)
• Create topics/acls/quotas/schemas/connectors/processors
• Change or retrieve configurations to store in github

Documentation

Please navigate to https://lenses.stream/dev/lenses-cli/ to learn how to install and use the lenses-cli.

Client

The lenses-go package is made to be used by Go developers to communicate with Lenses by calling the REST and Websocket APIs.

Getting started

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

Authentication

// Prepare authentication using raw Username and Password.
//
// Use it when Lenses setup with "BASIC" or "LDAP" authentication.
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"},
}

Custom auth can be implement as well: Authenticate(client *lenses.Client) error, see client_authentication.go file for more.

Config

// 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())

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))

Example on how deeply we make the difference here: Client#GetTopics returns []lenses.Topic, so you can work safely.

topics[0].ConsumersGroup[0].Coordinator.Host

Documentation

Detailed documentation can be found at godocs.

Versioning

Current: v2.1.9

Read more about Semantic Versioning 2.0.0

• http://semver.org/
• https://en.wikipedia.org/wiki/Software_versioning
• https://wiki.debian.org/UpstreamGuide#Releases_and_Versions

License

Distributed under Apache Version 2.0 License, click here for more details.