When you are developing a microservices arquitecture, you often have to call some of them, for manual testing, scripting and/or operations. Given the dynamic nature of Groovy, could it be used to make easier these calls? * Could we call our services with a syntax shorter and more natural, instead of using long curls, but not losing the history capability of a shell? * Could we query the documentation of the operations in the same way? * Could we even have autocomplete features of our service operations, so that we don’t have to remember their names? * Could we do all this dynamically, without having to create a specific client for each service, but calling it as if it were? * Could we have a directory of available services, so that we don’t have to remember them? * Could this directory and the utility classes be updated automatically for all the team when someone makes a change, using a Git repository? You are invited to a journey through the mud, exploring features such as Groovy metaclasses, class loading, REST services, shell capabilities and AST transformations, and making some dark tricks to achieve what we want. Repositories with the presentation code: https://github.com/andresviedma/groovy-assets-directory-example https://github.com/andresviedma/dynapiclient-groovy https://github.com/andresviedma/sourcegrape [Presented at Greach 2016]

1. Operating
Microservices
with
Andrés Viedma
@andres_viedma

2. Andrés ViedmaAndrés Viedma
@andres_viedma@andres_viedma

3. Andrés ViedmaAndrés Viedma
@andres_viedma@andres_viedma

5. curl
-u "jsonrpc:19ffd9709d03ce50675c3a43d1c49c1ac207f4bc45f06c5b2701fbdf8929"
-d '{"jsonrpc": "2.0", "id": 1,
"method": "getAllTasks", "params": , {"project_id": 1, "status_id": 1} }'
http://demo.kanboard.net/jsonrpc.php

6. 01 LET'S PLAY!
(IN THE MUD)

7. Our weapon: the Groovy shell groovysh

8. Our basic Groovy Client
class JsonRpcClient {
(...)
def makeCall(String method, Map params = [:]) {
try {
(... json call ...)
return json.result
} catch (HttpResponseException e) {
(...)
}
}
}

9. class JsonRpcClient {
def methodMissing(String name, args) {
return makeCall(name, args)
}
def makeCall(String method, Map params = [:]) {
(...)
}
(...)
}
Our dynamic Groovy Client

10. class JsonRpcClient {
def methodMissing(String name, args) {
return makeCall(name, args)
}
def makeCall(String method, Map params = [:]) {
(...)
}
(...)
}
groovy:000> client = new JsonRpcClient(...)
===> jsonrpc.JsonRpcClient@a0a9fa5
groovy:000> client.getAllTasks(project_id: 1, status_id: 2)
Our dynamic Groovy Client

11. Our dynamic REST Groovy Client
blog.posts.”37”.comments()
blog.posts.”37”.delete()
blog.posts.”37” = [text: 'xxx', ...]
GET
POST
PUT
DELETE
blog.posts.”37”.comments << [text: 'xxx', …]
blog.posts.”37”.comments.add(text: 'xxx', …)

12. class RestGroovyClient extends RestGroovyClientPath {
String base
(...)
private doGet(String path, params = [:]) { … }
private doPut(String path, params = [:]) { … }
private doPost(String path, params = [:]) { … }
private doDelete(String path, params = [:]) { … }
}
class RestGroovyClientPath {
RestGroovyClient client = null
String path = ''
(...)
}
Our dynamic REST Groovy Client

13. class RestGroovyClientPath {
def propertyMissing(String name) {
newPath(name)
}
def getAt(name) {
newPath(name.toString())
}
private RestGroovyClientPath newPath(String name) {
return new RestGroovyClientPath(
client: client, path: nextpath(name))
}
(...)
}
Our dynamic REST Groovy Client
blog.posts.”37”.comments()
blog['posts'][37].comments()

14. class RestGroovyClientPath {
def methodMissing(String name, args) {
return client.doGet(nextpath(name), args)
}
def propertyMissing(String name, value) {
return client.doPut(nextpath(name), args)
}
def leftShift(value) {
return client.doPost(path, value)
}
def delete() {
return client.doDelete(path)
}
}
Our dynamic REST Groovy Client
blog.posts.”37”.comments()
blog.posts.”37” = [...]
blog.posts << [...]
blog.posts.”37”.delete()

15. 02 YOUR LITTLE
BLACK BOOK

17. What if we create a directory of our services?
Organized as a tree
Grouped by features, by environment...
Register as shell variables

18. The ConfigSlurper
import dynapiclient.rest.*
jsonrpc {
kanboard = new JsonRpcClient(
base: 'http://demo.kanboard.net/jsonrpc.php',
clientHandler: { it.auth.basic 'demo', 'demo123' } )
}
rest {
(...)
marvel = new RestDynClient(
base: 'http://gateway.marvel.com/', path: '/v1/public',
paramsHandler: this.&marvelAuthenticate)
}
void marvelAuthenticate(Map callParams, String method) {
(...)
}
jsonrpc.kanboard.getMyProjects()

19. The ConfigSlurper
import dynapiclient.rest.*
jsonrpc {
kanboard = new JsonRpcClient(
base: 'http://demo.kanboard.net/jsonrpc.php',
clientHandler: { it.auth.basic 'demo', 'demo123' } )
}
rest {
(...)
marvel = new RestDynClient(
base: 'http://gateway.marvel.com/', path: '/v1/public',
paramsHandler: this.&marvelAuthenticate)
}
void marvelAuthenticate(Map callParams, String method) {
(...)
}

20. Available on startup: ~/.groovy/groovysh.profile
groovyUserHome = new File(System.getProperty('user.home'), '.groovy')
file = new File(groovyUserHome, 'assets.groovy')
binding.variables <<
new ConfigSlurper().parse(file.toURI().toURL())

21. Teamwork: share the directory
@Grab(group='org.springframework',
module='spring-orm',
version='3.2.5.RELEASE')

22. Teamwork: share the directory
Fast release cycle
@Grab(group='org.springframework',
module='spring-orm',
version='3.2.5.RELEASE')
@SourceGrab(
'https://github.com/andresviedma/
groovy-assets-directory-example.git')

23. AST transformation
Source Grapes Available in
Classpath
@SourceGrab('<url>')
public class myscript extends Script {
static {
SourceGrape.grab("<url>");
}
(...)
}
TRICK Add the sources directory to the classpath
in runtime and... it just works!

24. Merge directory parts (ConfigSlurper)
1. Passwords (local)
2. The main directory (git)
3. Personal / dev assets (local)
TRICK Merge config files: append all the files
and then parse them

25. 03 I NEVER FORGET
A FACE
(BUT IN YOUR CASE, I'LL MAKE
AN EXCEPTION)

28. Asking for help
marvel.characters(doc)
groovy:000> rest.marvel.characters
===> **** /v1/public/characters
** GET: Fetches lists of characters.
Params: name, nameStartsWith, modifiedSince, comics, series, events,
stories, orderBy, limit, offset
Next: {characterId}
groovy:000>
marvel.characters()GET
marvel.characters.help()(doc)

29. Asking for help
groovy:000> rest.marvel.characters."1010354"
===> **** /v1/public/characters/{characterId}
** GET: Fetches a single character by id.
[characterId(*)]
Next: comics, events, series, stories
groovy:000>
Replaceable URL path sections

30. What about Autocomplete?
We have the ExpandoMetaClass!
groovy:000> x = 2
===> 2
groovy:000> x.metaClass.sayHello = { args -> println 'hello' }
===> groovysh_evaluate$_run_closure1@57adfab0
groovy:000> x.sayHello()
hello
===> null
groovy:000> x.
abs() byteValue() compareTo( doubleValue() downto(
floatValue()
intValue() longValue() power( shortValue() times(
upto(
groovy:000>

31. What about Autocomplete?
We have the ExpandoMetaClass!
groovy:000> x = 2
===> 2
groovy:000> x.metaClass.sayHello = { args -> println 'hello' }
===> groovysh_evaluate$_run_closure1@57adfab0
groovy:000> x.sayHello()
hello
===> null
groovy:000> x.
abs() byteValue() compareTo( doubleValue() downto(
floatValue()
intValue() longValue() power( shortValue() times(
upto(
groovy:000>

32. What about Autocomplete?
The shell wraps the Expando In a HandleMetaClass
groovy:000> x.metaClass
===> HandleMetaClass[MetaClassImpl[class java.lang.String]]
groovy:000> x.metaClass."hello" = { name -> "Hello ${name}" }
===> groovysh_evaluate$_run_closure1@feba70e
groovy:000> x.metaClass
===> HandleMetaClass[ExpandoMetaClass[class java.lang.String]]
groovy:000> x.metaClass.getMetaMethods()*.name.findAll { it.startsWith('h') }
===> [hasProperty]
TRICK Use InvokerHelper.getMetaClass(x)
instead of x.metaClass

33. class AutocompleteMetaClass extends DelegatingMetaClass {
static void addFakeMethodsToObject(Object object, methods, properties) {
def autocomplete = configureMetaClass(object)
def innerMeta = autocomplete.originalMetaClass
addFakeMethodsToExpando(innerMeta, object, methods, properties)
}
private static MetaClass configureMetaClass(Object object) {
def metaOld = InvokerHelper.getMetaClass(object)
if (metaOld.getClass().name != AutocompleteMetaClass.class.name) {
object.metaClass = new AutocompleteMetaClass(metaOld)
}
return InvokerHelper.getMetaClass(object)
}
(...)
}
Create your own brand AutocompleteMetaClass

34. class AutocompleteMetaClass extends DelegatingMetaClass {
(...)
final MetaClass expando
AutocompleteMetaClass(MetaClass originalMetaClass) {
super(originalMetaClass)
this.expando = originalMetaClass
}
List<MetaMethod> getMetaMethods() {
return expando.getExpandoMethods()
}
List<MetaBeanProperty> getProperties() {
return expando.getExpandoProperties()
}
}
Create your own brand AutocompleteMetaClass

35. Let's demo!!!

36. 04 So...?
(JUST ENDING, I PROMISE...)

37. Give me the code!!!
https://github.com/andresviedma/sourcegrape
https://github.com/andresviedma/dynapiclient-groovy
https://github.com/andresviedma/groovy-assets-directory-example

38. Where did all this led us?
Shared microservices directory
Dynamic service calls
Autocomplete
Integrated help
A powerful shell

39. But, in the way there, mostly...
Learning about Groovy scripting black magic
Having fun!
Andrés ViedmaAndrés Viedma
@andres_viedma@andres_viedma
Questions?