This document provides an overview of design patterns in microservices architectures using Gilmour, an open-source library for building distributed systems. Key topics covered include request-response and asynchronous communication patterns, service discovery and load balancing without an external process, error handling, monitoring, and service composition capabilities for building complex workflows from simpler microservices. Examples demonstrated include echo clients and servers, popular word counting from text, and weather data aggregation across multiple services.

1. GILMOUR
DESIGN PATTERNS IN MICRO-SERVICES
ARCHITECTURES &

2. ABOUT
WHO AM I?
▸ twitter: @meson10
▸ mailto: piyush@piyushverma.net
▸ piyushverma.net

3. SOA (VS SERVERS)
WHAT ARE SERVICES
▸ Logical Entities
▸ Independent
▸ Comprised of more services
▸ Multiple servers for load and tolerance
▸ Scalability
▸ Flexibility

4. TO ERR IS HUMAN, TO BLAME IT ON
SOMEONE IS MANAGEMENT POTENTIAL.
- Someone on Internet
WHY?

5. WHO DUN IT?
WHY SERVICES?
▸ Software Problem
▸ Scalability
▸ Management Problem
▸ Authority
▸ Responsibility.

6. DESIGN PATTERNS

7. REQUEST RESPONSE

8. REQUEST RESPONSE
CALLER SERVICE
HELLO?
ALOHA!WRONG NUMBER
Message {
“Data”nterface{} `json:"data"`
//Actual Payload
Code int `json:"code"`
//Response code if this is a response. This uses HTTP error codes
Sender string `json:"sender"`
//Origin of the request (unique for each request)
}
SENDER_ID
CODE

9. REQUEST
data := G.NewMessage().SetData("hello?")
resp := g.Request(“echo", data, nil)
var msg string
req.Data(&msg);
fmt.Println("Echoclient: received", msg)
opts := G.NewHandlerOpts().SetGroup("exclusive")
g.ReplyTo("echo", func(req *G.Request, resp *G.Message) {
var msg string
req.Data(&msg)
resp.SetData(fmt.Sprintf("Pong %v", msg))
}, opts)
RESPONSE
REQUEST

10. ASYNC / SIGNAL-SLOTS

11. ASYNC: SIGNALS AND SLOTS
Slots
Signal
ITEM.BUY.500
ITEM.BUY.*
ITEM.BUY.*
ITEM.BUY.*
GROUP: PUSH_MSG
FP SCALING
PUSH MESSAGE
SERVERPUSH MESSAGE
SERVER
WEB GILMOUR
EMAIL
NOTIFIER
SMS
NOTIFIER
PUSH MESSAGE
SERVER
ITEM PURCHASED
VIP ITEM
PURCHASED
ITEM.BUY.420

12. ASYNC: SLOTS
g := G.Get(redis)
g.Slot("example.log", func(req *G.Request) {
var msg string
req.Data(&msg)
log.Println(req.Sender(), "->", msg)
})
g.Start()
g.Signal("example.log", G.NewMessage().SetData("log message emitted"))
SIGNAL
RECEIVER / SLOT

13. SIGNAL-SLOT
VS.
REQUEST-RESPONSE

14. ASYNC VS SYNC
WHAT TO USE WHEN?
▸ Request-Response
▸ Confirmed delivery.
▸ Response or Error Guaranteed.
▸ HTTP Like.
▸ Sender responsible for errors.

15. ASYNC VS SYNC
WHAT TO USE WHEN?
▸ Signal-Slots
▸ UDP-like.
▸ Broadcasting
▸ Wildcard topics
▸ Unreliable delivery.
▸ Receiver responsible for errors.

16. SERVICE DISCOVERY
&
LOAD BALANCING

17. NOTIFICATION
SERVER 1
REPLICATED
LOAD
BALANCER
X.Y.Y.Z?CALLER
SERVICE
REGISTER
I, AM
HEALTHY?
NOTIFICATION
SERVER 2
NOTIFICATION
SERVER 3

18. NOTIFICATION
SERVER 2
GILMOUR
MANAGER.NOTIFICATION
NOTIFICATION
SERVER 1
NOTIFICATION
SERVER 3
MANAGER.NOTIFICATION
MANAGER.NOTIFICATION
CALLER
SERVICE
MANAGER.NOTIFICATION
{“NOTIFICATION”: “DATA”}

19. DISCOVERY AND LOAD BALANCING
LOOK MA, NO SERVICE DISCOVERY
▸ Gilmour works on Redis Subscriber Publisher.
▸ No querying discovery process.
▸ Call service and not servers.

20. DISCOVERY AND LOAD BALANCING
LOOK MA, NO LOAD BALANCING
▸ Has Capacity, Will Serve.
▸ Message delivered to one and all.
▸ Fittest node acquires lock first.

21. ERRORS:
DETECTION & HANDLING

22. GILMOUR ERRORS
ERROR DETECTION
▸ Timeouts
▸ server side - execution timed out.
▸ client side - response too late
▸ confirm_subscribers

23. GILMOUR ERRORS
WEB GILMOUR
EMAIL
NOTIFIER
SMS
NOTIFIER
PUSH
MESSAGE
Slots
ERROR
REPORTER
Signal

24. GILMOUR ERRORS
CALLER SERVICE
HELLO?
WRONG NUMBER
SENDER_ID
CODE
ERROR
REPORTER
type gilmourError struct {
topic string //topic to which the request was sent
requestData string //request payload
userData string //implementation dependent information
sender string //sender from the request
timestamp string //timestamp of error
backtrace interface{} //backtrace of the error
code int //response code (non-200)
}

25. GILMOUR ERRORS
ERROR HANDLING
▸ Ignore
▸ Publish
▸ Queue
func main() {
redis := backends.MakeRedis("127.0.0.1:6379", "pass")
g := G.Get(redis)
//g.SetErrorPolicy(protocol.ErrorPolicyQueue)
//g.SetErrorPolicy(protocol.ErrorPolicyIgnore)
g.SetErrorPolicy(protocol.ErrorPolicyPublish)
}

26. GILMOUR ERRORS
ERROR SAMPLE

27. OPS: MONITORING

28. OPS: MONITORING
SERVERS
▸ Log forwarding & aggregation
▸ Error Reporting
▸ Server and Health Monitoring

29. OPS: MONITORING
SERVICES
▸ Are the services servicing?
▸ Do services have spare capacity?
▸ Do services respond in time?
▸ Health Bulletin: github.com/gilmour-libs/health-bulletin

30. OPS: MONITORING

31. OPS: MONITORING

32. OPS: MONITORING
Feb 23 12:25:14 qa-next-backend-manager0.datascale.io gilmour_health: D, [2016-02-23T06:55:12.930435
#22111] DEBUG -- : Ensuring topics have at least one subscriber
Feb 23 12:25:14 qa-next-backend-manager0.datascale.io gilmour_health: D, [2016-02-23T06:55:12.931160
#22111] DEBUG -- : Ensuring that gilmour servers respond to health ping
Feb 23 12:26:14 qa-next-backend-manager0.datascale.io backend_manager: D, [2016-02-23T06:56:12.932775
#9605] DEBUG -- : Executing handler for gilmour.health.ip-10-0-0-146-pid-9605-uuid-9d0484dd-08e5-4ec3-
a3e4-9a109634712b from 2881867d41f24228b462b9eff0b7e88e
2016-04-03 00:06:56 d0e4ea929645600e2fa97657091613a4 -> Cleared VPC jenkins-backend-manager-pipeline-qa-17
2016-04-03 00:06:56 d0e4ea929645600e2fa97657091613a4 -> Clearing databag customer_jenkins-backend-manager-
pipeline-qa-17_config::vpc_config
2016-04-03 00:06:57 d0e4ea929645600e2fa97657091613a4 -> Deleted data_bag[customer_jenkins-backend-manager-
pipeline-qa-17_config]
2016-04-03 00:06:57 d0e4ea929645600e2fa97657091613a4 -> Clearing DNS entries
2016-04-03 00:07:00 d0e4ea929645600e2fa97657091613a4 -> Cleaning Chef environment
2016-04-03 00:07:01 d0e4ea929645600e2fa97657091613a4 -> Deleted customer_jenkins-backend-manager-pipeline-
qa-17
REQUEST LOGGING

33.
COMPOSITION

34. COMPOSITION
▸ compose - service1 | service2 | composition3
▸ andand - service1 && service2 && composition3
▸ oror - service1 || composition2 || service3
▸ batch
▸ (service1; service2; service3) > out
▸ service1; composition2; service3 > out
▸ parallel
▸ lambda functions

35. COMPOSITION
popular := g.NewParallel(
g.NewRequestComposition("example.popular3"),
g.NewRequestComposition("example.popular4"),
)
batch := g.NewPipe(
g.NewRequestComposition("example.fetch"),
g.NewRequestComposition("example.words"),
g.NewRequestComposition("example.count"),
popular,
)
data := G.NewMessage()
data.SetData("https://s3.amazonaws.com/ds-data-sample/test.txt")
msg := <-batch.Execute(data)

36. COMPOSITION
popular := g.NewParallel(
g.NewRequestComposition("example.popular3"),
g.NewRequestComposition(“example.popular4"),
g.NewRequestComposition("example.popular5"),
)
batch := g.NewPipe(
g.NewRequestComposition("example.fetch"),
g.NewRequestComposition("example.words"),
g.NewRequestComposition("example.stopfilter"),
g.NewRequestComposition("example.count"),
popular,
&MyComposer{},
)
data := G.NewMessage()
data.SetData("https://s3.amazonaws.com/ds-data-sample/test.txt")
msg := <-batch.Execute(data)

37. COMPOSITION
batch := e.NewPipe(
e.NewRequest("weather.fetch"),
e.NewRequest("weather.group"),
e.NewParallel(
e.NewPipe(
e.NewLambda(monthLambda("jan")),
e.NewParallel(
e.NewRequest("weather.min"),
e.NewRequest("weather.max"),
),
),
e.NewPipe(
e.NewLambda(monthLambda("feb")),
e.NewParallel(
e.NewRequest("weather.min"),
e.NewRequest("weather.max"),
),
),
),
)

38.
TALK IS CHEAP:
SHOW SOME DEMO

39. EXAMPLES: ECHO SERVERS & CLIENT

40. SAMPLE TEXT

41. EXAMPLES: POPULAR WORD COUNT
▸ Given
▸ A S3 URL pointing to a file that has (lot of) random text.
▸ Goal
▸ Eliminate stop words from the file.
▸ Find most popular 3, 4, and 5 letter words.
▸ Find these in parallel.

42. EXAMPLES: WEATHER AGGREGATION
▸ Output
▸ Popular 3 letter words: [way, for]
▸ Popular 4 letter words: [Text, copy]
▸ Popular 5 letter words: [Blind, blind]

43. EXAMPLES: COMPOSITION

44. EXAMPLES: WEATHER AGGREGATION
▸ Given
▸ Weather data as per hour, per day, per month of form:
▸ {"Day": 10, "Month": "jan", "Hour": 13, "Degrees": 56}

45. EXAMPLES: WEATHER AGGREGATION
▸ Goal
▸ For the months of Jan & Feb
▸ Find the maximum temperature recorded.
▸ Find the minimum temperature recorded.
▸ If possible do 3a and 3b in parallel, and in parallel for both months

46. EXAMPLES: WEATHER AGGREGATION
▸ Output
▸ Temperature on 19th Feb at 2100 hours was 50ºF
▸ Temperature on 21st Feb at 0500 hours was 94ºF
▸ Temperature on 19th Jan at 1900 hours was 50ºF
▸ Temperature on 17th Jan at 2200 hours was 94ºF

47. EXAMPLES: COMPOSITION

48. GILMOUR
RECAP
▸ Library only; no external process.
▸ No Load Balancer
▸ No Service Discovery
▸ Signal, Slots.
▸ Broadcast, Wildcard Topics.
▸ Exclusion groups.
▸ Sync - Request, Reply
▸ Error and Health Monitoring - HealthBulletin.
▸ Failure Detection
▸ Composition - Real micro-services.
▸ No message persistence.

49. GILMOUR
CREDITS & LINKS
▸ Aditya Godbole
▸ aa@gdbl.me
▸ Datascale.IO
▸ datascale.io
▸ Repository
▸ github.com/gilmour-libs