The document covers an in-depth case study of using AWS services like DynamoDB, Simple Workflow, and CloudWatch with F# domain-specific languages (DSLs). It discusses query capabilities, error handling, and activity worker implementation while emphasizing the importance of automating decision workflows. Additionally, it highlights the benefits of abstraction and code simplicity in functional programming.

1. tame
|> (cloud <| complexity)
|> with
|> (fsharp >> powered >> DSLs)

2. hi,I’mYanCui

6. AWS user since 2009

8. image by nerovivo license : https://creativecommons.org/licenses/by-sa/2.0/

9. Under-Abstraction

10. Oversimplification

11. Impedance Mismatch

12. Amazon
DynamoDB
Amazon
SimpleWorkflow
Amazon
CloudWatch
CASE STUDY

13. F# DSLs. Awesome!

14. Amazon
DynamoDB
Amazon
SimpleWorkflow
Amazon
CloudWatch
CASE STUDY

16. managed
key-value store

17. redundancy
9-9s guarantee

18. great performance

19. name your
throughput

21. can be changed on-the-fly

23. infinitely scalable
(but you still have to pay for it)

25. Hash Key
Range Key

26. Query:
given a hash key
filter on
range key, or
local secondary index

28. Hash Key Range Key
Local Secondary Index
Global Secondary Index

29. Scan:
FULL TABLE search
(performance + cost concern)

31. Hash Key Range Key
Local Secondary Index
Global Secondary Index

32. Hash Key Range Key
Local Secondary Index
Who are the TOP 3 players in “Starship
X” with a score of at least 1000?
Global Secondary Index

34. select GameTitle, UserId, TopScore
from GameScores
where GameTitle = “Starship X”
and TopScore >= 1000
order desc
limit 3
with (NoConsistentRead, Index(GameTitleIndex, true))

35. DynamoDB.SQL
github.com/fsprojects/DynamoDb.SQL

36. GOAL
Disguise
complexity

37. GOAL
Prevent
abstraction leak

38. GOAL
SELECT UserId, TopScore
FROM GameScore
WHERE GameTitle CONTAINS “Zelda”
ORDER DESC
LIMIT 3
WITH (NoConsistentRead)

39. Query
AST
Execution

40. F# & FParsec*
*www.quanttec.com/fparsec
External DSL
via

42. SELECT * FROM GameScore
Abstract Syntax Tree (AST)
FParsec

43. SELECT * FROM GameScore
keyword keyword
* | attribute, attribute, …
table name

44. SELECT * FROM GameScore
type Attributes =
| Asterisk
| Attributes of string[]

45. SELECT * FROM GameScore
type Query =
{
Attributes : Attributes
Table : string
}

46. SELECT * FROM GameScore
Parser for “SELECT” keyword
pSelect

47. SELECT * FROM GameScore
pSelect
let pSelect = skipStringCI "select"

48. SELECT * FROM GameScore
pSelect
let pSelect = skipStringCI "select"
matches the string “select” (Case
Insensitive) and ignores it

49. SELECT * FROM GameScore
pFrom
let pFrom = skipStringCI "from"

50. SELECT * FROM GameScore
Parser for a string that
represents the table name
pTableName

51. SELECT * FROM GameScore
pTableName
let isTableName = isLetter <||> isDigit
let pTableName =
many1Satisfy isTableName

52. SELECT * FROM GameScore
pTableName
let isTableName = isLetter <||> isDigit
let pTableName =
many1Satisfy isTableName

53. SELECT * FROM GameScore
pTableName
let isTableName = isLetter <||> isDigit
let pTableName =
many1Satisfy isTableName

54. SELECT * FROM GameScore
pTableName
let isTableName = isLetter <||> isDigit
let pTableName =
many1Satisfy isTableName

55. SELECT * FROM GameScore
pTableName
let isTableName = isLetter <||> isDigit
let pTableName =
many1Satisfy isTableName
parses a sequence of one or
more chars that satisfies the
predicate function

56. SELECT * FROM GameScore
pAsterisk
*
pAttributeName
UserId, GameTitle, TopScore, …

57. SELECT * FROM GameScore
pAsterisk
*
pAttributeName
UserId, GameTitle, TopScore, …
let pAsterisk = stringCIReturn "*" Asterisk

58. SELECT * FROM GameScore
pAsterisk
*
pAttributeName
UserId, GameTitle, TopScore, …
let pAsterisk = stringCIReturn "*" Asterisk
matches the specified string
and return the given value

59. SELECT * FROM GameScore
pAsterisk
*
pAttributeName
UserId, GameTitle, TopScore, …
let isAttributeName = isLetter <||> isDigit
let pAttributeName =
many1Satisfy isAttributeName

60. SELECT * FROM GameScore
UserId, GameTitle, TopScore, …
pAttributeName pCommapAsterisk
*
let pComma = skipStringCI ","

61. SELECT * FROM GameScore
UserId, GameTitle, TopScore, …
pAttributeName pCommapAsterisk
*
let pAttributeNames =
sepBy1 pAttributeName pComma

62. SELECT * FROM GameScore
UserId, GameTitle, TopScore, …
pAttributeName pCommapAsterisk
*
let pAttributeNames =
sepBy1 pAttributeName pComma
parses one or more occurrences of
pAttributeName separated by pComma

63. SELECT * FROM GameScore
UserId, GameTitle, TopScore, …
pAttributeName pComma
sepBy1
pAttributeNames
pAsterisk
*

64. SELECT * FROM GameScore
pAsterisk
*
pAttributeNames
UserId, GameTitle, TopScore, …

65. SELECT * FROM GameScore
pAsterisk
*
pAttributeNames
UserId, GameTitle, TopScore, …
let pAttribute =
pAsterisk <|> pAttributeNames

66. SELECT * FROM GameScore
pAsterisk
*
pAttributeNames
UserId, GameTitle, TopScore, …
let pAttribute =
pAsterisk <|> pAttributeNames

67. SELECT * FROM GameScore
pAsterisk
*
pAttributeNames
UserId, GameTitle, TopScore, …
choice
pAttribute

68. SELECT * FROM GameScore
pAttribute

69. SELECT * FROM GameScore
pAttribute pTableNamepFrompSelect

70. SELECT * FROM GameScore
pAttribute pTableNamepFrompSelect
let pQuery =
tuple4 pSelect pAttribute
pFrom pTableName
|>> (fun (_, attributes, _, table) ->
{ Attributes = attributes
Table = table })

71. SELECT * FROM GameScore
pAttribute pTableNamepFrompSelect
let pQuery =
tuple4 pSelect pAttribute
pFrom pTableName
|>> (fun (_, attributes, _, table) ->
{ Attributes = attributes
Table = table })

72. SELECT * FROM GameScore
pAttribute pTableNamepFrompSelect
let pQuery =
tuple4 pSelect pAttribute
pFrom pTableName
|>> (fun (_, attributes, _, table) ->
{ Attributes = attributes
Table = table })

73. SELECT * FROM GameScore
pAttribute pTableNamepFrompSelect
let pQuery =
tuple4 pSelect pAttribute
pFrom pTableName
|>> (fun (_, attributes, _, table) ->
{ Attributes = attributes
Table = table })
Query

74. SELECT * FROM GameScore
pAttribute pTableNamepFrompSelect
tuple4
pQuery

76. < 50 lines of code

77. Amazing
F# + FParsec
=

78. Recap

80. select GameTitle, UserId, TopScore
from GameScores
where GameTitle = “Starship X”
and TopScore >= 1000
order desc
limit 3
with (NoConsistentRead, Index(GameTitleIndex, true))

81. Amazon
DynamoDB
Amazon
SimpleWorkflow
Amazon
CloudWatch
CASE STUDY

83. Decision Worker

84. Decision Worker
Poll

85. Decision Worker
Decision
Task

86. Decision WorkerDecide

87. Activity Worker
Decision Worker

88. Activity Worker
Decision Worker
Poll

89. Activity Worker
Decision Worker
Activity
Task

90. Activity Worker
Decision Worker
Complete

91. Workers can run from
anywhere

93. input = “Yan”
result = “Hello Yan!”
Start
Finish
Activity

95. image by Ryan Hageman license : https://creativecommons.org/licenses/by-sa/2.0/

96. SWF-based Application

97. API

98. Heartbeats
Error
Handling
Polling
API

99. Activity
Worker
Decision
Worker
Heartbeats
Error
Handling
Polling
API

100. Activity
Worker
Decision
Worker
Heartbeats
Error
Handling
Polling
API
Boilerplate

101. – Kris Jordan
“Good simplicity is less with
leverage, not less with less.
Good simplicity is complexity
disguised, not complexity denied.”

102. http://bit.ly/1pOLeKl

104. Start
Finish
Activity
?

105. the workflow is
implied by decision
worker logic…

106. instead..

107. the workflow should
drive decision
worker logic

108. the workflow should
driveautomate
decision worker logic

109. Amazon
.SimpleWorkflow
.Extensions
github.com/fsprojects/Amazon.SimpleWorkflow.Extensions

110. GOAL
Remove
boilerplates

111. GOAL
Code that matches
the way you think

112. Start
Finish
Activity

115. Start
Finish
Activity

117. Workflows can be
nested

120. input
result

122. Recap

123. Activity
Worker
Decision
Worker
Heartbeats
Error
Handling
Polling
API

125. Amazon
DynamoDB
Amazon
SimpleWorkflow
Amazon
CloudWatch
CASE STUDY

128. wanna find
correlations?

129. wanna find
correlations?
you can DIY it!
;-)

130. “what latencies spiked
at the same time as
payment service?”

131. Amazon
.CloudWatch
.Selector
github.com/fsprojects/Amazon.CloudWatch.Selector

132. Find metrics whose 5
min average exceeded
1 second during last
12 hours

133. cloudWatch.Select(
unitIs “milliseconds” +
average (>) 1000.0
@ last 12 hours
|> intervalOf 5 minutes)

134. cloudWatch.Select(“
unitIs ‘milliseconds’ and
average > 1000.0
duringLast 12 hours
at intervalOf 5 minutes”)

135. “did any cache
nodes’ CPU spike
yesterday?”

136. cloudWatch.Select(
namespaceLike “elasticache” +
nameLike “cpu” +
max (>) 80.0
@ last 24 hours
|> intervalOf 15 minutes)

137. cloudWatch.Select(
namespaceLike “elasticache” +
nameLike “cpu” +
max (>) 80.0
@ last 24 hours
|> intervalOf 15 minutes)
Regex

141. namespaceIs ‘JustEat’ and
nameLike ‘cpu’ and
unitIs ‘milliseconds’ and
average > 1000.0
duringLast 12 hours
at intervalOf 5 minutes

142. namespaceIs ‘JustEat’ and
nameLike ‘cpu’ and
unitIs ‘milliseconds’ and
average > 1000.0
duringLast 12 hours
at intervalOf 5 minutes
Filters

143. namespaceIs ‘JustEat’ and
nameLike ‘cpu’ and
unitIs ‘milliseconds’ and
average > 1000.0
duringLast 12 hours
at intervalOf 5 minutes
TimeFrame

144. namespaceIs ‘JustEat’ and
nameLike ‘cpu’ and
unitIs ‘milliseconds’ and
average > 1000.0
duringLast 12 hours
at intervalOf 5 minutes
Period

145. type Query =
{
Filter : Filter
TimeFrame : TimeFrame
Period : Period option
}

146. Query
Internal
DSL
External
DSL

147. namespaceIs ‘JustEat’ and
nameLike ‘cpu’ and
unitIs ‘milliseconds’ and
average > 1000.0
duringLast 12 hours
at intervalOf 5 minutes

148. type MetricTerm = Namespace | Name
type Filter =
| MetricFilter of MetricTerm * (string -> bool)

149. namespaceIs ‘JustEat’ and
nameLike ‘cpu’ and
unitIs ‘milliseconds’ and
average > 1000.0
duringLast 12 hours
at intervalOf 5 minutes

150. type MetricTerm = Namespace | Name
type Unit = | Unit
type Filter =
| MetricFilter of MetricTerm * (string -> bool)
| UnitFilter of Unit * (string -> bool)

151. namespaceIs ‘JustEat’ and
nameLike ‘cpu’ and
unitIs ‘milliseconds’ and
average > 1000.0
duringLast 12 hours
at intervalOf 5 minutes

152. type MetricTerm = Namespace | Name
type Unit = | Unit
type StatsTerm =
| Average | Min | Max | Sum | SampleCount
type Filter =
| MetricFilter of MetricTerm * (string -> bool)
| UnitFilter of Unit * (string -> bool)
| StatsFilter of StatsTerm * (float -> bool)

153. namespaceIs ‘JustEat’ and
nameLike ‘cpu’ and
unitIs ‘milliseconds’ and
average > 1000.0
duringLast 12 hours
at intervalOf 5 minutes

154. type MetricTerm = Namespace | Name
type Unit = | Unit
type StatsTerm =
| Average | Min | Max | Sum | SampleCount
type Filter =
| MetricFilter of MetricTerm * (string -> bool)
| UnitFilter of Unit * (string -> bool)
| StatsFilter of StatsTerm * (float -> bool)
| CompositeFilter of Filter * Filter

155. namespaceIs ‘JustEat’ and
nameLike ‘cpu’ and
unitIs ‘milliseconds’ and
average > 1000.0
duringLast 12 hours
at intervalOf 5 minutes

156. type TimeFrame =
| Last of TimeSpan
| Since of DateTime
| Between of DateTime * DateTime

157. namespaceIs ‘JustEat’ and
nameLike ‘cpu’ and
unitIs ‘milliseconds’ and
average > 1000.0
duringLast 12 hours
at intervalOf 5 minutes

158. type Period = | Period of TimeSpan

159. type Query =
{
Filter : Filter
TimeFrame : TimeFrame
Period : Period option
}

160. Active Patterns
a primer on

161. allow patterns to be
abstracted away into
named functions

162. Single-Case Patterns

163. let (|Float|) input =
match Double.TryParse input with
| true, n -> n
| _ ->
failwithf “not a float [%s]” input

164. let (|Float|) input =
match Double.TryParse input with
| true, n -> n
| _ ->
failwithf “not a float [%s]” input

165. let (|Float|) input =
match Double.TryParse input with
| true, n -> n
| _ ->
failwithf “not a float [%s]” input
Float : string -> float

166. match someString with
| Float 42.0 -> “ftw”
| Float 11.0 -> “palprime”
| Float x -> sprintf “just %f” x

167. let (|Float|) input =
match Double.TryParse input with
| true, n -> n
match someString with
| Float 42.0 -> “ftw”
| Float 11.0 -> “palprime”
| Float x -> sprintf “just %f” x

168. let (|Float|) input =
match Double.TryParse input with
| true, n -> n
match someString with
| Float 42.0 -> “ftw”
| Float 11.0 -> “palprime”
| Float x -> sprintf “just %f” x

169. match someString with
| Float 42.0 -> “ftw”
| Float 11.0 -> “palprime”
| Float x -> sprintf “just %f” x
let (|Float|) input =
match Double.TryParse input with
| true, n -> n

170. match someString with
| Float 42.0 -> “ftw”
| Float 11.0 -> “palprime”
| Float x -> sprintf “just %f” x
let (|Float|) input =
match Double.TryParse input with
| true, n -> n

171. match “42” with
| Float 42.0 -> “ftw”
| Float 11.0 -> “palprime”
| Float x -> sprintf “just %f” x

172. match “boo” with
| Float 42.0 -> “ftw”
| Float 11.0 -> “palprime”
| Float x -> sprintf “just %f” x
Error!!!

173. Partial Patterns

174. let (|Float|_|) input =
match Double.TryParse input with
| true, n -> Some n
| _ -> None

175. let (|Float|_|) input =
match Double.TryParse input with
| true, n -> Some n
| _ -> None
Float : string -> float option

176. match “boo” with
| Float 42.0 -> “ftw”
| Float 11.0 -> “palprime”
| Float x -> sprintf “just %f” x
| _ -> “not a float”

177. match “boo” with
| Float 42.0 -> “ftw”
| Float 11.0 -> “palprime”
| Float x -> sprintf “just %f” x
| _ -> “not a float”

178. Multi-Case Patterns

179. let (|Prime|NotPrime|NaN|) input =
match Double.TryParse input with
| true, n when isPrime n -> Prime n
| true, n -> NotPrime n
| _ -> NaN

180. let (|Prime|NotPrime|NaN|) input =
match Double.TryParse input with
| true, n when isPrime n -> Prime n
| true, n -> NotPrime n
| _ -> NaN

181. let (|Prime|NotPrime|NaN|) input =
match Double.TryParse input with
| true, n when isPrime n -> Prime n
| true, n -> NotPrime n
| _ -> NaN

182. let (|Prime|NotPrime|NaN|) input =
match Double.TryParse input with
| true, n when isPrime n -> Prime n
| true, n -> NotPrime n
| _ -> NaN

183. let (|Prime|NotPrime|NaN|) input =
match Double.TryParse input with
| true, n when isPrime n -> Prime n
| true, n -> NotPrime n
| _ -> NaN

184. match someString with
| Prime n -> …
| NotPrime n -> …
| NaN -> …

185. match someString with
| Prime n & Float 11.0 -> …
| Prime n -> …
| Float 42.0 | Float 8.0 -> …
| NotPrime n -> …
| NaN -> …

186. match someString with
| Prime n & Float 11.0 -> …
| Prime n -> …
| Float 42.0 | Float 8.0 -> …
| NotPrime n -> …
| NaN -> …

187. match someString with
| Prime (IsPalindrome n) -> …
| Prime (IsEven n) -> …
| _ -> …

188. Tokenise
(string -> string list)

189. [
“namespaceIs”; “‘JustEat’”; “and”;
“nameLike”; “‘cpu’”; “and”;
…
]

190. “namespaceIs” “and” …
F# List = LinkedList
“‘JustEat’”

191. “namespaceIs” “and” …
F# List = LinkedList
“namespaceIs” “‘JustEat’” “and”:::: :: tail
cons (::) operator to prepend
“‘JustEat’”

192. “namespaceIs” “and” …
F# List = LinkedList
“namespaceIs” “‘JustEat’” “and”:::: :: tail
match aList with
|
“‘JustEat’”
works as a pattern too!

193. let (|StringCI|_|) (str : string) (input : string) =
if str.ToLower() = input.ToLower()
then Some ()
else None
let (|Float|_|) input =
match System.Double.TryParse input with
| true, n -> Some n
| _ -> None

194. let (|EmptyString|_|) input =
if String.IsNullOrWhiteSpace input
then Some ()
else None
let (|StartsWith|_|) char (input : string) =
if input.[0] = char then Some () else None
let (|EndsWith|_|) char (input : string) =
if input.[input.Length-1] = char
then Some ()
else None

195. let (|QuotedString|_|) (input : string) =
match input with
| EmptyString -> None
| str when str.Length < 2 -> None
| StartsWith ''' & EndsWith ''' ->
Some <| input.Substring(1, input.Length - 2)
| _ -> None

196. let (|QuotedString|_|) (input : string) =
match input with
| EmptyString -> None
| str when str.Length < 2 -> None
| StartsWith ''' & EndsWith ''' ->
Some <| input.Substring(1, input.Length - 2)
| _ -> None

197. let (|NamespaceIs|_|) = function
| StringCI “NamespaceIs" :: QuotedString ns :: tl
-> Some (eqFilter MetricFilter Namespace ns, tl)
| _ -> None

198. let (|NamespaceIs|_|) = function
| StringCI “NamespaceIs" :: QuotedString ns :: tl
-> Some (eqFilter MetricFilter Namespace ns, tl)
| _ -> None
namespaceIs ‘JustEat’ and
nameLike ‘cpu’ and
…

199. let (|NamespaceIs|_|) = function
| StringCI “NamespaceIs" :: QuotedString ns :: tl
-> Some (eqFilter MetricFilter Namespace ns, tl)
| _ -> None
“namespaceIs” “‘JustEat’” :::: …

200. let (|NamespaceIs|_|) = function
| StringCI “NamespaceIs" :: QuotedString ns :: tl
-> Some (eqFilter MetricFilter Namespace ns, tl)
| _ -> None
type MetricTerm = Namespace | Name
type Filter =
| MetricFilter of MetricTerm * (string -> bool)

201. let (|NamespaceIs|_|) = function
| StringCI “NamespaceIs" :: QuotedString ns :: tl
-> Some (eqFilter MetricFilter Namespace ns, tl)
| _ -> None
“and” :: “nameLike” :: “‘cpu’” :: “and” :: …

202. let rec loop acc = function
| NamespaceIs (filter, tl)
| NamespaceLike (filter, tl)
| NameIs (filter, tl) | NameLike (filter, tl)
| UnitIs (filter, tl)
| Average (filter, tl) | Sum (filter, tl)
| Min (filter, tl) | Max (filter, tl)
| SampleCount (filter, tl)
-> match tl with
| And tl -> loop (filter::acc) tl
| _ -> flatten (filter::acc), tl
| _ -> failwith “No filters?!?!?”

203. let rec loop acc = function
| NamespaceIs (filter, tl)
| NamespaceLike (filter, tl)
| NameIs (filter, tl) | NameLike (filter, tl)
| UnitIs (filter, tl)
| Average (filter, tl) | Sum (filter, tl)
| Min (filter, tl) | Max (filter, tl)
| SampleCount (filter, tl)
-> match tl with
| And tl -> loop (filter::acc) tl
| _ -> flatten (filter::acc), tl
| _ -> failwith “No filters?!?!?”

204. let rec loop acc = function
| NamespaceIs (filter, tl)
| NamespaceLike (filter, tl)
| NameIs (filter, tl) | NameLike (filter, tl)
| UnitIs (filter, tl)
| Average (filter, tl) | Sum (filter, tl)
| Min (filter, tl) | Max (filter, tl)
| SampleCount (filter, tl)
-> match tl with
| And tl -> loop (filter::acc) tl
| _ -> flatten (filter::acc), tl
| _ -> failwith “No filters?!?!?”

205. let rec loop acc = function
| NamespaceIs (filter, tl)
| NamespaceLike (filter, tl)
| NameIs (filter, tl) | NameLike (filter, tl)
| UnitIs (filter, tl)
| Average (filter, tl) | Sum (filter, tl)
| Min (filter, tl) | Max (filter, tl)
| SampleCount (filter, tl)
-> match tl with
| And tl -> loop (filter::acc) tl
| _ -> flatten (filter::acc), tl
| _ -> failwith “No filters?!?!?”

206. let rec loop acc = function
| NamespaceIs (filter, tl)
| NamespaceLike (filter, tl)
| NameIs (filter, tl) | NameLike (filter, tl)
| UnitIs (filter, tl)
| Average (filter, tl) | Sum (filter, tl)
| Min (filter, tl) | Max (filter, tl)
| SampleCount (filter, tl)
-> match tl with
| And tl -> loop (filter::acc) tl
| _ -> flatten (filter::acc), tl
| _ -> failwith “No filters?!?!?”

207. let parse (input : string) =
input
|> tokenize
|> parseFilter
|> parseTimeFrame
|> parsePeriod

208. Amazing
F#
=

209. usable from anywhere you
can run F# code
e.g. F# REPL, executable, ..
Internal DSL

210. useful for building tools
e.g. CLI, …
External DSL

214. Recap

217. Amazon
DynamoDB
Amazon
SimpleWorkflow
Amazon
CloudWatch
CASE STUDY

218. @theburningmonk
theburningmonk.com
github.com/theburningmonk