## CS 591 K1: Data Stream Processing and Analytics Spring 2020 ## 4 /09: Flow control and load shedding Vasiliki (Vasia) Kalavri vkalavri@bu.edu ## Keeping up with the producers • Producers can generate queue: what if the queue grows larger than available memory? • block the producer (back-pressure, flow control) ## Load management approaches ![Image](/uploads/documents/1/8/5/2/1852496083fa00bab53cdd69c80bfbf6/p7_1 applications with strict latency constraints that can tolerate approximate results. Slow down the flow of data: - The system buffers excess data for later processing, once input rates stabilize. •

## CurveBS I/O processing flow Before introducing IO processing flow, we first describe the overall architecture, data organization and topology structure of CURVE.  The flow of user’s read and write request to curve:

# Optimization for number of goroutines using feedback control Yusuke MIYAKE / Pepabo R&D Institute, GMO Pepabo, Inc. 2019.07.25 GopherCon 2019 ![Image](/uploads/documents/4/2/d/f/42dfd7f07b1ef4 ## I ssues to solve for the realization 1. Selection of performance metrics 2. Finding how to control rapidly and continuously ## Performance metrics ## Performance metrics • Independent resource type based on the metrics • Continuously • Rapidly • Accurately • Feedback control meets these conditions. ## Feedback control • Tracking a given set-point using errors from the set-point. • Applying

Configuration 1.31 Flow Control 1.32 Guarantees of sends and commits 1.33 Message Redelivery and Undelivered Messages 1.34 Message Expiry 1.35 Large Messages 1.36 Paging 1.37 Scheduled Messages instructions outlined here. #### 2.25. 0 Full release notes Highlights: • Improvement on Paging Flow Control • Many other bug fixes and improvements #### 2.24. 0 Full release notes Highlights: - Diverts now support multiple addresses - Runtime configuration reloading now supports bridges. • Paging can now be configured by message count. ## Upgrading from older versions 1. Due to XML schema changes

77 8.18 Dot Syntax for Vectorizing Functions ..... 78 8.19 Further Reading ..... 80 9 Control Flow ..... 81 9.1 Compound Expressions ..... 81 9.2 Conditional Evaluation ..... 82 9.3 Short-Circuit 263 20.2 Equality and Comparison Operators ..... 264 20.3 Logical operators ..... 265 20.4 Control Flow and Short-Circuiting Operators ..... 266 20.5 Arrays With Missing Values ..... 267 20.6 Skipping 196cc600891be3364176e58343/p18_1.jpg) To exit the interactive session, type CTRL-D (press the Control/^ key together with the d key), or type exit(). When run in interactive mode, julia displays a banner

and piping 74 8.16 Dot Syntax for Vectorizing Functions 75 8.17 Further Reading 77 9 Control Flow 79 9.1 Compound Expressions 79 9.2 Conditional Evaluation 80 9.3 Short-Circuit Evaluation 239 20.2 Equality and Comparison Operators ..... 239 20.3 Logical operators ..... 240 20.4 Control Flow and Short-Circuiting Operators ..... 242 20.5 Arrays With Missing Values ..... 243 20.6 Skipping | | | | | | | | | | | | | | | | | | | | To exit the interactive session, type CTRL-D (press the Control/^ key together with the d key), or type exit(). When run in interactive mode, Julia displays a banner

16.16 Dot Syntax for Vectorizing Functions ..... 94 16.17 Further Reading ..... 96 17 Control Flow ..... 97 17.1 Compound Expressions ..... 97 17.2 Conditional Evaluation ..... 98 17.3 Short-Circuit Missing Values 257 28.2 Equality and Comparison Operators 257 28.3 Logical operators 258 28.4 Control Flow and Short-Circuiting Operators 260 28.5 Arrays With Missing Values 260 28.6 Skipping Missing Julia from the command line: | | | | | | To exit the interactive session, type CTRL-D (press the Control/^ key together with the d key), or type exit (). When run in interactive mode, julia displays a banner

15.16 Dot Syntax for Vectorizing Functions ..... 92 15.17 Further Reading ..... 94 16 Control Flow ..... 95 16.1 Compound Expressions ..... 95 16.2 Conditional Evaluation ..... 96 16.3 Short-Circuit Missing Values 255 27.2 Equality and Comparison Operators 255 27.3 Logical operators 256 27.4 Control Flow and Short-Circuiting Operators 258 27.5 Arrays With Missing Values 258 27.6 Skipping Missing | | | | | | | | | | | | | | | | | | | | To exit the interactive session, type CTRL-D (press the Control/^ key together with the d key), or type exit (). When run in interactive mode, julia displays a banner

pass an argument to a function. 1 shoppingList = [] // Went shopping and bought everything. ## Control Flow Use if and switch to make conditionals, and use for-in, for, while, and do-while to make loops horrible." Conditional statements such as the if statement are covered in more detail in Control Flow. Swift’s type safety prevents non-Boolean values from being be substituted for Bool. The following integer") } // prints "123 has an integer value of 123" For more on the if statement, see Control Flow. NOTE Trying to use ! to access a non-existent optional value triggers a runtime error. Always

The var statement 3 5 The assignment statement 3 6 Constants 4 7 The let statement 4 8 Control flow statements 4 8.1 If statement 4 8.2 Case statement 5 8.3 While statement 5 8.4 For statement readLine(stdin) # Error: constant expression expected let input = readLine(stdin) # works ## 8 Control flow statements The greetings program consists of 3 statements that are executed sequentially. Only branching and looping are needed too. ### 8.1 If statement The if statement is one way to branch the control flow: let name = readLine(stdin) if name == "": echo "Poor soul, you lost your name