Design Document Example

Problem Description

• Find all occurrences of a string within text files• Start search in all drives on the local machine• Search all folders and subfolders• Only search files with a specific name pattern• Report the name of the files containing match• Report total number of files matchingSee the example code in the PPCP Unit 2 source code.Filename: ArchitecturalPatternsTests.csMethod: CompositionTest_FindFilesContainingText()

Pipeline

1. Producer: Enumerate thru each drive and add the path as a folder to search (into folder queue)

2. Worklist: Traverse FoldersFor each folder in search queue:

1. Find files matching given search pattern(s) and pass to next stage.

2. Enumerate sub folders and pass back to folder queue. This is where the worklist pattern is used.

Pipeline (cont.)

3. Stage: Search text file for an occurrence of string. Matching files should pass on the path to the next stage via another blocking collection.

4. Final Stage: Report each matching file to output. Increment the count of matching files.

5. After all stages: Report the total number of files matched.

Concurrency & Parallelism

Since we’ve described our solution in terms of parallel pattern names, it’s easy to identify concurrency.– Each stage (consumer, stage, worklist) can be done

concurrently.– Furthermore, we can create multiple workers per

stage to process work in parallel.– Since we’re using a pipeline approach, it’s most

likely that simple Parallel.For/ForEach may not be suited; but we can try.

Limitations & Shared Resources

• Producer would be a single worker since it needs to control and prevent duplicate starting folders.

• Each stage would need input and output queues (perhaps via blocking collections).

• Final Stage:– Needs to increment a global counter of how many files

were found.– Needs to output to Console one result at a time. If we

use the Console.WriteLine, the thread-safety is guaranteed.