Lightweight Collection and Storage of Software Repository Data with DataRover Thomas Kowark, Christoph Matthies, Matthias Uflacker and Hasso Plattner HPI, Enterprise Platform and Integration Concepts Chair, Potsdam, Germany ASE 2016 Demo Track September, 5th 

Christoph Matthies Sep 5 DataRover Background — Collecting Software Repository Data Chart 2 Collaboration Infrastructure Wiki Version Control Issue Tracker CI Server … Development Teams use MSR* Researchers * MSR – Mining Software Repositories transform load Interlinked Data Set extract ● How do teams develop software? ● What separates good from bad teams? ● How are we doing as a team? ETL Software 

■ Plugin/service-based architectures □ One plugin/service per data source □ Custom data schema □ Alitheia-Core [Gousios et al., 2009], SOFAS [Ghezzi, 2012], Sonarqube ■ Graphical ETL-Tools □ Plugin for each data source connection □ Visual creation of ETL processes □ RapidMiner, KNIME ■ Collections of Repository Data □ Pre-collected, cleansed, and interlinked data sets □ Boa [Dyer et al., 2013] with custom query language □ GHTorrent [Gousios, 2013 and ongoing], StackExchange dumps Christoph Matthies Sep 5 DataRover Related Work Chart 3 

■ Why doesn’t this mining tool support my new/updated data source? □ “The development team has migrated to Gitlab” ■ How are the peculiarities of my project reflected in the standard data schema and analyses? □ “We use JIRA with custom fields” ■ Can I store this data in a graph or document database to perform network analyses or text mining? □ “Neo4J already offers the graph algorithms that I need.” □ “All my existing queries rely on MySQL.” Christoph Matthies Sep 5 DataRover Chart 4 Common Issues 

■ Goals □ Minimal implementation effort for each data source □ Separate collection and linking □ Reuse existing implementations whenever possible □ Allow focus on linking and analysis, not data collection ■ Concepts □ Collection: Explorer (OAuth, Query Parameters) => JSON – Stackoverflow Client: ~12 LoC + logging □ Linking: Define generic mappings using GUI – Map JSON attributes to links, new nodes or node values □ Storage: Graph database (Neo4J) – No explicit database scheme, easily add connections at runtime Christoph Matthies Sep 5 DataRover Chart 5 Lightweight Data Collection — DataRover 

Christoph Matthies Sep 5 DataRover Chart 6 Data Collection — Explorers https://bitbucket.org/tkowark/data-rover/src/b37e79847a7b08a604688133834a0592b9320b57/app/models/explorers/stackoverflow_explorer.rb 

Christoph Matthies Sep 5 DataRover Chart 7 

■ Mappings: define transformations of JSON to property graph Christoph Matthies Sep 5 DataRover Chart 8 From JSON to Property Graphs 

Christoph Matthies Sep 5 DataRover Chart 9 Linking Data ■ Linking performed by attribute equality □ New relation indicating node similarity □ Node merging in case of equal node types ■ For Ruby-on-Rails Github repo: 2320 of 3075 users found in SO data StackoverflowUser GithubUser same_as 

■ Export constructed interlinked graph □ Reuse existing analysis □ Use the technology you like / are most proficient in ■ Graph Databases □ Store the graph as-is ■ Relational Databases □ One table per node Class □ Separate relation tables ■ Document stores □ One collection per node class □ Links as properties or using internal document ids Christoph Matthies Sep 5 DataRover Chart 10 Storing Property Graphs 

■ Only storing what you really need □ Rails commit data w/o file changes (58k commits, 3k users) □ Example query: amount of commits performed by each user ■ Future Work □ User study (Mapping creation time, error-proneness, clarity, etc.) □ Measuring data import times for large datasets Christoph Matthies Sep 5 DataRover Chart 11 Evaluation (ongoing) 

■ DataRover □ Lightweight data collection, only code querying □ Minimalistic data sets tailored to specific use cases □ Ease of mapping creation, visualize mappings □ Data Linkage □ Storage in different target databases ■ Try it: http://bitbucket.org/tkowark/data-rover (MIT license) □ Screencast: https://www.youtube.com/watch?v=mt4ztff4SfU □ Sample datasets: https://bit.ly/kowark-ase-16-data Christoph Matthies Sep 5 DataRover Chart 12 Summary 

■ web developer by Hugo Alberto from the Noun Project ■ Communication by Role Play from the Noun Project ■ Browser by icon 54 from the Noun Project ■ Mars Rover by LA Hall from the Noun Project ■ discussion by Milka Dahan from the Noun Project Picture Sources