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An Introduction to Large-Scale Software Development

This presentation provides an overview of large-scale software development, including software change, configuration management, and the benefits of source control. It also includes a case study of the HP-UX operating system.

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An Introduction to Large-Scale Software Development

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  1. An Introduction to Large-Scale Software Development Steve VarnauCore HP-UX Operation October 31, 2000

  2. Agenda • Software Change • Software Configuration Management (SCM) • Change Control • Large-Scale Software Development • Example: HP-UX Operating System

  3. The Need for Managing Software Change Software Evolution • Environment Changes • Computer Hardware • Competition • Business Processes • External Requirements (Y2k, Euro,…) • New Standards (XML, MP3, e-Speak,…) • All Software Demands Change • Incremental Development • Maintenance (Corrective, Perfective, Adaptive)

  4. Benefits of Source Control / SCM SCM • Manage Constant Software Change • Improve Debugging Productivity • Trace Defect Reports to Correct Versions of Source Code • Understand Change History • Reproducibility • Build (Compile) Software Accurately, Repeatably • Grow Project Size • Avoid Over-writing and Losing Changes • Concurrent Development (Improve TTM) • Coordinate Work with Development Policies

  5. Terminology - File Versioning SCM • Revision / Version - Single copy of a source file as it appeared at given point in its change history (checkpoint) • File / Element - Complete change history; all versions • Branch - Set of successive versions; parallel to other branches • Delta - Change from one file version to the next

  6. Terminology - Version Tree SCM

  7. Terminology - Multiple File Configuration Management SCM • Variant - File based on another, co-exists with original • Derived Object - File automatically generated from source files • Change Set - Set of versions across multiple files making up a single logical change (e.g., feature or fix) • Baseline - Consistent set of versions across all files

  8. Terminology - Baseline SCM

  9. Coordinating Work SCM Problem: Multiple people working on same file at the same time can result in lost work. • Solution 1: Serialize work with file locking. • Solution 2: Work in isolation (branch) and merge. Branching and merging scales much better. Merging can be semi-automated using 3-way merge algorithms.

  10. Merging - Version Tree SCM

  11. Formal definition (IEEE) SCM SCM is the process of identifying and defining the items in the system, controlling the change of these items throughout their life cycle, recording and reporting the status of items and change requests and verifying the completeness and correctness of the items. Related Terms: Source Control, Version Control

  12. Managing Change Change Control Change Control -Formal processes for tracking and approval of software modifications. Managed with SCM and defect tracking tools. Usual Policy Areas: • Documentation - Change request / defect report filed. • Approval - Change request reviewed by release management or technical board. • Quality Requirements - Code reviewed, regression tests passed. Policies often change by release stage and in response to problems.

  13. Development Process Change Control Key Components of Development Process: • Software Configuration Management • Change Control • Quality Control

  14. Principles of Large-Scale Software Development Scaling • Reproducibility • Policy Enforcement versus Policy Auditing • Process, Process, Process A process must be defined to be improved • Automation A process must be automated to be repeatable • Continuous Functional Integration and Test

  15. Software Integration Scaling Integration: Combining multiple features or components developed in isolation. Large projects are subject to constant change, so isolation on a stable base is necessary. Continuous Functional Integration and Test (CFIT) • Changes integrated throughout development. • Changes not allowed to regress functionality or quality.

  16. HP-UX Development HP-UX • 220,000+ Source Files • ~2.5 Million Versions • 52,000+ Derived Files (Single Nightly Build) • 900+ User Accounts • More Than 1 Terabyte of Disk Space

  17. HP-UX Concurrent Development HP-UX • Normally 2-3 Releases Under Development • Several Releases Under Maintenance • Heavy Use of Branching and Merging

  18. HP-UX Multisite Development HP-UX • Four Primary Development Sites • Three in USA (Three Time Zones) • One in India • One USA Site Hosts Three Logical Sites • Partner Companies • Several Secondary Sites

  19. Tiered Software Integration Model HP-UX 1. Developer Task - Edit, Compile, Test 2. Submit - Batch Changes, Acceptance Test 3. Baseline - Nightly Build, Regression Test 4. Integration - Monthly Packaging, Partner Test 5. Release - Semi-annual Delivery, Production Use

  20. Integration Levels HP-UX Release Integration Cycle Baseline Submit Build Modifications

  21. Process Evolution • Continuous Process Improvement • Root Cause Analysis (RCA) • Capability Maturity Model (CMM) 1. Initial 2. Repeatable 3. Defined 4. Managed 5. Optimizing

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