Configuration Management for Components

Transcription

1 Configuration Management for Components Derived from collated works of Magnus Larsson Malardalen University, Uppsala University, Sweden ABB Automation Products, Sweden Presented at MFF UK Premysl Brada April 2001 Configuration Management for Component Systems (Magnus Larsson) Slide 1

2 Sources used Papers Larsson, M., Crnkovic, I.: New Challenges for Configuration Management. SCM Larsson, M., Crnkovic, I.: Component Configuration Management. ECOOP Component Workshop, 2000 Licentiate Thesis Applying Configuration Management Techniques to Component-Based Systems. Uppsala University 2000 Configuration Management for Component Systems (Magnus Larsson) Slide 2

3 Overview Introduction and Terminology Motivation for Component SCM Component Version Management version information change management Component Configuration Management dependencies in configuration Closing remarks Configuration Management for Component Systems (Magnus Larsson) Slide 3

4 Goals Components help software development faster, more reliable, cheaper Needs support for tracking relationships component dependencies effects of component upgrade Use SCM approach apply well-known techniques to the run-time case develop dependency description techniques industrial experience: COM dependency browser Configuration Management for Component Systems (Magnus Larsson) Slide 4

5 Concepts and Terms 1 Definition of a component many available from non-trivial, nearly independent, and replaceable part of a system which fulfils a clear function... to formal definitions close to the ADL view Szyperski s used: unit of composition contractually specified interfaces, context dependencies independent deployment subject to composition by 3rd parties Frameworks considered: COM, CORBA, EJB, COTS Configuration Management for Component Systems (Magnus Larsson) Slide 5

6 Concepts and Terms 2 Roles/Activities of Configuration Management version management identification of software entities and their different versions, version attributes, compatibility configuration and build management select (baseline) versions to aggregate into a composite, describe dependencies change management information about changes in the system introduced during the development, differences between versions release management workspace management Configuration Management for Component Systems (Magnus Larsson) Slide 6

7 Component Development - Source code into libraries - Libraries implement component - Co s assembled into product Configuration Management for Component Systems (Magnus Larsson) Slide 7

8 Motivation for Component CM Non-component systems: static libraries Τ less problems consistency checks at build time, tools abundant Component systems: source code management less critical higher chance on later upgrades problem: incompatible library/component upgrade key role of configuration and version management new aspects due to black-box components, run-time use Configuration Management for Component Systems (Magnus Larsson) Slide 8

9 Component CM New challenges: difficult prediction of the target environment component already present, same/different version unknown component relations [run-time] upgrades of black-box components Need for applicability in given configuration + results uncertain component identification compatibility types explicit dependency descriptions Configuration Management for Component Systems (Magnus Larsson) Slide 9

10 Identification of Components Levels of identification logical = interface descriptions versioning allegedly more difficult physical = implementation libraries need to know if implementation has changed Current approaches interfaces: immutable (COM) or recompilation needed (APIs) libraries: at most naming conventions (MFC) Configuration Management for Component Systems (Magnus Larsson) Slide 10

11 Version Information (1) Goal: standard way to track dependencies would prevent the new version of shared library can be requested at run-time Additional features: component meta-data version identification list of provided interfaces changes from previous versions COM has no such capability other systems not considered Configuration Management for Component Systems (Magnus Larsson) Slide 11

12 Change Description Motivation permit/refuse upgrade change between this and a previous version changes allowed in the given configuration Types of compatibility input/output format of consumed/produced data not changed interface different implementation, interface not changed behaviour semantic properties of implementation not changed Configuration Management for Component Systems (Magnus Larsson) Slide 12

13 Change Description (2) From previous version which compatibility level is affected From other version component history =? contains pairwise change information Basic compatibility assessment how computed, how used: no details given Configuration Management for Component Systems (Magnus Larsson) Slide 13

14 CM for Libraries (1) Need to care about dependencies new version of shared library problem filename-based solution akin to static linking cannot upgrade all running/deployed systems Main goal track changes in DLLs no explicit dependency information available Configuration Management for Component Systems (Magnus Larsson) Slide 14

15 CM for Libraries (2) Approach: controlled installations take snapshot current configuration: all libraries and applications install introduces new [versions of] libraries take snapshot Snapshots placed under version control understand effects of prospective upgrade Configuration Management for Component Systems (Magnus Larsson) Slide 15

16 Library Dependencies Dependency graph libraries as nodes information stored: date, time, size, name Configuration Management for Component Systems (Magnus Larsson) Slide 16

17 CM for Components Main problem considered: identification of components Τ vers. coexistence dependencies between components provide info about changes (on the interface level)? what meant by interface level Want to answer questions which components, dependencies added/removed components affected by an update difference between configurations Configuration Management for Component Systems (Magnus Larsson) Slide 17

18 Lack of it today Component Identification no version, history, dependency description meta-data needed for complete information creation of dependency graph May use Embedding pattern Proposal: interface for run-time version info name, origin, creation date, magic number revision, interfaces, dependencies behaviour, constraints, representation Configuration Management for Component Systems (Magnus Larsson) Slide 18

19 Version Information (2) Uniform access: IVersion Data input primarily by hand may parse source, track Registry changes Configuration Management for Component Systems (Magnus Larsson) Slide 19

20 Description of Dependencies S = set of components D = { (c i,c j ): c i c j } set of dependencies C = (S,D) configuration configuration stored under version control Critical component = must not be affected by a component update critical path in dependency graph active update approval Configuration Management for Component Systems (Magnus Larsson) Slide 20

21 Change Management Detecting change effects comparing two configurations C 1, C 2 S new = S 2 - S 1 ; S removed = S 1 - S 2 analyze D 1 and D 2 using S 1, S 2 to find affected new versions treated as new components Dependency browser for COM, from registry changed c s highlighted Configuration Management for Component Systems (Magnus Larsson) Slide 21

22 Remarks :-) Looks like active research plus links to practice of component development Positive points many similar views need for versioning, version co-existence types of change between versions component meta-data, run-time CM useful notions critical component i/o compatibility update viability dependent on target system Configuration Management for Component Systems (Magnus Larsson) Slide 22

23 Remarks :-( However mainly ideas, less working solutions based only on COM (author s experience) hacks instead of solutions too pessimistic (due to COM?) differences cannot be automatically computed dig into registry since no meta-data in current systems largely ignores ADLs no justification of version attributes why magic number, size of component Configuration Management for Component Systems (Magnus Larsson) Slide 23