Branches Are For Trees. How to Develop Software Without Them

Prepared for ThoughtWorks Australia away day

Transcript

1. Branches  are  for  trees.  How  to  develop  so4ware  without  them.   Chris  Bushell.  September  2010.  
2. Feature  branching   F1   F2   F3   Merge   Commit   Release  
3. What’s  the  problem?  
4. Trunk  development   Commit   Release  
5. Breaking  changes  
6. Branch  by  abstracIon   1  –  Introduce  an  abstracIon  over  area  of  the  system  you  want  to  change   3  –  Make  a  new  implementaIon  of  the  abstracIon   2  –  Update  all  code  to  rely  on  the  abstracIon   4  –  Remove  the  old  implementaIon   5  –  Remove  the  abstracIon  if  it’s  inelegant  
7. Cherry  picking  
8. Toggles/flippers/flags/bits  
9. Advantages   •   Decouples  code  deployment  from  feature   •   No  need  to  roll  back  a  release,  just  disable  problemaIc  feature   •   A/B  tesIng   •   Private  betas  e.g.  turn  on  a  feature  for  5%  of  users   •   Dark  launches   •   ConInuous  deployment/delivery    
10. Things  to  keep  in  mind…..   •   Complexity  and  overhead  explosion  if  toggles  aren’t  acIvely  decommissioned   •   Don’t  overload  toggles  e.g.  enItlements  (totally  different  life  spans)   •   Just  because  a  feature  is  dormant  doesn’t  mean  quality  is  not  as  important   •   Avoid  coupling  features  e.g.  feature  b  can  only  be  enabled  if  feature  a  is  enabled      
11. Conclusion   •   Branching  in  VCS  isn’t  bad     •   Long  lived  branches  in  VCS  are  bad   •   Working  in  isolaIon  for  prolonged  periods  of  Ime  is  bad     •   There’s  always  another  way,  it  just  might  require  some  careful  thought  and  design      
12. References   •   hap://marInfowler.com/bliki/FeatureBranch.html     •   hap://paulhammant.com/blog/branch_by_abstracIon.html     •   hap://www.se-­‐radio.net/2008/09/episode-­‐109-­‐ebays-­‐architecture-­‐principles-­‐with-­‐ randy-­‐shoup/     •   hap://velocityconference.blip.tv/file/2284377  (Flickr,  10+  releases  per  day)     •   hap://www.infoq.com/presentaIons/Feature-­‐Bits   •   ImplemenIng  Lean  So4ware  Development:  From  Concept  To  Cash,  Mary   Poppendieck,  Tom  Poppendieck