The Holy Java

Building the right thing, building it right, fast

Upgrade or not to upgrade dependencies? The eternal dilemma

Posted by Jakub Holý on October 20, 2015

Cross-posted from TeliaSonera Tech blog.

Handling dependencies is one of important challenges in any software project – and especially in the fast-moving JavaScript world. Our Nettbutikk team just had a heated discussion about handling upgrades of our dependencies that continuous our learning journey lined with failures (or rather “experiments that generated new knowledge” :-)).

Failed attempt one: Let tools do it

Originally we let npm automatically do minor upgrades but that turned out to be problematic as even minor version changes can introduce bugs and having potentially different (minor) versions on our different machines and in production makes troubleshooting difficult.

Also, this only takes care about minor version changes. When we decided to do the bigger updates, we had a lot of work and testing to do, making sure all the new versions work together. Troubleshooting of upgrade problems was difficult since many libraries were changed at once so pinpointing the source of a new defect was nontrivial.

Failed attempt two: Let a human do it

Next we decided to freeze the library versions completely and let the one of us that had the operations role that week run npm outdated, update all dependencies, and verify everything still worked.

Thus we ensured that we were almost always up-to-date and that we typically had only a small job to do, with just a small potential for problems. However it wasn’t frictionless either. It might require one or few hours (for proper testing and occasional troubleshooting) every week, a time we would have rather used on creating new value. And sometimes the upgrade did introduce problems – some spot and fixed immediately, but some taking more time to discover and fix. Once it took two weeks to find out that something broke due to a Reflux upgrade – and finding out that the cause was the upgrade wasn’t easy.

New experiment: Upgrade as-needed

Our reliable though-challenger Alex pointed out that upgrades give us typically little value at a relatively high cost. So we have decided to try not upgrading libraries unless we would have a good reason to do it (such as a known security problem or a new functionality we want). It is obviously not optimal and the upgrades might be big and painful but we will try it for a while and evaluate how it works for us.


Handling and upgrading dependencies is difficult and costly. It’s important to evaluate the cost-benefit ration and experiment to find the “least bad” approach and balance for a particular team. Development is fun.

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