NestJS 6 comes with all-new injection scope support. Namely, instead of enforcing every object managed by DI container to be a singleton, you can now freely assign three types of injection scope to them: singleton, request, and transient. We adopted the request-scoped injection in our project to achieve distributed tracing as well as context-aware logging. The result turned out to be not so great. For starters, the request-scoped injection is way too expensive.

We have carried out the first or maybe last round of rewrite of the Juhui DSP/SSP/ADX with Typescript. A few goals and non-goals have been set for this labor-intensive process. Goals Strong typed. Strong API contracts. Holistic Observability with logging, tracing, and metrics. Layered Architecture and dedicated component. Testcases can be run by anyone. Stateless over stateful. Improved readability. Proper code deprecation process. Non-Goals Use fancy technology.