A story: Harborline
Harborline is a mid-size retailer. The checkout service is .NET, started in 2018, grown through peak seasons and two agencies. It makes money. It is also the file nobody volunteers to own.
Friday, 18:12 — the store is open, checkout is not
Discount weekend. Orders stall. The on-call engineer opens the usual Serilog files. Some services are chatty. The order pipeline is quiet — the last person who touched it removed “noisy” logs before Black Friday. There is no ENTER, no parameters, no SQL. Support is guessing. Marketing is on the phone. Four hours later they find a null customer id in a helper that was never logged. Lost orders are already in the thousands.
The APM quote, and the rewrite nobody will fund
Leadership asks for “full observability.” An enterprise APM quote arrives with host counts and ingest tiers. Engineering proposes a six-month rewrite of checkout so it is “clean enough to instrument.” Finance sees two expensive projects. The spaghetti stays. The next peak season is twelve weeks away.
They put ArgusLogs on the code they already have
No rewrite. They generate a free ArgusLogs license, add [LogMethod] on the order and payment types, and ship a normal release. Build-time weaving records method entry, parameters, return, exceptions, and duration. SQL from the same process shows up beside the method that called it. The business logic does not change. The next build is the first one that can explain itself.
The next Friday
A payment provider times out. This time the log shows which method waited, for how long, with which order id, and which query ran. The fix is a retry and a timeout — forty minutes, not four hours. Harborline did not become a perfect codebase. They became a company that can see production. The rewrite, if it ever happens, can target the slow methods the logs already named.