Logging is for events with identity, metrics are for events without identity. They are not the same thing.
Sometimes I care about the bulk behaviour of my application. I hit 2757 RPS and suddenly find a catastrophic gap in the performance landscape of my application -- that's useful. I don't care much about the particulars of the requests. What matters is the statistical behaviour.
But sometimes the application crashes when a particular input is given. These are outliers, they don't show up clearly in statistical behaviour. In that case I care about the details.
Metrics are warnings that smokers die younger, on average, than non-smokers.
Logs are a biopsy showing which kind of lung cancer you have.
No sensible production system or PaaS treats them as identical, even if you can derive metrics from logs.
Sometimes I care about the bulk behaviour of my application. I hit 2757 RPS and suddenly find a catastrophic gap in the performance landscape of my application -- that's useful. I don't care much about the particulars of the requests. What matters is the statistical behaviour.
But sometimes the application crashes when a particular input is given. These are outliers, they don't show up clearly in statistical behaviour. In that case I care about the details.
Metrics are warnings that smokers die younger, on average, than non-smokers.
Logs are a biopsy showing which kind of lung cancer you have.
No sensible production system or PaaS treats them as identical, even if you can derive metrics from logs.