analytics: structured access logging for Plumber API

[bbest]

Context

The CalCOFI Plumber API has no usage logging. Add a request logging filter to capture endpoint usage over time.

Implementation

Add a plumber middleware filter before pr_run() in the run script or plumber.R:

pr |> pr_filter("logger", function(req, res) {
  cat(
    jsonlite::toJSON(list(
      ts     = format(Sys.time(), "%Y-%m-%dT%H:%M:%SZ"),
      method = req$REQUEST_METHOD,
      path   = req$PATH_INFO,
      query  = req$QUERY_STRING,
      ip     = req$REMOTE_ADDR
    ), auto_unbox = TRUE), "\n",
    file   = "/var/log/calcofi-api.log",
    append = TRUE
  )
  plumber::forward()
})

GCS Sync

Periodically sync /var/log/calcofi-api.log to a GCS bucket for long-term retention:

googleCloudStorageR::gcs_upload(
  "/var/log/calcofi-api.log",
  bucket = "calcofi-logs",
  name   = paste0("api/", Sys.Date(), ".log")
)

Consider the logger package for structured JSON output and log rotation.