CREATE TABLE IF NOT EXISTS traffic_collection_state (
  server_id BIGINT PRIMARY KEY REFERENCES servers(id) ON DELETE CASCADE,
  server_updated_at TIMESTAMPTZ NOT NULL,
  last_attempt_at TIMESTAMPTZ NOT NULL,
  last_succeeded_at TIMESTAMPTZ,
  status TEXT NOT NULL CHECK(status IN ('pending', 'ok', 'error')),
  error TEXT
);