一个典型的Haproxy_exporter的监控metric例子 包含指标 haproxy_backend_bytes_in_total haproxy_backend_bytes_out_total haproxy_backend_client_aborts_total haproxy_backend_compressor_bytes_bypassed_total haproxy_backend_compressor_bytes_in_total haproxy_backend_compressor_bytes_out_total haproxy_backend_connection_err