This is the default Serializer used by napalm-logs.

MessagePack is an efficient binary serialization format. It lets you exchange data among multiple languages like JSON. But it’s faster and smaller. Small integers are encoded into a single byte, and typical short strings require only one extra byte in addition to the strings themselves.

Source: MessagePack.

Given the following napalm-logs document (as JSON):

  "yang_message": {
        "bgp": {
          "neighbors": {
                "neighbor": {
                  "": {
                        "state": {
                          "session_state": "CONNECT"
  "message_details": {
        "processId": null,
        "severity": 4,
        "facility": 0,
        "hostPrefix": null,
        "pri": "4",
        "processName": "kernel",
        "host": "vmx01",
        "tag": "tcp_auth_ok",
        "time": "21:23:00",
        "date": "Jul 20",
        "message": "Packet from wrong MD5 digest"
  "timestamp": 1500585780,
  "facility": 0,
  "ip": "",
  "host": "vmx01",
  "yang_model": "openconfig-bgp",
  "error": "BGP_MD5_INCORRECT",
  "os": "junos",
  "severity": 4

The document will be binary serialized as:

\x8a\xacyang_message\x81\xa3bgp\x81\xa9neighbors\x81\xa8neighbor\x81\xaf192.168.140.254\x81\xa5state\x81\xadsession_state\xa7CONNECT\xafmessage_details\x8b\xa9processId\xc0\xa8severity\x04\xa8facility\x00\xaahostPrefix\xc0\xa3pri\xa14\xabprocessName\xa6kernel\xa4host\xa5vmx01\xa3tag\xabtcp_auth_ok\xa4time\xa821:23:00\xa4date\xa6Jul 20\xa7message\xd92Packet from wrong MD5 digest\xa8facility\x00\xa2ip\xa9127.0.0.1\xa5error\xb1BGP_MD5_INCORRECT\xa4host\xa5vmx01\xaayang_model\xaeopenconfig-bgp\xa9timestamp\xceYq\x1f4\xa2os\xa5junos\xa8severity\x04