Metricbeat couchbase module faced with "401 unauthorized error"

hi all,
I am going to use metricbeat in order to capture couchbase information. I have a cluster named as "Test1" and a Bucket named as " staging" on node "127.0.0.1" of couchbase.
I enabled couchbase module, and couchbase.yml has following configuration:

- module: couchbase
  metricsets:
    - bucket
    - cluster
    - node
  period: 10s
  hosts: ["localhost:8091"]

and metricbeat.yml has following configuration:

###################### Metricbeat Configuration Example #######################

# This file is an example configuration file highlighting only the most common
# options. The metricbeat.reference.yml file from the same directory contains all the
# supported options with more comments. You can use it as a reference.
#
# You can find the full configuration reference here:
# https://www.elastic.co/guide/en/beats/metricbeat/index.html

#==========================  Modules configuration ============================

metricbeat.config.modules:
  # Glob pattern for configuration loading
  path: ${path.config}/modules.d/*.yml

  # Set to true to enable config reloading
  reload.enabled: false

  # Period on which files under path should be checked for changes
  #reload.period: 10s

#==================== Elasticsearch template setting ==========================

setup.template.settings:
  index.number_of_shards: 1
  index.codec: best_compression
  #_source.enabled: false

#================================ General =====================================

# The name of the shipper that publishes the network data. It can be used to group
# all the transactions sent by a single shipper in the web interface.
#name:

# The tags of the shipper are included in their own field with each
# transaction published.
#tags: ["service-X", "web-tier"]

# Optional fields that you can specify to add additional information to the
# output.
#fields:
#  env: staging


#============================== Dashboards =====================================
# These settings control loading the sample dashboards to the Kibana index. Loading
# the dashboards is disabled by default and can be enabled either by setting the
# options here, or by using the `-setup` CLI flag or the `setup` command.
#setup.dashboards.enabled: false

# The URL from where to download the dashboards archive. By default this URL
# has a value which is computed based on the Beat name and version. For released
# versions, this URL points to the dashboard archive on the artifacts.elastic.co
# website.
#setup.dashboards.url:

#============================== Kibana =====================================

# Starting with Beats version 6.0.0, the dashboards are loaded via the Kibana API.
# This requires a Kibana endpoint configuration.
setup.kibana:

  # Kibana Host
  # Scheme and port can be left out and will be set to the default (http and 5601)
  # In case you specify and additional path, the scheme is required: http://localhost:5601/path
  # IPv6 addresses should always be defined as: https://[2001:db8::1]:5601
  #host: "localhost:5601"

  # Kibana Space ID
  # ID of the Kibana Space into which the dashboards should be loaded. By default,
  # the Default Space will be used.
  #space.id:

#============================= Elastic Cloud ==================================

# These settings simplify using metricbeat with the Elastic Cloud (https://cloud.elastic.co/).

# The cloud.id setting overwrites the `output.elasticsearch.hosts` and
# `setup.kibana.host` options.
# You can find the `cloud.id` in the Elastic Cloud web UI.
#cloud.id:

# The cloud.auth setting overwrites the `output.elasticsearch.username` and
# `output.elasticsearch.password` settings. The format is `<user>:<pass>`.
#cloud.auth:

#================================ Outputs =====================================

# Configure what output to use when sending the data collected by the beat.

#-------------------------- Elasticsearch output ------------------------------
output.elasticsearch:
  # Array of hosts to connect to.
  hosts: ["localhost:9200"]
  index: "couchbase-%{+yyy.MM.dd}"
setup.template:
  name: 'couchbase'
  pattern: 'couchbase-*'
  enabled: true  

  # Enabled ilm (beta) to use index lifecycle management instead daily indices.
  #ilm.enabled: false

  # Optional protocol and basic auth credentials.
  #protocol: "https"
  #username: "elastic"
  #password: "changeme"

#----------------------------- Logstash output --------------------------------
#output.logstash:
  # The Logstash hosts
  #hosts: ["localhost:5044"]

  # Optional SSL. By default is off.
  # List of root certificates for HTTPS server verifications
  #ssl.certificate_authorities: ["/etc/pki/root/ca.pem"]

  # Certificate for SSL client authentication
  #ssl.certificate: "/etc/pki/client/cert.pem"

  # Client Certificate Key
  #ssl.key: "/etc/pki/client/cert.key"

#================================ Processors =====================================

# Configure processors to enhance or manipulate events generated by the beat.

processors:
  - add_host_metadata: ~
  - add_cloud_metadata: ~

#================================ Logging =====================================

# Sets log level. The default log level is info.
# Available log levels are: error, warning, info, debug
#logging.level: debug

# At debug level, you can selectively enable logging only for some components.
# To enable all selectors use ["*"]. Examples of other selectors are "beat",
# "publish", "service".
#logging.selectors: ["*"]

#============================== Xpack Monitoring ===============================
# metricbeat can export internal metrics to a central Elasticsearch monitoring
# cluster.  This requires xpack monitoring to be enabled in Elasticsearch.  The
# reporting is disabled by default.

# Set to true to enable the monitoring reporter.
#xpack.monitoring.enabled: false

# Uncomment to send the metrics to Elasticsearch. Most settings from the
# Elasticsearch output are accepted here as well. Any setting that is not set is
# automatically inherited from the Elasticsearch output configuration, so if you
# have the Elasticsearch output configured, you can simply uncomment the
# following line.
#xpack.monitoring.elasticsearch:

but when i started metricbeat, following message (HTTP error 401 in node: 401 Unauthorized) can be found in index couchbase* of kibana. it is noted that I'm not using xpack

{
  "_index": "couchbase-2019.07.01",
  "_type": "doc",
  "_id": "B6pbrWsBN7CLu88wGL5k",
  "_version": 1,
  "_score": null,
  "_source": {
    "@timestamp": "2019-07-01T11:45:55.835Z",
    "metricset": {
      "name": "node",
      "module": "couchbase",
      "host": "localhost:8091",
      "rtt": 1000
    },
    "event": {
      "dataset": "couchbase.node",
      "duration": 1000800
    },
    "error": {
      "message": "HTTP error 401 in node: 401 Unauthorized"
    },
    "beat": {
      "name": "testsy",
      "hostname": "testsy",
      "version": "6.6.0"
    },
    "host": {
      "name": "testsy",
      "architecture": "x86_64",
      "os": {
        "platform": "windows",
        "version": "10.0",
        "family": "windows",
        "name": "Windows 10 Enterprise",
        "build": "16299.1217"
      },
      "id": "3331ff70-2b8b-43c0-bec2-1a099231739f"
    }
  },
  "fields": {
    "@timestamp": [
      "2019-07-01T11:45:55.835Z"
    ]
  },
  "sort": [
    1561981555835
  ]
}

any advice will be so appreciated

the issue solved.