BUG "ERROR source=exporter.go:154 msg="Error opening connection to database" err="dial tcp 127.0.0.1:3306: connect: connection refused" "

[Coffee-with-salt]

I did not specify the address 127.0.0.1:3306 in any configuration or startup parameters.

service
————————————————————————————————
[Unit]
Description=Prometheus MySQL Server Exporter
After=network-online.target

[Service]
Type=simple
User=root
Group=root
ExecStart=/usr/local/mysqld_exporter/mysqld_exporter --config.my-cnf="/usr/local/mysqld_exporter/.my.cnf"
--collect.info_schema.processlist
--collect.info_schema.innodb_metrics
--collect.info_schema.tablestats
--collect.info_schema.userstats
--collect.engine_innodb_status
--collect.perf_schema.replication_group_members
--collect.perf_schema.replication_group_member_stats
--collect.perf_schema.replication_applier_status_by_worker

[Install]
WantedBy=multi-user.target
————————————————————————————————————————

,my.cnf

---

[client]
user=mysqld_exporter2
password=********

---

prometheus

---

  - job_name: 'mysql'
    metrics_path: /probe
    static_configs:
      - targets: ['192.168.3.102:3306']
        labels:
          grep: 'mysql2'
          auth_module: 'client'
      - targets: ['192.168.3.103:3306']
        labels:
          grep: 'mysql3'
          auth_module: 'client'
      - targets: ['192.168.3.104:3306']
        labels:
          grep: 'mysql4'
          auth_module: 'client' 
      - targets: ['mysql.yxuer.com:6446']
        labels:
          grep: 'mysqlroute'
          auth_module: 'client'        
    relabel_configs:
      - source_labels: [__address__]
        target_label: __param_target
      - source_labels: [auth_module]
        target_label: __param_module
      - source_labels: [__param_target]
        target_label: instance
      - target_label: __address__
        replacement: 192.168.3.200:9104

---

logs

---

Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=mysqld_exporter.go:256 msg="Starting mysqld_exporter" version="(version=0.18.0, branch=HEAD, revision=4df239645fa28c4ed811fd697e42f7178d81e999)"
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=mysqld_exporter.go:257 msg="Build context" build_context="(go=go1.25.1, platform=linux/amd64, user=root@5f7e05caa051, date=20250929-08:51:44, tags=unknown)"
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=mysqld_exporter.go:269 msg="Scraper enabled" scraper=info_schema.innodb_metrics
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=mysqld_exporter.go:269 msg="Scraper enabled" scraper=perf_schema.replication_group_members
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=mysqld_exporter.go:269 msg="Scraper enabled" scraper=perf_schema.replication_group_member_stats
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=mysqld_exporter.go:269 msg="Scraper enabled" scraper=info_schema.query_response_time
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=mysqld_exporter.go:269 msg="Scraper enabled" scraper=engine_innodb_status
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=mysqld_exporter.go:269 msg="Scraper enabled" scraper=global_status
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=mysqld_exporter.go:269 msg="Scraper enabled" scraper=global_variables
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=mysqld_exporter.go:269 msg="Scraper enabled" scraper=slave_status
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=mysqld_exporter.go:269 msg="Scraper enabled" scraper=info_schema.processlist
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=mysqld_exporter.go:269 msg="Scraper enabled" scraper=perf_schema.replication_applier_status_by_worker
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=mysqld_exporter.go:269 msg="Scraper enabled" scraper=info_schema.userstats
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=mysqld_exporter.go:269 msg="Scraper enabled" scraper=info_schema.tablestats
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=mysqld_exporter.go:269 msg="Scraper enabled" scraper=info_schema.innodb_cmp
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=mysqld_exporter.go:269 msg="Scraper enabled" scraper=info_schema.innodb_cmpmem
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=tls_config.go:346 msg="Listening on" address=[::]:9104
Mar 17 18:43:01 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:01.839+08:00 level=INFO source=tls_config.go:349 msg="TLS is disabled." http2=false address=[::]:9104
Mar 17 18:43:04 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:04.010+08:00 level=ERROR source=exporter.go:154 msg="Error opening connection to database" err="dial tcp 127.0.0.1:3306: connect: connection refused"
Mar 17 18:43:14 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:14.006+08:00 level=ERROR source=exporter.go:154 msg="Error opening connection to database" err="dial tcp 127.0.0.1:3306: connect: connection refused"
Mar 17 18:43:24 server101 mysqld_exporter[2148893]: time=2026-03-17T18:43:24.006+08:00 level=ERROR source=exporter.go:154 msg="Error opening connection to database" err="dial tcp 127.0.0.1:3306: connect: connection refused"