Enable support for v0.15.0 and later mysqld_exporter

[mattlord]

The operator was stuck on an old version (v0.14.0) of the mysqld_exporter because in v0.15.0 — which is 2.5 years old now — they removed the DATA_SOURCE_NAME environment variable that the operator used to specify how to connect to the mysqld container.

When upgrading the mysqld_exporter to v0.18.0 on main the vttablet pods fail to come up because of the noted issue:

❯ kubectl -n example logs example-vttablet-zone1-0790125915-4e37d9d5 -c mysqld-exporter
time=2025-12-04T03:35:38.702Z level=INFO source=mysqld_exporter.go:256 msg="Starting mysqld_exporter" version="(version=0.18.0, branch=HEAD, revision=4df239645fa28c4ed811fd697e42f7178d81e999)"
time=2025-12-04T03:35:38.702Z level=INFO source=mysqld_exporter.go:257 msg="Build context" build_context="(go=go1.25.1, platform=linux/arm64, user=root@6f5155465331, date=20250929-08:50:39, tags=unknown)"
time=2025-12-04T03:35:38.702Z level=ERROR source=config.go:145 msg="failed to validate config" section=client err="no user specified in section or parent"
time=2025-12-04T03:35:38.702Z level=ERROR source=config.go:145 msg="failed to validate config" section=mysqld err="no user specified in section or parent"
time=2025-12-04T03:35:38.702Z level=INFO source=mysqld_exporter.go:261 msg="Error parsing host config" file=/vt/vtdataroot/vt_0790125915/my.cnf err="no configuration found"

This PR enables support of v0.15.0 and later of the mysqld_exporter by using a standard MySQL my.cnf file which will work with any version of the exporter or any other client more broadly. We also then upgrade the version of the mysqld_exporter that we bundle and test with from v0.14.0 to the latest release: v0.18.0.

Fixes: #696

[mattlord]

@bluecrabs007 am I missing something here? The test updates also pass on main, so I'm not sure about things now...

./test/endtoend/backup_restore_test.sh
...

Confirming that the mysqld_exporter is working in example-vttablet-zone1-0790125915-4e37d9d5
Confirmed working mysqld_exporter metrics: mysql_global_status_open_files = 6
Confirming that the mysqld_exporter is working in example-vttablet-zone1-2469782763-bfadd780
Confirmed working mysqld_exporter metrics: mysql_global_status_open_files = 5
Confirming that the mysqld_exporter is working in example-vttablet-zone1-2548885007-46a852d0
Confirmed working mysqld_exporter metrics: mysql_global_status_open_files = 6
...

[bluecrabs007]

@bluecrabs007 am I missing something here? The test updates also pass on main, so I'm not sure about things now...

./test/endtoend/backup_restore_test.sh
...

Confirming that the mysqld_exporter is working in example-vttablet-zone1-0790125915-4e37d9d5
Confirmed working mysqld_exporter metrics: mysql_global_status_open_files = 6
Confirming that the mysqld_exporter is working in example-vttablet-zone1-2469782763-bfadd780
Confirmed working mysqld_exporter metrics: mysql_global_status_open_files = 5
Confirming that the mysqld_exporter is working in example-vttablet-zone1-2548885007-46a852d0
Confirmed working mysqld_exporter metrics: mysql_global_status_open_files = 6
...

Was the exporter version bumped to 0.18.0?

[mattlord]

Was the exporter version bumped to 0.18.0?

Aha! Thanks 😄

pkg/apis/planetscale/v2/defaults.go:    MysqldExporter: "prom/mysqld-exporter:v0.14.0",
test/endtoend/operator/101_initial_cluster.yaml:    mysqldExporter: prom/mysqld-exporter:v0.14.0
test/endtoend/operator/101_initial_cluster_autoscale.yaml:    mysqldExporter: prom/mysqld-exporter:v0.14.0
test/endtoend/operator/101_initial_cluster_backup.yaml:    mysqldExporter: prom/mysqld-exporter:v0.14.0
test/endtoend/operator/101_initial_cluster_backup_schedule.yaml:    mysqldExporter: prom/mysqld-exporter:v0.14.0
test/endtoend/operator/101_initial_cluster_unmanaged_tablet.yaml:    mysqldExporter: prom/mysqld-exporter:v0.14.0
test/endtoend/operator/101_initial_cluster_vtorc_vtadmin.yaml:    mysqldExporter: prom/mysqld-exporter:v0.14.0
test/endtoend/operator/102_keyspace_teardown.yaml:    mysqldExporter: prom/mysqld-exporter:v0.14.0
test/endtoend/operator/201_customer_tablets.yaml:    mysqldExporter: prom/mysqld-exporter:v0.14.0
test/endtoend/operator/302_new_shards.yaml:    mysqldExporter: prom/mysqld-exporter:v0.14.0
test/endtoend/operator/306_down_shard_0.yaml:    mysqldExporter: prom/mysqld-exporter:v0.14.0
test/endtoend/operator/401_scheduled_backups.yaml:    mysqldExporter: prom/mysqld-exporter:v0.14.0
test/endtoend/operator/cluster_autoscale.yaml:    mysqldExporter: prom/mysqld-exporter:v0.14.0
test/endtoend/operator/cluster_upgrade.yaml:    mysqldExporter: prom/mysqld-exporter:v0.14.0

[mattlord]

@bluecrabs007 anything else you'd like to see changed or added? Thanks again for all of the help!

[bluecrabs007]

@bluecrabs007 anything else you'd like to see changed or added? Thanks again for all of the help!

Thank you! The changes look good.
I am assuming we are leaving the DATA_SOURCE_NAME ENV for backwards compatibility?

vitess-operator/pkg/operator/vttablet/env_vars.go

Line 49 in 91c619f

Name: "DATA_SOURCE_NAME",

[mattlord]

Thank you! The changes look good.

❤️

I am assuming we are leaving the DATA_SOURCE_NAME ENV for backwards compatibility?

Yeah, I figured we can leave it in there just to be backwards compatible too. It doesn't hurt anything.