influxdb's ConcurrentWrites must be a positive number

Error message

influxdb's ConcurrentWrites must be a positive number

What it means

The InfluxDB output validates that the configured concurrency for parallel metric writes is a positive integer before constructing the output. K6_INFLUXDB_CONCURRENT_WRITES (or the equivalent JSON/CLI config) of 0 or a negative number fails with this error, because the output sizes its semaphore channel from this value.

Solutions

Set a positive integer, e.g. K6_INFLUXDB_CONCURRENT_WRITES=8 (the documented default)
Unset the variable to fall back to the default
Check for typos or empty values in wrapper scripts that export the variable

Example fix

# before
export K6_INFLUXDB_CONCURRENT_WRITES=0
k6 run -o influxdb=http://localhost:8086/k6 script.js
# after
unset K6_INFLUXDB_CONCURRENT_WRITES   # default applies
k6 run -o influxdb=http://localhost:8086/k6 script.js

Defensive patterns

Strategy: validation

Validate before calling

// Shell
n="${K6_INFLUXDB_CONCURRENT_WRITES:-}"
if [ -n "$n" ] && ! [ "$n" -gt 0 ] 2>/dev/null; then
  echo "K6_INFLUXDB_CONCURRENT_WRITES must be a positive integer" >&2; exit 1
fi

Type guard

function isPositiveInt(v) {
  return /^\d+$/.test(v) && parseInt(v, 10) > 0;
}

Prevention

Don't repurpose K6_INFLUXDB_CONCURRENT_WRITES=0 to disable anything — unset it instead
Validate numeric env overrides once in a shared pre-run hook
Document the default (8-ish concurrency) so nobody invents values

When it happens

Trigger: K6_INFLUXDB_CONCURRENT_WRITES=0 or a negative value in the environment; the corresponding -o influxdb=...,concurrentWrites=0 argument; empty-string values that parse to 0 in some wrappers.

Common situations: CI templates that define the variable but leave it empty/zero; attempts to 'disable' concurrency by setting 0; copy-pasted dashboards from old blog posts using invalid values.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

AI-assisted analysis of grafana/k6@01ffac6f24 (2026-08-18). Data as JSON: /api/errors/e85cbf0aa367677b. Report an issue: GitHub.

Appendix: source

Thrown at internal/output/influxdb/output.go:69

}

// New returns new influxdb output
func New(params output.Params) (output.Output, error) {
	return newOutput(params)
}

func newOutput(params output.Params) (*Output, error) {
	conf, err := GetConsolidatedConfig(params.JSONConfig, params.Environment, params.ConfigArgument)
	if err != nil {
		return nil, err
	}
	cl, err := MakeClient(conf)
	if err != nil {
		return nil, err
	}
	batchConf := MakeBatchConfig(conf)
	if conf.ConcurrentWrites.Int64 <= 0 {
		return nil, errors.New("influxdb's ConcurrentWrites must be a positive number")
	}
	fldKinds, err := MakeFieldKinds(conf)
	return &Output{
		params: params,
		logger: params.Logger.WithFields(logrus.Fields{
			"output": "InfluxDBv1",
		}),
		Client:      cl,
		Config:      conf,
		BatchConf:   batchConf,
		fieldKinds:  fldKinds,
		semaphoreCh: make(chan struct{}, conf.ConcurrentWrites.Int64),
		wg:          sync.WaitGroup{},
	}, err
}

func (o *Output) extractTagsToValues(tags map[string]string, values map[string]any) map[string]any {
	for tag, kind := range o.fieldKinds {

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