pinpoint-apm/pinpoint · warning

hostName is empty

Error message

hostName is empty

What it means

TelegrafMetricController.saveSystemMetric rejects a telegraf metrics batch when no hostname can be extracted from any of the collected TelegrafMetric entries. Each metric carries a hostGroupName and a set of tags; the controller derives hostName from the first metric's tags, and if every entry lacks it the batch is unusable because Pinpoint's system-metric storage is keyed by (hostGroupName, hostName). It returns HTTP 400 with the body 'hostName is empty' rather than throwing.

Solutions

1. Ensure the Telegraf agent sets the hostname tag (verify '[agent] hostname = "..."' and omit_hostname = false in telegraf.conf).
2. Check the pinot-kafka/metric pipeline or any relays for tag-stripping filters and re-add 'hostname'.
3. If posting manually, include a non-empty hostname tag on every metric entry.
4. Log the full request payload when this 400 occurs to confirm which tag key the collector expects and match it exactly (case-sensitive).

Example fix

// before (telegraf.conf)
[agent]
  omit_hostname = true

// after
[agent]
  hostname = "app-server-01"
  omit_hostname = false

// client-side, before POSTing to the collector
boolean hasHost = metrics.stream()
    .allMatch(m -> m.getTags() != null && StringUtils.isNotBlank(m.getTags().get("hostname")));
if (!hasHost || metrics.isEmpty()) {
    throw new IllegalArgumentException("telegraf batch must include a non-empty hostname tag");
}

When it happens

Trigger: POSTing telegraf metrics to the system-metric collect endpoint where getHost(telegrafMetrics) returns null/empty — i.e., the batch is empty, or none of the metrics' tag maps contain the hostname tag (typically 'hostname' as sent by Telegraf's output).

Common situations: Telegraf agent configured without the default 'host' tag, a custom tag_filter stripping the hostname tag, or a proxy/relay re-serializing the payload and dropping tags; also misconfigured clients posting hand-built JSON without per-metric tags.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• invalid hostGroupName=
• Failed to create MetricId. metricName
• Inserted customMetricName
• Invalid linkKey format: expected 'fromApp~toApp' but got:
• Resource attribute `service.name` is required to save OTLP…

AI-assisted analysis of pinpoint-apm/pinpoint@744c3d3075 (2026-09-07). Data as JSON: /api/errors/4604deaf3a0efb1b. Report an issue: GitHub.

Appendix: source

Thrown at metric-module/metric/src/main/java/com/navercorp/pinpoint/metric/collector/controller/TelegrafMetricController.java:97

            @RequestHeader(value = "hostGroupName") String hostGroupName,
            @RequestBody TelegrafMetrics telegrafMetrics, BindingResult bindingResult
    ) throws BindException {
        if (bindingResult.hasErrors()) {
            SimpleErrorMessage simpleErrorMessage = new SimpleErrorMessage(bindingResult);
            logger.warn("metric binding error. header=hostGroupName:{} errorCount:{} {}", hostGroupName, bindingResult.getErrorCount(), simpleErrorMessage);
            throw new BindException(bindingResult);
        }

        if (!isValidGroupName(hostGroupName)) {
            logger.warn("invalid hostGroupName='{}'", hostGroupName);
            return ResponseEntity.badRequest().body("invalid hostGroupName='" + hostGroupName + "'");
        }

        String hostName = getHost(telegrafMetrics);
        if (StringUtils.isEmpty(hostName)) {
            // hostname null check
            logger.info("hostName is empty. hostGroupName={}", hostGroupName);
            return ResponseEntity.badRequest().body("hostName is empty");
        }

        if (!isValidHostName(hostName)) {
            logger.warn("invalid hostName='{}', hostGroupName='{}'", hostName, hostGroupName);
        }

        if (logger.isDebugEnabled()) {
            logger.debug("hostGroupName:{} host:{} size:{}", hostGroupName, hostName, telegrafMetrics.size());
        }

        String tenantId = tenantProvider.getTenantId();

        Metrics systemMetric = toMetrics(tenantId, hostGroupName, hostName, telegrafMetrics);

        updateMetadata(systemMetric);
        systemMetricService.insert(systemMetric);

        return ResponseEntity.ok(null);

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