springboot2自定义statsd指标前缀

序

本文主要研究下springboot2自定义statsd指标前缀

背景

springboot2引入了micrometer，1.x版本的spring.metrics.export.statsd.prefix在2版本中已经被标记为废弃，但是2版本没有给出对应的配置项。

FlavorStatsdLineBuilder

micrometer-registry-statsd-1.0.1-sources.jar!/io/micrometer/statsd/internal/FlavorStatsdLineBuilder.java

/**
 * A Statsd serializer for a particular {@link Meter} that formats the line in different
 * ways depending on the prevailing {@link StatsdFlavor}.
 *
 * @author Jon Schneider
 */
public class FlavorStatsdLineBuilder implements StatsdLineBuilder {
    private final Meter.Id id;
    private final StatsdFlavor flavor;
    private final HierarchicalNameMapper nameMapper;
    private final MeterRegistry.Config config;

    private final Function<NamingConvention, String> datadogTagString;
    private final Function<NamingConvention, String> telegrafTagString;

    public FlavorStatsdLineBuilder(Meter.Id id, StatsdFlavor flavor, HierarchicalNameMapper nameMapper, MeterRegistry.Config config) {
        this.id = id;
        this.flavor = flavor;
        this.nameMapper = nameMapper;
        this.config = config;

        // service:payroll,region:us-west
        this.datadogTagString = memoize(convention ->
                id.getTags().iterator().hasNext() ?
                        id.getConventionTags(convention).stream()
                                .map(t -> t.getKey() + ":" + t.getValue())
                                .collect(Collectors.joining(","))
                        : null
        );

        // service=payroll,region=us-west
        this.telegrafTagString = memoize(convention ->
                id.getTags().iterator().hasNext() ?
                        id.getConventionTags(convention).stream()
                                .map(t -> t.getKey() + "=" + t.getValue())
                                .collect(Collectors.joining(","))
                        : null
        );
    }

    @Override
    public String count(long amount, Statistic stat) {
        return line(Long.toString(amount), stat, "c");
    }

    @Override
    public String gauge(double amount, Statistic stat) {
        return line(DoubleFormat.decimalOrNan(amount), stat, "g");
    }

    @Override
    public String histogram(double amount) {
        return line(DoubleFormat.decimalOrNan(amount), null, "h");
    }

    @Override
    public String timing(double timeMs) {
        return line(DoubleFormat.decimalOrNan(timeMs), null, "ms");
    }

    private String line(String amount, @Nullable Statistic stat, String type) {
        switch (flavor) {
            case ETSY:
                return metricName(stat) + ":" + amount + "|" + type;
            case DATADOG:
                return metricName(stat) + ":" + amount + "|" + type + tags(stat, datadogTagString.apply(config.namingConvention()),":", "|#");
            case TELEGRAF:
            default:
                return metricName(stat) + tags(stat, telegrafTagString.apply(config.namingConvention()),"=", ",") + ":" + amount + "|" + type;
        }
    }

    private String tags(@Nullable Statistic stat, String otherTags, String keyValueSeparator, String preamble) {
        String tags = of(stat == null ? null : "statistic" + keyValueSeparator + stat.getTagValueRepresentation(), otherTags)
                .filter(Objects::nonNull)
                .collect(Collectors.joining(","));

        if(!tags.isEmpty())
            tags = preamble + tags;
        return tags;
    }

    private String metricName(@Nullable Statistic stat) {
        switch (flavor) {
            case ETSY:
                return nameMapper.toHierarchicalName(stat != null ? id.withTag(stat) : id, config.namingConvention());
            case DATADOG:
            case TELEGRAF:
            default:
                return config.namingConvention().name(id.getName(), id.getType(), id.getBaseUnit());
        }
    }
}

可以看到count、gauge、histogram、timing方法内部都调用了line方法，而line方法调用metricName来构造指标名称，而metricName则是调用HierarchicalNameMapper的toHierarchicalName方法(flavor为ESTY)

HierarchicalNameMapper

micrometer-core-1.0.1-sources.jar!/io/micrometer/core/instrument/util/HierarchicalNameMapper.java

/**
 * Defines the mapping between a combination of name + dimensional tags and a hierarchical name.
 *
 * @author Jon Schneider
 */
public interface HierarchicalNameMapper {
    /**
     * Sort tags alphabetically by key and append tag key values to the name with '.', e.g.
     * {@code http_server_requests.response.200.method.GET}
     */
    HierarchicalNameMapper DEFAULT = (id, convention) -> {
        String tags = "";

        if (id.getTags().iterator().hasNext()) {
            tags = "." + id.getConventionTags(convention).stream()
                .map(t -> t.getKey() + "." + t.getValue())
                .map(nameSegment -> nameSegment.replace(" ", "_"))
                .collect(Collectors.joining("."));
        }

        return id.getConventionName(convention) + tags;
    };

    String toHierarchicalName(Meter.Id id, NamingConvention convention);
}

HierarchicalNameMapper接口定义了一个DEFAULT实现，而在StatsdMetricsExportAutoConfiguration则是默认使用这个DEFAULT实现

• StatsdMetricsExportAutoConfiguration

spring-boot-actuator-autoconfigure-2.0.0.RELEASE-sources.jar!/org/springframework/boot/actuate/autoconfigure/metrics/export/statsd/StatsdMetricsExportAutoConfiguration.java

    @Bean
    @ConditionalOnMissingBean
    public HierarchicalNameMapper hierarchicalNameMapper() {
        return HierarchicalNameMapper.DEFAULT;
    }

自定义

通过自定义个HierarchicalNameMapper，就可以自定义statsd指标的prefix，实例如下

    @Bean
    public HierarchicalNameMapper hierarchicalNameMapper() {
        return new HierarchicalNameMapper(){

            @Override
            public String toHierarchicalName(Meter.Id id, NamingConvention convention) {
                String tags = "";

                if (id.getTags().iterator().hasNext()) {
                    tags = "." + id.getConventionTags(convention).stream()
                            .map(t -> t.getKey() + "." + t.getValue())
                            .map(nameSegment -> nameSegment.replace(" ", "_"))
                            .collect(Collectors.joining("."));
                }

                return "demo." + id.getConventionName(convention) + tags;
            }
        };
    }

这里修改了DEFAULT方法，在return那里添加了一个demo作为prefix，这样就大功告成了。

小结

springboot2目前虽然没有通过配置文件直接支持指定statsd的prefix，但是可以通过少许代码自定义HierarchicalNameMapper来实现。

doc

• management.metrics.export.tags-as-prefix property seems not to be honored in Spring Boot 2.0.0.RELEASE #12557