Application metrics

Metrics are the numbers your app produces that aren't errors: orders placed, queue depth, checkout latency, unique visitors. Errora accepts both wire formats Sentry SDKs emit.

Metric types

Type	Use it for	Aggregates
counter (c)	Things that happen	sum, count
distribution (d)	Measured values (latency, size)	avg, min, max, p50–p99
gauge (g)	A level at a point in time	last, min, max, avg
set (s)	Distinct things	count_unique

Setup — SDK

Sentry.metrics.increment("checkout.attempt", 1, { tags: { plan: "pro" } });
Sentry.metrics.distribution("checkout.latency", 421, { unit: "millisecond", tags: { route: "/pay" } });
Sentry.metrics.gauge("queue.depth", 128, { tags: { queue: "ingest" } });
Sentry.metrics.set("visitors", userId);

sentry_sdk.metrics.incr("orders.created", 1, tags={"plan": "pro"})
sentry_sdk.metrics.distribution("orders.total", order.total, unit="none")
sentry_sdk.metrics.gauge("queue.depth", depth, tags={"queue": "ingest"})
sentry_sdk.metrics.set("visitors", user_id)

SDKs pre-aggregate before sending: what arrives is a bucket per metric per time window, not one message per call. Distributions keep a sample of the raw values, so percentiles stay answerable, and sets count distinct members as a union across buckets rather than a sum.

Setup — raw wire formats

1. trace_metric items (current SDKs) — the same batch container as logs:

{"items":[{"timestamp":1767225600.0,"name":"checkout.latency","type":"distribution",
           "value":42.0,"unit":"millisecond","trace_id":"7b3f…",
           "attributes":{"route":{"value":"/pay","type":"string"}}}]}

2. statsd text (the original protocol), newline-delimited:

<name>[@<unit>]:<v1>[:<v2>…]|<type>|#<tag>:<value>,…|T<unix_seconds>

endpoint.response_time@millisecond:57:92|d|#route:/pay,method:POST|T1615889449
button_click@none:1|c|#browser:firefox

A statsd gauge with exactly five values is the pre-aggregated last:min:max:sum:count form, not five readings.

Limits per batch: 1000 items, 30 tags per metric, 200 characters per name or tag value.

Querying

Metrics in the sidebar lists the metric names a project has sent. Pick one and choose:

• an aggregate — sum, avg, min, max, p50, p75, p90, p95, p99, count_unique
• a group-by tag, to split the series
• an environment and a time period

avg is always the true sum / count over the window, never the average of per-bucket averages.

GET /api/v1/projects/{project_id}/metrics?q=&stats_period=24h
GET /api/v1/projects/{project_id}/metrics/series?name=&op=&group_by=&environment=&stats_period=24h
GET /api/v1/projects/{project_id}/metrics/summary?name=&environment=&stats_period=24h
GET /api/v1/projects/{project_id}/metrics/tags?name=&stats_period=24h

Naming that stays useful

• domain.thing.measure — checkout.latency, queue.depth, sms.sent.
• Put varying values in tags, never in the name. orders.created tagged plan:pro beats orders.created.pro.
• Keep tag cardinality low: route yes, user_id no. Every distinct tag combination is its own bucket, and you are billed per metric bucket.

Dashboards

Metrics are a dashboard dataset — put a metric series next to your error counts and transaction latency on the same board.

Troubleshooting

Symptom	Cause / fix
Metric name missing from the list	Nothing has arrived in the selected period — widen it
Percentiles look approximate	A bucket kept a bounded sample (100 values); that is by design
count_unique lower than expected	Set members are hashed and bounded per bucket (500)
Tag missing	It exceeded the 30-tag or 200-character limit and was dropped
Costs climbing	Tag cardinality — one high-cardinality tag multiplies your bucket count