InfluxDB

-- InfluxDB InfluxQL (SQL-like)

-- Indsæt data (line protocol via HTTP eller CLI)
INSERT cpu,host=server01,region=eu-west value=64.3 1609459200000000000
INSERT cpu,host=server01,region=eu-west value=72.1 1609459260000000000
INSERT memory,host=server01,region=eu-west used=8.2,total=16.0 1609459200000000000

-- SELECT basics
SELECT * FROM cpu WHERE time > now() - 1h

-- Aggregations
SELECT MEAN(value) FROM cpu 
WHERE time > now() - 1h 
GROUP BY time(5m), host

-- Multiple fields
SELECT used, total, (used/total)*100 AS usage_percent 
FROM memory 
WHERE time > now() - 24h

-- Window functions
SELECT DERIVATIVE(MEAN(value), 1s) 
FROM cpu 
WHERE time > now() - 1h 
GROUP BY time(1m)

-- SHOW kommandoer
SHOW MEASUREMENTS
SHOW TAG KEYS FROM cpu
SHOW TAG VALUES FROM cpu WITH KEY = "host"
SHOW FIELD KEYS FROM cpu

-- Retention policy
CREATE RETENTION POLICY "one_week" ON "mydb" 
DURATION 7d 
REPLICATION 1 
DEFAULT

-- Continuous query (auto-aggregation)
CREATE CONTINUOUS QUERY "cpu_mean_5m" ON "mydb"
BEGIN
  SELECT MEAN(value) AS mean_value 
  INTO "cpu_mean_5m"
  FROM "cpu"
  GROUP BY time(5m), *
END

-- Flux query language (InfluxDB 2.0+)
from(bucket: "metrics")
  |> range(start: -1h)
  |> filter(fn: (r) => r._measurement == "cpu")
  |> filter(fn: (r) => r.host == "server01")
  |> aggregateWindow(every: 5m, fn: mean)
  |> yield(name: "mean")

-- JavaScript client eksempel
const { InfluxDB, Point } = require('@influxdata/influxdb-client');

const client = new InfluxDB({ url: 'http://localhost:8086', token: 'mytoken' });
const writeApi = client.getWriteApi('myorg', 'mybucket');

// Write data
const point = new Point('cpu')
  .tag('host', 'server01')
  .tag('region', 'eu-west')
  .floatField('value', 64.3);

writeApi.writePoint(point);
await writeApi.close();

// Query data
const queryApi = client.getQueryApi('myorg');
const query = `from(bucket: "mybucket")
  |> range(start: -1h)
  |> filter(fn: (r) => r._measurement == "cpu")`;

for await (const { values, tableMeta } of queryApi.iterateRows(query)) {
  console.log(values);
}