InfluxDB任务更新失败：如何将查询首个值888设为ref？

在InfluxDB中更新任务时遇到错误：Failed to update task : Invalid flux script，目标是把查询结果里的首个值888赋值给ref变量，原脚本如下：

import "influxdata/influxdb/monitor"
import "influxdata/influxdb/v1"

option task = {name: "Demo3 Grocery Task", every: 1m, offset: 0s}

data =
    from(bucket: "demo3")
        |> range(start: 0)
        |> filter(fn: (r) => r["_measurement"] == "may")
        |> filter(fn: (r) => r["_field"] == "order_original_billing_amount")
        |> group(columns: ["marketplace_id"], mode: "by")
        |> filter(fn: (r) => r.marketplace_id == "GROCERY")
        |> aggregateWindow(every: 1d, fn: count, createEmpty: false)

// Extracting _value from data directly
reference = data
        |> first(column: "_value")        

ref= reference._value

check = {
    _check_id: "Demo3 Check",
    _check_name: "Demo3 Grocery Count Check per day",
    _type: "threshold",
    tags: {},
}

// Define crit and ok functions based on ref
crit = (r) => r._value > ref
ok = (r) => r._value <= ref

// Define messageFn to format the message
messageFn = (r) => "Check: ${r._check_name} is: ${r._level} at ${r._time} with value=${r._value}"

// Monitor check based on crit, ok, and messageFn
data
    |> v1["fieldsAsCols"]()
    |> monitor["check"](data: check, messageFn: messageFn, crit: crit, ok: ok)

查询返回的数据：

错误原因 #

原脚本中reference = data |> first(column: "_value")得到的是Flux表对象，不是单个数值，直接用reference._value无法正确提取值，这导致脚本无效。

修正方法 #

需要从表对象中提取具体的记录，再获取_value字段，推荐用findRecord函数实现：

关键修正代码 #

把原脚本中ref= reference._value替换为：

// 从reference表中提取第一条记录，再获取_value字段
ref = reference |> findRecord(fn: (key) => true, idx: 0)._value

完整修正后的脚本 #

import "influxdata/influxdb/monitor"
import "influxdata/influxdb/v1"

option task = {name: "Demo3 Grocery Task", every: 1m, offset: 0s}

data =
    from(bucket: "demo3")
        |> range(start: 0)
        |> filter(fn: (r) => r["_measurement"] == "may")
        |> filter(fn: (r) => r["_field"] == "order_original_billing_amount")
        |> group(columns: ["marketplace_id"], mode: "by")
        |> filter(fn: (r) => r.marketplace_id == "GROCERY")
        |> aggregateWindow(every: 1d, fn: count, createEmpty: false)

// 提取首个值对应的记录
reference = data |> first(column: "_value")
// 从记录中获取具体的_value数值
ref = reference |> findRecord(fn: (key) => true, idx: 0)._value

check = {
    _check_id: "Demo3 Check",
    _check_name: "Demo3 Grocery Count Check per day",
    _type: "threshold",
    tags: {},
}

// Define crit and ok functions based on ref
crit = (r) => r._value > ref
ok = (r) => r._value <= ref

// Define messageFn to format the message
messageFn = (r) => "Check: ${r._check_name} is: ${r._level} at ${r._time} with value=${r._value}"

// Monitor check based on crit, ok, and messageFn
data
    |> v1["fieldsAsCols"]()
    |> monitor["check"](data: check, messageFn: messageFn, crit: crit, ok: ok)

验证说明 #

修正后ref会被正确赋值为查询结果的首个值888，脚本可以正常通过任务更新，不会再触发无效脚本的错误。

内容的提问来源于stack exchange，提问作者Nisrayani Raj