IOT Core rules to map timestamp to timestream

Question

I'm trying out IoT core.  I have data going into a topic, and a rule is being triggered to write that data to timescale.  The input data is JSON and it contains a field 'timestamp' at the top level, it's a standard ISO8660 string.

The part I'm having trouble with is understanding how to set up the Rule to tell timestream to get the time from a property of my json rather than the default ${timestamp()}.  Since my data is an ISO8660 string I know I need to parse it, so I can

```
SELECT
   fields.rms0 as rms0,
   fields.rms1 as rms2,
   parse_time(timestamp) as ts
}
```

but adding it as 'ts' doesn't do what I want.  What do I put in the rule box, `${ts}` is my first guess, but I don't want ts to also end up as a metric, and I'm not sure how to prevent that.

For reference, my input format is this:
```
{
   measurement: "something",
   timestamp: "2022-01-01T00:00:00Z",
   fields: {
        "rms0": 1.23456,
       /* more fields */
   },
   tags: {
       /* some other stuff */
   }
}
```

Accepted Answer

Hi. You should use the `time_to_epoch()` function in the Timestamp value of the Rule Action. In your case:

```
${time_to_epoch(timestamp,"yyyy-MM-dd'T'HH:mm:ss'Z'")}
```

Please see the discussion of `time_to_epoch()` here: https://docs.aws.amazon.com/iot/latest/developerguide/timestream-rule-action.html

> I don't want ts to also end up as a metric, and I'm not sure how to prevent that.

Please change your rule query statement to:

```
SELECT fields.rms0 as rms0, fields.rms1 as rms1 FROM 'foo/bar'
```

IOT Core rules to map timestamp to timestream

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