AWS Documentation » AWS IoT Analytics » AWS IoT Analytics User Guide » Pipeline Activities

Pipeline Activities

The simplest functional pipeline connects a channel to a data store, which makes it a pipeline with two activities: a channel activity and a datastore activity. You can achieve more powerful message processing by adding additional activities to your pipeline.

AWS IoT Analytics provides the RunPipelineActivity command which enables you to simulate the results of running a pipeline activity on a message payload you provide. You might find this helpful when you are developing and debugging your pipeline activities. RunPipelineActivity Example demonstrates how it is used.

Channel Activity

The first activity in a pipeline must be the channel activity which determines the source of the messages to be processed.

{
    "channel": {
        "name": "MyChannelActivity",
        "channelName": "mychannel",
        "next": "MyLambdaActivity"
    }
}

Datastore Activity

The datastore activity, which specifies where to store the processed data, is the last activity.

{
    "datastore": {
        "name": "MyDatastoreActivity",
        "datastoreName": "mydatastore"
    }
}

Lambda Activity

A lambda activity can be used to perform more complex processing on the message. Examples include enriching the message with data from the output of external APIs or filtering the message based on logic from DynamoDB. However, you can use this activity to perform any sort of message-based processing, including filtering which messages are stored in the data store.

The AWS Lambda function used in this activity must receive and return an array of JSON objects. In the following example, the Lambda function modifies, and then returns, its event parameter.

The batchSize determines how many messages your Lambda function receives on each invocation. When you set it, keep in mind that an AWS Lambda function has a maximum timeout of five minutes. So the Lambda function must be able to process all messages in the batch in less than five minutes.

{
    "lambda": {
        "name": "MyLambdaActivity",
        "lambdaName": "mylambda",
        "batchSize": 10,
        "next": "MyDatastoreActivity"
    }
}

You must add a function policy to allow AWS IoT Analytics to invoke your Lambda function. Use the following CLI command:

aws lambda add-permission --function-name <lambda-function-name> --statement-id <your-statement> --principal iotanalytics.amazonaws.com --action lambda:InvokeFunction

Lambda Function Example 1

In this example, the Lambda function adds additional information based on data in the original message. Given a device that publishes a message with a payload similar to:

{
  "thingid": "00001234abcd",
  "temperature": 26,
  "humidity": 29,
  "location": {
    "lat": 52.4332935,
    "lon": 13.231694
  },
  "ip": "192.168.178.54",
  "datetime": "2018-02-15T07:06:01"
}

and the following pipeline definition:

{
    "pipeline": {
        "activities": [
            {
                "channel": {
                    "channelName": "foobar_channel",
                    "name": "foobar_channel_activity",
                    "next": "lambda_foobar_activity"
                }
            },
            {
                "lambda": {
                    "lambdaName": "MyAnalyticsLambdaFunction",
                    "batchSize": 5,
                    "name": "lambda_foobar_activity",
                    "next": "foobar_store_activity"
                }
            },
            {
                "datastore": {
                    "datastoreName": "foobar_datastore",
                    "name": "foobar_store_activity"
                }
            }
        ],
        "name": "foobar_pipeline",
        "arn": "arn:aws:iotanalytics:eu-west-1:123456789012:pipeline/foobar_pipeline"
    }
}

The following Lambda Python function (MyAnalyticsLambdaFunction) adds the GMaps URL and the temperature, in Fahrenheit, to the message:

import logging
import sys

# Configure logging
logger = logging.getLogger()
logger.setLevel(logging.INFO)
streamHandler = logging.StreamHandler(stream=sys.stdout)
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
streamHandler.setFormatter(formatter)
logger.addHandler(streamHandler)

def c_to_f(c):
    return 9.0/5.0 * c + 32

def lambda_handler(event, context):
    logger.info("event before processing: {}".format(event))
    maps_url = 'N/A'

    for e in event:
        #e['foo'] = 'addedByLambda'
        if 'location' in e:
            lat = e['location']['lat']
            lon = e['location']['lon']
            maps_url = "http://maps.google.com/maps?q={},{}".format(lat,lon)

        if 'temperature' in e:
            e['temperature_f'] = c_to_f(e['temperature'])

        logger.info("maps_url: {}".format(maps_url))
        e['maps_url'] = maps_url

    logger.info("event after processing: {}".format(event))

    return event

Lambda Function Example 2

A useful technique is to compress and serialize message payloads to reduce transport and storage costs. In this second example, the Lambda function assumes the message payload represents a JSON original which has been compressed and then base64-encoded (serialized) as a string. It returns the original JSON:

import base64
import gzip
import json
import logging
import sys

# Configure logging
logger = logging.getLogger()
logger.setLevel(logging.INFO)
streamHandler = logging.StreamHandler(stream=sys.stdout)
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
streamHandler.setFormatter(formatter)
logger.addHandler(streamHandler)

def decode_to_bytes(e):
    return base64.b64decode(e)

def decompress_to_string(binary_data):
    return gzip.decompress(binary_data).decode('utf-8')

def lambda_handler(event, context):
    logger.info("event before processing: {}".format(event))

    decompressed_data = []

    for e in event:
        binary_data = decode_to_bytes(e)
        decompressed_string = decompress_to_string(binary_data)

        decompressed_data.append(json.loads(decompressed_string))

    logger.info("event after processing: {}".format(decompressed_data))

    return decompressed_data

AddAttributes Activity

An addAttributes activity adds attributes based on existing attributes in the message. This lets you alter the shape of the message before it is stored. For example, you can use addAttributes to normalize data coming from different generations of device firmware.

This is best explained by example. Consider the input message:

{
    "device": {
        "id": "device-123",
        "coord": [ 47.6152543, -122.3354883 ]
    }
}

and an addAttributes activity that looks like this:

{
    "addAttributes": {
        "name": "MyAddAttributesActivity",
        "attributes": {
            "device.id": "id",
            "device.coord[0]": "lat",
            "device.coord[1]": "lon"
        },
        "next": "MyRemoveAttributesActivity"
    }
}

This activity moves the device ID to the root level and extracts the values in the coord array, promoting them to top-level attributes called lat and lon. As a result of this activity, the input message is transformed to the following:

{
    "device": {
        "id": "device-123",
        "coord": [ 47.6, -122.3 ]
    },
    "id": "device-123",
    "lat": 47.6,
    "lon": -122.3
}

The original device attribute is still present. If you want to remove it, you can use the removeAttributes activity.

RemoveAttributes Activity

A removeAttributes activity removes attributes from a message. For example, given the message that was the result of the addAttributes activity:

{
    "device": {
        "id": "device-123",
        "coord": [ 47.6, -122.3 ]
    },
    "id": "device-123",
    "lat": 47.6,
    "lon": -122.3
}

To normalize that message so that it includes only the required data at the root level, use the following removeAttributes activity:

{
    "removeAttributes": {
        "name": "MyRemoveAttributesActivity",
        "attributes": [
            "device"
        ],
        "next": "MyDatastoreActivity"
    }
}

This results in the following message flowing along the pipeline:

{
    "id": "device-123",
    "lat": 47.6,
    "lon": -122.3
}

SelectAttributes Activity

The selectAttributes activity creates a new message using only the specified attributes from the original message. Every other attribute is dropped. selectAttributes creates new attributes under the root of the message only. So given this message:

{
    "device": {
        "id": "device-123",
        "coord": [ 47.6152543, -122.3354883 ],
        "temp": 50,
        "hum": 40
    },
    "light": 90
}

and this activity:

{
    "selectAttributes": {
        "name": "MySelectAttributesActivity",
        "attributes": [
            "device.temp",
            "device.hum",
            "light"
        ],
        "next": "MyDatastoreActivity"
    }
}

The result is the following message flowing through the pipeline:

{
    "temp": 50,
    "hum": 40,
    "light": 90
}

Again, selectAttributes can only create root-level objects.

Filter Activity

A filter activity filters a message based on its attributes. The expression used in this activity looks like an SQL WHERE clause which must return a boolean:

{
    "filter": {
        "name": "MyFilterActivity",
        "filter": "temp > 40 AND hum < 20",
        "next": "MyDatastoreActivity"
    }
}

DeviceRegistryEnrich Activity

The deviceRegistryEnrich activity enables you to add data from the AWS IoT device registry to your message payload. For example, given the following message:

{
    "temp": 50,
    "hum": 40,
    "device" {
        "thingName": "my-thing"
    }
}

and a deviceRegistryEnrich activity that looks like this:

{
    "deviceRegistryEnrich": {
        "name": "MyDeviceRegistryEnrichActivity",
        "attribute": "metadata",
        "thingName": "device.thingName",
        "roleArn": "arn:aws:iam::<your-account-number>:role:MyEnrichRole",
        "next": "MyDatastoreActivity"
    }
}

The output message now looks like this:

{
    "temp" : 50,
    "hum" : 40,
    "device" {
        "thingName" : "my-thing"
    },
    "metadata" : {
        "defaultClientId": "my-thing",
        "thingTypeName": "my-thing",
        "thingArn": "arn:aws:iot:us-east-1:<your-account-number>:thing/my-thing",
        "version": 1,
        "thingName": "my-thing",
        "attributes": {},
        "thingId": "aaabbbccc-dddeeef-gghh-jjkk-llmmnnoopp"
    }
}

You must specify a role in the roleArn field of the activity definition that has the appropriate permissions attached. The role must have a permissions policy that looks like:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "iot:DescribeThing"
            ],
            "Resource": [
                "arn:aws:iot:<region>:<account-id>:thing/<thing-name>
            ]
        }
    ]
}

and a trust policy that looks like:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "",
            "Effect": "Allow",
            "Principal": {
                "Service": "iotanalytics.amazonaws.com"
            },
            "Action": [
                "sts:AssumeRole"
            ]
        }
    ]
}

DeviceShadowEnrich Activity

A deviceShadowEnrich activity adds information from the AWS IoT Device Shadows service to a message. For example, given the message:

{
    "temp": 50,
    "hum": 40,
    "device": { "thingName": "my-thing" }
}

and the following deviceShadowEnrich activity:

{
    "deviceShadowEnrich": {
        "name": "MyDeviceShadowEnrichActivity",
        "attribute": "shadow",
        "thingName": "device.thingName",
        "roleArn": "arn:aws:iam::<your-account-number>:role:MyEnrichRole",
        "next": "MyDatastoreActivity"
    }
}

the result is a message that looks like this:

{
    "temp": 50,
    "hum": 40,
    "device": {
        "thingName": "my-thing"
    },
    "shadow": {
        "state": {
            "desired": {
                "attributeX": valueX, ...
            },
            "reported": {
                "attributeX": valueX, ...
            },
            "delta": {
                "attributeX": valueX, ...
            }
        },
        "metadata": {
            "desired": {
                "attribute1": {
                    "timestamp": timestamp
                }, ...
            },
            "reported": ": {
                "attribute1": {
                    "timestamp": timestamp
                }, ...
            }
        },
        "timestamp": timestamp,
        "clientToken": "token",
        "version": version
    }
}

You must specify a role in the roleArn field of the activity definition that has the appropriate permissions attached. The role must have a permissions policy that looks like:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "iot:GetThingShadow"
            ],
            "Resource": [
                "arn:aws:iot:<region>:<account-id>:thing/<thing-name>
            ]
        }
    ]
}

and a trust policy that looks like:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "",
            "Effect": "Allow",
            "Principal": {
                "Service": "iotanalytics.amazonaws.com"
            },
            "Action": [
                "sts:AssumeRole"
            ]
        }
    ]
}

Math Activity

A math activity computes an arithmetic expression using the message's attributes. The expression must return a number. For example, given the following input message:

{
    "tempF": 50,
}

after processing by the following math activity:

{
    "math": {
        "name": "MyMathActivity",
        "math": "(tempF - 32) / 2",
        "attribute": "tempC",
        "next": "MyDatastoreActivity"
    }
}

the resulting message looks like:

{
    "tempF" : 50,
    "tempC": 9
}

Math Activity Operators and Functions

You can use the following operators in a math activity:

+	addition
-	subtraction
*	multiplication
/	division
%	modulo

You can use the following functions in a math activity:

abs(Decimal)

Returns the absolute value of a number.

Example: abs(-5) returns 5.

Argument Type	Result
Int	Int, the absolute value of the argument.
Decimal	Decimal, the absolute value of the argument.
Boolean	Undefined.
String	Decimal. The result is the absolute value of the argument. If the string cannot be converted, the result is Undefined.
Array	Undefined.
Object	Undefined.
Null	Undefined.
Undefined	Undefined.

acos(Decimal)

Returns the inverse cosine of a number in radians. Decimal arguments are rounded to double precision before function application.

Example: acos(0) = 1.5707963267948966

Argument Type	Result
Int	Decimal (with double precision), the inverse cosine of the argument. Imaginary results are returned as Undefined.
Decimal	Decimal (with double precision), the inverse cosine of the argument. Imaginary results are returned as Undefined.
Boolean	Undefined.
String	Decimal, the inverse cosine of the argument. If the string cannot be converted, the result is Undefined. Imaginary results are returned as Undefined.
Array	Undefined.
Object	Undefined.
Null	Undefined.
Undefined	Undefined.

asin(Decimal)

Returns the inverse sine of a number in radians. Decimal arguments are rounded to double precision before function application.

Example: asin(0) = 0.0

Argument Type	Result
Int	Decimal (with double precision), the inverse sine of the argument. Imaginary results are returned as Undefined.
Decimal	Decimal (with double precision), the inverse sine of the argument. Imaginary results are returned as Undefined.
Boolean	Undefined.
String	Decimal (with double precision), the inverse sine of the argument. If the string cannot be converted, the result is Undefined. Imaginary results are returned as Undefined.
Array	Undefined.
Object	Undefined.
Null	Undefined.
Undefined	Undefined.

atan(Decimal)

Returns the inverse tangent of a number in radians. Decimal arguments are rounded to double precision before function application.

Example: atan(0) = 0.0

Argument Type	Result
Int	Decimal (with double precision), the inverse tangent of the argument. Imaginary results are returned as Undefined.
Decimal	Decimal (with double precision), the inverse tangent of the argument. Imaginary results are returned as Undefined.
Boolean	Undefined.
String	Decimal, the inverse tangent of the argument. If the string cannot be converted, the result is Undefined. Imaginary results are returned as Undefined.
Array	Undefined.
Object	Undefined.
Null	Undefined.
Undefined	Undefined.

atan2(Decimal, Decimal)

Returns the angle, in radians, between the positive x-axis and the (x, y) point defined in the two arguments.  The angle is positive for counter-clockwise angles (upper half-plane, y > 0), and negative for clockwise angles (lower half-plane, y < 0). Decimal arguments are rounded to double precision before function application.

Example: atan2(1, 0) = 1.5707963267948966

Argument Type	Argument Type	Result
Int / Decimal	Int / Decimal	Decimal (with double precision), the angle between the x-axis and the specified (x,y) point.
Int / Decimal / String	Int / Decimal / String	Decimal, the inverse tangent of the point described. If a string cannot be converted, the result is Undefined.
Other Value	Other Value	Undefined.

ceil(Decimal)

Rounds the given Decimal up to the nearest Int.

Examples:

ceil(1.2) = 2

ceil(11.2) = -1

Argument Type	Result
Int	Int, the argument value.
Decimal	Int, the Decimal value rounded up to the nearest Int.
String	Int. The string is converted to Decimal and rounded up to the nearest Int. If the string cannot be converted to a Decimal, the result is Undefined.
Other Value	Undefined.

cos(Decimal)

Returns the cosine of a number in radians. Decimal arguments are rounded to double precision before function application.

Example:

cos(0) = 1.

Argument Type	Result
Int	Decimal (with double precision), the cosine of the argument. Imaginary results are returned as Undefined.
Decimal	Decimal (with double precision), the cosine of the argument. Imaginary results are returned as Undefined.
Boolean	Undefined.
String	Decimal (with double precision), the cosine of the argument. If the string cannot be converted to a Decimal, the result is Undefined. Imaginary results are returned as Undefined.
Array	Undefined.
Object	Undefined.
Null	Undefined.
Undefined	Undefined.

cosh(Decimal)

Returns the hyperbolic cosine of a number in radians. Decimal arguments are rounded to double precision before function application.

Example: cosh(2.3) = 5.037220649268761.

Argument Type	Result
Int	Decimal (with double precision), the hyperbolic cosine of the argument. Imaginary results are returned as Undefined.
Decimal	Decimal (with double precision), the hyperbolic cosine of the argument. Imaginary results are returned as Undefined.
Boolean	Undefined.
String	Decimal (with double precision), the hyperbolic cosine of the argument. If the string cannot be converted to a Decimal, the result is Undefined. Imaginary results are returned as Undefined.
Array	Undefined.
Object	Undefined.
Null	Undefined.
Undefined	Undefined.

exp(Decimal)

Returns e raised to the Decimal argument. Decimal arguments are rounded to double precision before function application.

Example: exp(1) = e.

Argument Type	Result
Int	Decimal (with double precision), e ^ argument.
Decimal	Decimal (with double precision), e ^ argument.
String	Decimal (with double precision), e ^ argument. If the String cannot be converted to a Decimal, the result is Undefined.
Other Value	Undefined.

ln(Decimal)

Returns the natural logarithm of the argument. Decimal arguments are rounded to double precision before function application.

Example: ln(e) = 1.

Argument Type	Result
Int	Decimal (with double precision), the natural log of the argument.
Decimal	Decimal (with double precision), the natural log of the argument.
Boolean	Undefined.
String	Decimal (with double precision), the natural log of the argument. If the string cannot be converted to a Decimal the result is Undefined.
Array	Undefined.
Object	Undefined.
Null	Undefined.
Undefined	Undefined.

log(Decimal)

Returns the base 10 logarithm of the argument. Decimal arguments are rounded to double precision before function application.

Example: log(100) = 2.0.

Argument Type	Result
Int	Decimal (with double precision), the base 10 log of the argument.
Decimal	Decimal (with double precision), the base 10 log of the argument.
Boolean	Undefined.
String	Decimal (with double precision), the base 10 log of the argument. If the String cannot be converted to a Decimal, the result is Undefined.
Array	Undefined.
Object	Undefined.
Null	Undefined.
Undefined	Undefined.

mod(Decimal, Decimal)

Returns the remainder of the division of the first argument by the second argument. You can also use "%" as an infix operator for the same modulo functionality.

Example: mod(8, 3) = 2.

Left Operand	Right Operand	Output
Int	Int	Int, the first argument modulo the second argument.
Int / Decimal	Int / Decimal	Decimal, the first argument modulo the second operand.
String / Int / Decimal	String / Int / Decimal	If all strings convert to Decimals, the result is the first argument modulo the second argument. Otherwise, Undefined.
Other Value	Other Value	Undefined.

power(Decimal, Decimal)

Returns the first argument raised to the second argument. Decimal arguments are rounded to double precision before function application.

Example: power(2, 5) = 32.0.

argument Type 1	argument Type 2	Output
Int / Decimal	Int / Decimal	A Decimal (with double precision), the first argument raised to the second argument's power.
Int / Decimal / String	Int / Decimal String	A Decimal (with double precision), the first argument raised to the second argument's power. Any strings are converted to Decimals. If any String fails to be converted to Decimal, the result is Undefined.
Other Value	Other Value	Undefined.

round(Decimal)

Rounds the given Decimal to the nearest Int. If the Decimal is equidistant from two Int values (for example, 0.5), the Decimal is rounded up.

Example: Round(1.2) = 1.

Round(1.5) = 2.

Round(1.7) = 2.

Round(-1.1) = -1.

Round(-1.5) = -2.

Argument Type	Result
Int	The argument.
Decimal	Decimal is rounded down to the nearest Int.
String	Decimal is rounded down to the nearest Int. If the string cannot be converted to a Decimal, the result is Undefined.
Other Value	Undefined.

sign(Decimal)

Returns the sign of the given number. When the sign of the argument is positive, 1 is returned. When the sign of the argument is negative, -1 is returned. If the argument is 0, 0 is returned.

Examples:

sign(-7) = -1.

sign(0) = 0.

sign(13) = 1.

Argument Type	Result
Int	Int, the sign of the Int value.
Decimal	Int, the sign of the Decimal value.
String	Int, the sign of the Decimal value. The string is converted to a Decimal value, and the sign of the Decimal value is returned. If the String cannot be converted to a Decimal, the result is Undefined.
Other Value	Undefined.

sin(Decimal)

Returns the sine of a number in radians. Decimal arguments are rounded to double precision before function application.

Example: sin(0) = 0.0

Argument Type	Result
Int	Decimal (with double precision), the sine of the argument.
Decimal	Decimal (with double precision), the sine of the argument.
Boolean	Undefined.
String	Decimal (with double precision), the sine of the argument. If the string cannot be converted to a Decimal, the result is Undefined.
Array	Undefined.
Object	Undefined.
Null	Undefined.
Undefined	Undefined.

sinh(Decimal)

Returns the hyperbolic sine of a number. Decimal values are rounded to double precision before function application. The result is a Decimal value of double precision.

Example: sinh(2.3) = 4.936961805545957

Argument Type	Result
Int	Decimal (with double precision), the hyperbolic sine of the argument.
Decimal	Decimal (with double precision), the hyperbolic sine of the argument.
Boolean	Undefined.
String	Decimal (with double precision), the hyperbolic sine of the argument. If the string cannot be converted to a Decimal, the result is Undefined.
Array	Undefined.
Object	Undefined.
Null	Undefined.
Undefined	Undefined.

sqrt(Decimal)

Returns the square root of a number. Decimal arguments are rounded to double precision before function application.

Example: sqrt(9) = 3.0.

Argument Type	Result
Int	The square root of the argument.
Decimal	The square root of the argument.
Boolean	Undefined.
String	The square root of the argument. If the string cannot be converted to a Decimal, the result is Undefined.
Array	Undefined.
Object	Undefined.
Null	Undefined.
Undefined	Undefined.

tan(Decimal)

Returns the tangent of a number in radians. Decimal values are rounded to double precision before function application.

Example: tan(3) = -0.1425465430742778

Argument Type	Result
Int	Decimal (with double precision), the tangent of the argument.
Decimal	Decimal (with double precision), the tangent of the argument.
Boolean	Undefined.
String	Decimal (with double precision), the tangent of the argument. If the string cannot be converted to a Decimal, the result is Undefined.
Array	Undefined.
Object	Undefined.
Null	Undefined.
Undefined	Undefined.

tanh(Decimal)

Returns the hyperbolic tangent of a number in radians. Decimal values are rounded to double precision before function application.

Example: tanh(2.3) = 0.9800963962661914

Argument Type	Result
Int	Decimal (with double precision), the hyperbolic tangent of the argument.
Decimal	Decimal (with double precision), the hyperbolic tangent of the argument.
Boolean	Undefined.
String	Decimal (with double precision), the hyperbolic tangent of the argument. If the string cannot be converted to a Decimal, the result is Undefined.
Array	Undefined.
Object	Undefined.
Null	Undefined.
Undefined	Undefined.

trunc(Decimal, Int)

Truncates the first argument to the number of Decimal places specified by the second argument. If the second argument is less than zero, it will be set to zero. If the second argument is greater than 34, it will be set to 34. Trailing zeroes are stripped from the result.

Examples:

trunc(2.3, 0) = 2.

trunc(2.3123, 2 = 2.31.

trunc(2.888, 2) = 2.88.

(2.00, 5) = 2.

argument Type 1	argument Type 2	Result
Int	Int	The source value.
Int / Decimal / String	Int / Decimal	The first argument is truncated to the length described by the second argument. The second argument, if not an Int, will be rounded down to the nearest Int. Strings are converted to Decimal values. If the string conversion fails, the result is Undefined.
Other Value		Undefined.

RunPipelineActivity Example

Here is an example of how you would use the "RunPipelineActivity" command to test a pipeline activity. For this example we test a Math activity:

1. Create a file "maths.json" which contains the definition of the pipeline activity you want to test:

   {
       "math": {
           "name": "MyMathActivity",
           "math": "((temp - 32) * 5.0) / 9.0",
           "attribute": "tempC"
       }
   }

2. Create a file "payloads.json" which contains the example payloads that are used to test the pipeline activity:

   [
       "{\"humidity\": 52, \"temp\": 68 }",
       "{\"humidity\": 52, \"temp\": 32 }"
   ]

3. Call "RunPipelineActivities" from the command line:

   aws iotanalytics run-pipeline-activity  --pipeline-activity file://maths.json  --payloads file://payloads.json

4. This produces the following results:

   {
       "logResult": "",
       "payloads": [
           "eyJodW1pZGl0eSI6NTIsInRlbXAiOjY4LCJ0ZW1wQyI6MjB9",
           "eyJodW1pZGl0eSI6NTIsInRlbXAiOjMyLCJ0ZW1wQyI6MH0="
       ]
   }

5. The "payloads" listed in the results are Base64-encoded strings. When these strings are decoded, you get the following results:

   {"humidity":52,"temp":68,"tempC":20}
   {"humidity":52,"temp":32,"tempC":0}