For Each Parallel Loop

For each parallel loop is similar to For each activity but only difference is that it’s iteration will be process by different thread. For each is sequential execution whereas For each parallel as name suggest is parallel execution.

For each parallel is still not available in Mule Pallet and if you want to use it then you have to add and update the XML tags manually.

To illustrate the difference between two – we will create a POC having both flow

In For Loop iteration we will perform two activities

• Add a logger to print current payload
• Wait for 5 seconds

Dataweave expression

%dw 2.0
import * from dw::Runtime
output application/json
---
{
} wait 5000

Last we add logger to complete the execution

Similarly, we add the same activities in For Each Parallel flow

<parallel-foreach collection="#[payload.Employees]" xmlns="http://www.mulesoft.org/schema/mule/core">
		<logger level="INFO" xmlns:doc="http://www.mulesoft.org/schema/mule/documentation" doc:name="Logger" doc:id="02123f76-5ee6-4630-ae8a-097eaa1a3ae9" message="within for each #[payload]"/>
		<ee:transform xmlns:doc="http://www.mulesoft.org/schema/mule/documentation" doc:name="wait" doc:id="17b9c033-89fe-419e-9b1f-b928710261a0" xmlns:ee="http://www.mulesoft.org/schema/mule/ee/core">
			<ee:message>
				<ee:set-payload><![CDATA[%dw 2.0 import * from dw::Runtime output application/json --- { } wait 5000]]>
				</ee:set-payload>
			</ee:message>
		</ee:transform>
</parallel-foreach>

Now we will run and test both flow through SOAP UI

For Each Flow execution

• Processing is sequential as we can see there is a 5 sec gap in each payload processing
• In case of sequential processing, single thread will execute the whole For Each processing e.g. cpuLight.06
• So overall flow took more than 15 secs to complete

INFO  2020-04-13 16:37:16,123 [[MuleRuntime].cpuLight.06: [for-each-sample].for-each-sampleFlow.CPU_LITE @5bd5a737] [event: ef3767a0-7d76-11ea-8fe4-9aaf65ed66d8] org.mule.runtime.core.internal.processor.LoggerMessageProcessor: received payload {
  "Employees": [
    {
      "userId": "rirani"
    },
    {
      "userId": "nirani"
    },
    {
      "userId": "thanks"
    }
  ]
}
INFO  2020-04-13 16:37:16,126 [[MuleRuntime].cpuLight.06: [for-each-sample].for-each-sampleFlow.CPU_LITE @5bd5a737] [event: ef3767a0-7d76-11ea-8fe4-9aaf65ed66d8] org.mule.runtime.core.internal.processor.LoggerMessageProcessor: within for each {
  "userId": "rirani"
}
INFO  2020-04-13 16:37:21,134 [[MuleRuntime].cpuIntensive.04: [for-each-sample].for-each-sampleFlow.CPU_INTENSIVE @3ecfc783] [event: ef3767a0-7d76-11ea-8fe4-9aaf65ed66d8] org.mule.runtime.core.internal.processor.LoggerMessageProcessor: within for each {
  "userId": "nirani"
}
INFO  2020-04-13 16:37:26,145 [[MuleRuntime].cpuIntensive.05: [for-each-sample].for-each-sampleFlow.CPU_INTENSIVE @3ecfc783] [event: ef3767a0-7d76-11ea-8fe4-9aaf65ed66d8] org.mule.runtime.core.internal.processor.LoggerMessageProcessor: within for each {
  "userId": "thanks"
}
INFO  2020-04-13 16:37:31,150 [[MuleRuntime].cpuIntensive.06: [for-each-sample].for-each-sampleFlow.CPU_INTENSIVE @3ecfc783] [event: ef3767a0-7d76-11ea-8fe4-9aaf65ed66d8] org.mule.runtime.core.internal.processor.LoggerMessageProcessor: processing complete

For Each Parallel Execution

• Processing is parallel as we can see there is no 5 sec gap in each payload processing
• All For each iteration are processed by different threads e.g. cpuLight.16, cpuLight.15 and cpuLight.01
• So overall it took less than 6 seconds to complete the processing
• Loop will wait for completion of all different threads before exiting the for activity

INFO  2020-04-13 16:40:36,321 [[MuleRuntime].cpuLight.06: [for-each-sample].for-each-parallel-sampleFlow.CPU_LITE @6780c0db] [event: 668b0af0-7d77-11ea-8fe4-9aaf65ed66d8] org.mule.runtime.core.internal.processor.LoggerMessageProcessor: received payload {
  "Employees": [
    {
      "userId": "rirani"
    },
    {
      "userId": "nirani"
    },
    {
      "userId": "thanks"
    }
  ]
}
INFO  2020-04-13 16:40:36,323 [[MuleRuntime].cpuLight.16: [for-each-sample].for-each-parallel-sampleFlow.CPU_LITE @6780c0db] [event: 668b0af0-7d77-11ea-8fe4-9aaf65ed66d8] org.mule.runtime.core.internal.processor.LoggerMessageProcessor: within for each {
  "userId": "rirani"
}
INFO  2020-04-13 16:40:36,324 [[MuleRuntime].cpuLight.01: [for-each-sample].for-each-parallel-sampleFlow.CPU_LITE @6780c0db] [event: 668b0af0-7d77-11ea-8fe4-9aaf65ed66d8] org.mule.runtime.core.internal.processor.LoggerMessageProcessor: within for each {
  "userId": "nirani"
}
INFO  2020-04-13 16:40:36,324 [[MuleRuntime].cpuLight.15: [for-each-sample].for-each-parallel-sampleFlow.CPU_LITE @6780c0db] [event: 668b0af0-7d77-11ea-8fe4-9aaf65ed66d8] org.mule.runtime.core.internal.processor.LoggerMessageProcessor: within for each {
  "userId": "thanks"
}
INFO  2020-04-13 16:40:41,328 [[MuleRuntime].cpuIntensive.07: [for-each-sample].for-each-parallel-sampleFlow.CPU_INTENSIVE @76b8ab26] [event: 668b0af0-7d77-11ea-8fe4-9aaf65ed66d8] org.mule.runtime.core.internal.processor.LoggerMessageProcessor: processing complete

Sample Application – for-each-parallel-sample

Sample SOAP UI project – For-Each-Parallel-Sample-soapui-project