backend-and-orchestration-toolkit/code/aws/lambda-function/sqs-sns_example/README.md

AWS Lambda Function to Trim Videos with FFMPEG

An AWS Lambda Function to trim videos served from an API endpoint, within two given NTP UTC timestamps.

The stack also uses SQS, SNS, and S3 resources.

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Table of Contents

• Introduction
• Running Locally
  • Create a virtual environment
  • Configure the environment
    • Changes when moving to another environment
  • Install the dependencies
  • Create Sample SQS events
  • Running the App locally
• AWS Deploynment
  • Running the App as a Lambda Function
  • Testing the flow in AWS
  • Debugging Errors
• Contributing
  • Committing new code

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Introduction

As we see in this diagram, this application performs the following steps:

1. Receive a SQS event requesting a clip for a given time interval. An example of SQS event is the follow:

        {
          "Records": [
            {
              "body": "{'clipId': '1111111111111', 'retryTimestamps': [], 'cameraId': '1111111111111', 'startTimestampInMs': 1537119363000, 'endTimestampInMs': 1537119423000}",
              "receiptHandle": "MessageReceiptHandle",
              "md5OfBody": "7b270e59b47ff90a553787216d55d91d",
              "eventSourceARN": "arn:aws:sqs:us-west-1:123456789012:MyQueue",
              "eventSource": "aws:sqs",
              "awsRegion": "us-west-1",
              "messageId": "19dd0b57-b21e-4ac1-bd88-01bbb068cb78",
              "attributes": {
                "ApproximateFirstReceiveTimestamp": "1523232000001",
                "SenderId": "123456789012",
                "ApproximateReceiveCount": "1",
                "SentTimestamp": "1523232000000"
              },
              "messageAttributes": {
                "SentTimestamp": "1523232000000"
              }
            }
          ]
        }

2. Call the camera API with the endpoint /cameras/cameraID to retrieve a camera alias for the given camera id.

3. Call the camera API with the endpoint /cameras/recording/ to retrieve a list of cam rewind source files within the given time range.

Which would generate this response:

        [{
            "startDate":"2018-09-16T16:00:17.000Z",
            "endDate":"2018-09-16T16:10:17.000Z",
            "thumbLargeUrl":URL,
            "recordingUrl":URL,
            "thumbSmallUrl":URL,
            "alias":"test"
         }]

4. Retrieve the cam rewind source files from the origin S3 bucket (downloading them on disk).

5. Use ffmpeg to trim and merge clips into a single clip and to create several thumbnails.

6. If the clips are available, store them in the destination S3 bucket.

7. If the clips are not available, send a SQS message back to the queue, similar to the initial SQS, with a visibility timeout.

8. Call the camera API with endpoint /cameras/clips to update the information about the new clip and send a SNS message with the resulting metadata. An example of SNS message:

       { 
          "clipId": "1111111111111",
          "cameraId": "1111111111111",
          "startTimestampInMs": 1534305591000,
          "endTimestampInMs": 1534305611000,
          "status": "CLIP_AVAILABLE",
          "bucket": "s3-test",
          "clip": {
            "url": URL,
            "key": "/test.mp4"
          },
          "thumbnail": {
            "url": "https://url_{size}.png",
            "key": "/1111111111111/1111111111111{size}.png",
            "sizes": [300, 640, 1500, 3000]
          }
        }

Running Locally

To add new features to this application, follow these steps:

Create a virtual environment

virtualenv venv
source venv/bin/activate

Configure the environment

cp .env.sample_{env} .env
vim .env

Where these are the global variables in this file:

Constant	Definition
CLIP_DOWNLOAD_DEST	Where the clips are going to be downloaded in disk
TIMESTAMP_FORMAT	The timestamp we will be parsing from the clip name strings
OLD_FILE_FORMAT	False if the clips to be downloaded have seconds encoded in their names (new format)
SQS_RETRY_LIMIT	The limit, in seconds, of retries for CLIP PENDING (default: 15 minutes)
OUT_OF_RANGE_LIMIT	The limit, in seconds, of how back in the past clips can be retrieved (default: 3 days)
CAM_SERVICES_URL	The url where the camera services is available
CLIP_URL	The url where the clips are posted to, accordingly to the environment
RECORDINGS_URL	The url where the source recordings are retrieved.
THUMBNAIL_SIZES	List of values for which clip thumbnails need to be created
VIDEO_MAX_LEN	Maximum length allowed for a clip
S3_BUCKET_ORIGIN	AWS S3 bucket where the rewinds are available
S3_BUCKET_ORIGIN_DIR	AWS S3 'folder' where the rewinds are available
S3_BUCKET_DESTINATION	AWS S3 bucket where the clips will be upload to.
AWS_SNS_TOPIC	AWS SNS topic arn
AWS_SQS_QUEUE	AWS SQS queue arn
AWS_SQS_QUEUE_URL	AWS SQS queue url
SQS_TIMEOUT	AWS SQS invisibility timeout in seconds

Changes when moving to another environment

Whenever you move among the environments (prod, sandbox, or staging), you need to change the following variables:

Constant	Possible value
CLIP_URL	https://camclips.{ENV}.test.com
S3_BUCKET_DESTINATION	cameras-service-clips-cdn-{ENV}
AWS_SNS_TOPIC	arn:aws:sns:test_{ENV}
AWS_SQS_QUEUE	arn:aws:sqs:test-sqs-{ENV}
AWS_SQS_QUEUE_URL	https://sqs.test-sqs-{ENV}

Install the dependencies

make install

Create Sample SQS events

To create an event.json file to be tested in this application, run:

make event

Note that this command runs ./scripts/create_test_event.py considering that the camera test is up. In case it is down, you should add a valid camera to the global variables section in that script.

You can create testing event.json to test alternate flows such as:

• Clip pending (i.e. when the requested clip is within 15 minutes to the SQS message timestamp but it was not created yet):

python scripts/create_test_event.py -p

• Clip not available (i.e. when the requested clip is later than 15 minutes but within 3 days to the SQS message timestamp):

python scripts/create_test_event.py -n

• Clip out of range (i.e. when the requested clip is later than 3 days to the SQS message timestamp):

python scripts/create_test_event.py -o

Running the App locally

make invoke

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AWS Deploynment

Running the App as a Lambda Function

This creates a .zip package and deploys it to the lambda function:

make deploy

Check whether the package has the expected content:

unzip -l dist/cameras-service-generate-clip.zip

Note that this adds FFMPEG's dependencies manually and the Python dependencies are built within a Dockerfile.

Testing the flow in AWS

You can test this application flow in sandbox and/or staging environment following theses steps:

1. In the SQS dashboard, select SQS queue and click Queue action -> Send a Message.
2. Type the value for body, similarly as the a message created in event.json. For instance:

{'clipId': '111111111111','retryTimestamps': [],'cameraId': '111111111111','startTimestampInMs': 1538412898000,'endTimestampInMs': 1538413498000}

1. This should trigger the lambda function and you should see the clips and thumbnails in the environment's S3 bucket in around 20-40 seconds.

Debugging Errors

Errors will be logged in CloudWatch. To make sense of logs in the CLI, you should install saw.

For instance, to check error logs for staging in the last hour:

saw get /aws/lambda/clip-function -1h --filter error

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Contributing

Committing new code

Run unit tests with:

make test

When deploying scripts (or to report back to Github on PRs), we ensure that code follows style guidelines with:

make lint

To fix lint errors, use:

make fixlint

Update the documentation (README.md) with:

make doctoc