Type the below command to run your first docker container
docker container run hello-world
$ docker container run hello-world
Hello from Docker!
This message shows that your installation appears to be working correctly.
To generate this message, Docker took the following steps:
1. The Docker client contacted the Docker daemon.
2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
(amd64)
3. The Docker daemon created a new container from that image which runs the
executable that produces the output you are currently reading.
4. The Docker daemon streamed that output to the Docker client, which sent it
to your terminal.
To try something more ambitious, you can run an Ubuntu container with:
$ docker run -it ubuntu bash
Share images, automate workflows, and more with a free Docker ID:
https://hub.docker.com/
For more examples and ideas, visit:
https://docs.docker.com/engine/userguide/
Let see what happen behind the scene
As this is my first container, docker engine tried to find an image named hello-world.
But as we just get started, there is no such image stored locally
Unable to find image 'hello-world:latest' locally
Docker engine goes to DockerHub(For the time being think DockerHub as a GitHub for Docker containers), looking for this image named hello-world
Docker is an open platform for developing, shipping and running application. Its main benefit is to package applications in containers, allowing them to be portable to any system running a Linux, Mac or Windows operating system (OS).
It follows the build once and runs anywhere approach.
Docker Engine
Docker Engine is a client-server application with these major components:
A server which is a type of long-running program called a daemon process (the dockerd command).
A REST API that specifies interfaces that programs can use to talk to the daemon and instruct it what to do.
A command line interface (CLI) client (the docker command).
The CLI uses the Docker REST API to control or interact with the Docker daemon through scripting or direct CLI commands. Many other Docker applications use the underlying API and CLI.
The daemon creates and manages Docker objects, such as images, containers, networks, and volumes.
With AWS Lambda, you can run code without provisioning or managing servers. You pay only for the compute time that you consume — there’s no charge when your code isn’t running. You can run code for virtually any type of application or backend service — all with zero administration. Just upload your code and Lambda takes care of everything required to run and scale your code with high availability. You can set up your code to automatically trigger from other AWS services or call it directly from any web or mobile app.
* Author from scratch: Which is self explanatory, i.e you are writing your own function
* Use a blueprint: Build a lambda application from sample code and configuration preset for common use cases(Provided by AWS)
* Browse serverless app repository: Deploy a sample lambda application from the AWS Serverless Application Repository(Published by other developers and AWS Patners)
Function name: HelloWorld
Runtime: Choose Python3.7 from the dropdown
Permission: For the time being choose the default permission
Click Create Function
Invoking Lambda Function
When building applications on AWS Lambda the core components are Lambda functions and event sources. An event source is the AWS service or custom application that publishes events, and a Lambda function is the custom code that processes the events
* Amazon S3 Pushes Events * AWS Lambda Pulls Events from a Kinesis Stream * HTTP API requests through API Gateway * CloudWatch Schedule Events
def lambda_handler(event, context): # TODO implement print(event) <-------- return { 'statusCode': 200, 'body': json.dumps('Hello from Lambda!') }
Add this entry, which simply means we are trying to print the event
Again save it
Let’s try to set a simple test event, Click on Test
Under Event template, search for Amazon CloudWatch
Event Name: Give your event some name and test it
Go back and this time Click on Monitoring
Click on View logs in CloudWatch
Click on the log stream and you will see the same logs you see in Lambda console
Lambda Programming Model
Lambda supports a bunch of programming languages
You write code for your Lambda function in one of the languages AWS Lambda supports. Regardless of the language you choose, there is a common pattern to writing code for a Lambda function that includes the following core concepts.
* Handler: Handler is the function AWS Lambda calls to start execution of your Lambda function, it act as an entry point.
As you can see handle start with lambda_function which is a Python Script Name and then lambda_handler which is a function and act as an entry point for event and context
Event: We already saw in the previous example where we passed the CloudWatch Event to our code
Context — AWS Lambda also passes a context object to the handler function, as the second parameter. Via this context object, your code can interact with AWS Lambda. For example, your code can find the execution time remaining before AWS Lambda terminates your Lambda function.
Logging — Your Lambda function can contain logging statements. AWS Lambda writes these logs to CloudWatch Logs.
Exceptions — Your Lambda function needs to communicate the result of the function execution to AWS Lambda. Depending on the language you author your Lambda function code, there are different ways to end a request successfully or to notify AWS Lambda an error occurred during the execution.
One more thing, I want to highlight is the timeout
You can now set the timeout value for a function to any value up to 15 minutes. When the specified timeout is reached, AWS Lambda terminates execution of your Lambda function. As a best practice, you should set the timeout value based on your expected execution time to prevent your function from running longer than intended.
Common Use case of Lambda
Terraform Code
All the steps we have performed manually. let’s try to automate it using terraform
Step1: Create your test Python function
def lambda_handler(event, context):
print ("Hello from terraform world")
return "hello from terraform world"
Now let’s zip it up
$ zip lambda.zip lambda.py
adding: lambda.py (deflated 27%)
Step2: Define your Lambda resource
resource "aws_lambda_function" "test_lambda" { filename = "lambda.zip" function_name = "lambda_handler" role = "${aws_iam_role.iam_for_lambda.arn}" handler = "lambda.lambda_handler" # The filebase64sha256() function is available in Terraform 0.11.12 and later # For Terraform 0.11.11 and earlier, use the base64sha256() function and the file() function: # source_code_hash = "${base64sha256(file("lambda_function_payload.zip"))}" source_code_hash = "${base64sha256("lambda.zip")}" runtime = "python2.7" }
filename: Is the name of the file, you zipped in the previous step
function name: Is the name of the function you defined in your python code
role: IAM role attached to the Lambda Function. This governs both who / what can invoke your Lambda Function, as well as what resources our Lambda Function has access to
handler: Function entry point in our code(python code filename.method name) (filename: lambda.py we don’t need to include file extension) and (lambda function is lambda_handler def lambda_handler(event, context))
source_code_hash: Used to trigger updates. Must be set to a base64-encoded SHA256 hash of the package file specified with either filename or s3_key. The usual way to set this is filebase64sha256("file.zip") (Terraform 0.11.12 and later) or base64sha256(file("file.zip")) (Terraform 0.11.11 and earlier), where “file.zip” is the local filename of the lambda function source archive.
Step4: Terraform Init: Initialize a Terraform working directory, containing Terraform configuration files. This is the first command that should be run after writing a new Terraform configuration or cloning an existing one from version control.
$ terraform init
Initializing provider plugins...
- Checking for available provider plugins on https://releases.hashicorp.com...
- Downloading plugin for provider "aws" (2.23.0)...
The following providers do not have any version constraints in configuration,
so the latest version was installed.
To prevent automatic upgrades to new major versions that may contain breaking
changes, it is recommended to add version = "..." constraints to the
corresponding provider blocks in configuration, with the constraint strings
suggested below.
* provider.aws: version = "~> 2.23"
Terraform has been successfully initialized!
You may now begin working with Terraform. Try running "terraform plan" to see
any changes that are required for your infrastructure. All Terraform commands
should now work.
If you ever set or change modules or backend configuration for Terraform,
rerun this command to reinitialize your working directory. If you forget, other
commands will detect it and remind you to do so if necessary.
Step5: Terraform plan: The terraform plan command is used to create an execution plan. Terraform performs a refresh, unless explicitly disabled, and then determines what actions are necessary to achieve the desired state specified in the configuration files.
$ terraform plan
Refreshing Terraform state in-memory prior to plan...
The refreshed state will be used to calculate this plan, but will not be
persisted to local or remote state storage.
------------------------------------------------------------------------
An execution plan has been generated and is shown below.
Resource actions are indicated with the following symbols:
+ create
Terraform will perform the following actions:
+ aws_cloudwatch_log_group.example
id: <computed>
arn: <computed>
name: "/aws/lambda/lambda_handler"
retention_in_days: "14"
+ aws_iam_policy.lambda_logging
id: <computed>
arn: <computed>
description: "IAM policy for logging from a lambda"
name: "lambda_logging"
path: "/"
policy: "{\n \"Version\": \"2012-10-17\",\n \"Statement\": [\n {\n \"Action\": [\n \"logs:CreateLogStream\",\n \"logs:PutLogEvents\"\n ],\n \"Resource\": \"arn:aws:logs:*:*:*\",\n \"Effect\": \"Allow\"\n }\n ]\n}\n"
+ aws_iam_role.iam_for_lambda
id: <computed>
arn: <computed>
assume_role_policy: "{\n \"Version\": \"2012-10-17\",\n \"Statement\": [\n {\n \"Action\": \"sts:AssumeRole\",\n \"Principal\": {\n \"Service\": \"lambda.amazonaws.com\"\n },\n \"Effect\": \"Allow\",\n \"Sid\": \"\"\n }\n ]\n}\n"
create_date: <computed>
force_detach_policies: "false"
max_session_duration: "3600"
name: "iam_for_lambda"
path: "/"
unique_id: <computed>
+ aws_iam_role_policy_attachment.lambda_logs
id: <computed>
policy_arn: "${aws_iam_policy.lambda_logging.arn}"
role: "iam_for_lambda"
+ aws_lambda_function.test_lambda
id: <computed>
arn: <computed>
filename: "lambda.zip"
function_name: "lambda_handler"
handler: "lambda.lambda_handler"
invoke_arn: <computed>
last_modified: <computed>
memory_size: "128"
publish: "false"
qualified_arn: <computed>
reserved_concurrent_executions: "-1"
role: "${aws_iam_role.iam_for_lambda.arn}"
runtime: "python2.7"
source_code_hash: "Gpu07NPcj26NrKv0Ne6BbZkfDRuM3ozHHqCFUWH9Sqg="
source_code_size: <computed>
timeout: "3"
tracing_config.#: <computed>
version: <computed>
Plan: 5 to add, 0 to change, 0 to destroy.
------------------------------------------------------------------------
Note: You didn't specify an "-out" parameter to save this plan, so Terraform
can't guarantee that exactly these actions will be performed if
"terraform apply" is subsequently run.
Step6: terraform apply: The terraform apply command is used to apply the changes required to reach the desired state of the configuration, or the pre-determined set of actions generated by a terraform plan execution plan.
$ terraform apply
An execution plan has been generated and is shown below.
Resource actions are indicated with the following symbols:
+ create
Terraform will perform the following actions:
+ aws_cloudwatch_log_group.example
id: <computed>
arn: <computed>
name: "/aws/lambda/lambda_handler"
retention_in_days: "14"
+ aws_iam_policy.lambda_logging
id: <computed>
arn: <computed>
description: "IAM policy for logging from a lambda"
name: "lambda_logging"
path: "/"
policy: "{\n \"Version\": \"2012-10-17\",\n \"Statement\": [\n {\n \"Action\": [\n \"logs:CreateLogStream\",\n \"logs:PutLogEvents\"\n ],\n \"Resource\": \"arn:aws:logs:*:*:*\",\n \"Effect\": \"Allow\"\n }\n ]\n}\n"
+ aws_iam_role.iam_for_lambda
id: <computed>
arn: <computed>
assume_role_policy: "{\n \"Version\": \"2012-10-17\",\n \"Statement\": [\n {\n \"Action\": \"sts:AssumeRole\",\n \"Principal\": {\n \"Service\": \"lambda.amazonaws.com\"\n },\n \"Effect\": \"Allow\",\n \"Sid\": \"\"\n }\n ]\n}\n"
create_date: <computed>
force_detach_policies: "false"
max_session_duration: "3600"
name: "iam_for_lambda"
path: "/"
unique_id: <computed>
+ aws_iam_role_policy_attachment.lambda_logs
id: <computed>
policy_arn: "${aws_iam_policy.lambda_logging.arn}"
role: "iam_for_lambda"
+ aws_lambda_function.test_lambda
id: <computed>
arn: <computed>
filename: "lambda.zip"
function_name: "lambda_handler"
handler: "lambda.lambda_handler"
invoke_arn: <computed>
last_modified: <computed>
memory_size: "128"
publish: "false"
qualified_arn: <computed>
reserved_concurrent_executions: "-1"
role: "${aws_iam_role.iam_for_lambda.arn}"
runtime: "python2.7"
source_code_hash: "Gpu07NPcj26NrKv0Ne6BbZkfDRuM3ozHHqCFUWH9Sqg="
source_code_size: <computed>
timeout: "3"
tracing_config.#: <computed>
version: <computed>
Plan: 5 to add, 0 to change, 0 to destroy.
Do you want to perform these actions?
Terraform will perform the actions described above.
Only 'yes' will be accepted to approve.
Enter a value: yes
aws_iam_policy.lambda_logging: Creating...
arn: "" => "<computed>"
description: "" => "IAM policy for logging from a lambda"
name: "" => "lambda_logging"
path: "" => "/"
policy: "" => "{\n \"Version\": \"2012-10-17\",\n \"Statement\": [\n {\n \"Action\": [\n \"logs:CreateLogStream\",\n \"logs:PutLogEvents\"\n ],\n \"Resource\": \"arn:aws:logs:*:*:*\",\n \"Effect\": \"Allow\"\n }\n ]\n}\n"
aws_iam_role.iam_for_lambda: Creating...
arn: "" => "<computed>"
assume_role_policy: "" => "{\n \"Version\": \"2012-10-17\",\n \"Statement\": [\n {\n \"Action\": \"sts:AssumeRole\",\n \"Principal\": {\n \"Service\": \"lambda.amazonaws.com\"\n },\n \"Effect\": \"Allow\",\n \"Sid\": \"\"\n }\n ]\n}\n"
create_date: "" => "<computed>"
force_detach_policies: "" => "false"
max_session_duration: "" => "3600"
name: "" => "iam_for_lambda"
path: "" => "/"
unique_id: "" => "<computed>"
aws_iam_policy.lambda_logging: Still creating... (10s elapsed)
aws_iam_role.iam_for_lambda: Still creating... (10s elapsed)
aws_iam_role.iam_for_lambda: Creation complete after 10s (ID: iam_for_lambda)
aws_lambda_function.test_lambda: Creating...
arn: "" => "<computed>"
filename: "" => "lambda.zip"
function_name: "" => "lambda_handler"
handler: "" => "lambda.lambda_handler"
invoke_arn: "" => "<computed>"
last_modified: "" => "<computed>"
memory_size: "" => "128"
publish: "" => "false"
qualified_arn: "" => "<computed>"
reserved_concurrent_executions: "" => "-1"
role: "" => "arn:aws:iam::XXXXXX:role/iam_for_lambda"
runtime: "" => "python2.7"
source_code_hash: "" => "Gpu07NPcj26NrKv0Ne6BbZkfDRuM3ozHHqCFUWH9Sqg="
source_code_size: "" => "<computed>"
timeout: "" => "3"
tracing_config.#: "" => "<computed>"
version: "" => "<computed>"
aws_iam_policy.lambda_logging: Creation complete after 11s (ID: arn:aws:iam::355622012945:policy/lambda_logging)
aws_iam_role_policy_attachment.lambda_logs: Creating...
policy_arn: "" => "arn:aws:iam::XXXXXX:policy/lambda_logging"
role: "" => "iam_for_lambda"
aws_iam_role_policy_attachment.lambda_logs: Creation complete after 0s (ID: iam_for_lambda-20190814010350932300000001)
aws_lambda_function.test_lambda: Still creating... (10s elapsed)
aws_lambda_function.test_lambda: Still creating... (20s elapsed)
aws_lambda_function.test_lambda: Still creating... (30s elapsed)
aws_lambda_function.test_lambda: Still creating... (40s elapsed)
aws_lambda_function.test_lambda: Creation complete after 41s (ID: lambda_handler)
aws_cloudwatch_log_group.example: Creating...
arn: "" => "<computed>"
name: "" => "/aws/lambda/lambda_handler"
retention_in_days: "" => "14"
aws_cloudwatch_log_group.example: Still creating... (10s elapsed)
aws_cloudwatch_log_group.example: Creation complete after 11s (ID: /aws/lambda/lambda_handler)
Apply complete! Resources: 5 added, 0 changed, 0 destroyed.
