notes on AWS Lambda

DevOps/AWS/AWS_Lambda/Practical_walkthrough_Lambda_creation.md

@@ -25,7 +25,7 @@ Beneath this we have a code editor with the handler function with a basic boiler
 
 Next we need to add a [trigger](/DevOps/AWS/AWS_Lambda/Lambda_triggers.md) that execute the handler.
 
-We will do this using [AWS API Gateway](/DevOps/AWS/AWS_Api_Gateway.md). We select "Add trigger" from the dashboard view and input basic settings:
+We will do this using [AWS API Gateway](/DevOps/AWS/AWS_API_Gateway.md). We select "Add trigger" from the dashboard view and input basic settings:
 
 ![](/_img/api-gateway-trigger.png)
 

DevOps/AWS/AWS_SAM/AWS_SAM.md

@@ -0,0 +1,115 @@
+---
+categories:
+  - DevOps
+  - Backend
+tags: [AWS]
+---
+
+# AWS SAM
+
+SAM stands for **serverless application model**. It is a framework developed by AWS to simplify the process of building, deploying and managing serverless applications. It provides a concise syntax for defining the components of a serverless application, such as [Lambda functions](/DevOps/AWS/AWS_Lambda/Lambda_programming_model.md), [API gateway](/DevOps/AWS/AWS_API_Gateway.md) and database tables.
+
+The SAM infrastructure is defined in a YAML file which is then deployed to AWS. SAM syntax gets transformed into CloudFormation during the deployment process. (CloudFormation is a broader and more robust AWS tool for large, highly scaleable infrastructures).
+
+## Key features of SAM
+
+- Single deployment configuration
+- Integration with development tools
+- Local testing and debugging
+- Built on AWS CloudFormation
+
+## Main technologies required
+
+### Docker
+
+Whilst SAM can be used to create a deployable file for AWS it can also be run as a container for local development with Docker.
+
+### AWS CLI
+
+This is installed using Python and allows you to interact directly with AWS via the command-line.
+
+### AWS SAM CLI
+
+See [https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/install-sam-cli.html](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/install-sam-cli.html)
+
+## Setting up credentials for the AWS CLI
+
+```
+aws configure
+AWS Access Key ID [None]: AK*******
+AWS Secret Access Key [None]: ukp******
+Default region name [None]:
+Default output format [None]:
+```
+
+This information can be found in the Security Credentials section of the given [IAM](/DevOps/AWS/AWS_User_management_and_roles.md#iam) user:
+
+![](/_img/access-key-aws.png)
+
+## Starting a SAM project
+
+First create a directory for your project which will serve as the repository:
+
+```sh
+mkdir aws-sam-learning
+cd aws-sam-learning
+```
+
+Then we can use the `sam` cli to bootstrap the project:
+
+```sh
+sam init --runtime nodejs16.x
+```
+
+We can just click through and accept the basic HelloWorld Lambda.
+
+This will create the Lambda as well as an API Gateway trigger URL.
+
+### `template.yaml`
+
+This is autogenerated and details the main constituents of the project. There are lots of fields but the most important are the following:
+
+```yaml
+HelloWorldFunction:
+  Type: AWS::Serverless::Function
+  Properties:
+    CodeUri: hello-world/
+    Handler: app.lambdaHandler
+    Runtime: nodejs16.x
+    Architectures:
+      - x86_64
+    Events:
+      HelloWorld:
+        Type: Api
+        Properties:
+          Path: /hello
+          Method: get
+```
+
+This details the location of the [handler function](/DevOps/AWS/AWS_Lambda/Lambda_handler_function.md) which is contained at the path `hello-world/app.js`:
+
+```js
+exports.lambdaHandler = async (event, context) => {
+  try {
+    // const ret = await axios(url);
+    response = {
+      statusCode: 200,
+      body: JSON.stringify({
+        message: "hello world",
+        // location: ret.data.trim()
+      }),
+    };
+  } catch (err) {
+    console.log(err);
+    return err;
+  }
+
+  return response;
+};
+```
+
+It also lists the `get` event that we can use to call API Gateway and trigger the Lambda.
+
+The full template is below:
+
+![](/_img/sam-template-yaml.png)

DevOps/AWS/Developing_AWS_projects_locally.md

@@ -0,0 +1,15 @@
+---
+categories:
+  - DevOps
+tags: [AWS]
+---
+
+# Developing AWS projects locally
+
+To develop AWS projects locally the following core tools can be used to set up a local development environment that simulates AWS services:
+
+- AWS CLI
+  - Interact with AWS services from your local machine
+- AWS SDK
+  - Integrate AWS services into your given programming language and application code
+- [AWS SAM](/DevOps/AWS/AWS_SAM/AWS_SAM.md)

Electronics_and_Hardware/Analogue_circuits/Cells_and_batteries.md

@@ -6,7 +6,7 @@ tags: [physics, electricity]
 
 # Cells and batteries
 
-Cells are a [voltage source](/Electronics_and_Hardware/Analogue_circuits/Voltage.md#chemicals-cells-and-batteries) that generate a difference of potential via a positive and negative electrode separated by an electrolytic solution. The electrolytes pull free electrons from one of the materials which creates a positive charge. The other material gains the free electrons creating a negative charge.
+Cells are a [voltage source](/Electronics_and_Hardware/Analogue_circuits/Voltage.md) that generate a difference of potential via a positive and negative electrode separated by an electrolytic solution. The electrolytes pull free electrons from one of the materials which creates a positive charge. The other material gains the free electrons creating a negative charge.
 
 > A battery is a combination of two or more cells.