Autosave: 2024-11-25 07:19:28

neuron/6bd22abe-1c26-4082-9ee1-2e98738d9784/Messaging_services.md

@@ -1,19 +0,0 @@
----
-tags: [AWS]
----
-
-# AWS Messaging services
-
-## SNS
-
-> SNS: Simple Notification Service
-
-Similar to SQS but the focus is on notifications rather than messages, i.e
-events that fire when something specific happens, not just a message-send event.
-It can be used for passing notifications between applications or to persons
-through SMS, text, push notifications and email.
-
-**SNS pushes messages out to subscribers while SQS stores the messages until
-someone reads them.**
-
-Relation between SNS and SQS - typically paired aren't they.

neuron/f3ec2d6c-97a4-4a7a-9dfe-64824a6e94ae/AWS_SNS.md

@@ -0,0 +1,42 @@
+---
+tags: [AWS, SNS, SQS]
+created: Monday, November 25, 2024
+---
+
+# AWS SNS
+
+The Simple Notification Service is another form of messaging service in AWS,
+similar to [SQS](AWS_SQS.md). The key difference is that SNS pushes messages out
+to subscribers whereas SQS stores the messages until they are processed.
+
+Before a message can be sent, and SNS topic must exist. One service such as a
+lambda will _publish_ to this topic. Another service, will _subscribe_ to the
+topic and be alerted when a message is sent to it.
+
+With SNS, one message can be sent to multiple subscribers simultaneously. In
+addition there is message filtering at the subscription level so subscribers can
+choose to receive only the messages they are interested in.
+
+Many other AWS services can act as SNS subscribers. Some common examples:
+
+- SQS queues
+- Lambda functions (trigger on receipt of a message)
+- HTTP endpoints
+- Email/SMS/Push notifications to mobile apps
+
+## Combining with SQS
+
+Utilising SNS with SQS is a common pattern in serverless applications.
+
+We use SNS to decouple publishers from subscribers and then use SQS to handle
+the different subscriber tasks. This is known as the "Fanout-Queue" pattern.
+
+![SQS fanout pattern](static/sns-example.png)
+
+For example, an order is placed which results in a publication event to an SNS
+topic.
+
+Multiple systems subscribe to this topic, e.g. an inventory system, a shipping
+system and an analytics system.
+
+Each system has its own queue for processing the message.

neuron/f3ec2d6c-97a4-4a7a-9dfe-64824a6e94ae/AWS_SQS.md

@@ -50,3 +50,8 @@ to the dead letter queue (DLQ) and remove it from the main queue.
 If the DLQ reaches a certain threshold this can trigger additional handling such
 as raising an Alert in [CloudWatch](./AWS_CloudWatch.md) or other monitoring
 tool.
+
+Note that a DLQ is not a distinct entity within the SDK, it is just another SQS
+queue that is designated to store failures.
+
+See [AWS SDK Syntax](AWS_SQS_SDK.md).

neuron/f3ec2d6c-97a4-4a7a-9dfe-64824a6e94ae/AWS_SQS_SDK.md

@@ -0,0 +1,85 @@
+---
+tags: [AWS, SQS]
+created: Monday, November 25, 2024
+---
+
+# AWS SQS SDK
+
+## Initialising the SQS client
+
+```ts
+import { SQSClient } from "@aws-sdk/client-sqs";
+
+const sqs = new SQSClient({ region: "us-east-1" });
+```
+
+## Sending a message to the queue
+
+```ts
+import { SendMessageCommand } from "@aws-sdk/client-sqs";
+
+const command = new SendMessageCommand({
+  QueueUrl: queueUrl,
+  MessageBody: messageBody,
+  // Optional parameters
+  DelaySeconds: 0,
+  MessageAttributes: {
+    CustomAttribute: {
+      DataType: "String",
+      StringValue: "CustomValue",
+    },
+  },
+});
+
+return await sqs.send(command);
+```
+
+## Processing messages on the queue
+
+```ts
+import { ReceiveMessageCommand } from "@aws-sdk/client-sqs";
+
+const command = new ReceiveMessageCommand({
+  QueueUrl: queueUrl,
+  MaxNumberOfMessages: 10,
+  WaitTimeSeconds: 20, // Long polling
+  VisibilityTimeout: 30, // Time other consumers won't see this message
+});
+
+const response = await sqs.send(command);
+
+// Then do something
+
+for (const message of response.Messages || []) {
+  console.log(message);
+}
+```
+
+## Removing message from queue
+
+```ts
+import { DeleteMessageCommand } from "@aws-sdk/client-sqs";
+
+for (const message of response.Messages || []) {
+  await sqs.send(
+    new DeleteMessageCommand({
+      QueueUrl: queueUrl,
+      ReceiptHandle: message.ReceiptHandle,
+    }),
+  );
+}
+```
+
+## Query a DLQ
+
+```ts
+const checkDLQ = async (dlqUrl: string) => {
+  const command = new GetQueueAttributesCommand({
+    QueueUrl: dlqUrl,
+    AttributeNames: ["ApproximateNumberOfMessages"],
+  });
+
+  const response = await sqs.send(command);
+  return response.Attributes?.ApproximateNumberOfMessages;
+};
+```

neuron/f3ec2d6c-97a4-4a7a-9dfe-64824a6e94ae/index.md

@@ -13,16 +13,17 @@ computer science.
 
 ![not-by-ai-badge](static/not-by-ai-alternative--light.svg)
  
-**Build ID:** 6bd22abe-1c26-4082-9ee1-2e98738d9784
+**Build ID:** f3ec2d6c-97a4-4a7a-9dfe-64824a6e94ae
 
-**Published:** Sun 24 Nov 2024 10:53:17
+**Published:** Mon 25 Nov 2024 07:19:27
 
 ### Recent edits 
 
+- [[AWS_SNS]] 
+- [[AWS_SQS]] 
+- [[AWS_SQS_SDK]] 
 - [[a771a6d9_attributes_of_internet_enclosure]] 
 - [[JavaScript_module_types]] 
-- [[AWS_SQS]] 
-- [[Messaging_services]] 
 - [[0716531c_rewilding_the_internet]] 
 - [[f6564af9_AOL_and_early_internet_enclosure]] 
 - [[Bauman_quote]] 
@@ -30,10 +31,9 @@ computer science.
 - [[Pacman]] 
 - [[Passing_arguments_and_options_to_Bash_scripts]] 
 - [[Functions_in_Bash]] 
-- [[Bash_file_exists]] 
 
 
-### All notes (498) 
+### All notes (499) 
 
 - [[0716531c_rewilding_the_internet]] 
 - [[241fe1a3_the_Web_versus_modem_BBSs]] 
@@ -48,7 +48,9 @@ computer science.
 - [[AWS_CLI]] 
 - [[AWS_CloudWatch]] 
 - [[AWS_SAM_and_Docker]] 
+- [[AWS_SNS]] 
 - [[AWS_SQS]] 
+- [[AWS_SQS_SDK]] 
 - [[AWS_architecture_hierarchy]] 
 - [[Accessing_metadata_about_SQL_database]] 
 - [[Accessing_secrets_from_a_Lambda]] 
@@ -305,7 +307,6 @@ computer science.
 - [[Memory_addresses]] 
 - [[Memory_leaks]] 
 - [[Memory_versus_processor]] 
-- [[Messaging_services]] 
 - [[Middleware_in_NodeJS]] 
 - [[Mixed_and_improper_fractions]] 
 - [[Modelling_relationships_in_MongoDB]] 

zk/AWS_SNS.md

@@ -0,0 +1,42 @@
+---
+tags: [AWS, SNS, SQS]
+created: Monday, November 25, 2024
+---
+
+# AWS SNS
+
+The Simple Notification Service is another form of messaging service in AWS,
+similar to [SQS](AWS_SQS.md). The key difference is that SNS pushes messages out
+to subscribers whereas SQS stores the messages until they are processed.
+
+Before a message can be sent, and SNS topic must exist. One service such as a
+lambda will _publish_ to this topic. Another service, will _subscribe_ to the
+topic and be alerted when a message is sent to it.
+
+With SNS, one message can be sent to multiple subscribers simultaneously. In
+addition there is message filtering at the subscription level so subscribers can
+choose to receive only the messages they are interested in.
+
+Many other AWS services can act as SNS subscribers. Some common examples:
+
+- SQS queues
+- Lambda functions (trigger on receipt of a message)
+- HTTP endpoints
+- Email/SMS/Push notifications to mobile apps
+
+## Combining with SQS
+
+Utilising SNS with SQS is a common pattern in serverless applications.
+
+We use SNS to decouple publishers from subscribers and then use SQS to handle
+the different subscriber tasks. This is known as the "Fanout-Queue" pattern.
+
+![SQS fanout pattern](../img/sns-example.png)
+
+For example, an order is placed which results in a publication event to an SNS
+topic.
+
+Multiple systems subscribe to this topic, e.g. an inventory system, a shipping
+system and an analytics system.
+
+Each system has its own queue for processing the message.

zk/AWS_SQS.md

@@ -50,3 +50,8 @@ to the dead letter queue (DLQ) and remove it from the main queue.
 If the DLQ reaches a certain threshold this can trigger additional handling such
 as raising an Alert in [CloudWatch](./AWS_CloudWatch.md) or other monitoring
 tool.
+
+Note that a DLQ is not a distinct entity within the SDK, it is just another SQS
+queue that is designated to store failures.
+
+See [AWS SDK Syntax](AWS_SQS_SDK.md).

zk/AWS_SQS_SDK.md

@@ -0,0 +1,85 @@
+---
+tags: [AWS, SQS]
+created: Monday, November 25, 2024
+---
+
+# AWS SQS SDK
+
+## Initialising the SQS client
+
+```ts
+import { SQSClient } from "@aws-sdk/client-sqs";
+
+const sqs = new SQSClient({ region: "us-east-1" });
+```
+
+## Sending a message to the queue
+
+```ts
+import { SendMessageCommand } from "@aws-sdk/client-sqs";
+
+const command = new SendMessageCommand({
+  QueueUrl: queueUrl,
+  MessageBody: messageBody,
+  // Optional parameters
+  DelaySeconds: 0,
+  MessageAttributes: {
+    CustomAttribute: {
+      DataType: "String",
+      StringValue: "CustomValue",
+    },
+  },
+});
+
+return await sqs.send(command);
+```
+
+## Processing messages on the queue
+
+```ts
+import { ReceiveMessageCommand } from "@aws-sdk/client-sqs";
+
+const command = new ReceiveMessageCommand({
+  QueueUrl: queueUrl,
+  MaxNumberOfMessages: 10,
+  WaitTimeSeconds: 20, // Long polling
+  VisibilityTimeout: 30, // Time other consumers won't see this message
+});
+
+const response = await sqs.send(command);
+
+// Then do something
+
+for (const message of response.Messages || []) {
+  console.log(message);
+}
+```
+
+## Removing message from queue
+
+```ts
+import { DeleteMessageCommand } from "@aws-sdk/client-sqs";
+
+for (const message of response.Messages || []) {
+  await sqs.send(
+    new DeleteMessageCommand({
+      QueueUrl: queueUrl,
+      ReceiptHandle: message.ReceiptHandle,
+    }),
+  );
+}
+```
+
+## Query a DLQ
+
+```ts
+const checkDLQ = async (dlqUrl: string) => {
+  const command = new GetQueueAttributesCommand({
+    QueueUrl: dlqUrl,
+    AttributeNames: ["ApproximateNumberOfMessages"],
+  });
+
+  const response = await sqs.send(command);
+  return response.Attributes?.ApproximateNumberOfMessages;
+};
+```

zk/Messaging_services.md

@@ -1,19 +0,0 @@
----
-tags: [AWS]
----
-
-# AWS Messaging services
-
-## SNS
-
-> SNS: Simple Notification Service
-
-Similar to SQS but the focus is on notifications rather than messages, i.e
-events that fire when something specific happens, not just a message-send event.
-It can be used for passing notifications between applications or to persons
-through SMS, text, push notifications and email.
-
-**SNS pushes messages out to subscribers while SQS stores the messages until
-someone reads them.**
-
-Relation between SNS and SQS - typically paired aren't they.