Add day 85 - Queues Workers and Tasks

Signed-off-by: Alistair Hey <alistair@heyal.co.uk>

2023.md

@@ -156,8 +156,8 @@ Or contact us via Twitter, my handle is [@MichaelCade1](https://twitter.com/Mich
 
 ### Engineering for Day 2 Ops
 
-- [✔] 👷🏻‍♀️ 84 > [Writing an API - What is an API?](2023/day84.md)
-- [] 👷🏻‍♀️ 85 > [](2023/day85.md)
+- [] 👷🏻‍♀️ 84 > [Writing an API - What is an API?](2023/day84.md)
+- [] 👷🏻‍♀️ 85 > [Queues, Queue workers and Tasks (Asynchronous architecture)](2023/day85.md)
 - [] 👷🏻‍♀️ 86 > [](2023/day86.md)
 - [] 👷🏻‍♀️ 87 > [](2023/day87.md)
 - [] 👷🏻‍♀️ 88 > [](2023/day88.md)

2023/day2-ops-code/async/generator/Dockerfile

@@ -0,0 +1,17 @@
+# Set the base image to use
+FROM golang:1.17-alpine
+
+# Set the working directory inside the container
+WORKDIR /app
+
+# Copy the source code into the container
+COPY . .
+
+# Build the Go application
+RUN go build -o main .
+
+# Expose the port that the application will run on
+EXPOSE 8080
+
+# Define the command that will run when the container starts
+CMD ["/app/main"]

2023/day2-ops-code/async/generator/go.mod

@@ -0,0 +1,17 @@
+module main
+
+go 1.20
+
+require (
+	github.com/go-sql-driver/mysql v1.7.0
+	github.com/nats-io/nats.go v1.24.0
+)
+
+require (
+	github.com/golang/protobuf v1.5.3 // indirect
+	github.com/nats-io/nats-server/v2 v2.9.15 // indirect
+	github.com/nats-io/nkeys v0.3.0 // indirect
+	github.com/nats-io/nuid v1.0.1 // indirect
+	golang.org/x/crypto v0.6.0 // indirect
+	google.golang.org/protobuf v1.30.0 // indirect
+)

2023/day2-ops-code/async/generator/go.sum

@@ -0,0 +1,32 @@
+github.com/go-sql-driver/mysql v1.7.0 h1:ueSltNNllEqE3qcWBTD0iQd3IpL/6U+mJxLkazJ7YPc=
+github.com/go-sql-driver/mysql v1.7.0/go.mod h1:OXbVy3sEdcQ2Doequ6Z5BW6fXNQTmx+9S1MCJN5yJMI=
+github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
+github.com/golang/protobuf v1.5.3 h1:KhyjKVUg7Usr/dYsdSqoFveMYd5ko72D+zANwlG1mmg=
+github.com/golang/protobuf v1.5.3/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
+github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/klauspost/compress v1.16.0 h1:iULayQNOReoYUe+1qtKOqw9CwJv3aNQu8ivo7lw1HU4=
+github.com/minio/highwayhash v1.0.2 h1:Aak5U0nElisjDCfPSG79Tgzkn2gl66NxOMspRrKnA/g=
+github.com/nats-io/jwt/v2 v2.3.0 h1:z2mA1a7tIf5ShggOFlR1oBPgd6hGqcDYsISxZByUzdI=
+github.com/nats-io/nats-server/v2 v2.9.15 h1:MuwEJheIwpvFgqvbs20W8Ish2azcygjf4Z0liVu2I4c=
+github.com/nats-io/nats-server/v2 v2.9.15/go.mod h1:QlCTy115fqpx4KSOPFIxSV7DdI6OxtZsGOL1JLdeRlE=
+github.com/nats-io/nats.go v1.24.0 h1:CRiD8L5GOQu/DcfkmgBcTTIQORMwizF+rPk6T0RaHVQ=
+github.com/nats-io/nats.go v1.24.0/go.mod h1:dVQF+BK3SzUZpwyzHedXsvH3EO38aVKuOPkkHlv5hXA=
+github.com/nats-io/nkeys v0.3.0 h1:cgM5tL53EvYRU+2YLXIK0G2mJtK12Ft9oeooSZMA2G8=
+github.com/nats-io/nkeys v0.3.0/go.mod h1:gvUNGjVcM2IPr5rCsRsC6Wb3Hr2CQAm08dsxtV6A5y4=
+github.com/nats-io/nuid v1.0.1 h1:5iA8DT8V7q8WK2EScv2padNa/rTESc1KdnPw4TC2paw=
+github.com/nats-io/nuid v1.0.1/go.mod h1:19wcPz3Ph3q0Jbyiqsd0kePYG7A95tJPxeL+1OSON2c=
+golang.org/x/crypto v0.0.0-20210314154223-e6e6c4f2bb5b/go.mod h1:T9bdIzuCu7OtxOm1hfPfRQxPLYneinmdGuTeoZ9dtd4=
+golang.org/x/crypto v0.6.0 h1:qfktjS5LUO+fFKeJXZ+ikTRijMmljikvG68fpMMruSc=
+golang.org/x/crypto v0.6.0/go.mod h1:OFC/31mSvZgRz0V1QTNCzfAI1aIRzbiufJtkMIlEp58=
+golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.5.0 h1:MUK/U/4lj1t1oPg0HfuXDN/Z1wv31ZJ/YcPiGccS4DU=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
+golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/time v0.3.0 h1:rg5rLMjNzMS1RkNLzCG38eapWhnYLFYXDXj2gOlr8j4=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
+google.golang.org/protobuf v1.26.0/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=
+google.golang.org/protobuf v1.30.0 h1:kPPoIgf3TsEvrm0PFe15JQ+570QVxYzEvvHqChK+cng=
+google.golang.org/protobuf v1.30.0/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=

2023/day2-ops-code/async/generator/main.go

@@ -0,0 +1,100 @@
+package main
+
+import (
+	"database/sql"
+	"fmt"
+	_ "github.com/go-sql-driver/mysql"
+	nats "github.com/nats-io/nats.go"
+	"math/rand"
+	"time"
+)
+
+func generateAndStoreString() (string, error) {
+	// Connect to the database
+	db, err := sql.Open("mysql", "root:password@tcp(mysql:3306)/mysql")
+	if err != nil {
+		return "", err
+	}
+	defer db.Close()
+
+	// Generate a random string
+	// Define a string of characters to use
+	characters := "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+
+	// Generate a random string of length 10
+	randomString := make([]byte, 64)
+	for i := range randomString {
+		randomString[i] = characters[rand.Intn(len(characters))]
+	}
+
+	// Insert the random number into the database
+	_, err = db.Exec("INSERT INTO generator_async(random_string) VALUES(?)", string(randomString))
+	if err != nil {
+		return "", err
+	}
+
+	fmt.Printf("Random string %s has been inserted into the database\n", string(randomString))
+	return string(randomString), nil
+}
+
+func main() {
+	err := createGeneratordb()
+	if err != nil {
+		panic(err.Error())
+	}
+
+	nc, _ := nats.Connect("nats://my-nats:4222")
+	defer nc.Close()
+
+	nc.Subscribe("generator", func(msg *nats.Msg) {
+		s, err := generateAndStoreString()
+		if err != nil {
+			print(err)
+		}
+		nc.Publish("generator_reply", []byte(s))
+		nc.Publish("confirmation", []byte(s))
+	})
+
+	nc.Subscribe("confirmation_reply", func(msg *nats.Msg) {
+		stringReceived(string(msg.Data))
+	})
+	// Subscribe to the queue
+	// when a message comes in call generateAndStoreString() then put the string on the
+	// reply queue. also add a message onto the confirmation queue
+
+	// subscribe to the confirmation reply queue
+	// when a message comes in call
+
+	for {
+		time.Sleep(1 * time.Second)
+	}
+
+}
+
+func createGeneratordb() error {
+	db, err := sql.Open("mysql", "root:password@tcp(mysql:3306)/mysql")
+	if err != nil {
+		return err
+	}
+	defer db.Close()
+
+	// try to create a table for us
+	_, err = db.Exec("CREATE TABLE IF NOT EXISTS generator_async(random_string VARCHAR(100), seen BOOLEAN, requested BOOLEAN)")
+
+	return err
+}
+
+func stringReceived(input string) {
+
+	// Connect to the database
+	db, err := sql.Open("mysql", "root:password@tcp(mysql:3306)/mysql")
+	if err != nil {
+		print(err)
+	}
+	defer db.Close()
+
+	_, err = db.Exec("UPDATE generator_async SET requested = true WHERE random_string = ?", input)
+	if err != nil {
+		print(err)
+	}
+}

2023/day2-ops-code/async/k8s.yaml

@@ -0,0 +1,69 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: requestor
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: requestor
+  template:
+    metadata:
+      labels:
+        app: requestor
+    spec:
+      containers:
+        - name: requestor
+          image: heyal/requestor:async
+          imagePullPolicy: Always
+          ports:
+            - containerPort: 8080
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: requestor-service
+spec:
+  selector:
+    app: requestor
+  ports:
+    - name: http
+      protocol: TCP
+      port: 8080
+      targetPort: 8080
+  type: ClusterIP
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: generator
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: generator
+  template:
+    metadata:
+      labels:
+        app: generator
+    spec:
+      containers:
+        - name: generator
+          image: heyal/generator:async
+          imagePullPolicy: Always
+          ports:
+            - containerPort: 8080
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: generator-service
+spec:
+  selector:
+    app: generator
+  ports:
+    - name: http
+      protocol: TCP
+      port: 8080
+      targetPort: 8080
+  type: ClusterIP

2023/day2-ops-code/async/requestor/Dockerfile

@@ -0,0 +1,17 @@
+# Set the base image to use
+FROM golang:1.17-alpine
+
+# Set the working directory inside the container
+WORKDIR /app
+
+# Copy the source code into the container
+COPY . .
+
+# Build the Go application
+RUN go build -o main .
+
+# Expose the port that the application will run on
+EXPOSE 8080
+
+# Define the command that will run when the container starts
+CMD ["/app/main"]

2023/day2-ops-code/async/requestor/go.mod

@@ -0,0 +1,17 @@
+module main
+
+go 1.20
+
+require (
+	github.com/go-sql-driver/mysql v1.7.0
+	github.com/nats-io/nats.go v1.24.0
+)
+
+require (
+	github.com/golang/protobuf v1.5.3 // indirect
+	github.com/nats-io/nats-server/v2 v2.9.15 // indirect
+	github.com/nats-io/nkeys v0.3.0 // indirect
+	github.com/nats-io/nuid v1.0.1 // indirect
+	golang.org/x/crypto v0.6.0 // indirect
+	google.golang.org/protobuf v1.30.0 // indirect
+)

2023/day2-ops-code/async/requestor/go.sum

@@ -0,0 +1,32 @@
+github.com/go-sql-driver/mysql v1.7.0 h1:ueSltNNllEqE3qcWBTD0iQd3IpL/6U+mJxLkazJ7YPc=
+github.com/go-sql-driver/mysql v1.7.0/go.mod h1:OXbVy3sEdcQ2Doequ6Z5BW6fXNQTmx+9S1MCJN5yJMI=
+github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
+github.com/golang/protobuf v1.5.3 h1:KhyjKVUg7Usr/dYsdSqoFveMYd5ko72D+zANwlG1mmg=
+github.com/golang/protobuf v1.5.3/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
+github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/klauspost/compress v1.16.0 h1:iULayQNOReoYUe+1qtKOqw9CwJv3aNQu8ivo7lw1HU4=
+github.com/minio/highwayhash v1.0.2 h1:Aak5U0nElisjDCfPSG79Tgzkn2gl66NxOMspRrKnA/g=
+github.com/nats-io/jwt/v2 v2.3.0 h1:z2mA1a7tIf5ShggOFlR1oBPgd6hGqcDYsISxZByUzdI=
+github.com/nats-io/nats-server/v2 v2.9.15 h1:MuwEJheIwpvFgqvbs20W8Ish2azcygjf4Z0liVu2I4c=
+github.com/nats-io/nats-server/v2 v2.9.15/go.mod h1:QlCTy115fqpx4KSOPFIxSV7DdI6OxtZsGOL1JLdeRlE=
+github.com/nats-io/nats.go v1.24.0 h1:CRiD8L5GOQu/DcfkmgBcTTIQORMwizF+rPk6T0RaHVQ=
+github.com/nats-io/nats.go v1.24.0/go.mod h1:dVQF+BK3SzUZpwyzHedXsvH3EO38aVKuOPkkHlv5hXA=
+github.com/nats-io/nkeys v0.3.0 h1:cgM5tL53EvYRU+2YLXIK0G2mJtK12Ft9oeooSZMA2G8=
+github.com/nats-io/nkeys v0.3.0/go.mod h1:gvUNGjVcM2IPr5rCsRsC6Wb3Hr2CQAm08dsxtV6A5y4=
+github.com/nats-io/nuid v1.0.1 h1:5iA8DT8V7q8WK2EScv2padNa/rTESc1KdnPw4TC2paw=
+github.com/nats-io/nuid v1.0.1/go.mod h1:19wcPz3Ph3q0Jbyiqsd0kePYG7A95tJPxeL+1OSON2c=
+golang.org/x/crypto v0.0.0-20210314154223-e6e6c4f2bb5b/go.mod h1:T9bdIzuCu7OtxOm1hfPfRQxPLYneinmdGuTeoZ9dtd4=
+golang.org/x/crypto v0.6.0 h1:qfktjS5LUO+fFKeJXZ+ikTRijMmljikvG68fpMMruSc=
+golang.org/x/crypto v0.6.0/go.mod h1:OFC/31mSvZgRz0V1QTNCzfAI1aIRzbiufJtkMIlEp58=
+golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.5.0 h1:MUK/U/4lj1t1oPg0HfuXDN/Z1wv31ZJ/YcPiGccS4DU=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
+golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/time v0.3.0 h1:rg5rLMjNzMS1RkNLzCG38eapWhnYLFYXDXj2gOlr8j4=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
+google.golang.org/protobuf v1.26.0/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=
+google.golang.org/protobuf v1.30.0 h1:kPPoIgf3TsEvrm0PFe15JQ+570QVxYzEvvHqChK+cng=
+google.golang.org/protobuf v1.30.0/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=

2023/day2-ops-code/async/requestor/main.go

@@ -0,0 +1,108 @@
+package main
+
+import (
+	"database/sql"
+	"errors"
+	"fmt"
+	_ "github.com/go-sql-driver/mysql"
+	nats "github.com/nats-io/nats.go"
+	"time"
+)
+
+func storeString(input string) error {
+	// Connect to the database
+	db, err := sql.Open("mysql", "root:password@tcp(mysql:3306)/mysql")
+	defer db.Close()
+	// Insert the random number into the database
+	_, err = db.Exec("INSERT INTO requestor_async(random_string) VALUES(?)", input)
+	if err != nil {
+		return err
+	}
+
+	fmt.Printf("Random string %s has been inserted into the database\n", input)
+	return nil
+}
+
+func getStringFromDB(input string) error {
+	// see if the string exists in the db, if so return nil
+	// if not, return an error
+	db, err := sql.Open("mysql", "root:password@tcp(mysql:3306)/mysql")
+	defer db.Close()
+	result, err := db.Query("SELECT * FROM requestor_async WHERE random_string = ?", input)
+	if err != nil {
+		return err
+	}
+
+	for result.Next() {
+		var randomString string
+		err = result.Scan(&randomString)
+		if err != nil {
+			return err
+		}
+		if randomString == input {
+			return nil
+		}
+	}
+
+	return errors.New("string not found")
+}
+
+func main() {
+
+	err := createRequestordb()
+	if err != nil {
+		panic(err.Error())
+	}
+	// setup a goroutine loop calling the generator every minute, saving the result in the DB
+
+	nc, _ := nats.Connect("nats://my-nats:4222")
+	defer nc.Close()
+
+	ticker := time.NewTicker(60 * time.Second)
+	quit := make(chan struct{})
+	go func() {
+		for {
+			select {
+			case <-ticker.C:
+				nc.Publish("generator", []byte(""))
+			case <-quit:
+				ticker.Stop()
+				return
+			}
+		}
+	}()
+
+	nc.Subscribe("generator_reply", func(msg *nats.Msg) {
+		err := storeString(string(msg.Data))
+		if err != nil {
+			print(err)
+		}
+	})
+
+	nc.Subscribe("confirmation", func(msg *nats.Msg) {
+		err := getStringFromDB(string(msg.Data))
+		if err != nil {
+			print(err)
+		}
+		nc.Publish("confirmation_reply", []byte(string(msg.Data)))
+	})
+	// create a goroutine here to listen for messages on the queue to check, see if we have them
+
+	for {
+		time.Sleep(10 * time.Second)
+	}
+
+}
+
+func createRequestordb() error {
+	db, err := sql.Open("mysql", "root:password@tcp(mysql:3306)/mysql")
+	if err != nil {
+		return err
+	}
+	defer db.Close()
+
+	// try to create a table for us
+	_, err = db.Exec("CREATE TABLE IF NOT EXISTS requestor_async(random_string VARCHAR(100))")
+
+	return err
+}

2023/day2-ops-code/buildpush.sh

@@ -0,0 +1,2 @@
+docker build ./async/requestor/ -f async/requestor/Dockerfile -t heyal/requestor:async && docker push heyal/requestor:async
+docker build ./async/generator/ -f async/generator/Dockerfile -t heyal/generator:async&& docker push heyal/generator:async

2023/day85.md

@@ -0,0 +1,62 @@
+# Queues, Queue workers and Tasks (Asynchronous architecture)
+Yesterday we looked at how we can use HTTP based APIs for communication between services. This works well until you need
+to scale, release a new version or one of your services goes down. Then we start to see the calling service fail because
+it’s dependency is not working as expected. We have tightly coupled our two services, one can’t work without the other.
+
+There are many ways to solve this problem, a light touch approach for existing applications is to use something called a
+circuit breaker to buffer failures and retry until we get a successful response. This is explained well in this blog
+by [Martin Fowler](https://martinfowler.com/bliki/CircuitBreaker.html). However, this is synchronous, if we were to wrap
+our calls in a circuit breaker we would start to block processes and our user could see a slowdown in response times.
+
+Additionally, we can’t scale our applications using this approach, the way that the code is currently written every
+instance of our `generator` api would be asking
+the `requestor for confirmation of receiving the string. This won’t scale well when we move to having 2, 5, 10, or 100 instances running. We would quickly see the `
+requestor` being overwhelmed with requests from the 100 generator applications.
+
+There is a way to solve these problems which is to use Queues. This is a shift in thinking to using an asynchronous
+approach to solving our problem. This can work well when the responses don’t need to be immediate between applications.
+In this case it doesn't matter if we add some delay in the requests between the applications. As long as the data
+eventually flows between them we are happy.
+
+![Queues, producers and Consumers](./images/day84-queues.png)
+(https://dashbird.io/knowledge-base/well-architected/queue-and-asynchronous-processing/)
+
+In the drawing above we can see how we can add a Queue in between our applications and the Queue stores the intent of
+the message across the bridge. If the Consumer was to fail and stop reacting messages then, providing our Queue software
+has sufficient storage, the messages to the consumer would still “succeed” as far as the producer is concerned.
+
+This is a powerful pattern that isolates components of a system from each other and limits the blast radius of failure.
+It does however add complexity. The Consumer and Producer must share a common understanding of the shape of a message
+otherwise the Consumer will be unable to act on the message.
+
+We are going to implement a Queue in between our two applications in our data flows.
+
+By the end of the section we will have the following data flows
+
+Requestor (asks for a random string) → Queue → Generator (gets the message, generates a string and passes it back to the
+Requestor on another Queue) → Requestor (gets the string back on a queue and stores it, then sends a message to the
+queue saying it has received it) → Queue → Generator (marks that the message was received)
+
+The last section here, where the Generator needs to know if the Requestor got the message is a simplification of a real
+process where an application may pass back an enriched data record or some further information but it allows us to have
+a simple two way communication.
+
+Can you see how by the end of this section we will be able to stop, scale, deploy or modify each of the two components
+without the other needing to know?
+
+## Modifying our application
+
+We are now going to modify our app to fit the model described above. Where we previously made a HTTP api call to our
+partner app we are now going to place a message on a named queue and then subscribe to the corresponding response
+queues.
+
+Finally we are going to stop using HTTP endpoints to listen for requests, we are now subscribing to queues and waiting
+for messages before we perform any work.
+
+I have picked [NATSio](https://nats.io/) as the queue technology as I have worked with it previously and it’s very easy
+to set up and use.
+
+Head over to the 2023/day2-ops-code/README.md to see how to deploy day 2's application.
+
+It sends messages to a queue and then waits for a response. The response is a message on a different queue. The message
+contains the data that we are interested in.