gh-2: adds load balancing example

code/tic-tac-tow-service/README.md

@@ -21,4 +21,14 @@ psql -U dbuser -d db
   * `\h` - show help. 
   * `\d <table>` - show table.
   * `select ... ;` - execute query.
-  * `\q` - quit `psql`.
+  * `\q` - quit `psql`.
+
+* Start the full composition
+```
+./gradlew composeUp
+```
+
+* Loop curl
+```
+while true; do curl -w "\n" http://localhost:8080/status/hostname; done
+```

code/tic-tac-tow-service/build.gradle.kts

@@ -59,6 +59,14 @@ tasks.withType<Test> {
 	useJUnitPlatform()
 }
 
+task<Copy>("extractUberJar") {
+    dependsOn("assemble")
+    // opens the JAR containing everything...
+    from(zipTree("$buildDir/libs/${rootProject.name}-$version.jar"))
+    // ... into the 'build/dependency' folder
+    into("build/dependency")
+}
+
 task<Exec>("dbTestsUp") {
     commandLine("docker-compose", "up", "-d", "--build", "--force-recreate", "db-tests")
 }
@@ -72,6 +80,11 @@ task<Exec>("dbTestsDown") {
     commandLine("docker-compose", "down")
 }
 
+task<Exec>("composeUp") {
+    commandLine("docker-compose", "up", "--build", "--force-recreate")
+    dependsOn("extractUberJar")
+}
+
 // from https://pinterest.github.io/ktlint/install/integrations/#custom-gradle-integration-with-kotlin-dsl
 val outputDir = "${project.buildDir}/reports/ktlint/"
 val inputFiles = project.fileTree(mapOf("dir" to "src", "include" to "**/*.kt"))
@@ -91,4 +104,4 @@ tasks.named("check") {
 	dependsOn(ktlintCheck)
     dependsOn("dbTestsWait")
     finalizedBy("dbTestsDown")
-}
+}

code/tic-tac-tow-service/docker-compose.yml

@@ -1,7 +1,9 @@
 version: "3.3"
 services:
+  # The service running the DB
   db-tests:
     container_name: db-tests
+    hostname: db-tests
     build:
       context: .
       dockerfile: ./tests/Dockerfile-db-test
@@ -10,4 +12,62 @@ services:
       - POSTGRES_PASSWORD=changeit
       - POSTGRES_DB=db
     ports:
-      - 5432:5432
+      - 5432:5432
+
+  # spring-service-1 and spring-service-2 are used to illustrate scenarios with a fixed number of servers
+  # with static and well know names.
+  spring-service-1:
+    container_name: spring-service-1
+    hostname: spring-service-1
+    build:
+      context: .
+      dockerfile: ./tests/Dockerfile-spring
+    environment:
+      PORT: 8081
+      POSTGRES_URI: "jdbc:postgresql://db-tests:5432/db?user=dbuser&password=changeit"
+    ports:
+      - 8081:8081
+
+  spring-service-2:
+    container_name: spring-service-2
+    hostname: spring-service-2
+    build:
+      context: .
+      dockerfile: ./tests/Dockerfile-spring
+    environment:
+      PORT: 8082
+      POSTGRES_URI: "jdbc:postgresql://db-tests:5432/db?user=dbuser&password=changeit"
+    ports:
+      - 8082:8082
+
+  # spring-service is used to illustrate scenario with a dynamic number of servers
+  # without static and well know names.
+  # We will use docker compose scaling to create multiple instances of this service
+  spring-service:
+    build:
+      context: .
+      dockerfile: ./tests/Dockerfile-spring
+    environment:
+      PORT: 8080
+      POSTGRES_URI: "jdbc:postgresql://db-tests:5432/db?user=dbuser&password=changeit"
+
+  # The service running the load-balancer
+  nginx:
+    container_name: nginx
+    image: nginx
+    ports:
+      - 8080:8080
+      - 8088:8088
+    volumes:
+      - ./tests/nginx:/etc/nginx
+    depends_on:
+      - spring-service-1
+      - spring-service-2
+
+  # Just a machine running ubuntu, with 'dig' installed so that we can observe the docker compose environment.
+  ubuntu:
+    container_name: ubuntu
+    build:
+      context: .
+      dockerfile: ./tests/Dockerfile-ubuntu
+    tty: true

code/tic-tac-tow-service/src/main/kotlin/pt/isel/daw/tictactow/TicTacTowApplication.kt

@@ -1,7 +1,10 @@
 package pt.isel.daw.tictactow
 
 import org.jdbi.v3.core.Jdbi
+import org.postgresql.PGProperty
 import org.postgresql.ds.PGSimpleDataSource
+import org.slf4j.Logger
+import org.slf4j.LoggerFactory
 import org.springframework.boot.autoconfigure.SpringBootApplication
 import org.springframework.boot.runApplication
 import org.springframework.context.annotation.Bean
@@ -19,11 +22,24 @@ import java.time.Instant
 @SpringBootApplication
 class TicTacTowApplication {
     @Bean
-    fun jdbi() = Jdbi.create(
-        PGSimpleDataSource().apply {
-            setURL("jdbc:postgresql://localhost:5432/db?user=dbuser&password=changeit")
+    fun jdbi(): Jdbi {
+        val postgresUri =
+            System.getenv("POSTGRES_URI")
+                ?: "jdbc:postgresql://localhost:5432/db?user=dbuser&password=changeit"
+
+        val dataSource = PGSimpleDataSource().apply {
+            setURL(postgresUri)
         }
-    ).configure()
+
+        // Be careful not to disclose the credentials.
+        logger.info(
+            "Using PostgreSQL located at '{}:{}'",
+            dataSource.getProperty(PGProperty.PG_HOST),
+            dataSource.getProperty(PGProperty.PG_PORT),
+        )
+
+        return Jdbi.create(dataSource).configure()
+    }
 
     @Bean
     fun passwordEncoder() = BCryptPasswordEncoder()
@@ -35,6 +51,10 @@ class TicTacTowApplication {
     fun clock() = object : Clock {
         override fun now() = Instant.now()
     }
+
+    companion object {
+        private val logger: Logger = LoggerFactory.getLogger(TicTacTowApplication::class.java)
+    }
 }
 
 // QUESTION: why cannot this be in TicTacTowApplication

code/tic-tac-tow-service/src/main/kotlin/pt/isel/daw/tictactow/http/HomeController.kt

@@ -9,7 +9,11 @@ import pt.isel.daw.tictactow.infra.siren
 class HomeController {
 
     @GetMapping(Uris.HOME)
-    fun getHome() = siren(HomeOutputModel("Made for teaching purposes by P. Félix")) {
+    fun getHome() = siren(
+        HomeOutputModel(
+            credits = "Made for teaching purposes by P. Félix",
+        )
+    ) {
         link(Uris.home(), Rels.SELF)
         link(Uris.home(), Rels.HOME)
     }

code/tic-tac-tow-service/src/main/kotlin/pt/isel/daw/tictactow/http/StatusController.kt

@@ -0,0 +1,32 @@
+package pt.isel.daw.tictactow.http
+
+import org.springframework.web.bind.annotation.GetMapping
+import org.springframework.web.bind.annotation.RestController
+import pt.isel.daw.tictactow.http.model.StatusOutputModel
+import pt.isel.daw.tictactow.infra.siren
+import pt.isel.daw.tictactow.repository.TransactionManager
+import java.net.InetAddress
+
+@RestController
+class StatusController(
+    val transactionManager: TransactionManager
+) {
+
+    @GetMapping(Uris.STATUS)
+    fun getStatus() = transactionManager.run { transaction ->
+        siren(
+            StatusOutputModel(
+                hostname = System.getenv("HOSTNAME"),
+                gamesCount = transaction.gamesRepository.count()
+            )
+        ) {
+            // For now, nothing more to add.
+        }
+    }
+
+    @GetMapping(Uris.STATUS_HOSTNAME)
+    fun getStatusHostname(): String = System.getenv("HOSTNAME")
+
+    @GetMapping(Uris.STATUS_IP)
+    fun getStatusIp(): String = InetAddress.getLocalHost().hostAddress
+}

code/tic-tac-tow-service/src/main/kotlin/pt/isel/daw/tictactow/http/Uris.kt

@@ -7,6 +7,9 @@ import java.net.URI
 object Uris {
 
     const val HOME = "/"
+    const val STATUS = "/status"
+    const val STATUS_HOSTNAME = "/status/hostname"
+    const val STATUS_IP = "/status/ip"
     const val GAME_BY_ID = "/games/{gid}"
 
     fun home(): URI = URI(HOME)

code/tic-tac-tow-service/src/main/kotlin/pt/isel/daw/tictactow/http/model/StatusOutputModel.kt

@@ -0,0 +1,6 @@
+package pt.isel.daw.tictactow.http.model
+
+data class StatusOutputModel(
+    val hostname: String,
+    val gamesCount: Int,
+)

code/tic-tac-tow-service/src/main/kotlin/pt/isel/daw/tictactow/repository/GamesRepository.kt

@@ -7,4 +7,5 @@ interface GamesRepository {
     fun insert(game: Game)
     fun getById(id: UUID): Game?
     fun update(game: Game)
+    fun count(): Int
 }

code/tic-tac-tow-service/src/main/kotlin/pt/isel/daw/tictactow/repository/jdbi/JdbiGamesRepository.kt

@@ -71,6 +71,11 @@ class JdbiGamesRepository(
             .execute()
     }
 
+    override fun count(): Int =
+        handle.createQuery("select count(*) as count from dbo.Games")
+            .mapTo<Int>()
+            .single()
+
     companion object {
         private fun Update.bindBoard(name: String, board: Board) = run {
             bind(

code/tic-tac-tow-service/src/main/resources/application.properties

@@ -1 +1 @@
-
+server.port=${port:8080}

code/tic-tac-tow-service/tests/Dockerfile-spring

@@ -0,0 +1,9 @@
+FROM openjdk:17
+ARG DEPENDENCY=build/dependency
+# first layer with the external libs (i.e. the files that change the least).
+COPY ${DEPENDENCY}/BOOT-INF/lib /app/lib
+# second layer with the 'META-INF' contents.
+COPY ${DEPENDENCY}/META-INF /app/META-INF
+# last layer with the application JARs (i.e. the files that change the most).
+COPY ${DEPENDENCY}/BOOT-INF/classes /app
+ENTRYPOINT ["java","-cp","app:app/lib/*","pt.isel.daw.tictactow.TicTacTowApplicationKt"]

code/tic-tac-tow-service/tests/Dockerfile-ubuntu

@@ -0,0 +1,3 @@
+FROM ubuntu
+RUN apt -y update
+RUN apt -y install dnsutils

code/tic-tac-tow-service/tests/nginx/nginx.conf

@@ -0,0 +1,35 @@
+events {
+  worker_connections 1024;
+}
+
+http {
+
+  upstream static-spring-service {
+    server spring-service-1:8081 max_fails=3 fail_timeout=10s;
+    server spring-service-2:8082 max_fails=3 fail_timeout=10s;
+  }
+
+  upstream dynamic-spring-service {
+    server spring-service:8080 max_fails=3 fail_timeout=10s;
+  }
+
+  server {
+    listen        8080;
+
+    location / {
+      proxy_pass http://static-spring-service;
+      proxy_connect_timeout 5s;
+      proxy_next_upstream error timeout http_500;
+    }
+  }
+
+  server {
+    listen        8088;
+
+    location / {
+      proxy_pass http://dynamic-spring-service;
+      proxy_connect_timeout 5s;
+      proxy_next_upstream error timeout http_500;
+    }
+  }
+}