856: Add health endpoint

backend/src/main/kotlin/app/ehrenamtskarte/backend/common/webservice/HealthHandler.kt

@@ -0,0 +1,29 @@
+package app.ehrenamtskarte.backend.application.webservice
+
+import app.ehrenamtskarte.backend.config.BackendConfiguration
+import app.ehrenamtskarte.backend.projects.database.ProjectEntity
+import app.ehrenamtskarte.backend.projects.database.Projects
+import io.javalin.http.Context
+import org.jetbrains.exposed.sql.transactions.transaction
+import org.jetbrains.exposed.exceptions.ExposedSQLException
+import org.postgresql.util.PSQLException
+import java.lang.System
+import java.net.ConnectException
+
+class HealthHandler(private val config: BackendConfiguration) {
+    fun handle(ctx: Context) {
+        try {
+            transaction {
+                val projectIds = config.projects.map { it.id }
+                val projects = ProjectEntity.find { Projects.project inList projectIds }
+                if (projects.empty()) {
+                    ctx.status(502)
+                    return
+                }
+            }
+            ctx.status(200)
+        } catch (exception: ExposedSQLException) {
+            ctx.status(502)
+        }
+    }
+}

backend/src/main/kotlin/app/ehrenamtskarte/backend/common/webservice/WebService.kt

@@ -1,6 +1,7 @@
 package app.ehrenamtskarte.backend.common.webservice
 
 import app.ehrenamtskarte.backend.application.webservice.ApplicationAttachmentHandler
+import app.ehrenamtskarte.backend.application.webservice.HealthHandler
 import app.ehrenamtskarte.backend.config.BackendConfiguration
 import app.ehrenamtskarte.backend.map.webservice.MapStyleHandler
 import io.javalin.Javalin
@@ -50,6 +51,7 @@ class WebService {
         val graphQLHandler = GraphQLHandler(config)
         val mapStyleHandler = MapStyleHandler(config)
         val applicationHandler = ApplicationAttachmentHandler(applicationData)
+        val healthHandler = HealthHandler(config)
 
         app.post("/") { ctx ->
             if (!production) {
@@ -71,6 +73,8 @@ class WebService {
             applicationHandler.handle(ctx)
         }
 
+        app.get("/health") { ctx -> healthHandler.handle(ctx) }
+
         app.start(host, port)
         println("Server is running at http://$host:$port")
         println("Goto http://$host:$port/graphiql/ for a graphical editor")