feat(server): cache the generation of the metadata files (#1911)

Fixes #1903

Author: Vampire

jit-binding-server/src/main/kotlin/io/github/typesafegithub/workflows/jitbindingserver/Main.kt

@@ -45,7 +45,7 @@ fun main() {
             internalRoutes(prometheusRegistry)
 
             artifactRoutes(prometheusRegistry)
-            metadataRoutes()
+            metadataRoutes(prometheusRegistry)
         }
     }.start(wait = true)
 }

jit-binding-server/src/main/kotlin/io/github/typesafegithub/workflows/jitbindingserver/MetadataRoutes.kt

@@ -1,19 +1,40 @@
 package io.github.typesafegithub.workflows.jitbindingserver
 
+import com.github.benmanes.caffeine.cache.Caffeine
+import com.sksamuel.aedile.core.asLoadingCache
+import com.sksamuel.aedile.core.refreshAfterWrite
 import io.github.oshai.kotlinlogging.KotlinLogging.logger
+import io.github.typesafegithub.workflows.actionbindinggenerator.domain.ActionCoords
 import io.github.typesafegithub.workflows.actionbindinggenerator.domain.prettyPrintWithoutVersion
 import io.github.typesafegithub.workflows.mavenbinding.buildPackageArtifacts
 import io.github.typesafegithub.workflows.shared.internal.getGithubAuthToken
-import io.ktor.http.HttpStatusCode
 import io.ktor.server.response.respondText
 import io.ktor.server.routing.Route
 import io.ktor.server.routing.Routing
 import io.ktor.server.routing.get
 import io.ktor.server.routing.route
+import io.micrometer.core.instrument.binder.cache.CaffeineCacheMetrics
+import io.micrometer.prometheusmetrics.PrometheusMeterRegistry
+import kotlin.time.Duration.Companion.hours
 
 private val logger = logger { }
 
-fun Routing.metadataRoutes() {
+typealias MetadataResult = Result<Map<String, String>>
+
+private val metadataCache =
+    Caffeine
+        .newBuilder()
+        .refreshAfterWrite(1.hours)
+        .recordStats()
+        .asLoadingCache<ActionCoords, MetadataResult> {
+            runCatching {
+                it.buildPackageArtifacts(githubAuthToken = getGithubAuthToken())
+            }
+        }
+
+fun Routing.metadataRoutes(prometheusRegistry: PrometheusMeterRegistry) {
+    CaffeineCacheMetrics.monitor(prometheusRegistry, metadataCache.underlying(), "metadata_cache")
+
     route("{owner}/{name}/{file}") {
         metadata()
     }
@@ -25,21 +46,26 @@ fun Routing.metadataRoutes() {
 
 private fun Route.metadata(refresh: Boolean = false) {
     get {
-        if (refresh && !deliverOnRefreshRoute) return@get call.respondNotFound()
-
-        val file = call.parameters["file"] ?: return@get call.respondNotFound()
         val actionCoords = call.parameters.extractActionCoords(extractVersion = false)
 
         logger.info { "➡️ Requesting metadata for ${actionCoords.prettyPrintWithoutVersion}" }
 
-        val bindingArtifacts = actionCoords.buildPackageArtifacts(githubAuthToken = getGithubAuthToken())
-        if (file in bindingArtifacts) {
-            when (val artifact = bindingArtifacts[file]) {
+        if (refresh) {
+            metadataCache.invalidate(actionCoords)
+        }
+        val metadataArtifacts = metadataCache.get(actionCoords).getOrThrow()
+
+        if (refresh && !deliverOnRefreshRoute) return@get call.respondText(text = "OK")
+
+        val file = call.parameters["file"] ?: return@get call.respondNotFound()
+
+        if (file in metadataArtifacts) {
+            when (val artifact = metadataArtifacts[file]) {
                 is String -> call.respondText(text = artifact)
-                else -> call.respondText(text = "Not found", status = HttpStatusCode.NotFound)
+                else -> call.respondNotFound()
             }
         } else {
-            call.respondText(text = "Not found", status = HttpStatusCode.NotFound)
+            call.respondNotFound()
         }
     }
 }