Revert "Revert "Merge branch 'fix-4xx-caching' into expermential_buffer_size_knob""

This reverts commit e85b77569b

settings.sample.json

@@ -13,5 +13,9 @@
   "web_settings": { //delete this block to disable webui
     "ui_hostname": "127.0.0.1", // "127.0.0.1" is the default and binds to localhost only
     "ui_port": 8080
+  },
+  "experimental": {
+    "max_buffer_size_for_cache_hit": 0 // Size is n * 8kiB. 0 uses the JDK default (which is likely 8kiB).
+    // May improve diskIO at the cost of memory pressure. Testing needed
   }
 }

src/main/kotlin/mdnet/base/Main.kt

@@ -129,6 +129,10 @@ object Main {
                 dieWithError("Config Error: Invalid UI port number")
             }
         }
+        if (settings.experimental != null) {
+            if (settings.experimental.maxBufferSizeForCacheHit < 0)
+            dieWithError("Config Error: Max cache buffer multiple must be >= 0")
+        }
     }
 
     private const val CLIENT_KEY_LENGTH = 52

src/main/kotlin/mdnet/base/server/Application.kt

@@ -63,7 +63,7 @@ fun getServer(cache: DiskLruCache, serverSettings: ServerSettings, clientSetting
         .setMaxConnPerRoute(3000)
         .build())
 
-    val imageServer = ImageServer(cache, database, statistics, serverSettings, client)
+    val imageServer = ImageServer(cache, database, statistics, serverSettings, clientSettings, client)
 
     return timeRequest()
         .then(catchAllHideDetails())

src/main/kotlin/mdnet/base/server/ImageServer.kt

@@ -48,6 +48,7 @@ import mdnet.base.data.ImageDatum
 import mdnet.base.data.Statistics
 import mdnet.base.data.Token
 import mdnet.base.info
+import mdnet.base.settings.ClientSettings
 import mdnet.base.settings.ServerSettings
 import mdnet.base.trace
 import mdnet.base.warn
@@ -66,6 +67,7 @@ class ImageServer(
     private val database: Database,
     private val statistics: AtomicReference<Statistics>,
     private val serverSettings: ServerSettings,
+    private val clientSettings: ClientSettings,
     private val client: HttpHandler
 ) {
     init {
@@ -74,6 +76,9 @@ class ImageServer(
         }
     }
     private val executor = Executors.newCachedThreadPool()
+    private val maxBufferSizeForCacheHit: Int? = clientSettings.experimental?.maxBufferSizeForCacheHit
+            ?.takeUnless { it == 0 }
+            ?.times(8 * 1024)
 
     fun handler(dataSaver: Boolean, tokenized: Boolean = false): HttpHandler {
         val sodium = LazySodiumJava(SodiumJava())
@@ -203,11 +208,16 @@ class ImageServer(
             }
 
             LOGGER.info { "Request for $sanitizedUri hit cache" }
+            val cacheStream = snapshot.getInputStream(0)
+            val bufferSize = maxBufferSizeForCacheHit?.coerceAtMost(snapshot.getLength(0).toInt())
+            val bufferedStream = bufferSize?.let {
+                BufferedInputStream(cacheStream, bufferSize)
+            } ?: BufferedInputStream(cacheStream) // Todo: Move into builder. It's untidy having the null propagate all the way here but I'm tired and tomorrow is a fast day.
 
             respondWithImage(
-                CipherInputStream(BufferedInputStream(snapshot.getInputStream(0)), cipher),
-                snapshot.getLength(0).toString(), imageDatum.contentType, imageDatum.lastModified,
-                true
+                    CipherInputStream(bufferedStream, cipher),
+                    snapshot.getLength(0).toString(), imageDatum.contentType, imageDatum.lastModified,
+                    true
             )
         }
     }

src/main/kotlin/mdnet/base/settings/ClientSettings.kt

@@ -35,7 +35,8 @@ data class ClientSettings(
     val threads: Int = 4,
     val gracefulShutdownWaitSeconds: Int = 60,
     val webSettings: WebSettings? = null,
-    val devSettings: DevSettings? = null
+    val devSettings: DevSettings? = null,
+    val experimental: Experimental? = null
 )
 
 @JsonNaming(PropertyNamingStrategy.SnakeCaseStrategy::class)
@@ -48,3 +49,8 @@ data class WebSettings(
 data class DevSettings(
     val isDev: Boolean = false
 )
+
+@JsonNaming(PropertyNamingStrategy.SnakeCaseStrategy::class)
+data class Experimental(
+    val maxBufferSizeForCacheHit: Int = 0
+)