Properly synchronised sqlite3 handler across threads

CHANGELOG.md

@@ -30,8 +30,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - [2020-06-14] Removed old cache subdirectory migration system by [@carbotaniuman].
 
 ### Fixed
-- [2020-06-15] Fixed tokenized data-saver parser not working by [@lflare].
 - [2020-06-14] Switched cache metadata over to a MySql instance [@carbotaniuman].
+- [2020-06-15] Fixed tokenized data-saver parser not working by [@lflare].
+- [2020-06-15] Properly synchronised sqlite3 handler across threads by [@lflare].
 
 ## [1.0.0-RC16] - 2020-06-14
 ### Added

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

@@ -77,9 +77,11 @@ class ImageServer(private val cache: DiskLruCache, private val statistics: Atomi
         val imageId = printHexString(rc4Bytes)
 
         val snapshot = cache.getUnsafe(imageId.toCacheId())
-        val imageDatum = transaction(database) {
+        val imageDatum = synchronized(database) {
+            transaction(database) {
                 ImageDatum.findById(imageId)
             }
+        }
 
         if (snapshot != null && imageDatum != null) {
             request.handleCacheHit(sanitizedUri, getRc4(rc4Bytes), snapshot, imageDatum)
@@ -96,10 +98,12 @@ class ImageServer(private val cache: DiskLruCache, private val statistics: Atomi
                 if (LOGGER.isWarnEnabled) {
                     LOGGER.warn("Deleting DB entry for $sanitizedUri without corresponding file")
                 }
+                synchronized(database) {
                     transaction(database) {
                         imageDatum.delete()
                     }
                 }
+            }
 
             request.handleCacheMiss(sanitizedUri, getRc4(rc4Bytes), imageId)
                 .header("X-Uri", sanitizedUri)
@@ -174,12 +178,14 @@ class ImageServer(private val cache: DiskLruCache, private val statistics: Atomi
                 LOGGER.trace("Request for $sanitizedUri is being cached and served")
             }
 
+            synchronized(database) {
                 transaction(database) {
                     ImageDatum.new(imageId) {
                         this.contentType = contentType
                         this.lastModified = lastModified
                     }
                 }
+            }
 
             val tee = CachingInputStream(
                 mdResponse.body.stream,