chore: Use fixed thread pool to perform disk I/O.

Author: nstdio

src/main/java/io/github/nstdio/http/ext/DiskCache.java

@@ -51,7 +51,7 @@ class DiskCache extends SizeConstrainedCache {
     this.metadataSerializer = metadataSerializer;
     this.streamFactory = streamFactory;
     this.dir = dir;
-    this.executor = Executors.newSingleThreadExecutor(r -> new Thread(r, "disk-cache-io"));
+    this.executor = Executors.newFixedThreadPool(1, r -> new Thread(r, "disk-cache-io"));
 
     restore();
   }

src/test/kotlin/io/github/nstdio/http/ext/BuffersTest.kt

@@ -17,7 +17,6 @@ package io.github.nstdio.http.ext
 
 import io.kotest.matchers.types.shouldBeSameInstanceAs
 import io.kotest.property.Arb
-import io.kotest.property.arbitrary.int
 import io.kotest.property.arbitrary.map
 import io.kotest.property.arbitrary.next
 import org.assertj.core.api.Assertions.assertThat
@@ -72,12 +71,17 @@ internal class BuffersTest {
     fun listBuffersData(): Stream<List<ByteBuffer>> {
       return Stream.of(
         listOf(),
-        listOf("abcde".repeat(16).toByteBuffer()),
+        listOf("abcde".repeat(8).toByteBuffer()),
         listOf(
-          "ab".repeat(16).toByteBuffer(),
-          "cd".repeat(16).toByteBuffer()
+          "ab".repeat(8).toByteBuffer(),
+          "cd".repeat(8).toByteBuffer()
         ),
-        Arb.byteArray(Arb.int(96, 96)).next().toChunkedBuffers(true)
+        listOf(
+          "ab".repeat(8).toByteBuffer(),
+          "cd".repeat(8).toByteBuffer(),
+          "ef".repeat(8).toByteBuffer()
+        ),
+        Arb.byteArray(96).next().toChunkedBuffers(true)
       )
     }
   }