[core] require a Scheduler (=ThreadPool) for DefaultFileSource construction

this is a preparatory commit; the Scheduler is currently unused

23 files changed, 167 insertions, 56 deletions

diff --git a/benchmark/api/query.benchmark.cpp b/benchmark/api/query.benchmark.cpp
index 456f43af7e..928386c596 100644
--- a/benchmark/api/query.benchmark.cpp
+++ b/benchmark/api/query.benchmark.cpp
@@ -35,8 +35,8 @@ public:
     util::RunLoop loop;
     HeadlessBackend backend;
     OffscreenView view{ backend.getContext(), { 1000, 1000 } };
-    DefaultFileSource fileSource{ "benchmark/fixtures/api/cache.db", "." };
     ThreadPool threadPool{ 4, { "Worker" } };
+    DefaultFileSource fileSource{ threadPool, "benchmark/fixtures/api/cache.db", "." };
     Map map{ backend, view.size, 1, fileSource, threadPool, MapMode::Still };
     ScreenBox box{{ 0, 0 }, { 1000, 1000 }};
 };
diff --git a/bin/offline.cpp b/bin/offline.cpp
index 502561d0a1..068de9ee8d 100644
--- a/bin/offline.cpp
+++ b/bin/offline.cpp
@@ -1,5 +1,6 @@
 #include <mbgl/util/default_styles.hpp>
 #include <mbgl/util/run_loop.hpp>
+#include <mbgl/util/default_thread_pool.hpp>
 #include <mbgl/util/string.hpp>
 #include <mbgl/util/io.hpp>
 
@@ -55,7 +56,8 @@ int main(int argc, char *argv[]) {
     using namespace mbgl;
 
     util::RunLoop loop;
-    DefaultFileSource fileSource(output, ".");
+    ThreadPool threadPool{ 2, { "Worker" } };
+    DefaultFileSource fileSource(threadPool, output, ".");
     std::unique_ptr<OfflineRegion> region;
 
     fileSource.setAccessToken(token);
diff --git a/bin/render.cpp b/bin/render.cpp
index 0f6ff5f207..aa2a3408a2 100644
--- a/bin/render.cpp
+++ b/bin/render.cpp
@@ -69,7 +69,8 @@ int main(int argc, char *argv[]) {
     using namespace mbgl;
 
     util::RunLoop loop;
-    DefaultFileSource fileSource(cache_file, asset_root);
+    ThreadPool threadPool(4, { "Worker" });
+    DefaultFileSource fileSource(threadPool, cache_file, asset_root);
 
     // Try to load the token from the environment.
     if (!token.size()) {
@@ -86,7 +87,6 @@ int main(int argc, char *argv[]) {
 
     HeadlessBackend backend;
     OffscreenView view(backend.getContext(), { width * pixelRatio, height * pixelRatio });
-    ThreadPool threadPool(4, { "Worker" });
     Map map(backend, mbgl::Size { width, height }, pixelRatio, fileSource, threadPool, MapMode::Still);
 
     if (util::isURL(style_path)) {
diff --git a/include/mbgl/storage/default_file_source.hpp b/include/mbgl/storage/default_file_source.hpp
index b8f5e1167e..4bf1681c77 100644
--- a/include/mbgl/storage/default_file_source.hpp
+++ b/include/mbgl/storage/default_file_source.hpp
@@ -8,6 +8,8 @@
 
 namespace mbgl {
 
+class Scheduler;
+
 namespace util {
 template <typename T> class Thread;
 } // namespace util
@@ -21,7 +23,8 @@ public:
      * regions, we want the database to remain fairly small (order tens or low hundreds
      * of megabytes).
      */
-    DefaultFileSource(const std::string& cachePath,
+    DefaultFileSource(Scheduler&,
+                      const std::string& cachePath,
                       const std::string& assetRoot,
                       uint64_t maximumCacheSize = util::DEFAULT_MAX_CACHE_SIZE);
     ~DefaultFileSource() override;
diff --git a/platform/android/src/jni.cpp b/platform/android/src/jni.cpp
index 5182e268f3..d3bd4e02dd 100755
--- a/platform/android/src/jni.cpp
+++ b/platform/android/src/jni.cpp
@@ -11,6 +11,7 @@
 #include "jni.hpp"
 #include "java_types.hpp"
 #include "native_map_view.hpp"
+#include "shared_thread_pool.hpp"
 #include "connectivity_listener.hpp"
 #include "style/layers/layers.hpp"
 #include "style/sources/sources.hpp"
@@ -1236,7 +1237,8 @@ void nativeScheduleTakeSnapshot(JNIEnv *env, jni::jobject* obj, jlong nativeMapV
 jlong createDefaultFileSource(JNIEnv *env, jni::jobject* obj, jni::jstring* cachePath_, jni::jstring* assetRoot_, jlong maximumCacheSize) {
     std::string cachePath = std_string_from_jstring(env, cachePath_);
     std::string assetRoot = std_string_from_jstring(env, assetRoot_);
-    mbgl::DefaultFileSource *defaultFileSource = new mbgl::DefaultFileSource(cachePath, assetRoot, maximumCacheSize);
+    mbgl::DefaultFileSource* defaultFileSource = new mbgl::DefaultFileSource(
+        mbgl::android::sharedThreadPool(), cachePath, assetRoot, maximumCacheSize);
     jlong defaultFileSourcePtr = reinterpret_cast<jlong>(defaultFileSource);
     return defaultFileSourcePtr;
 }
diff --git a/platform/android/src/native_map_view.cpp b/platform/android/src/native_map_view.cpp
index d2ee1a64fe..6293aed759 100755
--- a/platform/android/src/native_map_view.cpp
+++ b/platform/android/src/native_map_view.cpp
@@ -1,5 +1,6 @@
 #include "native_map_view.hpp"
 #include "jni.hpp"
+#include "shared_thread_pool.hpp"
 
 #include <cstdlib>
 #include <ctime>
@@ -40,8 +41,7 @@ void log_egl_string(EGLDisplay display, EGLint name, const char *label) {
 NativeMapView::NativeMapView(JNIEnv *env_, jobject obj_, float pixelRatio, int availableProcessors_, size_t totalMemory_)
     : env(env_),
       availableProcessors(availableProcessors_),
-      totalMemory(totalMemory_),
-      threadPool(4, { "Worker" }) {
+      totalMemory(totalMemory_) {
     mbgl::Log::Debug(mbgl::Event::Android, "NativeMapView::NativeMapView");
 
     assert(env_ != nullptr);
@@ -59,12 +59,13 @@ NativeMapView::NativeMapView(JNIEnv *env_, jobject obj_, float pixelRatio, int a
     }
 
     fileSource = std::make_unique<mbgl::DefaultFileSource>(
+        sharedThreadPool(),
         mbgl::android::cachePath + "/mbgl-offline.db",
         mbgl::android::apkPath);
 
     map = std::make_unique<mbgl::Map>(
         *this, mbgl::Size{ static_cast<uint32_t>(width), static_cast<uint32_t>(height) },
-        pixelRatio, *fileSource, threadPool, MapMode::Continuous);
+        pixelRatio, *fileSource, sharedThreadPool(), MapMode::Continuous);
 
     float zoomFactor   = map->getMaxZoom() - map->getMinZoom() + 1;
     float cpuFactor    = availableProcessors;
diff --git a/platform/android/src/native_map_view.hpp b/platform/android/src/native_map_view.hpp
index e7379700a9..b7513dc572 100755
--- a/platform/android/src/native_map_view.hpp
+++ b/platform/android/src/native_map_view.hpp
@@ -4,7 +4,6 @@
 #include <mbgl/map/view.hpp>
 #include <mbgl/map/backend.hpp>
 #include <mbgl/util/noncopyable.hpp>
-#include <mbgl/util/default_thread_pool.hpp>
 #include <mbgl/storage/default_file_source.hpp>
 
 #include <string>
@@ -97,7 +96,6 @@ private:
 
     // Ensure these are initialised last
     std::unique_ptr<mbgl::DefaultFileSource> fileSource;
-    mbgl::ThreadPool threadPool;
     std::unique_ptr<mbgl::Map> map;
     mbgl::EdgeInsets insets;
 
diff --git a/platform/android/src/shared_thread_pool.hpp b/platform/android/src/shared_thread_pool.hpp
new file mode 100644
index 0000000000..3229c03193
--- /dev/null
+++ b/platform/android/src/shared_thread_pool.hpp
@@ -0,0 +1,15 @@
+#pragma once
+
+#include <mbgl/util/default_thread_pool.hpp>
+
+namespace mbgl {
+namespace android {
+
+// May only be called from the main/UI thread.
+inline ThreadPool& sharedThreadPool() {
+    static ThreadPool threadPool{ 4, { "Worker" } };
+    return threadPool;
+}
+
+}
+}
diff --git a/platform/darwin/src/MGLOfflineStorage.mm b/platform/darwin/src/MGLOfflineStorage.mm
index 10acc58b25..81219ec820 100644
--- a/platform/darwin/src/MGLOfflineStorage.mm
+++ b/platform/darwin/src/MGLOfflineStorage.mm
@@ -5,6 +5,7 @@
 #import "MGLNetworkConfiguration.h"
 #import "MGLOfflinePack_Private.h"
 #import "MGLOfflineRegion_Private.h"
+#import "MGLThreadPool_Private.h"
 #import "MGLTilePyramidOfflineRegion.h"
 #import "NSValue+MGLAdditions.h"
 
@@ -130,7 +131,9 @@ NSString * const MGLOfflinePackMaximumCountUserInfoKey = MGLOfflinePackUserInfoK
             [[NSFileManager defaultManager] moveItemAtPath:subdirectorylessCacheURL.path toPath:cachePath error:NULL];
         }
 
-        _mbglFileSource = new mbgl::DefaultFileSource(cachePath.UTF8String, [NSBundle mainBundle].resourceURL.path.UTF8String);
+        _mbglFileSource = new mbgl::DefaultFileSource(
+            *[MGLThreadPool sharedPool].mbglThreadPool, cachePath.UTF8String,
+            [NSBundle mainBundle].resourceURL.path.UTF8String);
 
         // Observe for changes to the API base URL (and find out the current one).
         [[MGLNetworkConfiguration sharedManager] addObserver:self
diff --git a/platform/darwin/src/MGLThreadPool.mm b/platform/darwin/src/MGLThreadPool.mm
new file mode 100644
index 0000000000..fa57233fb8
--- /dev/null
+++ b/platform/darwin/src/MGLThreadPool.mm
@@ -0,0 +1,39 @@
+#import "MGLThreadPool_Private.h"
+
+#import "NSProcessInfo+MGLAdditions.h"
+
+@interface MGLThreadPool ()
+
+@property (nonatomic) mbgl::ThreadPool *mbglThreadPool;
+
+@end
+
+@implementation MGLThreadPool
+
+#pragma mark - Internal
+
++ (instancetype)sharedPool {
+    if (NSProcessInfo.processInfo.mgl_isInterfaceBuilderDesignablesAgent) {
+        return nil;
+    }
+    static dispatch_once_t onceToken;
+    static MGLThreadPool *sharedThreadPool;
+    dispatch_once(&onceToken, ^{
+        sharedThreadPool = [[self alloc] init];
+    });
+    return sharedThreadPool;
+}
+
+- (instancetype)init {
+    if (self = [super init]) {
+        _mbglThreadPool = new mbgl::ThreadPool(4, { "Worker" });
+    }
+    return self;
+}
+
+- (void)dealloc {
+    delete _mbglThreadPool;
+    _mbglThreadPool = nullptr;
+}
+
+@end
diff --git a/platform/darwin/src/MGLThreadPool_Private.h b/platform/darwin/src/MGLThreadPool_Private.h
new file mode 100644
index 0000000000..c1420ab310
--- /dev/null
+++ b/platform/darwin/src/MGLThreadPool_Private.h
@@ -0,0 +1,18 @@
+#import <Foundation/Foundation.h>
+
+#include <mbgl/util/default_thread_pool.hpp>
+
+@interface MGLThreadPool : NSObject
+@end
+
+@interface MGLThreadPool (Private)
+
+/// Returns the shared instance of the `MGLThreadPool` class.
++ (instancetype)sharedPool;
+
+/**
+ The shared thread pool object owned by the shared thread pool object.
+ */
+@property (nonatomic) mbgl::ThreadPool *mbglThreadPool;
+
+@end
diff --git a/platform/default/default_file_source.cpp b/platform/default/default_file_source.cpp
index c4222b5a12..80ddb23050 100644
--- a/platform/default/default_file_source.cpp
+++ b/platform/default/default_file_source.cpp
@@ -160,7 +160,8 @@ private:
     std::unordered_map<int64_t, std::unique_ptr<OfflineDownload>> downloads;
 };
 
-DefaultFileSource::DefaultFileSource(const std::string& cachePath,
+DefaultFileSource::DefaultFileSource(Scheduler&,
+                                     const std::string& cachePath,
                                      const std::string& assetRoot,
                                      uint64_t maximumCacheSize)
     : thread(std::make_unique<util::Thread<Impl>>(util::ThreadContext{"DefaultFileSource", util::ThreadPriority::Low},
diff --git a/platform/glfw/main.cpp b/platform/glfw/main.cpp
index f9b1ec93cc..bd7c6e7216 100644
--- a/platform/glfw/main.cpp
+++ b/platform/glfw/main.cpp
@@ -108,7 +108,9 @@ int main(int argc, char *argv[]) {
     GLFWView backend(fullscreen, benchmark);
     view = &backend;
 
-    mbgl::DefaultFileSource fileSource("/tmp/mbgl-cache.db", ".");
+    mbgl::ThreadPool threadPool(4, { "Worker" });
+
+    mbgl::DefaultFileSource fileSource(threadPool, "/tmp/mbgl-cache.db", ".");
 
     // Set access token if present
     const char *token = getenv("MAPBOX_ACCESS_TOKEN");
@@ -118,8 +120,6 @@ int main(int argc, char *argv[]) {
         fileSource.setAccessToken(std::string(token));
     }
 
-    mbgl::ThreadPool threadPool(4, { "Worker" });
-
     mbgl::Map map(backend, view->getSize(), view->getPixelRatio(), fileSource, threadPool);
 
     backend.setMap(&map);
diff --git a/platform/ios/ios.xcodeproj/project.pbxproj b/platform/ios/ios.xcodeproj/project.pbxproj
index 6f2ee38e94..3595e917b4 100644
--- a/platform/ios/ios.xcodeproj/project.pbxproj
+++ b/platform/ios/ios.xcodeproj/project.pbxproj
@@ -162,6 +162,10 @@
 		40F887701D7A1E58008ECB67 /* MGLShapeSource_Private.h in Headers */ = {isa = PBXBuildFile; fileRef = 40F8876F1D7A1DB8008ECB67 /* MGLShapeSource_Private.h */; };
 		40F887711D7A1E59008ECB67 /* MGLShapeSource_Private.h in Headers */ = {isa = PBXBuildFile; fileRef = 40F8876F1D7A1DB8008ECB67 /* MGLShapeSource_Private.h */; };
 		40FDA76B1CCAAA6800442548 /* MBXAnnotationView.m in Sources */ = {isa = PBXBuildFile; fileRef = 40FDA76A1CCAAA6800442548 /* MBXAnnotationView.m */; };
+		553B1F0B1E267D9500606163 /* MGLThreadPool_Private.h in Headers */ = {isa = PBXBuildFile; fileRef = 553B1F091E267D9500606163 /* MGLThreadPool_Private.h */; };
+		553B1F0C1E267D9500606163 /* MGLThreadPool_Private.h in Headers */ = {isa = PBXBuildFile; fileRef = 553B1F091E267D9500606163 /* MGLThreadPool_Private.h */; };
+		553B1F0D1E267D9500606163 /* MGLThreadPool.mm in Sources */ = {isa = PBXBuildFile; fileRef = 553B1F0A1E267D9500606163 /* MGLThreadPool.mm */; };
+		553B1F0E1E267D9500606163 /* MGLThreadPool.mm in Sources */ = {isa = PBXBuildFile; fileRef = 553B1F0A1E267D9500606163 /* MGLThreadPool.mm */; };
 		554180421D2E97DE00012372 /* OpenGLES.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 554180411D2E97DE00012372 /* OpenGLES.framework */; };
 		556660CA1E1BF3A900E2C41B /* MGLFoundation.h in Headers */ = {isa = PBXBuildFile; fileRef = 556660C91E1BF3A900E2C41B /* MGLFoundation.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		556660D81E1D085500E2C41B /* MGLVersionNumber.m in Sources */ = {isa = PBXBuildFile; fileRef = 556660D71E1D085500E2C41B /* MGLVersionNumber.m */; };
@@ -611,6 +615,8 @@
 		40F8876F1D7A1DB8008ECB67 /* MGLShapeSource_Private.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = MGLShapeSource_Private.h; sourceTree = "<group>"; };
 		40FDA7691CCAAA6800442548 /* MBXAnnotationView.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = MBXAnnotationView.h; sourceTree = "<group>"; };
 		40FDA76A1CCAAA6800442548 /* MBXAnnotationView.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = MBXAnnotationView.m; sourceTree = "<group>"; };
+		553B1F091E267D9500606163 /* MGLThreadPool_Private.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = MGLThreadPool_Private.h; sourceTree = "<group>"; };
+		553B1F0A1E267D9500606163 /* MGLThreadPool.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = MGLThreadPool.mm; sourceTree = "<group>"; };
 		554180411D2E97DE00012372 /* OpenGLES.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = OpenGLES.framework; path = System/Library/Frameworks/OpenGLES.framework; sourceTree = SDKROOT; };
 		556660C91E1BF3A900E2C41B /* MGLFoundation.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = MGLFoundation.h; sourceTree = "<group>"; };
 		556660D71E1D085500E2C41B /* MGLVersionNumber.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; name = MGLVersionNumber.m; path = ../../darwin/test/MGLVersionNumber.m; sourceTree = "<group>"; };
@@ -1149,6 +1155,8 @@
 				DA8847EC1CBAFA5100AB86E3 /* MGLStyle.h */,
 				35E0CFE51D3E501500188327 /* MGLStyle_Private.h */,
 				DA88480F1CBAFA6200AB86E3 /* MGLStyle.mm */,
+				553B1F091E267D9500606163 /* MGLThreadPool_Private.h */,
+				553B1F0A1E267D9500606163 /* MGLThreadPool.mm */,
 				DA8847EE1CBAFA5100AB86E3 /* MGLTypes.h */,
 				DA8848111CBAFA6200AB86E3 /* MGLTypes.m */,
 				DA8848911CBB049300AB86E3 /* reachability */,
@@ -1474,6 +1482,7 @@
 				3510FFF01D6D9D8C00F413B2 /* NSExpression+MGLAdditions.h in Headers */,
 				353AFA141D65AB17005A69F4 /* NSDate+MGLAdditions.h in Headers */,
 				DA8848531CBAFB9800AB86E3 /* MGLCompactCalloutView.h in Headers */,
+				553B1F0B1E267D9500606163 /* MGLThreadPool_Private.h in Headers */,
 				DA8847FB1CBAFA5100AB86E3 /* MGLShape.h in Headers */,
 				353933F51D3FB785003F57D7 /* MGLBackgroundStyleLayer.h in Headers */,
 				DA88485A1CBAFB9800AB86E3 /* MGLUserLocation_Private.h in Headers */,
@@ -1568,6 +1577,7 @@
 				35B82BF91D6C5F8400B1B721 /* NSPredicate+MGLAdditions.h in Headers */,
 				DA35A2CA1CCAAAD200E826B2 /* NSValue+MGLAdditions.h in Headers */,
 				350098BC1D480108004B2AF0 /* MGLVectorSource.h in Headers */,
+				553B1F0C1E267D9500606163 /* MGLThreadPool_Private.h in Headers */,
 				353933FC1D3FB7C0003F57D7 /* MGLRasterStyleLayer.h in Headers */,
 				3566C76D1D4A8DFA008152BC /* MGLRasterSource.h in Headers */,
 				DAED38641D62D0FC00D7640F /* NSURL+MGLAdditions.h in Headers */,
@@ -2003,6 +2013,7 @@
 				350098BD1D480108004B2AF0 /* MGLVectorSource.mm in Sources */,
 				3566C76E1D4A8DFA008152BC /* MGLRasterSource.mm in Sources */,
 				DA88488C1CBB037E00AB86E3 /* SMCalloutView.m in Sources */,
+				553B1F0D1E267D9500606163 /* MGLThreadPool.mm in Sources */,
 				35136D4E1D4277FC00C20EFD /* MGLSource.mm in Sources */,
 				DA35A2B81CCA9A5D00E826B2 /* MGLClockDirectionFormatter.m in Sources */,
 				DAD1657A1CF4CDFF001FF4B9 /* MGLShapeCollection.mm in Sources */,
@@ -2078,6 +2089,7 @@
 				350098BE1D480108004B2AF0 /* MGLVectorSource.mm in Sources */,
 				3566C76F1D4A8DFA008152BC /* MGLRasterSource.mm in Sources */,
 				DAA4E4351CBB730400178DFB /* SMCalloutView.m in Sources */,
+				553B1F0E1E267D9500606163 /* MGLThreadPool.mm in Sources */,
 				35136D4F1D4277FC00C20EFD /* MGLSource.mm in Sources */,
 				DA35A2B91CCA9A5D00E826B2 /* MGLClockDirectionFormatter.m in Sources */,
 				DAD1657B1CF4CDFF001FF4B9 /* MGLShapeCollection.mm in Sources */,
diff --git a/platform/macos/macos.xcodeproj/project.pbxproj b/platform/macos/macos.xcodeproj/project.pbxproj
index 6f6aad2436..dc0aa5e8e2 100644
--- a/platform/macos/macos.xcodeproj/project.pbxproj
+++ b/platform/macos/macos.xcodeproj/project.pbxproj
@@ -57,6 +57,8 @@
 		40B77E461DB11BCD003DA2FE /* NSArray+MGLAdditions.mm in Sources */ = {isa = PBXBuildFile; fileRef = 40B77E421DB11BB0003DA2FE /* NSArray+MGLAdditions.mm */; };
 		40E1601D1DF217D6005EA6D9 /* MGLStyleLayerTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 40E1601B1DF216E6005EA6D9 /* MGLStyleLayerTests.m */; };
 		52BECB0A1CC5A26F009CD791 /* SystemConfiguration.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 52BECB091CC5A26F009CD791 /* SystemConfiguration.framework */; };
+		553B1F051E267AD900606163 /* MGLThreadPool_Private.h in Headers */ = {isa = PBXBuildFile; fileRef = 553B1F021E267AD900606163 /* MGLThreadPool_Private.h */; };
+		553B1F071E267AD900606163 /* MGLThreadPool.mm in Sources */ = {isa = PBXBuildFile; fileRef = 553B1F041E267AD900606163 /* MGLThreadPool.mm */; };
 		5548BE781D09E718005DDE81 /* libmbgl-core.a in Frameworks */ = {isa = PBXBuildFile; fileRef = DAE6C3451CC31D1200DB3429 /* libmbgl-core.a */; };
 		556660C61E1BEA0100E2C41B /* MGLFoundation.h in Headers */ = {isa = PBXBuildFile; fileRef = 556660C51E1BEA0100E2C41B /* MGLFoundation.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		556660D61E1D07E400E2C41B /* MGLVersionNumber.m in Sources */ = {isa = PBXBuildFile; fileRef = 556660D51E1D07E400E2C41B /* MGLVersionNumber.m */; };
@@ -305,6 +307,8 @@
 		40E1601A1DF216E6005EA6D9 /* MGLStyleLayerTests.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = MGLStyleLayerTests.h; sourceTree = "<group>"; };
 		40E1601B1DF216E6005EA6D9 /* MGLStyleLayerTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = MGLStyleLayerTests.m; sourceTree = "<group>"; };
 		52BECB091CC5A26F009CD791 /* SystemConfiguration.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = SystemConfiguration.framework; path = System/Library/Frameworks/SystemConfiguration.framework; sourceTree = SDKROOT; };
+		553B1F021E267AD900606163 /* MGLThreadPool_Private.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = MGLThreadPool_Private.h; sourceTree = "<group>"; };
+		553B1F041E267AD900606163 /* MGLThreadPool.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = MGLThreadPool.mm; sourceTree = "<group>"; };
 		5548BE791D0ACBB2005DDE81 /* libmbgl-loop-darwin.a */ = {isa = PBXFileReference; lastKnownFileType = archive.ar; name = "libmbgl-loop-darwin.a"; path = "cmake/Debug/libmbgl-loop-darwin.a"; sourceTree = "<group>"; };
 		5548BE7B1D0ACBBD005DDE81 /* libmbgl-loop-darwin.a */ = {isa = PBXFileReference; lastKnownFileType = archive.ar; name = "libmbgl-loop-darwin.a"; path = "cmake/Debug/libmbgl-loop-darwin.a"; sourceTree = "<group>"; };
 		556660C51E1BEA0100E2C41B /* MGLFoundation.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = MGLFoundation.h; sourceTree = "<group>"; };
@@ -916,6 +920,8 @@
 				DAE6C3571CC31E0400DB3429 /* MGLStyle.h */,
 				3537CA731D3F93A600380318 /* MGLStyle_Private.h */,
 				DAE6C37A1CC31E2A00DB3429 /* MGLStyle.mm */,
+				553B1F021E267AD900606163 /* MGLThreadPool_Private.h */,
+				553B1F041E267AD900606163 /* MGLThreadPool.mm */,
 				DAE6C3591CC31E0400DB3429 /* MGLTypes.h */,
 				DAE6C37C1CC31E2A00DB3429 /* MGLTypes.m */,
 				DA87A99F1DC9DC6200810D09 /* MGLValueEvaluator.h */,
@@ -1009,6 +1015,7 @@
 				352742811D4C243B00A1ECE6 /* MGLSource.h in Headers */,
 				DAE6C3C21CC31F4500DB3429 /* Mapbox.h in Headers */,
 				DAE6C3641CC31E0400DB3429 /* MGLPolygon.h in Headers */,
+				553B1F051E267AD900606163 /* MGLThreadPool_Private.h in Headers */,
 				DA35A2BF1CCA9B1A00E826B2 /* MGLClockDirectionFormatter.h in Headers */,
 				35602BFA1D3EA99F0050646F /* MGLFillStyleLayer.h in Headers */,
 				DA35A2A41CC9EB1A00E826B2 /* MGLCoordinateFormatter.h in Headers */,
@@ -1267,6 +1274,7 @@
 				DA35A2D01CCAAED300E826B2 /* NSValue+MGLAdditions.m in Sources */,
 				3538AA241D542685008EC33D /* MGLStyleLayer.mm in Sources */,
 				DA35A2C01CCA9B1A00E826B2 /* MGLClockDirectionFormatter.m in Sources */,
+				553B1F071E267AD900606163 /* MGLThreadPool.mm in Sources */,
 				DAE6C3BA1CC31EF300DB3429 /* MGLOpenGLLayer.mm in Sources */,
 				DAE6C38A1CC31E2A00DB3429 /* MGLMultiPoint.mm in Sources */,
 				DAE6C3961CC31E2A00DB3429 /* MGLTypes.m in Sources */,
diff --git a/platform/macos/src/MGLMapView.mm b/platform/macos/src/MGLMapView.mm
index 5df5a1f957..a66f9666b1 100644
--- a/platform/macos/src/MGLMapView.mm
+++ b/platform/macos/src/MGLMapView.mm
@@ -10,6 +10,7 @@
 #import "MGLGeometry_Private.h"
 #import "MGLMultiPoint_Private.h"
 #import "MGLOfflineStorage_Private.h"
+#import "MGLThreadPool_Private.h"
 #import "MGLStyle_Private.h"
 
 #import "MGLAccountManager.h"
@@ -23,7 +24,6 @@
 #import <mbgl/annotation/annotation.hpp>
 #import <mbgl/map/camera.hpp>
 #import <mbgl/storage/reachability.h>
-#import <mbgl/util/default_thread_pool.hpp>
 #import <mbgl/gl/extension.hpp>
 #import <mbgl/gl/context.hpp>
 #import <mbgl/map/backend.hpp>
@@ -150,7 +150,6 @@ public:
     /// Cross-platform map view controller.
     mbgl::Map *_mbglMap;
     MGLMapViewImpl *_mbglView;
-    mbgl::ThreadPool *_mbglThreadPool;
 
     NSPanGestureRecognizer *_panGestureRecognizer;
     NSMagnificationGestureRecognizer *_magnificationGestureRecognizer;
@@ -257,10 +256,13 @@ public:
     NSURL *legacyCacheURL = [cachesDirectoryURL URLByAppendingPathComponent:@"cache.db"];
     [[NSFileManager defaultManager] removeItemAtURL:legacyCacheURL error:NULL];
 
-    mbgl::DefaultFileSource* mbglFileSource = [MGLOfflineStorage sharedOfflineStorage].mbglFileSource;
+    mbgl::DefaultFileSource* mbglFileSource =
+        [MGLOfflineStorage sharedOfflineStorage].mbglFileSource;
 
-    _mbglThreadPool = new mbgl::ThreadPool(4, { "Worker" });
-    _mbglMap = new mbgl::Map(*_mbglView, self.size, [NSScreen mainScreen].backingScaleFactor, *mbglFileSource, *_mbglThreadPool, mbgl::MapMode::Continuous, mbgl::GLContextMode::Unique, mbgl::ConstrainMode::None, mbgl::ViewportMode::Default);
+    _mbglMap = new mbgl::Map(*_mbglView, self.size, [NSScreen mainScreen].backingScaleFactor,
+                             *mbglFileSource, *[MGLThreadPool sharedPool].mbglThreadPool,
+                             mbgl::MapMode::Continuous, mbgl::GLContextMode::Unique,
+                             mbgl::ConstrainMode::None, mbgl::ViewportMode::Default);
     [self validateTileCacheSize];
 
     // Install the OpenGL layer. Interface Builder’s synchronous drawing means
@@ -510,10 +512,6 @@ public:
         delete _mbglView;
         _mbglView = nullptr;
     }
-    if (_mbglThreadPool) {
-        delete _mbglThreadPool;
-        _mbglThreadPool = nullptr;
-    }
 }
 
 - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(__unused NSDictionary *)change context:(void *)context {
diff --git a/platform/qt/src/qmapboxgl.cpp b/platform/qt/src/qmapboxgl.cpp
index 9d3b5dc099..87eb77554b 100644
--- a/platform/qt/src/qmapboxgl.cpp
+++ b/platform/qt/src/qmapboxgl.cpp
@@ -1494,11 +1494,12 @@ QMapboxGLPrivate::QMapboxGLPrivate(QMapboxGL *q, const QMapboxGLSettings &settin
     : QObject(q)
     , size(size_)
     , q_ptr(q)
+    , threadPool(4, { "Worker" })
     , fileSourceObj(std::make_unique<mbgl::DefaultFileSource>(
+        threadPool,
         settings.cacheDatabasePath().toStdString(),
         settings.assetPath().toStdString(),
         settings.cacheDatabaseMaximumSize()))
-    , threadPool(4, { "Worker" })
     , mapObj(std::make_unique<mbgl::Map>(
         *this, mbgl::Size{ static_cast<uint32_t>(size.width()), static_cast<uint32_t>(size.height()) },
         pixelRatio, *fileSourceObj, threadPool,
diff --git a/platform/qt/src/qmapboxgl_p.hpp b/platform/qt/src/qmapboxgl_p.hpp
index 3d2be90273..f6c13a8e5b 100644
--- a/platform/qt/src/qmapboxgl_p.hpp
+++ b/platform/qt/src/qmapboxgl_p.hpp
@@ -37,8 +37,8 @@ public:
 
     QMapboxGL *q_ptr { nullptr };
 
-    std::unique_ptr<mbgl::DefaultFileSource> fileSourceObj;
     mbgl::ThreadPool threadPool;
+    std::unique_ptr<mbgl::DefaultFileSource> fileSourceObj;
     std::unique_ptr<mbgl::Map> mapObj;
 
     bool dirty { false };
diff --git a/test/api/custom_layer.test.cpp b/test/api/custom_layer.test.cpp
index 227523d90a..afeb87a97e 100644
--- a/test/api/custom_layer.test.cpp
+++ b/test/api/custom_layer.test.cpp
@@ -84,19 +84,18 @@ public:
 
 TEST(CustomLayer, Basic) {
     util::RunLoop loop;
+    ThreadPool threadPool{ 4, { "Worker" } };
 
     HeadlessBackend backend { test::sharedDisplay() };
     OffscreenView view { backend.getContext() };
 
 #ifdef MBGL_ASSET_ZIP
     // Regenerate with `cd test/fixtures/api/ && zip -r assets.zip assets/`
-    DefaultFileSource fileSource(":memory:", "test/fixtures/api/assets.zip");
+    DefaultFileSource fileSource(threadPool, ":memory:", "test/fixtures/api/assets.zip");
 #else
-    DefaultFileSource fileSource(":memory:", "test/fixtures/api/assets");
+    DefaultFileSource fileSource(threadPool, ":memory:", "test/fixtures/api/assets");
 #endif
 
-    ThreadPool threadPool{ 4, { "Worker" } };
-
     Map map(backend, view.size, 1, fileSource, threadPool, MapMode::Still);
     map.setStyleJSON(util::read_file("test/fixtures/api/water.json"));
     map.setLatLngZoom({ 37.8, -122.5 }, 10);
diff --git a/test/api/render_missing.test.cpp b/test/api/render_missing.test.cpp
index 9c53f35102..8414acc191 100644
--- a/test/api/render_missing.test.cpp
+++ b/test/api/render_missing.test.cpp
@@ -22,6 +22,7 @@ TEST(API, TEST_REQUIRES_SERVER(RenderMissingTile)) {
     using namespace mbgl;
 
     util::RunLoop loop;
+    ThreadPool threadPool{ 4, { "Worker" } };
 
     const auto style = util::read_file("test/fixtures/api/water_missing_tiles.json");
 
@@ -29,13 +30,11 @@ TEST(API, TEST_REQUIRES_SERVER(RenderMissingTile)) {
     OffscreenView view { backend.getContext(), { 256, 512 } };
 #ifdef MBGL_ASSET_ZIP
     // Regenerate with `cd test/fixtures/api/ && zip -r assets.zip assets/`
-    DefaultFileSource fileSource(":memory:", "test/fixtures/api/assets.zip");
+    DefaultFileSource fileSource(threadPool, ":memory:", "test/fixtures/api/assets.zip");
 #else
-    DefaultFileSource fileSource(":memory:", "test/fixtures/api/assets");
+    DefaultFileSource fileSource(threadPool, ":memory:", "test/fixtures/api/assets");
 #endif
 
-    ThreadPool threadPool{ 4, { "Worker" } };
-
     Log::setObserver(std::make_unique<FixtureLogObserver>());
 
     Map map(backend, view.size, 1, fileSource, threadPool, MapMode::Still);
diff --git a/test/api/repeated_render.test.cpp b/test/api/repeated_render.test.cpp
index 4ece3c3150..e0cf3d427f 100644
--- a/test/api/repeated_render.test.cpp
+++ b/test/api/repeated_render.test.cpp
@@ -16,8 +16,8 @@ using namespace mbgl;
 
 
 TEST(API, RepeatedRender) {
-
     util::RunLoop loop;
+    ThreadPool threadPool{ 4, { "Worker" } };
 
     const auto style = util::read_file("test/fixtures/api/water.json");
 
@@ -25,13 +25,11 @@ TEST(API, RepeatedRender) {
     OffscreenView view { backend.getContext(), { 256, 512 } };
 #ifdef MBGL_ASSET_ZIP
     // Regenerate with `cd test/fixtures/api/ && zip -r assets.zip assets/`
-    DefaultFileSource fileSource(":memory:", "test/fixtures/api/assets.zip");
+    DefaultFileSource fileSource(threadPool, ":memory:", "test/fixtures/api/assets.zip");
 #else
-    DefaultFileSource fileSource(":memory:", "test/fixtures/api/assets");
+    DefaultFileSource fileSource(threadPool, ":memory:", "test/fixtures/api/assets");
 #endif
 
-    ThreadPool threadPool{ 4, { "Worker" } };
-
     Log::setObserver(std::make_unique<FixtureLogObserver>());
 
     Map map(backend, view.size, 1, fileSource, threadPool, MapMode::Still);
diff --git a/test/map/map.test.cpp b/test/map/map.test.cpp
index 9ee2d45a81..6821e1444a 100644
--- a/test/map/map.test.cpp
+++ b/test/map/map.test.cpp
@@ -47,7 +47,7 @@ TEST(Map, LatLngBehavior) {
 
 TEST(Map, Offline) {
     MapTest test;
-    DefaultFileSource fileSource(":memory:", ".");
+    DefaultFileSource fileSource(test.threadPool, ":memory:", ".");
 
     auto expiredItem = [] (const std::string& path) {
         Response response;
@@ -479,9 +479,9 @@ TEST(Map, TEST_DISABLED_ON_CI(ContinuousRendering)) {
 
 #ifdef MBGL_ASSET_ZIP
     // Regenerate with `cd test/fixtures/api/ && zip -r assets.zip assets/`
-    DefaultFileSource fileSource(":memory:", "test/fixtures/api/assets.zip");
+    DefaultFileSource fileSource(threadPool, ":memory:", "test/fixtures/api/assets.zip");
 #else
-    DefaultFileSource fileSource(":memory:", "test/fixtures/api/assets");
+    DefaultFileSource fileSource(threadPool, ":memory:", "test/fixtures/api/assets");
 #endif
 
     Map map(backend, view.size, 1, fileSource, threadPool, MapMode::Continuous);
diff --git a/test/storage/default_file_source.test.cpp b/test/storage/default_file_source.test.cpp
index f4c23c4c7a..3949b8271c 100644
--- a/test/storage/default_file_source.test.cpp
+++ b/test/storage/default_file_source.test.cpp
@@ -1,12 +1,14 @@
 #include <mbgl/test/util.hpp>
 #include <mbgl/storage/default_file_source.hpp>
+#include <mbgl/util/default_thread_pool.hpp>
 #include <mbgl/util/run_loop.hpp>
 
 using namespace mbgl;
 
 TEST(DefaultFileSource, TEST_REQUIRES_SERVER(CacheResponse)) {
     util::RunLoop loop;
-    DefaultFileSource fs(":memory:", ".");
+    ThreadPool threadPool{ 1, { "Worker" } };
+    DefaultFileSource fs(threadPool, ":memory:", ".");
 
     const Resource resource { Resource::Unknown, "http://127.0.0.1:3000/cache" };
     Response response;
@@ -44,7 +46,8 @@ TEST(DefaultFileSource, TEST_REQUIRES_SERVER(CacheResponse)) {
 
 TEST(DefaultFileSource, TEST_REQUIRES_SERVER(CacheRevalidateSame)) {
     util::RunLoop loop;
-    DefaultFileSource fs(":memory:", ".");
+    ThreadPool threadPool{ 1, { "Worker" } };
+    DefaultFileSource fs(threadPool, ":memory:", ".");
 
     const Resource revalidateSame { Resource::Unknown, "http://127.0.0.1:3000/revalidate-same" };
     std::unique_ptr<AsyncRequest> req1;
@@ -88,7 +91,8 @@ TEST(DefaultFileSource, TEST_REQUIRES_SERVER(CacheRevalidateSame)) {
 
 TEST(DefaultFileSource, TEST_REQUIRES_SERVER(CacheRevalidateModified)) {
     util::RunLoop loop;
-    DefaultFileSource fs(":memory:", ".");
+    ThreadPool threadPool{ 1, { "Worker" } };
+    DefaultFileSource fs(threadPool, ":memory:", ".");
 
     const Resource revalidateModified{ Resource::Unknown,
                                        "http://127.0.0.1:3000/revalidate-modified" };
@@ -132,7 +136,8 @@ TEST(DefaultFileSource, TEST_REQUIRES_SERVER(CacheRevalidateModified)) {
 
 TEST(DefaultFileSource, TEST_REQUIRES_SERVER(CacheRevalidateEtag)) {
     util::RunLoop loop;
-    DefaultFileSource fs(":memory:", ".");
+    ThreadPool threadPool{ 1, { "Worker" } };
+    DefaultFileSource fs(threadPool, ":memory:", ".");
 
     const Resource revalidateEtag { Resource::Unknown, "http://127.0.0.1:3000/revalidate-etag" };
     std::unique_ptr<AsyncRequest> req1;
@@ -187,7 +192,8 @@ TEST(DefaultFileSource, TEST_REQUIRES_SERVER(CacheRevalidateEtag)) {
 
 TEST(DefaultFileSource, TEST_REQUIRES_SERVER(HTTPIssue1369)) {
     util::RunLoop loop;
-    DefaultFileSource fs(":memory:", ".");
+    ThreadPool threadPool{ 1, { "Worker" } };
+    DefaultFileSource fs(threadPool, ":memory:", ".");
 
     const Resource resource { Resource::Unknown, "http://127.0.0.1:3000/test" };
 
@@ -211,7 +217,8 @@ TEST(DefaultFileSource, TEST_REQUIRES_SERVER(HTTPIssue1369)) {
 
 TEST(DefaultFileSource, OptionalNonExpired) {
     util::RunLoop loop;
-    DefaultFileSource fs(":memory:", ".");
+    ThreadPool threadPool{ 1, { "Worker" } };
+    DefaultFileSource fs(threadPool, ":memory:", ".");
 
     const Resource optionalResource { Resource::Unknown, "http://127.0.0.1:3000/test", {}, Resource::Optional };
 
@@ -240,7 +247,8 @@ TEST(DefaultFileSource, OptionalNonExpired) {
 
 TEST(DefaultFileSource, OptionalExpired) {
     util::RunLoop loop;
-    DefaultFileSource fs(":memory:", ".");
+    ThreadPool threadPool{ 1, { "Worker" } };
+    DefaultFileSource fs(threadPool, ":memory:", ".");
 
     const Resource optionalResource { Resource::Unknown, "http://127.0.0.1:3000/test", {}, Resource::Optional };
 
@@ -269,7 +277,8 @@ TEST(DefaultFileSource, OptionalExpired) {
 
 TEST(DefaultFileSource, OptionalNotFound) {
     util::RunLoop loop;
-    DefaultFileSource fs(":memory:", ".");
+    ThreadPool threadPool{ 1, { "Worker" } };
+    DefaultFileSource fs(threadPool, ":memory:", ".");
 
     const Resource optionalResource { Resource::Unknown, "http://127.0.0.1:3000/test", {}, Resource::Optional };
 
@@ -295,7 +304,8 @@ TEST(DefaultFileSource, OptionalNotFound) {
 // from cache like a regular request
 TEST(DefaultFileSource, TEST_REQUIRES_SERVER(NoCacheRefreshEtagNotModified)) {
     util::RunLoop loop;
-    DefaultFileSource fs(":memory:", ".");
+    ThreadPool threadPool{ 1, { "Worker" } };
+    DefaultFileSource fs(threadPool, ":memory:", ".");
 
     Resource resource { Resource::Unknown, "http://127.0.0.1:3000/revalidate-same" };
     resource.priorEtag.emplace("snowfall");
@@ -329,7 +339,8 @@ TEST(DefaultFileSource, TEST_REQUIRES_SERVER(NoCacheRefreshEtagNotModified)) {
 // from cache like a regular request
 TEST(DefaultFileSource, TEST_REQUIRES_SERVER(NoCacheRefreshEtagModified)) {
     util::RunLoop loop;
-    DefaultFileSource fs(":memory:", ".");
+    ThreadPool threadPool{ 1, { "Worker" } };
+    DefaultFileSource fs(threadPool, ":memory:", ".");
 
     Resource resource { Resource::Unknown, "http://127.0.0.1:3000/revalidate-same" };
     resource.priorEtag.emplace("sunshine");
@@ -363,7 +374,8 @@ TEST(DefaultFileSource, TEST_REQUIRES_SERVER(NoCacheRefreshEtagModified)) {
 // from cache like a regular request.
 TEST(DefaultFileSource, TEST_REQUIRES_SERVER(NoCacheFull)) {
     util::RunLoop loop;
-    DefaultFileSource fs(":memory:", ".");
+    ThreadPool threadPool{ 1, { "Worker" } };
+    DefaultFileSource fs(threadPool, ":memory:", ".");
 
     Resource resource { Resource::Unknown, "http://127.0.0.1:3000/revalidate-same" };
     // Setting any prior field results in skipping the cache.
@@ -398,7 +410,8 @@ TEST(DefaultFileSource, TEST_REQUIRES_SERVER(NoCacheFull)) {
 // from cache like a regular request
 TEST(DefaultFileSource, TEST_REQUIRES_SERVER(NoCacheRefreshModifiedNotModified)) {
     util::RunLoop loop;
-    DefaultFileSource fs(":memory:", ".");
+    ThreadPool threadPool{ 1, { "Worker" } };
+    DefaultFileSource fs(threadPool, ":memory:", ".");
 
     Resource resource { Resource::Unknown, "http://127.0.0.1:3000/revalidate-modified" };
     resource.priorModified.emplace(Seconds(1420070400)); // January 1, 2015
@@ -432,7 +445,8 @@ TEST(DefaultFileSource, TEST_REQUIRES_SERVER(NoCacheRefreshModifiedNotModified))
 // from cache like a regular request
 TEST(DefaultFileSource, TEST_REQUIRES_SERVER(NoCacheRefreshModifiedModified)) {
     util::RunLoop loop;
-    DefaultFileSource fs(":memory:", ".");
+    ThreadPool threadPool{ 1, { "Worker" } };
+    DefaultFileSource fs(threadPool, ":memory:", ".");
 
     Resource resource { Resource::Unknown, "http://127.0.0.1:3000/revalidate-modified" };
     resource.priorModified.emplace(Seconds(1417392000)); // December 1, 2014