make sqlite storage more resilient to sporadic errors

- catch SQLite exceptions and report them
- failed statements are ignored, we're really just caching here, so if it fails we're handling it gracefully elsewhere
- handle cases where the database file goes away after we opened it
- handle cases where the schema wasn't created after the database file was opened successfully
- add tests

1 files changed, 2 insertions, 0 deletions

diff --git a/include/mbgl/storage/default/sqlite_cache.hpp b/include/mbgl/storage/default/sqlite_cache.hpp
index 8f2746561c..fe80a41b52 100644
--- a/include/mbgl/storage/default/sqlite_cache.hpp
+++ b/include/mbgl/storage/default/sqlite_cache.hpp
@@ -38,6 +38,7 @@ private:
     void process(StopAction &action);
 
     void createDatabase();
+    void createSchema();
 
     const std::string path;
     uv_loop_t *loop = nullptr;
@@ -45,6 +46,7 @@ private:
     std::thread thread;
     std::unique_ptr<::mapbox::sqlite::Database> db;
     std::unique_ptr<::mapbox::sqlite::Statement> getStmt, putStmt, refreshStmt;
+    bool schema = false;
 };
 
 }