Index: clangd/ClangdLSPServer.h
===================================================================
--- clangd/ClangdLSPServer.h
+++ clangd/ClangdLSPServer.h
@@ -25,7 +25,7 @@
 /// dispatch and ClangdServer together.
 class ClangdLSPServer {
 public:
-  ClangdLSPServer(JSONOutput &Out, bool RunSynchronously);
+  ClangdLSPServer(JSONOutput &Out, bool RunSynchronously, Path CompileCommandsDir);
 
   /// Run LSP server loop, receiving input for it from \p In. \p In must be
   /// opened in binary mode. Output will be written using Out variable passed to
Index: clangd/ClangdLSPServer.cpp
===================================================================
--- clangd/ClangdLSPServer.cpp
+++ clangd/ClangdLSPServer.cpp
@@ -216,9 +216,9 @@
       R"(,"result":[)" + Locations + R"(]})");
 }
 
-ClangdLSPServer::ClangdLSPServer(JSONOutput &Out, bool RunSynchronously)
-    : Out(Out), DiagConsumer(*this),
-      Server(CDB, DiagConsumer, FSProvider, RunSynchronously) {}
+ClangdLSPServer::ClangdLSPServer(JSONOutput &Out, bool RunSynchronously, Path CompileCommandsDir)
+    : Out(Out), CDB(CompileCommandsDir), DiagConsumer(*this),
+      Server(CDB, DiagConsumer, FSProvider, RunSynchronously, CompileCommandsDir) {}
 
 void ClangdLSPServer::run(std::istream &In) {
   assert(!IsDone && "Run was called before");
Index: clangd/ClangdServer.h
===================================================================
--- clangd/ClangdServer.h
+++ clangd/ClangdServer.h
@@ -156,7 +156,7 @@
   /// location, obtained via CompilerInvocation::GetResourcePath.
   ClangdServer(GlobalCompilationDatabase &CDB,
                DiagnosticsConsumer &DiagConsumer,
-               FileSystemProvider &FSProvider, bool RunSynchronously,
+               FileSystemProvider &FSProvider, bool RunSynchronously, llvm::Optional<Path> CompileCommandsDir, 
                llvm::Optional<StringRef> ResourceDir = llvm::None);
 
   /// Add a \p File to the list of tracked C++ files or update the contents if
Index: clangd/ClangdServer.cpp
===================================================================
--- clangd/ClangdServer.cpp
+++ clangd/ClangdServer.cpp
@@ -147,6 +147,7 @@
                            DiagnosticsConsumer &DiagConsumer,
                            FileSystemProvider &FSProvider,
                            bool RunSynchronously,
+                           llvm::Optional<Path> CompileCommandsDir,
                            llvm::Optional<StringRef> ResourceDir)
     : CDB(CDB), DiagConsumer(DiagConsumer), FSProvider(FSProvider),
       ResourceDir(ResourceDir ? ResourceDir->str() : getStandardResourceDir()),
Index: clangd/GlobalCompilationDatabase.h
===================================================================
--- clangd/GlobalCompilationDatabase.h
+++ clangd/GlobalCompilationDatabase.h
@@ -33,9 +33,9 @@
 public:
   virtual ~GlobalCompilationDatabase() = default;
 
-  virtual std::vector<tooling::CompileCommand>
+  virtual std::vector<tooling::CompileCommand>  
   getCompileCommands(PathRef File) = 0;
-
+  
   /// FIXME(ibiryukov): add facilities to track changes to compilation flags of
   /// existing targets.
 };
@@ -45,13 +45,16 @@
 class DirectoryBasedGlobalCompilationDatabase
     : public GlobalCompilationDatabase {
 public:
+  DirectoryBasedGlobalCompilationDatabase(Path NewCompileCommandsDir): CompileCommandsDir(NewCompileCommandsDir){}
   std::vector<tooling::CompileCommand>
   getCompileCommands(PathRef File) override;
 
   void setExtraFlagsForFile(PathRef File, std::vector<std::string> ExtraFlags);
+  tooling::CompilationDatabase *tryLoadDatabaseFromPath(PathRef File, std::string &Error);
 
 private:
   tooling::CompilationDatabase *getCompilationDatabase(PathRef File);
+  Path CompileCommandsDir;  
 
   std::mutex Mutex;
   /// Caches compilation databases loaded from directories(keys are
Index: clangd/GlobalCompilationDatabase.cpp
===================================================================
--- clangd/GlobalCompilationDatabase.cpp
+++ clangd/GlobalCompilationDatabase.cpp
@@ -61,37 +61,47 @@
   ExtraFlagsForFile[File] = std::move(ExtraFlags);
 }
 
+tooling::CompilationDatabase * DirectoryBasedGlobalCompilationDatabase::tryLoadDatabaseFromPath(PathRef File, std::string &Error)
+{
+  auto CachedIt = CompilationDatabases.find(File);
+  if (CachedIt != CompilationDatabases.end())
+    return (CachedIt->second.get());
+  auto CDB = tooling::CompilationDatabase::loadFromDirectory(File, Error);
+  if (CDB && Error.empty())
+  {
+    auto result = CDB.get();
+    CompilationDatabases.insert(std::make_pair(File, std::move(CDB)));
+    return result;
+  }
+  return nullptr;
+}
+
 tooling::CompilationDatabase *
 DirectoryBasedGlobalCompilationDatabase::getCompilationDatabase(PathRef File) {
   std::lock_guard<std::mutex> Lock(Mutex);
-
+  
   namespace path = llvm::sys::path;
-
-  assert((path::is_absolute(File, path::Style::posix) ||
-          path::is_absolute(File, path::Style::windows)) &&
-         "path must be absolute");
+  std::string Error;
+  if (!CompileCommandsDir.empty()) {
+    File = CompileCommandsDir;
+    File = path::parent_path(File);
+    auto CDB = tryLoadDatabaseFromPath(File, Error);
+    
+    if (CDB && Error.empty())
+      return CDB;
+    else
+      return nullptr;
+  }
 
   for (auto Path = path::parent_path(File); !Path.empty();
-       Path = path::parent_path(Path)) {
-
-    auto CachedIt = CompilationDatabases.find(Path);
-    if (CachedIt != CompilationDatabases.end())
-      return CachedIt->second.get();
-    std::string Error;
-    auto CDB = tooling::CompilationDatabase::loadFromDirectory(Path, Error);
-    if (!CDB) {
-      if (!Error.empty()) {
-        // FIXME(ibiryukov): logging
-        // Output.log("Error when trying to load compilation database from " +
-        //            Twine(Path) + ": " + Twine(Error) + "\n");
-      }
+    Path = path::parent_path(Path)) {
+    Error = "";  
+    auto CDB = tryLoadDatabaseFromPath(Path, Error);
+    if (!CDB || !Error.empty())       
       continue;
-    }
-
+       
     // FIXME(ibiryukov): Invalidate cached compilation databases on changes
-    auto result = CDB.get();
-    CompilationDatabases.insert(std::make_pair(Path, std::move(CDB)));
-    return result;
+    return CDB;
   }
 
   // FIXME(ibiryukov): logging
Index: clangd/tool/ClangdMain.cpp
===================================================================
--- clangd/tool/ClangdMain.cpp
+++ clangd/tool/ClangdMain.cpp
@@ -12,7 +12,7 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Program.h"
-
+#include "llvm/Support/Path.h"
 #include <iostream>
 #include <memory>
 #include <string>
@@ -25,6 +25,11 @@
                      llvm::cl::desc("parse on main thread"),
                      llvm::cl::init(false), llvm::cl::Hidden);
 
+static llvm::cl::opt<Path>
+    CompileCommandsDir("compile-commands-dir",
+                     llvm::cl::desc("Specify a path to look for compile_commands.json. If path is invalid, clangd will look in the current directory and parent paths of each source file.")); 
+
+
 int main(int argc, char *argv[]) {
   llvm::cl::ParseCommandLineOptions(argc, argv, "clangd");
 
@@ -32,9 +37,24 @@
   llvm::raw_ostream &Logs = llvm::errs();
   JSONOutput Out(Outs, Logs);
 
+  // If --CompileCommandsDir arg was invoked, check value and override default path.
+  namespace path = llvm::sys::path;
+
+  if (!llvm::sys::path::is_absolute(CompileCommandsDir))
+  {
+    Logs << "Path specified by --compile-commands-dir must be an absolute path. The argument will be ignored.\n";
+    CompileCommandsDir = "";
+  }
+
+  if (!llvm::sys::fs::exists(CompileCommandsDir))
+  {
+    Logs << "File does not exist. The argument will be ignored.\n";
+    CompileCommandsDir = "";
+  }
+
   // Change stdin to binary to not lose \r\n on windows.
   llvm::sys::ChangeStdinToBinary();
 
-  ClangdLSPServer LSPServer(Out, RunSynchronously);
+  ClangdLSPServer LSPServer(Out, RunSynchronously, CompileCommandsDir);
   LSPServer.run(std::cin);
 }