llvm/clang-tools-extra/clangd/index/BackgroundRebuild.h

//===--- BackgroundIndexRebuild.h - when to rebuild the bg index--*- C++-*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains an implementation detail of the background indexer
// (Background.h), which is exposed for testing.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_BACKGROUNDREBUILD_H
#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_BACKGROUNDREBUILD_H

#include "index/FileIndex.h"
#include "index/Index.h"
#include <cstddef>

namespace clang {
namespace clangd {

// The BackgroundIndexRebuilder builds the serving data structures periodically
// in response to events in the background indexer. The goal is to ensure the
// served data stays fairly fresh, without wasting lots of CPU rebuilding it
// often.
//
// The index is always built after a set of shards are loaded from disk.
// This happens when clangd discovers a compilation database that we've
// previously built an index for. It's a fairly fast process that yields lots
// of data, so we wait to get all of it.
//
// The index is built after indexing a few translation units, if it wasn't built
// already. This ensures quick startup if there's no existing index.
// Waiting for a few random TUs yields coverage of the most common headers.
//
// The index is rebuilt every N TUs, to keep if fresh as files are indexed.
//
// The index is rebuilt every time the queue goes idle, if it's stale.
//
// All methods are threadsafe. They're called after FileSymbols is updated
// etc. Without external locking, the rebuilt index may include more updates
// than intended, which is fine.
//
// This class is exposed in the header so it can be tested.
class BackgroundIndexRebuilder { … };

} // namespace clangd
} // namespace clang

#endif