• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 //===-- Background.cpp - Build an index in a background thread ------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "index/Background.h"
10 #include "Compiler.h"
11 #include "Config.h"
12 #include "Headers.h"
13 #include "ParsedAST.h"
14 #include "SourceCode.h"
15 #include "Symbol.h"
16 #include "URI.h"
17 #include "index/BackgroundIndexLoader.h"
18 #include "index/FileIndex.h"
19 #include "index/Index.h"
20 #include "index/IndexAction.h"
21 #include "index/MemIndex.h"
22 #include "index/Ref.h"
23 #include "index/Relation.h"
24 #include "index/Serialization.h"
25 #include "index/SymbolCollector.h"
26 #include "support/Context.h"
27 #include "support/Logger.h"
28 #include "support/Path.h"
29 #include "support/Threading.h"
30 #include "support/ThreadsafeFS.h"
31 #include "support/Trace.h"
32 #include "clang/Basic/SourceLocation.h"
33 #include "clang/Basic/SourceManager.h"
34 #include "clang/Driver/Types.h"
35 #include "llvm/ADT/ArrayRef.h"
36 #include "llvm/ADT/DenseSet.h"
37 #include "llvm/ADT/Hashing.h"
38 #include "llvm/ADT/STLExtras.h"
39 #include "llvm/ADT/ScopeExit.h"
40 #include "llvm/ADT/StringMap.h"
41 #include "llvm/ADT/StringRef.h"
42 #include "llvm/ADT/StringSet.h"
43 #include "llvm/Support/Error.h"
44 #include "llvm/Support/Path.h"
45 #include "llvm/Support/Threading.h"
46 
47 #include <algorithm>
48 #include <atomic>
49 #include <chrono>
50 #include <condition_variable>
51 #include <cstddef>
52 #include <memory>
53 #include <mutex>
54 #include <numeric>
55 #include <queue>
56 #include <random>
57 #include <string>
58 #include <thread>
59 #include <utility>
60 #include <vector>
61 
62 namespace clang {
63 namespace clangd {
64 namespace {
65 
66 // We cannot use vfs->makeAbsolute because Cmd.FileName is either absolute or
67 // relative to Cmd.Directory, which might not be the same as current working
68 // directory.
getAbsolutePath(const tooling::CompileCommand & Cmd)69 llvm::SmallString<128> getAbsolutePath(const tooling::CompileCommand &Cmd) {
70   llvm::SmallString<128> AbsolutePath;
71   if (llvm::sys::path::is_absolute(Cmd.Filename)) {
72     AbsolutePath = Cmd.Filename;
73   } else {
74     AbsolutePath = Cmd.Directory;
75     llvm::sys::path::append(AbsolutePath, Cmd.Filename);
76     llvm::sys::path::remove_dots(AbsolutePath, true);
77   }
78   return AbsolutePath;
79 }
80 
shardIsStale(const LoadedShard & LS,llvm::vfs::FileSystem * FS)81 bool shardIsStale(const LoadedShard &LS, llvm::vfs::FileSystem *FS) {
82   auto Buf = FS->getBufferForFile(LS.AbsolutePath);
83   if (!Buf) {
84     elog("Background-index: Couldn't read {0} to validate stored index: {1}",
85          LS.AbsolutePath, Buf.getError().message());
86     // There is no point in indexing an unreadable file.
87     return false;
88   }
89   return digest(Buf->get()->getBuffer()) != LS.Digest;
90 }
91 
92 } // namespace
93 
BackgroundIndex(const ThreadsafeFS & TFS,const GlobalCompilationDatabase & CDB,BackgroundIndexStorage::Factory IndexStorageFactory,Options Opts)94 BackgroundIndex::BackgroundIndex(
95     const ThreadsafeFS &TFS, const GlobalCompilationDatabase &CDB,
96     BackgroundIndexStorage::Factory IndexStorageFactory, Options Opts)
97     : SwapIndex(std::make_unique<MemIndex>()), TFS(TFS), CDB(CDB),
98       ContextProvider(std::move(Opts.ContextProvider)),
99       CollectMainFileRefs(Opts.CollectMainFileRefs),
100       Rebuilder(this, &IndexedSymbols, Opts.ThreadPoolSize),
101       IndexStorageFactory(std::move(IndexStorageFactory)),
102       Queue(std::move(Opts.OnProgress)),
103       CommandsChanged(
104           CDB.watch([&](const std::vector<std::string> &ChangedFiles) {
105             enqueue(ChangedFiles);
106           })) {
107   assert(Opts.ThreadPoolSize > 0 && "Thread pool size can't be zero.");
108   assert(this->IndexStorageFactory && "Storage factory can not be null!");
109   for (unsigned I = 0; I < Opts.ThreadPoolSize; ++I) {
110     ThreadPool.runAsync("background-worker-" + llvm::Twine(I + 1),
__anonfb3054390302() 111                         [this, Ctx(Context::current().clone())]() mutable {
112                           WithContext BGContext(std::move(Ctx));
113                           Queue.work([&] { Rebuilder.idle(); });
114                         });
115   }
116 }
117 
~BackgroundIndex()118 BackgroundIndex::~BackgroundIndex() {
119   stop();
120   ThreadPool.wait();
121 }
122 
changedFilesTask(const std::vector<std::string> & ChangedFiles)123 BackgroundQueue::Task BackgroundIndex::changedFilesTask(
124     const std::vector<std::string> &ChangedFiles) {
125   BackgroundQueue::Task T([this, ChangedFiles] {
126     trace::Span Tracer("BackgroundIndexEnqueue");
127 
128     llvm::Optional<WithContext> WithProvidedContext;
129     if (ContextProvider)
130       WithProvidedContext.emplace(ContextProvider(/*Path=*/""));
131 
132     // We're doing this asynchronously, because we'll read shards here too.
133     log("Enqueueing {0} commands for indexing", ChangedFiles.size());
134     SPAN_ATTACH(Tracer, "files", int64_t(ChangedFiles.size()));
135 
136     auto NeedsReIndexing = loadProject(std::move(ChangedFiles));
137     // Run indexing for files that need to be updated.
138     std::shuffle(NeedsReIndexing.begin(), NeedsReIndexing.end(),
139                  std::mt19937(std::random_device{}()));
140     std::vector<BackgroundQueue::Task> Tasks;
141     Tasks.reserve(NeedsReIndexing.size());
142     for (auto &Cmd : NeedsReIndexing)
143       Tasks.push_back(indexFileTask(std::move(Cmd)));
144     Queue.append(std::move(Tasks));
145   });
146 
147   T.QueuePri = LoadShards;
148   T.ThreadPri = llvm::ThreadPriority::Default;
149   return T;
150 }
151 
filenameWithoutExtension(llvm::StringRef Path)152 static llvm::StringRef filenameWithoutExtension(llvm::StringRef Path) {
153   Path = llvm::sys::path::filename(Path);
154   return Path.drop_back(llvm::sys::path::extension(Path).size());
155 }
156 
indexFileTask(std::string Path)157 BackgroundQueue::Task BackgroundIndex::indexFileTask(std::string Path) {
158   std::string Tag = filenameWithoutExtension(Path).str();
159   BackgroundQueue::Task T([this, Path(std::move(Path))] {
160     llvm::Optional<WithContext> WithProvidedContext;
161     if (ContextProvider)
162       WithProvidedContext.emplace(ContextProvider(Path));
163     auto Cmd = CDB.getCompileCommand(Path);
164     if (!Cmd)
165       return;
166     if (auto Error = index(std::move(*Cmd)))
167       elog("Indexing {0} failed: {1}", Path, std::move(Error));
168   });
169   T.QueuePri = IndexFile;
170   T.Tag = std::move(Tag);
171   return T;
172 }
173 
boostRelated(llvm::StringRef Path)174 void BackgroundIndex::boostRelated(llvm::StringRef Path) {
175   if (isHeaderFile(Path))
176     Queue.boost(filenameWithoutExtension(Path), IndexBoostedFile);
177 }
178 
179 /// Given index results from a TU, only update symbols coming from files that
180 /// are different or missing from than \p ShardVersionsSnapshot. Also stores new
181 /// index information on IndexStorage.
update(llvm::StringRef MainFile,IndexFileIn Index,const llvm::StringMap<ShardVersion> & ShardVersionsSnapshot,bool HadErrors)182 void BackgroundIndex::update(
183     llvm::StringRef MainFile, IndexFileIn Index,
184     const llvm::StringMap<ShardVersion> &ShardVersionsSnapshot,
185     bool HadErrors) {
186   // Keys are URIs.
187   llvm::StringMap<std::pair<Path, FileDigest>> FilesToUpdate;
188   // Note that sources do not contain any information regarding missing headers,
189   // since we don't even know what absolute path they should fall in.
190   for (const auto &IndexIt : *Index.Sources) {
191     const auto &IGN = IndexIt.getValue();
192     auto AbsPath = URI::resolve(IGN.URI, MainFile);
193     if (!AbsPath) {
194       elog("Failed to resolve URI: {0}", AbsPath.takeError());
195       continue;
196     }
197     const auto DigestIt = ShardVersionsSnapshot.find(*AbsPath);
198     // File has different contents, or indexing was successful this time.
199     if (DigestIt == ShardVersionsSnapshot.end() ||
200         DigestIt->getValue().Digest != IGN.Digest ||
201         (DigestIt->getValue().HadErrors && !HadErrors))
202       FilesToUpdate[IGN.URI] = {std::move(*AbsPath), IGN.Digest};
203   }
204 
205   // Shard slabs into files.
206   FileShardedIndex ShardedIndex(std::move(Index));
207 
208   // Build and store new slabs for each updated file.
209   for (const auto &FileIt : FilesToUpdate) {
210     auto Uri = FileIt.first();
211     auto IF = ShardedIndex.getShard(Uri);
212     assert(IF && "no shard for file in Index.Sources?");
213     PathRef Path = FileIt.getValue().first;
214 
215     // Only store command line hash for main files of the TU, since our
216     // current model keeps only one version of a header file.
217     if (Path != MainFile)
218       IF->Cmd.reset();
219 
220     // We need to store shards before updating the index, since the latter
221     // consumes slabs.
222     // FIXME: Also skip serializing the shard if it is already up-to-date.
223     if (auto Error = IndexStorageFactory(Path)->storeShard(Path, *IF))
224       elog("Failed to write background-index shard for file {0}: {1}", Path,
225            std::move(Error));
226 
227     {
228       std::lock_guard<std::mutex> Lock(ShardVersionsMu);
229       const auto &Hash = FileIt.getValue().second;
230       auto DigestIt = ShardVersions.try_emplace(Path);
231       ShardVersion &SV = DigestIt.first->second;
232       // Skip if file is already up to date, unless previous index was broken
233       // and this one is not.
234       if (!DigestIt.second && SV.Digest == Hash && SV.HadErrors && !HadErrors)
235         continue;
236       SV.Digest = Hash;
237       SV.HadErrors = HadErrors;
238 
239       // This can override a newer version that is added in another thread, if
240       // this thread sees the older version but finishes later. This should be
241       // rare in practice.
242       IndexedSymbols.update(
243           Path, std::make_unique<SymbolSlab>(std::move(*IF->Symbols)),
244           std::make_unique<RefSlab>(std::move(*IF->Refs)),
245           std::make_unique<RelationSlab>(std::move(*IF->Relations)),
246           Path == MainFile);
247     }
248   }
249 }
250 
index(tooling::CompileCommand Cmd)251 llvm::Error BackgroundIndex::index(tooling::CompileCommand Cmd) {
252   trace::Span Tracer("BackgroundIndex");
253   SPAN_ATTACH(Tracer, "file", Cmd.Filename);
254   auto AbsolutePath = getAbsolutePath(Cmd);
255 
256   auto FS = TFS.view(Cmd.Directory);
257   auto Buf = FS->getBufferForFile(AbsolutePath);
258   if (!Buf)
259     return llvm::errorCodeToError(Buf.getError());
260   auto Hash = digest(Buf->get()->getBuffer());
261 
262   // Take a snapshot of the versions to avoid locking for each file in the TU.
263   llvm::StringMap<ShardVersion> ShardVersionsSnapshot;
264   {
265     std::lock_guard<std::mutex> Lock(ShardVersionsMu);
266     ShardVersionsSnapshot = ShardVersions;
267   }
268 
269   vlog("Indexing {0} (digest:={1})", Cmd.Filename, llvm::toHex(Hash));
270   ParseInputs Inputs;
271   Inputs.TFS = &TFS;
272   Inputs.CompileCommand = std::move(Cmd);
273   IgnoreDiagnostics IgnoreDiags;
274   auto CI = buildCompilerInvocation(Inputs, IgnoreDiags);
275   if (!CI)
276     return error("Couldn't build compiler invocation");
277 
278   auto Clang =
279       prepareCompilerInstance(std::move(CI), /*Preamble=*/nullptr,
280                               std::move(*Buf), std::move(FS), IgnoreDiags);
281   if (!Clang)
282     return error("Couldn't build compiler instance");
283 
284   SymbolCollector::Options IndexOpts;
285   // Creates a filter to not collect index results from files with unchanged
286   // digests.
287   IndexOpts.FileFilter = [&ShardVersionsSnapshot](const SourceManager &SM,
288                                                   FileID FID) {
289     const auto *F = SM.getFileEntryForID(FID);
290     if (!F)
291       return false; // Skip invalid files.
292     auto AbsPath = getCanonicalPath(F, SM);
293     if (!AbsPath)
294       return false; // Skip files without absolute path.
295     auto Digest = digestFile(SM, FID);
296     if (!Digest)
297       return false;
298     auto D = ShardVersionsSnapshot.find(*AbsPath);
299     if (D != ShardVersionsSnapshot.end() && D->second.Digest == Digest &&
300         !D->second.HadErrors)
301       return false; // Skip files that haven't changed, without errors.
302     return true;
303   };
304   IndexOpts.CollectMainFileRefs = CollectMainFileRefs;
305 
306   IndexFileIn Index;
307   auto Action = createStaticIndexingAction(
308       IndexOpts, [&](SymbolSlab S) { Index.Symbols = std::move(S); },
309       [&](RefSlab R) { Index.Refs = std::move(R); },
310       [&](RelationSlab R) { Index.Relations = std::move(R); },
311       [&](IncludeGraph IG) { Index.Sources = std::move(IG); });
312 
313   // We're going to run clang here, and it could potentially crash.
314   // We could use CrashRecoveryContext to try to make indexing crashes nonfatal,
315   // but the leaky "recovery" is pretty scary too in a long-running process.
316   // If crashes are a real problem, maybe we should fork a child process.
317 
318   const FrontendInputFile &Input = Clang->getFrontendOpts().Inputs.front();
319   if (!Action->BeginSourceFile(*Clang, Input))
320     return error("BeginSourceFile() failed");
321   if (llvm::Error Err = Action->Execute())
322     return Err;
323 
324   Action->EndSourceFile();
325 
326   Index.Cmd = Inputs.CompileCommand;
327   assert(Index.Symbols && Index.Refs && Index.Sources &&
328          "Symbols, Refs and Sources must be set.");
329 
330   log("Indexed {0} ({1} symbols, {2} refs, {3} files)",
331       Inputs.CompileCommand.Filename, Index.Symbols->size(),
332       Index.Refs->numRefs(), Index.Sources->size());
333   SPAN_ATTACH(Tracer, "symbols", int(Index.Symbols->size()));
334   SPAN_ATTACH(Tracer, "refs", int(Index.Refs->numRefs()));
335   SPAN_ATTACH(Tracer, "sources", int(Index.Sources->size()));
336 
337   bool HadErrors = Clang->hasDiagnostics() &&
338                    Clang->getDiagnostics().hasUncompilableErrorOccurred();
339   if (HadErrors) {
340     log("Failed to compile {0}, index may be incomplete", AbsolutePath);
341     for (auto &It : *Index.Sources)
342       It.second.Flags |= IncludeGraphNode::SourceFlag::HadErrors;
343   }
344   update(AbsolutePath, std::move(Index), ShardVersionsSnapshot, HadErrors);
345 
346   Rebuilder.indexedTU();
347   return llvm::Error::success();
348 }
349 
350 // Restores shards for \p MainFiles from index storage. Then checks staleness of
351 // those shards and returns a list of TUs that needs to be indexed to update
352 // staleness.
353 std::vector<std::string>
loadProject(std::vector<std::string> MainFiles)354 BackgroundIndex::loadProject(std::vector<std::string> MainFiles) {
355   // Drop files where background indexing is disabled in config.
356   if (ContextProvider)
357     llvm::erase_if(MainFiles, [&](const std::string &TU) {
358       // Load the config for each TU, as indexing may be selectively enabled.
359       WithContext WithProvidedContext(ContextProvider(TU));
360       return Config::current().Index.Background ==
361              Config::BackgroundPolicy::Skip;
362     });
363   Rebuilder.startLoading();
364   // Load shards for all of the mainfiles.
365   const std::vector<LoadedShard> Result =
366       loadIndexShards(MainFiles, IndexStorageFactory, CDB);
367   size_t LoadedShards = 0;
368   {
369     // Update in-memory state.
370     std::lock_guard<std::mutex> Lock(ShardVersionsMu);
371     for (auto &LS : Result) {
372       if (!LS.Shard)
373         continue;
374       auto SS =
375           LS.Shard->Symbols
376               ? std::make_unique<SymbolSlab>(std::move(*LS.Shard->Symbols))
377               : nullptr;
378       auto RS = LS.Shard->Refs
379                     ? std::make_unique<RefSlab>(std::move(*LS.Shard->Refs))
380                     : nullptr;
381       auto RelS =
382           LS.Shard->Relations
383               ? std::make_unique<RelationSlab>(std::move(*LS.Shard->Relations))
384               : nullptr;
385       ShardVersion &SV = ShardVersions[LS.AbsolutePath];
386       SV.Digest = LS.Digest;
387       SV.HadErrors = LS.HadErrors;
388       ++LoadedShards;
389 
390       IndexedSymbols.update(LS.AbsolutePath, std::move(SS), std::move(RS),
391                             std::move(RelS), LS.CountReferences);
392     }
393   }
394   Rebuilder.loadedShard(LoadedShards);
395   Rebuilder.doneLoading();
396 
397   auto FS = TFS.view(/*CWD=*/llvm::None);
398   llvm::DenseSet<PathRef> TUsToIndex;
399   // We'll accept data from stale shards, but ensure the files get reindexed
400   // soon.
401   for (auto &LS : Result) {
402     if (!shardIsStale(LS, FS.get()))
403       continue;
404     PathRef TUForFile = LS.DependentTU;
405     assert(!TUForFile.empty() && "File without a TU!");
406 
407     // FIXME: Currently, we simply schedule indexing on a TU whenever any of
408     // its dependencies needs re-indexing. We might do it smarter by figuring
409     // out a minimal set of TUs that will cover all the stale dependencies.
410     // FIXME: Try looking at other TUs if no compile commands are available
411     // for this TU, i.e TU was deleted after we performed indexing.
412     TUsToIndex.insert(TUForFile);
413   }
414 
415   return {TUsToIndex.begin(), TUsToIndex.end()};
416 }
417 
profile(MemoryTree & MT) const418 void BackgroundIndex::profile(MemoryTree &MT) const {
419   IndexedSymbols.profile(MT.child("slabs"));
420   // We don't want to mix memory used by index and symbols, so call base class.
421   MT.child("index").addUsage(SwapIndex::estimateMemoryUsage());
422 }
423 } // namespace clangd
424 } // namespace clang
425