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Merge "gc: refactor the gc server thread out into a class without changing it" into main

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jade 2024-07-21 10:36:10 +00:00 committed by Gerrit Code Review
parent 1917e6c765 77ff799cc8
commit 4fa6961aa2
4 changed files with 197 additions and 132 deletions
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176
src/libstore/gc.cc
View file

@ -22,8 +22,8 @@
namespace nix {
static std::string gcSocketPath = "/gc-socket/socket";
static std::string gcRootsDir = "gcroots";
constexpr static const std::string_view gcSocketPath = "/gc-socket/socket";
constexpr static const std::string_view gcRootsDir = "gcroots";
static void makeSymlink(const Path & link, const Path & target)
@ -359,16 +359,34 @@ void LocalStore::findRuntimeRoots(Roots & roots, bool censor)
}
struct GCLimitReached { };
struct GCLimitReached : std::exception { };
void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
{
bool shouldDelete = options.action == GCOptions::gcDeleteDead || options.action == GCOptions::gcDeleteSpecific;
bool gcKeepOutputs = settings.gcKeepOutputs;
bool gcKeepDerivations = settings.gcKeepDerivations;
/**
* Delegate class to expose just the operations required to perform GC on a store.
*/
class GCStoreDelegate {
LocalStore const & store;
StorePathSet roots, dead, alive;
public:
GCStoreDelegate(LocalStore const & store) : store(store) {}
std::optional<StorePath> maybeParseStorePath(std::string_view path) const {
return store.maybeParseStorePath(path);
}
};
/**
* Class holding a server to receive new GC roots.
*/
class GCOperation {
const GCStoreDelegate store;
std::thread serverThread;
Pipe shutdownPipe;
AutoCloseFD fdServer;
struct Shared
{
@ -381,45 +399,60 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
std::optional<std::string> pending;
};
Sync<Shared> _shared;
void runServerThread();
std::condition_variable wakeup;
Sync<Shared> _shared;
/* Using `--ignore-liveness' with `--delete' can have unintended
consequences if `keep-outputs' or `keep-derivations' are true
(the garbage collector will recurse into deleting the outputs
or derivers, respectively). So disable them. */
if (options.action == GCOptions::gcDeleteSpecific && options.ignoreLiveness) {
gcKeepOutputs = false;
gcKeepDerivations = false;
}
if (shouldDelete)
deletePath(reservedPath);
/* Acquire the global GC root. Note: we don't use fdGCLock
here because then in auto-gc mode, another thread could
downgrade our exclusive lock. */
auto fdGCLock = openGCLock();
FdLock gcLock(fdGCLock.get(), ltWrite, true, "waiting for the big garbage collector lock...");
/* Synchronisation point to test ENOENT handling in
addTempRoot(), see tests/gc-non-blocking.sh. */
if (auto p = getEnv("_NIX_TEST_GC_SYNC_1"))
readFile(*p);
public:
GCOperation(LocalStore const & store, Path stateDir) : store(store)
{
/* Start the server for receiving new roots. */
auto socketPath = stateDir.get() + gcSocketPath;
createDirs(dirOf(socketPath));
auto fdServer = createUnixDomainSocket(socketPath, 0666);
if (fcntl(fdServer.get(), F_SETFL, fcntl(fdServer.get(), F_GETFL) | O_NONBLOCK) == -1)
throw SysError("making socket '%1%' non-blocking", socketPath);
Pipe shutdownPipe;
shutdownPipe.create();
std::thread serverThread([&]() {
auto socketPath = stateDir + gcSocketPath;
createDirs(dirOf(socketPath));
fdServer = createUnixDomainSocket(socketPath, 0666);
if (fcntl(fdServer.get(), F_SETFL, fcntl(fdServer.get(), F_GETFL) | O_NONBLOCK) == -1) {
throw SysError("making socket '%1%' non-blocking", socketPath);
}
serverThread = std::thread([this]() { runServerThread(); });
}
void addTempRoot(std::string rootHashPart)
{
_shared.lock()->tempRoots.insert(rootHashPart);
}
void releasePending()
{
auto shared(_shared.lock());
shared->pending.reset();
wakeup.notify_all();
}
/**
* Marks a path as pending deletion if it is not in tempRoots.
*
* Returns whether it was marked for deletion.
*/
bool markPendingIfPresent(std::string const & hashPart)
{
auto shared(_shared.lock());
if (shared->tempRoots.count(hashPart)) {
return false;
}
shared->pending = hashPart;
return true;
}
~GCOperation();
};
void GCOperation::runServerThread()
{
Sync<std::map<int, std::thread>> connections;
Finally cleanup([&]() {
@ -474,7 +507,7 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
while (true) {
try {
auto path = readLine(fdClient.get());
auto storePath = maybeParseStorePath(path);
auto storePath = store.maybeParseStorePath(path);
if (storePath) {
debug("got new GC root '%s'", path);
auto hashPart = std::string(storePath->hashPart());
@ -505,13 +538,51 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
connections.lock()->insert({fdClient_, std::move(clientThread)});
}
}
});
}
Finally stopServer([&]() {
GCOperation::~GCOperation()
{
writeFull(shutdownPipe.writeSide.get(), "x", false);
{
auto shared(_shared.lock());
wakeup.notify_all();
}
if (serverThread.joinable()) serverThread.join();
});
}
void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
{
bool shouldDelete = options.action == GCOptions::gcDeleteDead || options.action == GCOptions::gcDeleteSpecific;
bool gcKeepOutputs = settings.gcKeepOutputs;
bool gcKeepDerivations = settings.gcKeepDerivations;
StorePathSet roots, dead, alive;
/* Using `--ignore-liveness' with `--delete' can have unintended
consequences if `keep-outputs' or `keep-derivations' are true
(the garbage collector will recurse into deleting the outputs
or derivers, respectively). So disable them. */
if (options.action == GCOptions::gcDeleteSpecific && options.ignoreLiveness) {
gcKeepOutputs = false;
gcKeepDerivations = false;
}
if (shouldDelete)
deletePath(reservedSpacePath);
/* Acquire the global GC root. Note: we don't use fdGCLock
here because then in auto-gc mode, another thread could
downgrade our exclusive lock. */
auto fdGCLock = openGCLock();
FdLock gcLock(fdGCLock.get(), ltWrite, true, "waiting for the big garbage collector lock...");
/* Synchronisation point to test ENOENT handling in
addTempRoot(), see tests/gc-non-blocking.sh. */
if (auto p = getEnv("_NIX_TEST_GC_SYNC_1"))
readFile(*p);
GCOperation gcServer {*this, stateDir.get()};
/* Find the roots. Since we've grabbed the GC lock, the set of
permanent roots cannot increase now. */
@ -527,7 +598,7 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
Roots tempRoots;
findTempRoots(tempRoots, true);
for (auto & root : tempRoots) {
_shared.lock()->tempRoots.insert(std::string(root.first.hashPart()));
gcServer.addTempRoot(std::string(root.first.hashPart()));
roots.insert(root.first);
}
@ -580,9 +651,7 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
/* Wake up any GC client waiting for deletion of the paths in
'visited' to finish. */
Finally releasePending([&]() {
auto shared(_shared.lock());
shared->pending.reset();
wakeup.notify_all();
gcServer.releasePending();
});
auto enqueue = [&](const StorePath & path) {
@ -629,15 +698,10 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
&& !options.pathsToDelete.count(*path))
return;
{
auto hashPart = std::string(path->hashPart());
auto shared(_shared.lock());
if (shared->tempRoots.count(hashPart)) {
if (!gcServer.markPendingIfPresent(std::string(path->hashPart()))) {
debug("cannot delete '%s' because it's a temporary root", printStorePath(*path));
return markAlive();
}
shared->pending = hashPart;
}
if (isValidPath(*path)) {

6
src/libstore/local-store.cc
View file

@ -181,7 +181,7 @@ LocalStore::LocalStore(const Params & params)
, LocalFSStore(params)
, dbDir(stateDir + "/db")
, linksDir(realStoreDir + "/.links")
, reservedPath(dbDir + "/reserved")
, reservedSpacePath(dbDir + "/reserved")
, schemaPath(dbDir + "/schema")
, tempRootsDir(stateDir + "/temproots")
, fnTempRoots(fmt("%s/%d", tempRootsDir, getpid()))
@ -259,10 +259,10 @@ LocalStore::LocalStore(const Params & params)
before doing a garbage collection. */
try {
struct stat st;
if (stat(reservedPath.c_str(), &st) == -1 ||
if (stat(reservedSpacePath.c_str(), &st) == -1 ||
st.st_size != settings.reservedSize)
{
AutoCloseFD fd{open(reservedPath.c_str(), O_WRONLY | O_CREAT | O_CLOEXEC, 0600)};
AutoCloseFD fd{open(reservedSpacePath.c_str(), O_WRONLY | O_CREAT | O_CLOEXEC, 0600)};
int res = -1;
#if HAVE_POSIX_FALLOCATE
res = posix_fallocate(fd.get(), 0, settings.reservedSize);

3
src/libstore/local-store.hh
View file

@ -119,7 +119,8 @@ public:
const Path dbDir;
const Path linksDir;
const Path reservedPath;
/** Path kept around to reserve some filesystem space to be able to begin a garbage collection */
const Path reservedSpacePath;
const Path schemaPath;
const Path tempRootsDir;
const Path fnTempRoots;

2
tests/functional/gc-non-blocking.sh
View file

@ -33,7 +33,7 @@ sleep 2
pid2=$!
# Start a build. This should not be blocked by the GC in progress.
outPath=$(nix-build --max-silent-time 60 -o "$TEST_ROOT/result" -E "
outPath=$(nix-build --max-silent-time 60 --debug -o "$TEST_ROOT/result" -E "
with import ./config.nix;
mkDerivation {
name = \"non-blocking\";