lix/src/nix-worker/main.cc
Eelco Dolstra 40c3529909 * Handle exceptions and stderr for all protocol functions.
* SIGIO -> SIGPOLL (POSIX calls it that).
* Use sigaction instead of signal to register the SIGPOLL handler.
  Sigaction is better defined, and a handler registered with signal
  appears not to interrupt fcntl(..., F_SETLKW, ...), which is bad.
2006-12-04 17:55:14 +00:00

488 lines
13 KiB
C++

#include "shared.hh"
#include "local-store.hh"
#include "util.hh"
#include "serialise.hh"
#include "worker-protocol.hh"
#include "archive.hh"
#include "globals.hh"
#include <iostream>
#include <unistd.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <fcntl.h>
using namespace nix;
static Path readStorePath(Source & from)
{
Path path = readString(from);
assertStorePath(path);
return path;
}
static PathSet readStorePaths(Source & from)
{
PathSet paths = readStringSet(from);
for (PathSet::iterator i = paths.begin(); i != paths.end(); ++i)
assertStorePath(*i);
return paths;
}
static FdSource from(STDIN_FILENO);
static FdSink to(STDOUT_FILENO);
bool canSendStderr;
/* This function is called anytime we want to write something to
stderr. If we're in a state where the protocol allows it (i.e.,
when canSendStderr), send the message to the client over the
socket. */
static void tunnelStderr(const unsigned char * buf, size_t count)
{
if (canSendStderr) {
try {
writeInt(STDERR_NEXT, to);
writeString(string((char *) buf, count), to);
} catch (...) {
/* Write failed; that means that the other side is
gone. */
canSendStderr = false;
throw;
}
}
}
/* A SIGPOLL signal is received when data is available on the client
communication scoket, or when the client has closed its side of the
socket. This handler is enabled at precisely those moments in the
protocol when we're doing work and the client is supposed to be
quiet. Thus, if we get a SIGPOLL signal, it means that the client
has quit. So we should quit as well.
Too bad most operating systems don't support the POLL_HUP value for
si_code in siginfo_t. That would make most of the SIGPOLL
complexity unnecessary, i.e., we could just enable SIGPOLL all the
time and wouldn't have to worry about races. */
static void sigioHandler(int sigNo)
{
if (!blockInt) {
_isInterrupted = 1;
blockInt = 1;
canSendStderr = false;
write(STDERR_FILENO, "SIGPOLL\n", 8);
}
}
static void setSigPollAction(bool ignore)
{
struct sigaction act, oact;
act.sa_handler = ignore ? SIG_IGN : sigioHandler;
sigfillset(&act.sa_mask);
act.sa_flags = 0;
if (sigaction(SIGPOLL, &act, &oact))
throw SysError("setting handler for SIGPOLL");
}
/* startWork() means that we're starting an operation for which we
want to send out stderr to the client. */
static void startWork()
{
canSendStderr = true;
/* Handle client death asynchronously. */
setSigPollAction(false);
/* Of course, there is a race condition here: the socket could
have closed between when we last read from / wrote to it, and
between the time we set the handler for SIGPOLL. In that case
we won't get the signal. So do a non-blocking select() to find
out if any input is available on the socket. If there is, it
has to be the 0-byte read that indicates that the socket has
closed. */
struct timeval timeout;
timeout.tv_sec = timeout.tv_usec = 0;
fd_set fds;
FD_ZERO(&fds);
FD_SET(from.fd, &fds);
if (select(from.fd + 1, &fds, 0, 0, &timeout) == -1)
throw SysError("select()");
if (FD_ISSET(from.fd, &fds)) {
char c;
if (read(from.fd, &c, 1) != 0)
throw Error("EOF expected (protocol error?)");
_isInterrupted = 1;
checkInterrupt();
}
}
/* stopWork() means that we're done; stop sending stderr to the
client. */
static void stopWork(bool success = true, const string & msg = "")
{
/* Stop handling async client death; we're going to a state where
we're either sending or receiving from the client, so we'll be
notified of client death anyway. */
setSigPollAction(true);
canSendStderr = false;
if (success)
writeInt(STDERR_LAST, to);
else {
writeInt(STDERR_ERROR, to);
writeString(msg, to);
}
}
static void performOp(Source & from, Sink & to, unsigned int op)
{
switch (op) {
#if 0
case wopQuit: {
/* Close the database. */
store.reset((StoreAPI *) 0);
writeInt(1, to);
break;
}
#endif
case wopIsValidPath: {
Path path = readStorePath(from);
startWork();
bool result = store->isValidPath(path);
stopWork();
writeInt(result, to);
break;
}
case wopHasSubstitutes: {
Path path = readStorePath(from);
startWork();
bool result = store->hasSubstitutes(path);
stopWork();
writeInt(result, to);
break;
}
case wopQueryPathHash: {
Path path = readStorePath(from);
startWork();
Hash hash = store->queryPathHash(path);
stopWork();
writeString(printHash(hash), to);
break;
}
case wopQueryReferences:
case wopQueryReferrers: {
Path path = readStorePath(from);
startWork();
PathSet paths;
if (op == wopQueryReferences)
store->queryReferences(path, paths);
else
store->queryReferrers(path, paths);
stopWork();
writeStringSet(paths, to);
break;
}
case wopAddToStore: {
/* !!! uberquick hack */
string baseName = readString(from);
bool fixed = readInt(from) == 1;
bool recursive = readInt(from) == 1;
string hashAlgo = readString(from);
Path tmp = createTempDir();
Path tmp2 = tmp + "/" + baseName;
restorePath(tmp2, from);
startWork();
Path path = store->addToStore(tmp2, fixed, recursive, hashAlgo);
stopWork();
writeString(path, to);
deletePath(tmp);
break;
}
case wopAddTextToStore: {
string suffix = readString(from);
string s = readString(from);
PathSet refs = readStorePaths(from);
startWork();
Path path = store->addTextToStore(suffix, s, refs);
stopWork();
writeString(path, to);
break;
}
case wopBuildDerivations: {
PathSet drvs = readStorePaths(from);
startWork();
store->buildDerivations(drvs);
stopWork();
writeInt(1, to);
break;
}
case wopEnsurePath: {
Path path = readStorePath(from);
startWork();
store->ensurePath(path);
stopWork();
writeInt(1, to);
break;
}
case wopAddTempRoot: {
Path path = readStorePath(from);
startWork();
store->addTempRoot(path);
stopWork();
writeInt(1, to);
break;
}
case wopSyncWithGC: {
startWork();
store->syncWithGC();
stopWork();
writeInt(1, to);
break;
}
default:
throw Error(format("invalid operation %1%") % op);
}
}
static void processConnection()
{
canSendStderr = false;
writeToStderr = tunnelStderr;
/* Allow us to receive SIGPOLL for events on the client socket. */
setSigPollAction(true);
if (fcntl(from.fd, F_SETOWN, getpid()) == -1)
throw SysError("F_SETOWN");
if (fcntl(from.fd, F_SETFL, fcntl(from.fd, F_GETFL, 0) | FASYNC) == -1)
throw SysError("F_SETFL");
/* Exchange the greeting. */
unsigned int magic = readInt(from);
if (magic != WORKER_MAGIC_1) throw Error("protocol mismatch");
verbosity = (Verbosity) readInt(from);
writeInt(WORKER_MAGIC_2, to);
/* Send startup error messages to the client. */
startWork();
try {
/* Prevent users from doing something very dangerous. */
if (setuidMode && geteuid() == 0 &&
querySetting("build-users", Strings()).size() == 0)
throw Error("if you run `nix-worker' setuid root, then you MUST set `build-users'!");
/* Open the store. */
store = boost::shared_ptr<StoreAPI>(new LocalStore(true));
stopWork();
} catch (Error & e) {
stopWork(false, e.msg());
return;
}
/* Process client requests. */
unsigned int opCount = 0;
while (true) {
WorkerOp op;
try {
op = (WorkerOp) readInt(from);
} catch (EndOfFile & e) {
break;
}
opCount++;
try {
performOp(from, to, op);
} catch (Error & e) {
stopWork(false, e.msg());
}
assert(!canSendStderr);
};
printMsg(lvlError, format("%1% worker operations") % opCount);
}
static void setSigChldAction(bool ignore)
{
struct sigaction act, oact;
act.sa_handler = ignore ? SIG_IGN : SIG_DFL;
sigfillset(&act.sa_mask);
act.sa_flags = 0;
if (sigaction(SIGCHLD, &act, &oact))
throw SysError("setting SIGCHLD handler");
}
static void daemonLoop()
{
/* Get rid of children automatically; don't let them become
zombies. */
setSigChldAction(true);
/* Create and bind to a Unix domain socket. */
AutoCloseFD fdSocket = socket(PF_UNIX, SOCK_STREAM, 0);
if (fdSocket == -1)
throw SysError("cannot create Unix domain socket");
string socketPath = nixStateDir + DEFAULT_SOCKET_PATH;
struct sockaddr_un addr;
addr.sun_family = AF_UNIX;
if (socketPath.size() >= sizeof(addr.sun_path))
throw Error(format("socket path `%1%' is too long") % socketPath);
strcpy(addr.sun_path, socketPath.c_str());
unlink(socketPath.c_str());
/* Make sure that the socket is created with 0666 permission
(everybody can connect). */
mode_t oldMode = umask(0111);
int res = bind(fdSocket, (struct sockaddr *) &addr, sizeof(addr));
umask(oldMode);
if (res == -1)
throw SysError(format("cannot bind to socket `%1%'") % socketPath);
if (listen(fdSocket, 5) == -1)
throw SysError(format("cannot listen on socket `%1%'") % socketPath);
/* Loop accepting connections. */
while (1) {
try {
/* Important: the server process *cannot* open the
Berkeley DB environment, because it doesn't like forks
very much. */
assert(!store);
/* Accept a connection. */
struct sockaddr_un remoteAddr;
socklen_t remoteAddrLen = sizeof(remoteAddr);
AutoCloseFD remote = accept(fdSocket,
(struct sockaddr *) &remoteAddr, &remoteAddrLen);
checkInterrupt();
if (remote == -1)
throw SysError("accepting connection");
printMsg(lvlInfo, format("accepted connection %1%") % remote);
/* Fork a child to handle the connection. */
pid_t child;
child = fork();
switch (child) {
case -1:
throw SysError("unable to fork");
case 0:
try { /* child */
/* Background the worker. */
if (setsid() == -1)
throw SysError(format("creating a new session"));
/* Restore normal handling of SIGCHLD. */
setSigChldAction(false);
/* Handle the connection. */
from.fd = remote;
to.fd = remote;
processConnection();
} catch (std::exception & e) {
std::cerr << format("child error: %1%\n") % e.what();
}
exit(0);
}
} catch (Interrupted & e) {
throw;
} catch (Error & e) {
printMsg(lvlError, format("error processing connection: %1%") % e.msg());
}
}
}
void run(Strings args)
{
bool slave = false;
bool daemon = false;
for (Strings::iterator i = args.begin(); i != args.end(); ) {
string arg = *i++;
if (arg == "--slave") slave = true;
if (arg == "--daemon") daemon = true;
}
if (slave) {
/* This prevents us from receiving signals from the terminal
when we're running in setuid mode. */
if (setsid() == -1)
throw SysError(format("creating a new session"));
processConnection();
}
else if (daemon) {
if (setuidMode)
throw Error("daemon cannot be started in setuid mode");
daemonLoop();
}
else
throw Error("must be run in either --slave or --daemon mode");
}
#include "help.txt.hh"
void printHelp()
{
std::cout << string((char *) helpText, sizeof helpText);
}
string programId = "nix-worker";