diff options
author | Ludovic Courtès <ludo@gnu.org> | 2020-09-11 12:34:25 +0200 |
---|---|---|
committer | Ludovic Courtès <ludo@gnu.org> | 2020-09-14 15:42:55 +0200 |
commit | ee9dff34f9317509cb2b833d07a0d5e01a36a4ae (patch) | |
tree | 47027d9453eb3fe69f61bdc31d6d480a20e1217a /nix/libutil | |
parent | 27cc51c269fbe9d2ca65711d281c63ae441a9b4a (diff) |
daemon: Move 'Agent' to libutil.
* nix/libstore/build.cc (DerivationGoal::tryBuildHook): Add "offload" to
'args' and pass settings.guixProgram as the first argument to
Agent::Agent.
(pathNullDevice, commonChildInit, Agent, Agent::Agent)
(Agent::~Agent): Move to...
* nix/libutil/util.cc: ... here.
* nix/libutil/util.hh (struct Agent, commonChildInit): New
declarations.
Diffstat (limited to 'nix/libutil')
-rw-r--r-- | nix/libutil/util.cc | 84 | ||||
-rw-r--r-- | nix/libutil/util.hh | 25 |
2 files changed, 109 insertions, 0 deletions
diff --git a/nix/libutil/util.cc b/nix/libutil/util.cc index 17d145b4c6..59a2981359 100644 --- a/nix/libutil/util.cc +++ b/nix/libutil/util.cc @@ -1142,5 +1142,89 @@ void ignoreException() } } +static const string pathNullDevice = "/dev/null"; + +/* Common initialisation performed in child processes. */ +void commonChildInit(Pipe & logPipe) +{ + /* Put the child in a separate session (and thus a separate + process group) so that it has no controlling terminal (meaning + that e.g. ssh cannot open /dev/tty) and it doesn't receive + terminal signals. */ + if (setsid() == -1) + throw SysError(format("creating a new session")); + + /* Dup the write side of the logger pipe into stderr. */ + if (dup2(logPipe.writeSide, STDERR_FILENO) == -1) + throw SysError("cannot pipe standard error into log file"); + + /* Dup stderr to stdout. */ + if (dup2(STDERR_FILENO, STDOUT_FILENO) == -1) + throw SysError("cannot dup stderr into stdout"); + + /* Reroute stdin to /dev/null. */ + int fdDevNull = open(pathNullDevice.c_str(), O_RDWR); + if (fdDevNull == -1) + throw SysError(format("cannot open `%1%'") % pathNullDevice); + if (dup2(fdDevNull, STDIN_FILENO) == -1) + throw SysError("cannot dup null device into stdin"); + close(fdDevNull); +} + +////////////////////////////////////////////////////////////////////// + +Agent::Agent(const string &command, const Strings &args) +{ + debug(format("starting agent '%1%'") % command); + + /* Create a pipe to get the output of the child. */ + fromAgent.create(); + + /* Create the communication pipes. */ + toAgent.create(); + + /* Create a pipe to get the output of the builder. */ + builderOut.create(); + + /* Fork the hook. */ + pid = startProcess([&]() { + + commonChildInit(fromAgent); + + if (chdir("/") == -1) throw SysError("changing into `/"); + + /* Dup the communication pipes. */ + if (dup2(toAgent.readSide, STDIN_FILENO) == -1) + throw SysError("dupping to-hook read side"); + + /* Use fd 4 for the builder's stdout/stderr. */ + if (dup2(builderOut.writeSide, 4) == -1) + throw SysError("dupping builder's stdout/stderr"); + + Strings allArgs; + allArgs.push_back(command); + allArgs.insert(allArgs.end(), args.begin(), args.end()); // append + + execv(command.c_str(), stringsToCharPtrs(allArgs).data()); + + throw SysError(format("executing `%1%'") % command); + }); + + pid.setSeparatePG(true); + fromAgent.writeSide.close(); + toAgent.readSide.close(); +} + + +Agent::~Agent() +{ + try { + toAgent.writeSide.close(); + pid.kill(true); + } catch (...) { + ignoreException(); + } +} + } diff --git a/nix/libutil/util.hh b/nix/libutil/util.hh index 9e3c14bdd4..13cff44316 100644 --- a/nix/libutil/util.hh +++ b/nix/libutil/util.hh @@ -264,6 +264,29 @@ public: void setKillSignal(int signal); }; +/* An "agent" is a helper program that runs in the background and that we talk + to over pipes, such as the "guix offload" program. */ +struct Agent +{ + /* Pipes for talking to the agent. */ + Pipe toAgent; + + /* Pipe for the agent's standard output/error. */ + Pipe fromAgent; + + /* Pipe for build standard output/error--e.g., for build processes started + by "guix offload". */ + Pipe builderOut; + + /* The process ID of the agent. */ + Pid pid; + + /* The command and arguments passed to the agent. */ + Agent(const string &command, const Strings &args); + + ~Agent(); +}; + /* Kill all processes running under the specified uid by sending them a SIGKILL. */ @@ -295,6 +318,8 @@ void closeMostFDs(const set<int> & exceptions); /* Set the close-on-exec flag for the given file descriptor. */ void closeOnExec(int fd); +/* Common initialisation performed in child processes. */ +void commonChildInit(Pipe & logPipe); /* User interruption. */ |