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Document the connection initialization process

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This commit is contained in:
John Ericson 2023-12-04 09:42:04 -05:00
parent 3c5636162a
commit 104baef503
2 changed files with 13 additions and 5 deletions
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16
src/hydra-queue-runner/build-remote.cc
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@ -195,6 +195,12 @@ static std::pair<Path, AutoCloseFD> openLogFile(const std::string & logDir, cons
return {std::move(logFile), std::move(logFD)}; return {std::move(logFile), std::move(logFD)};
} }
/**
* @param conn is not fully initialized; it is this functions job to set
* the `remoteVersion` field after the handshake is completed.
* Therefore, no `ServeProto::Serialize` functions can be used until
* that field is set.
*/
static void handshake(Machine::Connection & conn, unsigned int repeats) static void handshake(Machine::Connection & conn, unsigned int repeats)
{ {
conn.to << SERVE_MAGIC_1 << 0x206; conn.to << SERVE_MAGIC_1 << 0x206;
@ -204,6 +210,7 @@ static void handshake(Machine::Connection & conn, unsigned int repeats)
if (magic != SERVE_MAGIC_2) if (magic != SERVE_MAGIC_2)
throw Error("protocol mismatch with ‘nix-store --serve’ on ‘%1%’", conn.machine->sshName); throw Error("protocol mismatch with ‘nix-store --serve’ on ‘%1%’", conn.machine->sshName);
conn.remoteVersion = readInt(conn.from); conn.remoteVersion = readInt(conn.from);
// Now `conn` is initialized.
if (GET_PROTOCOL_MAJOR(conn.remoteVersion) != 0x200) if (GET_PROTOCOL_MAJOR(conn.remoteVersion) != 0x200)
throw Error("unsupported ‘nix-store --serve’ protocol version on ‘%1%’", conn.machine->sshName); throw Error("unsupported ‘nix-store --serve’ protocol version on ‘%1%’", conn.machine->sshName);
if (GET_PROTOCOL_MINOR(conn.remoteVersion) < 3 && repeats > 0) if (GET_PROTOCOL_MINOR(conn.remoteVersion) < 3 && repeats > 0)
@ -512,10 +519,11 @@ void State::buildRemote(ref<Store> destStore,
process. Meh. */ process. Meh. */
}); });
Machine::Connection conn; Machine::Connection conn {
conn.from = child.from.get(); .from = child.from.get(),
conn.to = child.to.get(); .to = child.to.get(),
conn.machine = machine; .machine = machine,
};
Finally updateStats([&]() { Finally updateStats([&]() {
bytesReceived += conn.from.read; bytesReceived += conn.from.read;

2
src/hydra-queue-runner/state.hh
View file

@ -303,8 +303,8 @@ struct Machine
// A connection to a machine // A connection to a machine
struct Connection { struct Connection {
nix::FdSink to;
nix::FdSource from; nix::FdSource from;
nix::FdSink to;
nix::ServeProto::Version remoteVersion; nix::ServeProto::Version remoteVersion;
// Backpointer to the machine // Backpointer to the machine