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Make adding paths via nix-store --serve run in constant memory

Browse source 
It adds a new operation, cmdAddToStoreNar, that does the same thing as
the corresponding nix-daemon operation, i.e. call addToStore(). This
replaces cmdImportPaths, which has the major issue that it sends the
NAR first and the store path second, thus requiring us to store the
incoming NAR either in memory or on disk until we decide what to do
with it.

For example, this reduces the memory usage of

  $ nix copy --to 'ssh://localhost?remote-store=/tmp/nix' /nix/store/95cwv4q54dc6giaqv6q6p4r02ia2km35-blender-2.79

from 267 MiB to 12 MiB.

Probably fixes #1988.
This commit is contained in:
Eelco Dolstra 2018-08-03 21:10:03 +02:00
parent 34c17fdae5
commit 2825e05d21
No known key found for this signature in database
GPG key ID: 8170B4726D7198DE
4 changed files with 70 additions and 15 deletions
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59
src/libstore/legacy-ssh-store.cc
View file

@ -28,6 +28,7 @@ struct LegacySSHStore : public Store
FdSink to;
FdSource from;
int remoteVersion;
bool good = true;
};
std::string host;
@ -42,7 +43,7 @@ struct LegacySSHStore : public Store
, connections(make_ref<Pool<Connection>>(
std::max(1, (int) maxConnections),
[this]() { return openConnection(); },
[](const ref<Connection> & r) { return true; }
[](const ref<Connection> & r) { return r->good; }
))
, master(
host,
@ -58,7 +59,7 @@ struct LegacySSHStore : public Store
{
auto conn = make_ref<Connection>();
conn->sshConn = master.startCommand(
fmt("%s --serve --write", remoteProgram)
fmt("command time %s --serve --write", remoteProgram)
+ (remoteStore.get() == "" ? "" : " --store " + shellEscape(remoteStore.get())));
conn->to = FdSink(conn->sshConn->in.get());
conn->from = FdSource(conn->sshConn->out.get());
@ -130,18 +131,48 @@ struct LegacySSHStore : public Store
auto conn(connections->get());
conn->to
<< cmdImportPaths
<< 1;
copyNAR(source, conn->to);
conn->to
<< exportMagic
<< info.path
<< info.references
<< info.deriver
<< 0
<< 0;
conn->to.flush();
if (GET_PROTOCOL_MINOR(conn->remoteVersion) >= 4) {
conn->to
<< cmdAddToStoreNar
<< info.path
<< info.deriver
<< info.narHash.to_string(Base16, false)
<< info.references
<< info.registrationTime
<< info.narSize
<< info.ultimate
<< info.sigs
<< info.ca;
try {
copyNAR(source, conn->to);
} catch (...) {
conn->good = false;
throw;
}
conn->to.flush();
} else {
conn->to
<< cmdImportPaths
<< 1;
try {
copyNAR(source, conn->to);
} catch (...) {
conn->good = false;
throw;
}
conn->to
<< exportMagic
<< info.path
<< info.references
<< info.deriver
<< 0
<< 0;
conn->to.flush();
}
if (readInt(conn->from) != 1)
throw Error("failed to add path '%s' to remote host '%s', info.path, host");