Caching path info is generally useful. For instance, it speeds up "nix
path-info -rS /run/current-system" (i.e. showing the closure sizes of
all paths in the closure of the current system) from 5.6s to 0.15s.
This also eliminates some APIs like Store::queryDeriver() and
Store::queryReferences().
These are content-addressed paths or outputs of locally performed
builds. They are trusted even if they don't have signatures, so "nix
verify-paths" won't complain about them.
This enables an optimisation in hydra-queue-runner, preventing a
download of a NAR it just uploaded to the cache when reading files
like hydra-build-products.
Also, move a few free-standing functions into StoreAPI and Derivation.
Also, introduce a non-nullable smart pointer, ref<T>, which is just a
wrapper around std::shared_ptr ensuring that the pointer is never
null. (For reference-counted values, this is better than passing a
"T&", because the latter doesn't maintain the refcount. Usually, the
caller will have a shared_ptr keeping the value alive, but that's not
always the case, e.g., when passing a reference to a std::thread via
std::bind.)
Some evidence that defining it to be 0 is right:
* OS X headers define it to be 0.
* Other code uses 0 instead of SOL_LOCAL to check for peer credentials
(e.g. FreeBSD's implementation of getpeereid).
Hello!
The patch below adds a ‘verifyStore’ RPC with the same signature as the
current LocalStore::verifyStore method.
Thanks,
Ludo’.
>From aef46c03ca77eb6344f4892672eb6d9d06432041 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludovic=20Court=C3=A8s?= <ludo@gnu.org>
Date: Mon, 1 Jun 2015 23:17:10 +0200
Subject: [PATCH] Add a 'verifyStore' remote procedure call.
This was preventing destructors from running. In particular, it was
preventing the deletion of the temproot file for each worker
process. It may also have been responsible for the excessive WAL
growth on Hydra (due to the SQLite database not being closed
properly).
Apparently broken by accident in
8e9140cfde.
The thread calls poll() to wait until a HUP (or other error event)
happens on the client connection. If so, it sends SIGINT to the main
thread, which is then cleaned up normally. This is much nicer than
messing around with SIGPOLL.
‘trusted-users’ is a list of users and groups that have elevated
rights, such as the ability to specify binary caches. It defaults to
‘root’. A typical value would be ‘@wheel’ to specify all users in the
wheel group.
‘allowed-users’ is a list of users and groups that are allowed to
connect to the daemon. It defaults to ‘*’. A typical value would be
‘@users’ to specify the ‘users’ group.
When copying a large path causes the daemon to run out of memory, you
now get:
error: Nix daemon out of memory
instead of:
error: writing to file: Broken pipe
Currently, clients cannot recover from an isValidPath RPC with an
invalid path parameter because the daemon closes the connection when
that happens.
More precisely:
1. in performOp, wopIsValidPath case, ‘readStorePath’ raises an
‘Error’ exception;
2. that exception is caught by the handler in ‘processConnection’;
3. the handler determines errorAllowed == false, and thus exits after
sending the message.
This last part is fixed by calling ‘startWork’ early on, as in the patch
below.
The same reasoning could be applied to all the RPCs that take one or
more store paths as inputs, but isValidPath is, by definition, likely to
be passed invalid paths in the first place, so it’s important for this
one to allow recovery.
