store: Add with-store/non-blocking.

For some applications, it's important to establish a non-blocking connection
rather than just making the socket non-blocking after the connection is
established. This is because there is I/O on the socket that will block during
the handshake.

I've noticed this blocking during the handshake causing issues in the build
coordinator for example.

This commit adds a new with-store variant to avoid changing the behaviour of
with-store/open-connection to ensure that this change can't break anything
that depends on the blocking nature of the socket.

* guix/store.scm (open-unix-domain-socket, open-inet-socket): Take
 #:non-blocking? and use SOCK_NONBLOCK when calling socket if appropriate.
(connect-to-daemon, open-connection, call-with-store): Take #:non-blocking?
and pass it on.
(with-store/non-blocking): New syntax rule.
* .dir-locals.el (scheme-mode): Add entry for with-store/non-blocking.

Change-Id: I8225762b78448bc1f7b698c8de5d736e13f577bf

1 files changed, 1 insertions, 0 deletions

diff --git a/.dir-locals.el b/.dir-locals.el
index d2f6037afe..d0c25b867b 100644
--- a/.dir-locals.el
+++ b/.dir-locals.el
@@ -88,6 +88,7 @@
    (eval . (put 'manifest-pattern 'scheme-indent-function 0))
    (eval . (put 'substitute-keyword-arguments 'scheme-indent-function 1))
    (eval . (put 'with-store 'scheme-indent-function 1))
+   (eval . (put 'with-store/non-blocking 'scheme-indent-function 1))
    (eval . (put 'with-external-store 'scheme-indent-function 1))
    (eval . (put 'with-error-handling 'scheme-indent-function 0))
    (eval . (put 'with-mutex 'scheme-indent-function 1))