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ccon: Add '--socket PATH' to support a create/start split
Along the lines of the create/start split we've been discussing for the OCI [1,2]. Pull some common functionality into a libccon, although I don't intend to make that a more than an internal helper. Post-error cleanup in ccon-cli is pretty slim, since the process is just about to die anyway. I'll probably go back through and add proper cleanup later. serve_socket gets too deeply nested for my taste, but it's not quite to the point where I'd pull out the request handling into a handle_start_request helper or some such. Mostly because I'd have to either setup a new buf/iov/msg in the helper's stack or pass that all through from serve_socket ;). A few notes on the tests: I don't have a stand-alone 'wait' on my system (it's built into most shells [3]), but I've added an explicit check for it because POSIX doesn't require it to be built in. The waiting in the create/start tests is a bit awkward, but here's the reasoning for the various steps: * Put the socket in a 'sock' subdirectory so we don't have to mess with inotifywait's --exclude (when what we really want is an --include). In most cases, the socket would be the first thing created in the test directory, but the process.host test will create a pivot-root.* before creating the socket. * Clear a 'wait' file before launching the inotifywait/start subshell and append to it from that subshell so grep has something to look at (even if it racily starts looking before the subshell processes the inotifywait line). * Block on a busy-wait grep until inotifywait sets up its watcher. This ensures we don't call ccon and create the socket before the watcher is looking. The zero-second sleep while we wait for inotifywait to setup its watcher is busy, but POSIX doesn't require 'sleep' to support non-integer times [4]. All of these issues could be abstracted out into an 'event' command [5], but they're fine for a proof-of-concept create/start split. [1]: https://groups.google.com/a/opencontainers.org/d/msg/dev/qWHoKs8Fsrk/k55FQrBzBgAJ Subject: Re: Splitting Start into create() and run() Date: Thu, 24 Mar 2016 15:04:14 -0700 Message-ID: <20160324220414.GC23066@odin.tremily.us> [2]: opencontainers/runtime-spec#384 Subject: Split create and start [3]: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap01.html#tag_17_06 [4]: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/sleep.html [5]: opencontainers/runtime-spec#508 Subject: runtime: Add an 'event' operation for subscribing to pushes
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