Acquire the send lock only while actually sending

Dependencies

• [2] UYDRSHYR Don't wait forever to acquire the send lock
• [3] DKJFD6JN Process Nix API changes
• [4] FITVNQ2S Keep track of the time we spend copying to/from build machines
• [5] DIEY5USN Keep better bytesReceived/bytesSent stats
• [6] 5AIYUMTB Basic remote building
• [7] BYVRA54Q Temporarily disable machines on any exception, not just connection failures
• [8] 73YR46NJ hydra-queue-runner: Write directly to a binary cache
• [9] RSISSEU6 Enable substitution on the build machines
• [10] CNLNT3T4 Allow only 1 thread to send a closure to a given machine at the same time
• [11] 6EO3HVNA Merge remote-tracking branch 'origin/master' into binary-cache
• [12] XCDTFZUY hydra-queue-runner: Fix build
• [*] 6TY4LNHH Finish copyClosure
• [*] NAYQT2GT hydra-queue-runner: Use cmdBuildDerivation

Change contents

• replacement in src/hydra-queue-runner/build-remote.cc at line 80
  [3.1290]→[3.123:171](∅→∅)
  − static void copyClosureTo(ref<Store> destStore,
  [3.1290]

  [3.1349]
  + static void copyClosureTo(std::timed_mutex & sendMutex, ref<Store> destStore,
• edit in src/hydra-queue-runner/build-remote.cc at line 110
  [14.286]

  [15.65]
  + std::unique_lock<std::timed_mutex> sendLock(sendMutex,

  + std::chrono::seconds(600));

  +
• edit in src/hydra-queue-runner/build-remote.cc at line 235
  [3.2711]→[2.0:127](∅→∅)
  − std::unique_lock<std::timed_mutex> sendLock(

  − machine->state->sendLock, std::chrono::seconds(600));
• replacement in src/hydra-queue-runner/build-remote.cc at line 241
  [3.56]→[3.3041:3103](∅→∅)
  − copyClosureTo(destStore, from, to, inputs, true);
  [3.56]

  [3.57]
  + copyClosureTo(machine->state->sendLock, destStore, from, to, inputs, true);