Guard against concurrent invocations of hydra-queue-runner

Dependencies

• [2] PLOZBRTR Add command ‘hydra-queue-runner --status’ to show current status
• [*] 24BMQDZA Start of single-process hydra-queue-runner
• [*] GS4BE6TB Asynchronously compress build logs
• [*] NJJ7H64S Very basic multi-threaded queue runner

Change contents

• edit in src/hydra-queue-runner/hydra-queue-runner.cc at line 29
  [2.28]

  [4.5036]
  + #include "pathlocks.hh"
• edit in src/hydra-queue-runner/hydra-queue-runner.cc at line 310
  [5.1020]

  [2.96]
  +

  + /* Acquire the global queue runner lock, or null if somebody else

  + has it. */

  + std::shared_ptr<PathLocks> acquireGlobalLock();
• edit in src/hydra-queue-runner/hydra-queue-runner.cc at line 1401
  [5.3005]

  [5.3005]
  + }

  +

  +

  + std::shared_ptr<PathLocks> State::acquireGlobalLock()

  + {

  + Path lockPath = hydraData + "/queue-runner";

  +

  + auto lock = std::make_shared<PathLocks>();

  + if (!lock->lockPaths(PathSet({lockPath}), "", false)) return 0;

  +

  + return lock;
• edit in src/hydra-queue-runner/hydra-queue-runner.cc at line 1524
  [2.3568]

  [2.3568]
  + auto lock = acquireGlobalLock();

  + if (!lock)

  + throw Error("hydra-queue-runner is currently running");

  +
• edit in src/hydra-queue-runner/hydra-queue-runner.cc at line 1542
  [6.3200]

  [2.3753]
  + auto lock = acquireGlobalLock();

  + if (!lock)

  + throw Error("hydra-queue-runner is already running");

  +