Adding SSH executor

libdaggy/include/daggy/executors/task/SSHTaskExecutor.hpp

@@ -0,0 +1,60 @@
+#pragma once
+
+#include "ForkingTaskExecutor.hpp"
+#include "TaskExecutor.hpp"
+
+namespace daggy::executors::task {
+  class SSHTaskExecutor : public TaskExecutor
+  {
+  public:
+    struct RemoteHost
+    {
+      size_t cores;
+      size_t memoryMB;
+    };
+
+    using Command = std::vector<std::string>;
+
+    explicit SSHTaskExecutor(std::unordered_map<std::string, RemoteHost> hosts);
+
+    // Validates the job to ensure that all required values are set and are of
+    // the right type,
+    bool validateTaskParameters(const ConfigValues &job) override;
+
+    std::vector<ConfigValues> expandTaskParameters(
+        const ConfigValues &job, const ConfigValues &expansionValues) override;
+
+    // Runs the task
+    TaskFuture execute(DAGRunID runID, const std::string &taskName,
+                       const Task &task) override;
+
+    bool stop(DAGRunID runID, const std::string &taskName) override;
+
+    std::string description() const override;
+
+  private:
+    struct RunningTask
+    {
+      std::string host;
+      size_t cores;
+      size_t memoryMB;
+      TaskFuture fut;
+      TaskFuture feFuture;
+      int sshRetries;
+      DAGRunID runID;
+      std::string taskName;
+      Task task;
+    };
+
+    std::unordered_map<std::string, RemoteHost> hosts_;
+    ForkingTaskExecutor fe_;
+    std::mutex hostGuard_;
+    std::condition_variable hostCV_;
+    std::deque<RunningTask> runningTasks_;
+
+    void monitor();
+    std::atomic<bool> running_;
+    std::thread monitorWorker_;
+  };
+}  // namespace daggy::executors::task
+