Initial framework for direct transfer of backups to remote storage.

[cumulus.git] / remote.h

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+/* LBS: An LFS-inspired filesystem backup system
+ * Copyright (C) 2006  Michael Vrable
+ *
+ * Backup data (segments and backup descriptors) may be stored on a remote
+ * fileserver instead of locally.  The only local storage needed is for the
+ * local database and some temporary space for staging files before they are
+ * transferred to the remote server.
+ *
+ * Like encryption, remote storage is handled through the use of external
+ * scripts that are called when a file is to be transferred. */
+
+#ifndef _LBS_REMOTE_H
+#define _LBS_REMOTE_H
+
+#include <list>
+#include <string>
+#include <pthread.h>
+
+class RemoteFile;
+
+class RemoteStore {
+public:
+    static const size_t MAX_QUEUE_SIZE = 4;
+
+    RemoteStore(const std::string &stagedir);
+    ~RemoteStore();
+    RemoteFile *alloc_file(const std::string &name);
+    void enqueue(RemoteFile *file);
+    void sync();
+
+private:
+    pthread_t thread;
+    pthread_mutex_t lock;
+    pthread_cond_t cond;
+
+    std::string staging_dir;
+    bool terminate;             // Set when thread should shut down
+    bool busy;                  // True while there are pending transfers
+    std::list<RemoteFile *> transfer_queue;
+
+    /* For error-checking purposes, track the number of files which have been
+     * allocated but not yet queued to be sent.  This should be zero when the
+     * RemoteStore is destroyed. */
+    int files_outstanding;
+
+    void transfer_thread();
+    static void *start_transfer_thread(void *arg);
+};
+
+class RemoteFile {
+public:
+    /* Get the file descriptor for writing to the (staging copy of the) file.
+     * The _caller_ is responsible for closing this file descriptor once all
+     * data is written, and before send() is called. */
+    int get_fd() const { return fd; }
+
+    const std::string &get_local_path() const { return local_path; }
+
+    /* Called when the file is finished--request that it be sent to the remote
+     * server.  This will delete the RemoteFile object. */
+    void send() { remote_store->enqueue(this); }
+private:
+    friend class RemoteStore;
+
+    RemoteFile(RemoteStore *remote,
+               const std::string &name, const std::string &local_path);
+
+    RemoteStore *remote_store;
+
+    int fd;
+    std::string local_path;
+    std::string remote_path;
+};
+
+#endif // _LBS_REMOTE_H