*
* Backup data is stored in a collection of objects, which are grouped together
* into segments for storage purposes. This implementation of the object store
- * is built on top of libtar, and represents segments as TAR files and objects
- * as files within them. */
+ * represents segments as TAR files and objects as files within them. */
#include <assert.h>
+#include <errno.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
+#include <sys/resource.h>
+#include <sys/wait.h>
#include <unistd.h>
#include <fcntl.h>
#include <time.h>
+#include <algorithm>
#include <list>
+#include <map>
#include <set>
#include <string>
#include <iostream>
#include "store.h"
#include "ref.h"
+using std::max;
using std::list;
+using std::map;
using std::set;
using std::string;
+/* Default filter program is bzip2 */
+const char *filter_program = "bzip2 -c";
+const char *filter_extension = ".bz2";
+
+static void cloexec(int fd)
+{
+ long flags = fcntl(fd, F_GETFD);
+
+ if (flags < 0)
+ return;
+
+ fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
+}
+
Tarfile::Tarfile(const string &path, const string &segment)
: size(0),
segment_name(segment)
{
- if (tar_open(&t, (char *)path.c_str(), NULL, O_WRONLY | O_CREAT, 0600,
- TAR_VERBOSE | TAR_GNU) == -1)
- throw IOException("Error opening Tarfile");
+ assert(sizeof(struct tar_header) == TAR_BLOCK_SIZE);
+
+ real_fd = open(path.c_str(), O_WRONLY | O_CREAT, 0666);
+ if (real_fd < 0)
+ throw IOException("Error opening output file");
+
+ filter_fd = spawn_filter(real_fd);
}
Tarfile::~Tarfile()
{
- tar_append_eof(t);
+ char buf[TAR_BLOCK_SIZE];
- if (tar_close(t) != 0)
+ /* Append the EOF marker: two blocks filled with nulls. */
+ memset(buf, 0, sizeof(buf));
+ tar_write(buf, TAR_BLOCK_SIZE);
+ tar_write(buf, TAR_BLOCK_SIZE);
+
+ if (close(filter_fd) != 0)
throw IOException("Error closing Tarfile");
+
+ /* ...and wait for filter process to finish. */
+ int status;
+ waitpid(filter_pid, &status, 0);
+
+ if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
+ throw IOException("Filter process error");
+ }
+
+ close(real_fd);
+}
+
+/* Launch a child process which can act as a filter (compress, encrypt, etc.)
+ * on the TAR output. The file descriptor to which output should be written
+ * must be specified; the return value is the file descriptor which will be
+ * attached to the standard input of the filter program. */
+int Tarfile::spawn_filter(int fd_out)
+{
+ int fds[2];
+
+ /* Create a pipe for communicating with the filter process. */
+ if (pipe(fds) < 0) {
+ throw IOException("Unable to create pipe for filter");
+ }
+
+ /* Create a child process which can exec() the filter program. */
+ filter_pid = fork();
+ if (filter_pid < 0)
+ throw IOException("Unable to fork filter process");
+
+ if (filter_pid > 0) {
+ /* Parent process */
+ close(fds[0]);
+ cloexec(fds[1]);
+ } else {
+ /* Child process. Rearrange file descriptors. stdin is fds[0], stdout
+ * is fd_out, stderr is unchanged. */
+ close(fds[1]);
+
+ if (dup2(fds[0], 0) < 0)
+ exit(1);
+ close(fds[0]);
+
+ if (dup2(fd_out, 1) < 0)
+ exit(1);
+ close(fd_out);
+
+ /* Exec the filter program. */
+ execlp("/bin/sh", "/bin/sh", "-c", filter_program, NULL);
+
+ /* Should not reach here except for error cases. */
+ fprintf(stderr, "Could not exec filter: %m\n");
+ exit(1);
+ }
+
+ return fds[1];
+}
+
+void Tarfile::tar_write(const char *data, size_t len)
+{
+ size += len;
+
+ while (len > 0) {
+ int res = write(filter_fd, data, len);
+
+ if (res < 0) {
+ if (errno == EINTR)
+ continue;
+ fprintf(stderr, "Write error: %m\n");
+ throw IOException("Write error");
+ }
+
+ len -= res;
+ data += res;
+ }
}
void Tarfile::write_object(int id, const char *data, size_t len)
void Tarfile::internal_write_object(const string &path,
const char *data, size_t len)
{
- memset(&t->th_buf, 0, sizeof(struct tar_header));
-
- th_set_type(t, S_IFREG | 0600);
- th_set_user(t, 0);
- th_set_group(t, 0);
- th_set_mode(t, 0600);
- th_set_size(t, len);
- th_set_mtime(t, time(NULL));
- th_set_path(t, const_cast<char *>(path.c_str()));
- th_finish(t);
-
- if (th_write(t) != 0)
- throw IOException("Error writing tar header");
+ struct tar_header header;
+ memset(&header, 0, sizeof(header));
+
+ assert(path.size() < 100);
+ memcpy(header.name, path.data(), path.size());
+ sprintf(header.mode, "%07o", 0600);
+ sprintf(header.uid, "%07o", 0);
+ sprintf(header.gid, "%07o", 0);
+ sprintf(header.size, "%011o", len);
+ sprintf(header.mtime, "%011o", (int)time(NULL));
+ header.typeflag = '0';
+ strcpy(header.magic, "ustar ");
+ strcpy(header.uname, "root");
+ strcpy(header.gname, "root");
+
+ memset(header.chksum, ' ', sizeof(header.chksum));
+ int checksum = 0;
+ for (int i = 0; i < TAR_BLOCK_SIZE; i++) {
+ checksum += ((uint8_t *)&header)[i];
+ }
+ sprintf(header.chksum, "%06o", checksum);
- size += T_BLOCKSIZE;
+ tar_write((const char *)&header, TAR_BLOCK_SIZE);
if (len == 0)
return;
- size_t blocks = (len + T_BLOCKSIZE - 1) / T_BLOCKSIZE;
- size_t padding = blocks * T_BLOCKSIZE - len;
+ tar_write(data, len);
- for (size_t i = 0; i < blocks - 1; i++) {
- if (tar_block_write(t, &data[i * T_BLOCKSIZE]) == -1)
- throw IOException("Error writing tar block");
- }
+ char padbuf[TAR_BLOCK_SIZE];
+ size_t blocks = (len + TAR_BLOCK_SIZE - 1) / TAR_BLOCK_SIZE;
+ size_t padding = blocks * TAR_BLOCK_SIZE - len;
+ memset(padbuf, 0, padding);
+ tar_write(padbuf, padding);
+}
+
+/* Estimate the size based on the size of the actual output file on disk.
+ * However, it might be the case that the filter program is buffering all its
+ * data, and might potentially not write a single byte until we have closed
+ * our end of the pipe. If we don't do so until we see data written, we have
+ * a problem. So, arbitrarily pick an upper bound on the compression ratio
+ * that the filter will achieve (128:1), and return a size estimate which is
+ * the larger of a) bytes actually seen written to disk, and b) input
+ * bytes/128. */
+size_t Tarfile::size_estimate()
+{
+ struct stat statbuf;
- char block[T_BLOCKSIZE];
- memset(block, 0, sizeof(block));
- memcpy(block, &data[T_BLOCKSIZE * (blocks - 1)], T_BLOCKSIZE - padding);
- if (tar_block_write(t, block) == -1)
- throw IOException("Error writing final tar block");
+ if (fstat(real_fd, &statbuf) == 0)
+ return max((int64_t)statbuf.st_size, (int64_t)(size / 128));
- size += blocks * T_BLOCKSIZE;
+ /* Couldn't stat the file on disk, so just return the actual number of
+ * bytes, before compression. */
+ return size;
}
static const size_t SEGMENT_SIZE = 4 * 1024 * 1024;
+static map<string, int64_t> group_sizes;
+
ObjectReference TarSegmentStore::write_object(const char *data, size_t len,
const std::string &group)
{
segment->name = generate_uuid();
string filename = path + "/" + segment->name + ".tar";
+ filename += filter_extension;
segment->file = new Tarfile(filename, segment->name);
segment->count = 0;
segment->file->write_object(id, data, len);
segment->count++;
+ group_sizes[group] += len;
+
ObjectReference ref(segment->name, id_buf);
// If this segment meets or exceeds the size target, close it so that
close_segment(segments.begin()->first);
}
+void TarSegmentStore::dump_stats()
+{
+ printf("Data written:\n");
+ for (map<string, int64_t>::iterator i = group_sizes.begin();
+ i != group_sizes.end(); ++i) {
+ printf(" %s: %lld\n", i->first.c_str(), i->second);
+ }
+}
+
void TarSegmentStore::close_segment(const string &group)
{
struct segment_info *segment = segments[group];
projects / cumulus.git / blobdiff