1 /* Cumulus: Smart Filesystem Backup to Dumb Servers
3 * Copyright (C) 2008 The Regents of the University of California
4 * Written by Michael Vrable <mvrable@cs.ucsd.edu>
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License along
17 * with this program; if not, write to the Free Software Foundation, Inc.,
18 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
21 /* Backup data is stored in a collection of objects, which are grouped together
22 * into segments for storage purposes. This implementation of the object store
23 * represents segments as TAR files and objects as files within them. */
29 #include <sys/types.h>
31 #include <sys/resource.h>
54 /* Default filter program is bzip2 */
55 const char *filter_program = "bzip2 -c";
56 const char *filter_extension = ".bz2";
58 static void cloexec(int fd)
60 long flags = fcntl(fd, F_GETFD);
65 fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
68 Tarfile::Tarfile(RemoteFile *file, const string &segment)
72 assert(sizeof(struct tar_header) == TAR_BLOCK_SIZE);
75 real_fd = file->get_fd();
76 filter_fd = spawn_filter(real_fd, filter_program, &filter_pid);
81 char buf[TAR_BLOCK_SIZE];
83 /* Append the EOF marker: two blocks filled with nulls. */
84 memset(buf, 0, sizeof(buf));
85 tar_write(buf, TAR_BLOCK_SIZE);
86 tar_write(buf, TAR_BLOCK_SIZE);
88 if (close(filter_fd) != 0)
89 throw IOException("Error closing Tarfile");
91 /* ...and wait for filter process to finish. */
93 waitpid(filter_pid, &status, 0);
95 if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
96 throw IOException("Filter process error");
102 /* Launch a child process which can act as a filter (compress, encrypt, etc.)
103 * on the TAR output. The file descriptor to which output should be written
104 * must be specified; the return value is the file descriptor which will be
105 * attached to the standard input of the filter program. */
106 int spawn_filter(int fd_out, const char *program, pid_t *filter_pid)
111 /* Create a pipe for communicating with the filter process. */
113 throw IOException("Unable to create pipe for filter");
116 /* Create a child process which can exec() the filter program. */
119 throw IOException("Unable to fork filter process");
125 if (filter_pid != NULL)
128 /* Child process. Rearrange file descriptors. stdin is fds[0], stdout
129 * is fd_out, stderr is unchanged. */
132 if (dup2(fds[0], 0) < 0)
136 if (dup2(fd_out, 1) < 0)
140 /* Exec the filter program. */
141 execlp("/bin/sh", "/bin/sh", "-c", program, NULL);
143 /* Should not reach here except for error cases. */
144 fprintf(stderr, "Could not exec filter: %m\n");
151 void Tarfile::tar_write(const char *data, size_t len)
156 int res = write(filter_fd, data, len);
161 fprintf(stderr, "Write error: %m\n");
162 throw IOException("Write error");
170 void Tarfile::write_object(int id, const char *data, size_t len)
172 struct tar_header header;
173 memset(&header, 0, sizeof(header));
176 sprintf(buf, "%08x", id);
177 string path = segment_name + "/" + buf;
179 assert(path.size() < 100);
180 memcpy(header.name, path.data(), path.size());
181 sprintf(header.mode, "%07o", 0600);
182 sprintf(header.uid, "%07o", 0);
183 sprintf(header.gid, "%07o", 0);
184 sprintf(header.size, "%011o", len);
185 sprintf(header.mtime, "%011o", (int)time(NULL));
186 header.typeflag = '0';
187 strcpy(header.magic, "ustar ");
188 strcpy(header.uname, "root");
189 strcpy(header.gname, "root");
191 memset(header.chksum, ' ', sizeof(header.chksum));
193 for (int i = 0; i < TAR_BLOCK_SIZE; i++) {
194 checksum += ((uint8_t *)&header)[i];
196 sprintf(header.chksum, "%06o", checksum);
198 tar_write((const char *)&header, TAR_BLOCK_SIZE);
203 tar_write(data, len);
205 char padbuf[TAR_BLOCK_SIZE];
206 size_t blocks = (len + TAR_BLOCK_SIZE - 1) / TAR_BLOCK_SIZE;
207 size_t padding = blocks * TAR_BLOCK_SIZE - len;
208 memset(padbuf, 0, padding);
209 tar_write(padbuf, padding);
212 /* Estimate the size based on the size of the actual output file on disk.
213 * However, it might be the case that the filter program is buffering all its
214 * data, and might potentially not write a single byte until we have closed
215 * our end of the pipe. If we don't do so until we see data written, we have
216 * a problem. So, arbitrarily pick an upper bound on the compression ratio
217 * that the filter will achieve (128:1), and return a size estimate which is
218 * the larger of a) bytes actually seen written to disk, and b) input
220 size_t Tarfile::size_estimate()
224 if (fstat(real_fd, &statbuf) == 0)
225 return max((int64_t)statbuf.st_size, (int64_t)(size / 128));
227 /* Couldn't stat the file on disk, so just return the actual number of
228 * bytes, before compression. */
232 static const size_t SEGMENT_SIZE = 4 * 1024 * 1024;
234 /* Backup size summary: segment type -> (uncompressed size, compressed size) */
235 static map<string, pair<int64_t, int64_t> > group_sizes;
237 ObjectReference TarSegmentStore::write_object(const char *data, size_t len,
238 const std::string &group)
240 struct segment_info *segment;
242 // Find the segment into which the object should be written, looking up by
243 // group. If no segment exists yet, create one.
244 if (segments.find(group) == segments.end()) {
245 segment = new segment_info;
247 segment->name = generate_uuid();
248 segment->group = group;
249 segment->basename = segment->name + ".tar";
250 segment->basename += filter_extension;
253 segment->rf = remote->alloc_file(segment->basename, "segments");
254 segment->file = new Tarfile(segment->rf, segment->name);
256 segments[group] = segment;
258 segment = segments[group];
261 int id = segment->count;
263 sprintf(id_buf, "%08x", id);
265 segment->file->write_object(id, data, len);
267 segment->size += len;
269 group_sizes[group].first += len;
271 ObjectReference ref(segment->name, id_buf);
273 // If this segment meets or exceeds the size target, close it so that
274 // future objects will go into a new segment.
275 if (segment->file->size_estimate() >= SEGMENT_SIZE)
276 close_segment(group);
281 void TarSegmentStore::sync()
283 while (!segments.empty())
284 close_segment(segments.begin()->first);
287 void TarSegmentStore::dump_stats()
289 printf("Data written:\n");
290 for (map<string, pair<int64_t, int64_t> >::iterator i = group_sizes.begin();
291 i != group_sizes.end(); ++i) {
292 printf(" %s: %lld (%lld compressed)\n", i->first.c_str(),
293 i->second.first, i->second.second);
297 void TarSegmentStore::close_segment(const string &group)
299 struct segment_info *segment = segments[group];
301 delete segment->file;
304 SHA1Checksum segment_checksum;
305 if (segment_checksum.process_file(segment->rf->get_local_path().c_str())) {
306 string checksum = segment_checksum.checksum_str();
307 db->SetSegmentChecksum(segment->name, segment->basename, checksum,
311 struct stat stat_buf;
312 if (stat(segment->rf->get_local_path().c_str(), &stat_buf) == 0) {
313 group_sizes[segment->group].second += stat_buf.st_size;
319 segments.erase(segments.find(group));
323 string TarSegmentStore::object_reference_to_segment(const string &object)
328 LbsObject::LbsObject()
329 : group(""), data(NULL), data_len(0), written(false)
333 LbsObject::~LbsObject()
337 void LbsObject::write(TarSegmentStore *store)
339 assert(data != NULL);
342 ref = store->write_object(data, data_len, group);
346 void LbsObject::checksum()
351 hash.process(data, data_len);
352 ref.set_checksum(hash.checksum_str());