X-Git-Url: http://git.vrable.net/?a=blobdiff_plain;f=store.cc;h=9d4d1bd8b0ec59c701021f98f2a9d2c7d5dc8dbc;hb=4c7c830e38130011d1f5cc68934a31619e3b8a85;hp=804992f105f4ff9b6ab0989ce82d52be717ef1e5;hpb=51859528c5de1c90c553d1f174869005711f162a;p=cumulus.git diff --git a/store.cc b/store.cc index 804992f..9d4d1bd 100644 --- a/store.cc +++ b/store.cc @@ -3,49 +3,148 @@ * * 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 +#include #include #include #include +#include +#include #include #include #include -#include +#include #include +#include #include #include #include #include "store.h" +#include "ref.h" +using std::max; using std::list; +using std::map; using std::set; using std::string; -list TarSegmentStore::norefs; +/* 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() { - string checksum_list = checksums.str(); - internal_write_object(segment_name + "/checksums", - checksum_list.data(), checksum_list.size()); - 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) @@ -55,59 +154,73 @@ void Tarfile::write_object(int id, const char *data, size_t len) string path = segment_name + "/" + buf; internal_write_object(path, data, len); - - // Compute a checksum for the data block, which will be stored at the end - // of the TAR file. - SHA1Checksum hash; - hash.process(data, len); - sprintf(buf, "%08x", id); - checksums << buf << " " << hash.checksum_str() << "\n"; } 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(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); +} - 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"); +/* 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; - size += blocks * T_BLOCKSIZE; + if (fstat(real_fd, &statbuf) == 0) + return max((int64_t)statbuf.st_size, (int64_t)(size / 128)); + + /* 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; -string TarSegmentStore::write_object(const char *data, size_t len, const - std::string &group, - const std::list &refs) +static map group_sizes; + +ObjectReference TarSegmentStore::write_object(const char *data, size_t len, + const std::string &group) { struct segment_info *segment; @@ -116,13 +229,10 @@ string TarSegmentStore::write_object(const char *data, size_t len, const if (segments.find(group) == segments.end()) { segment = new segment_info; - uint8_t uuid[16]; - char uuid_buf[40]; - uuid_generate(uuid); - uuid_unparse_lower(uuid, uuid_buf); - segment->name = uuid_buf; + segment->name = generate_uuid(); string filename = path + "/" + segment->name + ".tar"; + filename += filter_extension; segment->file = new Tarfile(filename, segment->name); segment->count = 0; @@ -139,20 +249,16 @@ string TarSegmentStore::write_object(const char *data, size_t len, const segment->file->write_object(id, data, len); segment->count++; - string full_name = segment->name + "/" + id_buf; + group_sizes[group] += len; - // Store any dependencies this object has on other segments, so they can be - // written when the segment is closed. - for (list::const_iterator i = refs.begin(); i != refs.end(); ++i) { - segment->refs.insert(*i); - } + ObjectReference ref(segment->name, id_buf); // If this segment meets or exceeds the size target, close it so that // future objects will go into a new segment. if (segment->file->size_estimate() >= SEGMENT_SIZE) close_segment(group); - return full_name; + return ref; } void TarSegmentStore::sync() @@ -161,19 +267,18 @@ void TarSegmentStore::sync() close_segment(segments.begin()->first); } +void TarSegmentStore::dump_stats() +{ + printf("Data written:\n"); + for (map::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]; - fprintf(stderr, "Closing segment group %s (%s)\n", - group.c_str(), segment->name.c_str()); - - string reflist; - for (set::iterator i = segment->refs.begin(); - i != segment->refs.end(); ++i) { - reflist += *i + "\n"; - } - segment->file->internal_write_object(segment->name + "/references", - reflist.data(), reflist.size()); delete segment->file; segments.erase(segments.find(group)); @@ -194,18 +299,20 @@ LbsObject::~LbsObject() { } -void LbsObject::add_reference(const LbsObject *o) -{ - // TODO: Implement -} - void LbsObject::write(TarSegmentStore *store) { assert(data != NULL); assert(!written); - name = store->write_object(data, data_len, group); - + ref = store->write_object(data, data_len, group); written = true; - data = NULL; +} + +void LbsObject::checksum() +{ + assert(written); + + SHA1Checksum hash; + hash.process(data, data_len); + ref.set_checksum(hash.checksum_str()); }