/* LBS: An LFS-inspired filesystem backup system
- * Copyright (C) 2006 Michael Vrable
+ * Copyright (C) 2007 Michael Vrable
*
* Backup data is stored in a collection of objects, which are grouped together
- * into segments for storage purposes. This file provides interfaces for
- * reading and writing objects and segments. */
+ * 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. */
#include <assert.h>
-#include <uuid/uuid.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 <set>
+#include <string>
+#include <iostream>
#include "store.h"
+#include "ref.h"
+using std::max;
+using std::list;
+using std::set;
using std::string;
-OutputStream::OutputStream()
- : bytes_written(0)
-{
-}
+static char *const filter_program[] = {"bzip2", "-c", NULL};
-void OutputStream::write(const void *data, size_t len)
+static void cloexec(int fd)
{
- write_internal(data, len);
- bytes_written += len;
-}
+ long flags = fcntl(fd, F_GETFD);
-void OutputStream::write_u8(uint8_t val)
-{
- write(&val, 1);
+ if (flags < 0)
+ return;
+
+ fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
}
-void OutputStream::write_u16(uint16_t val)
+Tarfile::Tarfile(const string &path, const string &segment)
+ : size(0),
+ segment_name(segment)
{
- unsigned char buf[2];
+ real_fd = open(path.c_str(), O_WRONLY | O_CREAT, 0600);
+ if (real_fd < 0)
+ throw IOException("Error opening output file");
+
+ filter_fd = spawn_filter(real_fd);
- buf[0] = val & 0xff;
- buf[1] = (val >> 8) & 0xff;
- write(buf, 2);
+ if (tar_fdopen(&t, filter_fd, (char *)path.c_str(), NULL,
+ O_WRONLY | O_CREAT, 0600, TAR_VERBOSE | TAR_GNU) == -1)
+ throw IOException("Error opening Tarfile");
}
-void OutputStream::write_u32(uint32_t val)
+Tarfile::~Tarfile()
{
- unsigned char buf[4];
+ /* Close the tar file... */
+ tar_append_eof(t);
- buf[0] = val & 0xff;
- buf[1] = (val >> 8) & 0xff;
- buf[2] = (val >> 16) & 0xff;
- buf[3] = (val >> 24) & 0xff;
- write(buf, 4);
-}
+ if (tar_close(t) != 0)
+ throw IOException("Error closing Tarfile");
-void OutputStream::write_u64(uint64_t val)
-{
- unsigned char buf[8];
-
- buf[0] = val & 0xff;
- buf[1] = (val >> 8) & 0xff;
- buf[2] = (val >> 16) & 0xff;
- buf[3] = (val >> 24) & 0xff;
- buf[4] = (val >> 32) & 0xff;
- buf[5] = (val >> 40) & 0xff;
- buf[6] = (val >> 48) & 0xff;
- buf[7] = (val >> 56) & 0xff;
- write(buf, 8);
-}
+ /* ...and wait for filter process to finish. */
+ int status;
+ waitpid(filter_pid, &status, 0);
-/* Writes an integer to an output stream using a variable-sized representation:
- * seven bits are written at a time (little-endian), and the eigth bit of each
- * byte is set if more data follows. */
-void OutputStream::write_varint(uint64_t val)
-{
- do {
- uint8_t remainder = (val & 0x7f);
- val >>= 7;
- if (val)
- remainder |= 0x80;
- write_u8(remainder);
- } while (val);
-}
+ if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
+ throw IOException("Filter process error");
+ }
-/* Write an arbitrary string by first writing out the length, followed by the
- * data itself. */
-void OutputStream::write_string(const string &s)
-{
- size_t len = s.length();
- write_varint(len);
- write(s.data(), len);
+ close(real_fd);
}
-void OutputStream::write_dictionary(const dictionary &d)
+/* 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)
{
- size_t size = d.size();
- size_t written = 0;
+ int fds[2];
- write_varint(size);
+ /* Create a pipe for communicating with the filter process. */
+ if (pipe(fds) < 0) {
+ throw IOException("Unable to create pipe for filter");
+ }
- for (dictionary::const_iterator i = d.begin(); i != d.end(); ++i) {
- write_string(i->first);
- write_string(i->second);
- written++;
+ /* 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. */
+ execvp(filter_program[0], filter_program);
+
+ /* Should not reach here except for error cases. */
+ fprintf(stderr, "Could not exec filter: %m\n");
+ exit(1);
}
- assert(written == size);
+ return fds[1];
}
-StringOutputStream::StringOutputStream()
- : buf(std::ios_base::out)
+void Tarfile::write_object(int id, const char *data, size_t len)
{
-}
+ char buf[64];
+ sprintf(buf, "%08x", id);
+ string path = segment_name + "/" + buf;
-void StringOutputStream::write_internal(const void *data, size_t len)
-{
- buf.write((const char *)data, len);
- if (!buf.good())
- throw IOException("error writing to StringOutputStream");
+ internal_write_object(path, data, len);
}
-FileOutputStream::FileOutputStream(FILE *file)
+void Tarfile::internal_write_object(const string &path,
+ const char *data, size_t len)
{
- f = file;
-}
+ memset(&t->th_buf, 0, sizeof(struct tar_header));
-FileOutputStream::~FileOutputStream()
-{
- fclose(f);
-}
+ 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);
-void FileOutputStream::write_internal(const void *data, size_t len)
-{
- size_t res;
+ if (th_write(t) != 0)
+ throw IOException("Error writing tar header");
+
+ size += T_BLOCKSIZE;
+
+ if (len == 0)
+ return;
- res = fwrite(data, 1, len, f);
- if (res != len) {
- throw IOException("write error");
+ size_t blocks = (len + T_BLOCKSIZE - 1) / T_BLOCKSIZE;
+ size_t padding = blocks * T_BLOCKSIZE - 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");
}
-}
-WrapperOutputStream::WrapperOutputStream(OutputStream &o)
- : real(o)
-{
-}
+ 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");
-void WrapperOutputStream::write_internal(const void *data, size_t len)
-{
- real.write(data, len);
+ size += blocks * T_BLOCKSIZE;
}
-/* Utility functions, for encoding data types to strings. */
-string encode_u16(uint16_t val)
+/* 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()
{
- StringOutputStream s;
- s.write_u16(val);
- return s.contents();
-}
+ struct stat statbuf;
-string encode_u32(uint32_t val)
-{
- StringOutputStream s;
- s.write_u32(val);
- return s.contents();
-}
+ if (fstat(real_fd, &statbuf) == 0)
+ return max((int64_t)statbuf.st_size, (int64_t)(size / 128));
-string encode_u64(uint64_t val)
-{
- StringOutputStream s;
- s.write_u64(val);
- return s.contents();
+ /* Couldn't stat the file on disk, so just return the actual number of
+ * bytes, before compression. */
+ return size;
}
-SegmentWriter::SegmentWriter(OutputStream &output, struct uuid u)
- : out(output),
- id(u),
- object_stream(NULL)
-{
- /* Write out the segment header first. */
- static const char signature[] = "LBSSEG0\n";
- out.write(signature, strlen(signature));
- out.write(id.bytes, sizeof(struct uuid));
-}
+static const size_t SEGMENT_SIZE = 4 * 1024 * 1024;
-SegmentWriter::~SegmentWriter()
+ObjectReference TarSegmentStore::write_object(const char *data, size_t len,
+ const std::string &group)
{
- if (object_stream)
- finish_object();
-
- // Write out the object table which gives the sizes and locations of all
- // objects, and then add the trailing signature, which indicates the end of
- // the segment and gives the offset of the object table.
- int64_t index_offset = out.get_pos();
-
- for (object_table::const_iterator i = objects.begin();
- i != objects.end(); ++i) {
- out.write_s64(i->first);
- out.write_s64(i->second);
+ struct segment_info *segment;
+
+ // Find the segment into which the object should be written, looking up by
+ // group. If no segment exists yet, create one.
+ if (segments.find(group) == segments.end()) {
+ segment = new segment_info;
+
+ segment->name = generate_uuid();
+
+ string filename = path + "/" + segment->name + ".tar.bz2";
+ segment->file = new Tarfile(filename, segment->name);
+
+ segment->count = 0;
+
+ segments[group] = segment;
+ } else {
+ segment = segments[group];
}
- static const char signature2[] = "LBSEND";
- out.write(signature2, strlen(signature2));
- out.write_s64(index_offset);
- out.write_u32(objects.size());
-}
+ int id = segment->count;
+ char id_buf[64];
+ sprintf(id_buf, "%08x", id);
-OutputStream *SegmentWriter::new_object()
-{
- if (object_stream)
- finish_object();
+ segment->file->write_object(id, data, len);
+ segment->count++;
+
+ ObjectReference ref(segment->name, id_buf);
- object_start_offset = out.get_pos();
- object_stream = new WrapperOutputStream(out);
+ // 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 object_stream;
+ return ref;
}
-void SegmentWriter::finish_object()
+void TarSegmentStore::sync()
{
- assert(object_stream != NULL);
+ while (!segments.empty())
+ close_segment(segments.begin()->first);
+}
- // store (start, length) information for locating this object
- objects.push_back(std::make_pair(object_start_offset,
- object_stream->get_pos()));
+void TarSegmentStore::close_segment(const string &group)
+{
+ struct segment_info *segment = segments[group];
- delete object_stream;
- object_stream = NULL;
+ delete segment->file;
+ segments.erase(segments.find(group));
+ delete segment;
}
-struct uuid SegmentWriter::generate_uuid()
+string TarSegmentStore::object_reference_to_segment(const string &object)
{
- struct uuid u;
+ return object;
+}
- uuid_generate(u.bytes);
+LbsObject::LbsObject()
+ : group(""), data(NULL), data_len(0), written(false)
+{
+}
- return u;
+LbsObject::~LbsObject()
+{
}
-string SegmentWriter::format_uuid(const struct uuid u)
+void LbsObject::write(TarSegmentStore *store)
{
- // A UUID only takes 36 bytes, plus the trailing '\0', so this is safe.
- char buf[40];
+ assert(data != NULL);
+ assert(!written);
- uuid_unparse_lower(u.bytes, buf);
+ ref = store->write_object(data, data_len, group);
+ written = true;
+}
+
+void LbsObject::checksum()
+{
+ assert(written);
- return string(buf);
+ SHA1Checksum hash;
+ hash.process(data, data_len);
+ ref.set_checksum(hash.checksum_str());
}
projects / cumulus.git / blobdiff