/* 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 <unistd.h>
+#include <fcntl.h>
+#include <time.h>
+
+#include <list>
+#include <set>
+#include <string>
+#include <iostream>
#include "store.h"
+#include "ref.h"
+using std::list;
+using std::set;
using std::string;
-OutputStream::OutputStream()
- : bytes_written(0)
-{
-}
-
-void OutputStream::write(const void *data, size_t len)
-{
- write_internal(data, len);
- bytes_written += len;
-}
+list<string> TarSegmentStore::norefs;
-void OutputStream::write_u8(uint8_t val)
+Tarfile::Tarfile(const string &path, const string &segment)
+ : size(0),
+ segment_name(segment)
{
- write(&val, 1);
+ if (tar_open(&t, (char *)path.c_str(), NULL, O_WRONLY | O_CREAT, 0600,
+ TAR_VERBOSE | TAR_GNU) == -1)
+ throw IOException("Error opening Tarfile");
}
-void OutputStream::write_u16(uint16_t val)
+Tarfile::~Tarfile()
{
- unsigned char buf[2];
+ string checksum_list = checksums.str();
+ internal_write_object(segment_name + "/checksums",
+ checksum_list.data(), checksum_list.size());
+ tar_append_eof(t);
- buf[0] = val & 0xff;
- buf[1] = (val >> 8) & 0xff;
- write(buf, 2);
+ if (tar_close(t) != 0)
+ throw IOException("Error closing Tarfile");
}
-void OutputStream::write_u32(uint32_t val)
+void Tarfile::write_object(int id, const char *data, size_t len)
{
- unsigned char buf[4];
+ char buf[64];
+ sprintf(buf, "%08x", id);
+ string path = segment_name + "/" + buf;
- buf[0] = val & 0xff;
- buf[1] = (val >> 8) & 0xff;
- buf[2] = (val >> 16) & 0xff;
- buf[3] = (val >> 24) & 0xff;
- write(buf, 4);
-}
+ internal_write_object(path, data, len);
-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);
+ // 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";
}
-/* 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)
+void Tarfile::internal_write_object(const string &path,
+ const char *data, size_t len)
{
- do {
- uint8_t remainder = (val & 0x7f);
- val >>= 7;
- if (val)
- remainder |= 0x80;
- write_u8(remainder);
- } while (val);
-}
+ memset(&t->th_buf, 0, sizeof(struct tar_header));
-void OutputStream::write_uuid(const struct uuid &u)
-{
- write(u.bytes, 16);
-}
-
-/* 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);
-}
+ 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 OutputStream::write_dictionary(const dictionary &d)
-{
- size_t size = d.size();
- size_t written = 0;
+ if (th_write(t) != 0)
+ throw IOException("Error writing tar header");
- write_varint(size);
+ size += T_BLOCKSIZE;
- for (dictionary::const_iterator i = d.begin(); i != d.end(); ++i) {
- write_string(i->first);
- write_string(i->second);
- written++;
- }
+ if (len == 0)
+ return;
- assert(written == size);
-}
+ size_t blocks = (len + T_BLOCKSIZE - 1) / T_BLOCKSIZE;
+ size_t padding = blocks * T_BLOCKSIZE - len;
-StringOutputStream::StringOutputStream()
- : buf(std::ios_base::out)
-{
-}
-
-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");
-}
-
-FileOutputStream::FileOutputStream(FILE *file)
-{
- f = file;
-}
-
-FileOutputStream::~FileOutputStream()
-{
- fclose(f);
-}
-
-void FileOutputStream::write_internal(const void *data, size_t len)
-{
- size_t res;
-
- res = fwrite(data, 1, len, f);
- if (res != len) {
- throw IOException("write error");
+ 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)
-{
-}
-void WrapperOutputStream::write_internal(const void *data, size_t len)
-{
- real.write(data, len);
-}
+ 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");
-/* Provide checksumming of a data stream. */
-ChecksumOutputStream::ChecksumOutputStream(OutputStream &o)
- : real(o)
-{
+ size += blocks * T_BLOCKSIZE;
}
-void ChecksumOutputStream::write_internal(const void *data, size_t len)
-{
- real.write(data, len);
- csum.process(data, len);
-}
+static const size_t SEGMENT_SIZE = 4 * 1024 * 1024;
-const uint8_t *ChecksumOutputStream::finish_and_checksum()
+string TarSegmentStore::write_object(const char *data, size_t len, const
+ std::string &group,
+ const std::list<std::string> &refs)
{
- return csum.checksum();
-}
+ struct segment_info *segment;
-/* Utility functions, for encoding data types to strings. */
-string encode_u16(uint16_t val)
-{
- StringOutputStream s;
- s.write_u16(val);
- return s.contents();
-}
+ // 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;
-string encode_u32(uint32_t val)
-{
- StringOutputStream s;
- s.write_u32(val);
- return s.contents();
-}
+ segment->name = generate_uuid();
-string encode_u64(uint64_t val)
-{
- StringOutputStream s;
- s.write_u64(val);
- return s.contents();
-}
+ string filename = path + "/" + segment->name + ".tar";
+ segment->file = new Tarfile(filename, segment->name);
-string encode_objref(const struct uuid &segment, uint32_t object)
-{
- StringOutputStream s;
- s.write_uuid(segment);
- s.write_u32(object);
- return s.contents();
-}
+ segment->count = 0;
-SegmentWriter::SegmentWriter(OutputStream *output, struct uuid u)
- : raw_out(output),
- id(u),
- object_stream(NULL)
-{
- /* All output data will be checksummed except the very last few bytes,
- * which are the checksum itself. */
- out = new ChecksumOutputStream(*raw_out);
-
- /* Write out the segment header first. */
- static const char signature[] = "LBSSEG0\n";
- out->write(signature, strlen(signature));
- out->write_uuid(id);
-}
-
-SegmentWriter::~SegmentWriter()
-{
- 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->offset);
- out->write_s64(i->size);
- out->write(i->type, sizeof(i->type));
+ 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);
- /* Finally, append a checksum to the end of the file, so that its integrity
- * (against accidental, not malicious, corruption) can be verified. */
- const uint8_t *csum = out->finish_and_checksum();
- raw_out->write(csum, out->checksum_size());
-
- /* The SegmentWriter takes ownership of the OutputStream it is writing to,
- * and destroys it automatically when done with the segment. */
- delete out;
- delete raw_out;
-}
+ segment->file->write_object(id, data, len);
+ segment->count++;
-OutputStream *SegmentWriter::new_object(int *id, const char *type)
-{
- if (object_stream)
- finish_object();
+ string full_name = segment->name + "/" + id_buf;
- if (id != NULL)
- *id = objects.size();
+ // Store any dependencies this object has on other segments, so they can be
+ // written when the segment is closed.
+ for (list<string>::const_iterator i = refs.begin(); i != refs.end(); ++i) {
+ segment->refs.insert(*i);
+ }
- struct index_info info;
- info.offset = out->get_pos();
- info.size = -1; // Will be filled in when object is finished
- strncpy(info.type, type, sizeof(info.type));
- objects.push_back(info);
+ // 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);
- object_stream = new WrapperOutputStream(*out);
- return object_stream;
+ return full_name;
}
-void SegmentWriter::finish_object()
+void TarSegmentStore::sync()
{
- assert(object_stream != NULL);
-
- // Fill in object size, which could not be stored at start
- objects.back().size = object_stream->get_pos();
-
- delete object_stream;
- object_stream = NULL;
+ while (!segments.empty())
+ close_segment(segments.begin()->first);
}
-struct uuid SegmentWriter::generate_uuid()
+void TarSegmentStore::close_segment(const string &group)
{
- struct uuid u;
+ struct segment_info *segment = segments[group];
+ fprintf(stderr, "Closing segment group %s (%s)\n",
+ group.c_str(), segment->name.c_str());
- uuid_generate(u.bytes);
+ string reflist;
+ for (set<string>::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());
- return u;
+ delete segment->file;
+ segments.erase(segments.find(group));
+ delete segment;
}
-string SegmentWriter::format_uuid(const struct uuid u)
+string TarSegmentStore::object_reference_to_segment(const string &object)
{
- // A UUID only takes 36 bytes, plus the trailing '\0', so this is safe.
- char buf[40];
-
- uuid_unparse_lower(u.bytes, buf);
-
- return string(buf);
+ return object;
}
-SegmentStore::SegmentStore(const string &path)
- : directory(path)
+LbsObject::LbsObject()
+ : group(""), data(NULL), data_len(0), written(false)
{
}
-SegmentWriter *SegmentStore::new_segment()
+LbsObject::~LbsObject()
{
- struct uuid id = SegmentWriter::generate_uuid();
- string filename = directory + "/" + SegmentWriter::format_uuid(id);
-
- FILE *f = fopen(filename.c_str(), "wb");
- if (f == NULL)
- throw IOException("Unable to open new segment");
-
- return new SegmentWriter(new FileOutputStream(f), id);
}
-SegmentPartitioner::SegmentPartitioner(SegmentStore *s)
- : store(s),
- segment(NULL),
- object(NULL)
+void LbsObject::add_reference(const LbsObject *o)
{
- // Default target size is around 1 MB
- target_size = 1024 * 1024;
+ refs.insert(o->get_name());
}
-SegmentPartitioner::~SegmentPartitioner()
+void LbsObject::write(TarSegmentStore *store)
{
- if (segment)
- delete segment;
-}
+ assert(data != NULL);
+ assert(!written);
-OutputStream *SegmentPartitioner::new_object(struct uuid *uuid, int *id,
- const char *type)
-{
- if (segment != NULL && segment->get_size() > target_size) {
- delete segment;
- segment = NULL;
+ list<string> reflist;
+ for (set<string>::iterator i = refs.begin(); i != refs.end(); ++i) {
+ reflist.push_back(*i);
}
- if (segment == NULL)
- segment = store->new_segment();
-
- if (uuid != NULL)
- *uuid = segment->get_uuid();
+ name = store->write_object(data, data_len, group, reflist);
- return segment->new_object(id, type);
+ written = true;
+ data = NULL;
}
projects / cumulus.git / blobdiff