diff options
Diffstat (limited to 'src/test/erasure-code/ErasureCodeExample.h')
| -rw-r--r-- | src/test/erasure-code/ErasureCodeExample.h | 195 |
1 files changed, 195 insertions, 0 deletions
diff --git a/src/test/erasure-code/ErasureCodeExample.h b/src/test/erasure-code/ErasureCodeExample.h new file mode 100644 index 000000000..125846538 --- /dev/null +++ b/src/test/erasure-code/ErasureCodeExample.h @@ -0,0 +1,195 @@ +// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*- +// vim: ts=8 sw=2 smarttab +/* + * Ceph distributed storage system + * + * Copyright (C) 2013 Cloudwatt <libre.licensing@cloudwatt.com> + * + * Author: Loic Dachary <loic@dachary.org> + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + */ + +#ifndef CEPH_ERASURE_CODE_EXAMPLE_H +#define CEPH_ERASURE_CODE_EXAMPLE_H + +#include <unistd.h> +#include <errno.h> +#include <algorithm> +#include <sstream> + +#include "crush/CrushWrapper.h" +#include "osd/osd_types.h" +#include "erasure-code/ErasureCode.h" + +#define FIRST_DATA_CHUNK 0 +#define SECOND_DATA_CHUNK 1 +#define DATA_CHUNKS 2u + +#define CODING_CHUNK 2 +#define CODING_CHUNKS 1u + +#define MINIMUM_TO_RECOVER 2u + +class ErasureCodeExample final : public ErasureCode { +public: + ~ErasureCodeExample() override {} + + int create_rule(const string &name, + CrushWrapper &crush, + ostream *ss) const override { + return crush.add_simple_rule(name, "default", "host", "", + "indep", pg_pool_t::TYPE_ERASURE, ss); + } + + int minimum_to_decode_with_cost(const set<int> &want_to_read, + const map<int, int> &available, + set<int> *minimum) override { + // + // If one chunk is more expensive to fetch than the others, + // recover it instead. For instance, if the cost reflects the + // time it takes for a chunk to be retrieved from a remote + // OSD and if CPU is cheap, it could make sense to recover + // instead of fetching the chunk. + // + map<int, int> c2c(available); + if (c2c.size() > DATA_CHUNKS) { + if (c2c[FIRST_DATA_CHUNK] > c2c[SECOND_DATA_CHUNK] && + c2c[FIRST_DATA_CHUNK] > c2c[CODING_CHUNK]) + c2c.erase(FIRST_DATA_CHUNK); + else if(c2c[SECOND_DATA_CHUNK] > c2c[FIRST_DATA_CHUNK] && + c2c[SECOND_DATA_CHUNK] > c2c[CODING_CHUNK]) + c2c.erase(SECOND_DATA_CHUNK); + else if(c2c[CODING_CHUNK] > c2c[FIRST_DATA_CHUNK] && + c2c[CODING_CHUNK] > c2c[SECOND_DATA_CHUNK]) + c2c.erase(CODING_CHUNK); + } + set <int> available_chunks; + for (map<int, int>::const_iterator i = c2c.begin(); + i != c2c.end(); + ++i) + available_chunks.insert(i->first); + return _minimum_to_decode(want_to_read, available_chunks, minimum); + } + + unsigned int get_chunk_count() const override { + return DATA_CHUNKS + CODING_CHUNKS; + } + + unsigned int get_data_chunk_count() const override { + return DATA_CHUNKS; + } + + unsigned int get_chunk_size(unsigned int object_size) const override { + return ( object_size / DATA_CHUNKS ) + 1; + } + + int encode(const set<int> &want_to_encode, + const bufferlist &in, + map<int, bufferlist> *encoded) override { + // + // make sure all data chunks have the same length, allocating + // padding if necessary. + // + unsigned int chunk_length = get_chunk_size(in.length()); + bufferlist out(in); + unsigned int width = get_chunk_count() * get_chunk_size(in.length()); + bufferptr pad(width - in.length()); + pad.zero(0, get_data_chunk_count()); + out.push_back(pad); + // + // compute the coding chunk with first chunk ^ second chunk + // + char *p = out.c_str(); + for (unsigned i = 0; i < chunk_length; i++) + p[i + CODING_CHUNK * chunk_length] = + p[i + FIRST_DATA_CHUNK * chunk_length] ^ + p[i + SECOND_DATA_CHUNK * chunk_length]; + // + // populate the bufferlist with bufferptr pointing + // to chunk boundaries + // + const bufferptr &ptr = out.front(); + for (set<int>::iterator j = want_to_encode.begin(); + j != want_to_encode.end(); + ++j) { + bufferlist tmp; + bufferptr chunk(ptr, (*j) * chunk_length, chunk_length); + tmp.push_back(chunk); + tmp.claim_append((*encoded)[*j]); + (*encoded)[*j].swap(tmp); + } + return 0; + } + + int encode_chunks(const set<int> &want_to_encode, + map<int, bufferlist> *encoded) override { + ceph_abort(); + return 0; + } + + int _decode(const set<int> &want_to_read, + const map<int, bufferlist> &chunks, + map<int, bufferlist> *decoded) { + // + // All chunks have the same size + // + unsigned chunk_length = (*chunks.begin()).second.length(); + for (set<int>::iterator i = want_to_read.begin(); + i != want_to_read.end(); + ++i) { + if (chunks.find(*i) != chunks.end()) { + // + // If the chunk is available, just copy the bufferptr pointer + // to the decoded argument. + // + (*decoded)[*i] = chunks.find(*i)->second; + } else if(chunks.size() != 2) { + // + // If a chunk is missing and there are not enough chunks + // to recover, abort. + // + return -ERANGE; + } else { + // + // No matter what the missing chunk is, XOR of the other + // two recovers it. + // + map<int, bufferlist>::const_iterator k = chunks.begin(); + const char *a = k->second.front().c_str(); + ++k; + const char *b = k->second.front().c_str(); + bufferptr chunk(chunk_length); + char *c = chunk.c_str(); + for (unsigned j = 0; j < chunk_length; j++) { + c[j] = a[j] ^ b[j]; + } + + bufferlist tmp; + tmp.append(chunk); + tmp.claim_append((*decoded)[*i]); + (*decoded)[*i].swap(tmp); + } + } + return 0; + } + + int decode_chunks(const set<int> &want_to_read, + const map<int, bufferlist> &chunks, + map<int, bufferlist> *decoded) override { + ceph_abort(); + return 0; + } + + const vector<int> &get_chunk_mapping() const override { + static vector<int> mapping; + return mapping; + } + +}; + +#endif |