Enable blobs to be fragmented
Summary: I have implemented a FreeList version that supports fragmented blob chunks. Each block gets allocated and freed in FIFO order. Since the idea for the blocks to be big, we will not take a big hit of non-sequential IO. Free list is also faster, taking only O(k) size in both free and allocate instead of O(N) as before. See more info on the task: https://our.intern.facebook.com/intern/tasks/?t=2990558 Also, I'm taking Slice instead of const char * and size in Put function. Test Plan: unittests Reviewers: haobo, kailiu, dhruba, emayanke Reviewed By: dhruba CC: leveldb Differential Revision: https://reviews.facebook.net/D13569
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@ -47,59 +47,15 @@ Blob::Blob(const std::string& blob) {
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}
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// FreeList
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FreeList::FreeList() {
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// We add (0, 0, 0) blob because it makes our life easier and
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// code cleaner. (0, 0, 0) is always in the list so we can
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// guarantee that free_chunks_list_ != nullptr, which avoids
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// lots of unnecessary ifs
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free_chunks_list_ = (FreeChunk *)malloc(sizeof(FreeChunk));
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free_chunks_list_->chunk = BlobChunk(0, 0, 0);
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free_chunks_list_->next = nullptr;
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}
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FreeList::~FreeList() {
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while (free_chunks_list_ != nullptr) {
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FreeChunk* t = free_chunks_list_;
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free_chunks_list_ = free_chunks_list_->next;
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free(t);
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}
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}
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Status FreeList::Free(const Blob& blob) {
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MutexLock l(&mutex_);
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// add it back to the free list
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for (auto chunk : blob.chunks) {
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FreeChunk* itr = free_chunks_list_;
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// find a node AFTER which we'll add the block
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for ( ; itr->next != nullptr && itr->next->chunk <= chunk;
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itr = itr->next) {
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}
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// try to merge with previous block
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if (itr->chunk.ImmediatelyBefore(chunk)) {
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// merge
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itr->chunk.size += chunk.size;
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free_blocks_ += chunk.size;
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if (fifo_free_chunks_.size() &&
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fifo_free_chunks_.back().ImmediatelyBefore(chunk)) {
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fifo_free_chunks_.back().size += chunk.size;
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} else {
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// Insert the block after itr
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FreeChunk* t = (FreeChunk*)malloc(sizeof(FreeChunk));
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if (t == nullptr) {
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throw runtime_error("Malloc failed");
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}
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t->chunk = chunk;
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t->next = itr->next;
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itr->next = t;
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itr = t;
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}
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// try to merge with the next block
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if (itr->next != nullptr &&
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itr->chunk.ImmediatelyBefore(itr->next->chunk)) {
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FreeChunk *tobedeleted = itr->next;
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itr->chunk.size += itr->next->chunk.size;
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itr->next = itr->next->next;
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free(tobedeleted);
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fifo_free_chunks_.push_back(chunk);
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}
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}
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@ -107,48 +63,38 @@ Status FreeList::Free(const Blob& blob) {
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}
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Status FreeList::Allocate(uint32_t blocks, Blob* blob) {
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MutexLock l(&mutex_);
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FreeChunk** best_fit_node = nullptr;
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// Find the smallest free chunk whose size is greater or equal to blocks
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for (FreeChunk** itr = &free_chunks_list_; (*itr) != nullptr;
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itr = &((*itr)->next)) {
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if ((*itr)->chunk.size >= blocks &&
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(best_fit_node == nullptr ||
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(*best_fit_node)->chunk.size > (*itr)->chunk.size)) {
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best_fit_node = itr;
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}
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}
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if (best_fit_node == nullptr || *best_fit_node == nullptr) {
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// Not enough memory
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if (free_blocks_ < blocks) {
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return Status::Incomplete("");
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}
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blob->SetOneChunk((*best_fit_node)->chunk.bucket_id,
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(*best_fit_node)->chunk.offset,
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blocks);
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blob->chunks.clear();
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free_blocks_ -= blocks;
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if ((*best_fit_node)->chunk.size > blocks) {
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// just shorten best_fit_node
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(*best_fit_node)->chunk.offset += blocks;
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(*best_fit_node)->chunk.size -= blocks;
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while (blocks > 0) {
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assert(fifo_free_chunks_.size() > 0);
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auto& front = fifo_free_chunks_.front();
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if (front.size > blocks) {
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blob->chunks.push_back(BlobChunk(front.bucket_id, front.offset, blocks));
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front.offset += blocks;
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front.size -= blocks;
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blocks = 0;
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} else {
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assert(blocks == (*best_fit_node)->chunk.size);
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// delete best_fit_node
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FreeChunk* t = *best_fit_node;
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(*best_fit_node) = (*best_fit_node)->next;
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free(t);
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blob->chunks.push_back(front);
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blocks -= front.size;
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fifo_free_chunks_.pop_front();
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}
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}
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assert(blocks == 0);
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return Status::OK();
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}
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bool FreeList::Overlap(const Blob &blob) const {
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MutexLock l(&mutex_);
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for (auto chunk : blob.chunks) {
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for (auto itr = free_chunks_list_; itr != nullptr; itr = itr->next) {
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if (itr->chunk.Overlap(chunk)) {
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for (auto itr = fifo_free_chunks_.begin();
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itr != fifo_free_chunks_.end();
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++itr) {
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if (itr->Overlap(chunk)) {
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return true;
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}
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}
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@ -177,26 +123,28 @@ BlobStore::~BlobStore() {
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// TODO we don't care about recovery for now
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}
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Status BlobStore::Put(const char* value, uint64_t size, Blob* blob) {
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Status BlobStore::Put(const Slice& value, Blob* blob) {
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// convert size to number of blocks
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Status s = Allocate((size + block_size_ - 1) / block_size_, blob);
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Status s = Allocate((value.size() + block_size_ - 1) / block_size_, blob);
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if (!s.ok()) {
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return s;
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}
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ReadLock l(&buckets_mutex_);
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size_t size_left = value.size();
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uint64_t offset = 0; // in bytes, not blocks
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for (auto chunk : blob->chunks) {
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uint64_t write_size = min(chunk.size * block_size_, size);
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uint64_t write_size = min(chunk.size * block_size_, size_left);
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assert(chunk.bucket_id < buckets_.size());
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s = buckets_[chunk.bucket_id].get()->Write(chunk.offset * block_size_,
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Slice(value + offset,
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Slice(value.data() + offset,
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write_size));
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if (!s.ok()) {
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Delete(*blob);
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return s;
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}
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offset += write_size;
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size -= write_size;
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size_left -= write_size;
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if (write_size < chunk.size * block_size_) {
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// if we have any space left in the block, fill it up with zeros
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string zero_string(chunk.size * block_size_ - write_size, 0);
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@ -206,7 +154,7 @@ Status BlobStore::Put(const char* value, uint64_t size, Blob* blob) {
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}
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}
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if (size > 0) {
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if (size_left > 0) {
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Delete(*blob);
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return Status::IOError("Tried to write more data than fits in the blob");
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}
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@ -216,16 +164,13 @@ Status BlobStore::Put(const char* value, uint64_t size, Blob* blob) {
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Status BlobStore::Get(const Blob& blob,
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string* value) const {
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ReadLock l(&buckets_mutex_);
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// assert that it doesn't overlap with free list
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// it will get compiled out for release
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assert(!free_list_.Overlap(blob));
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uint32_t total_size = 0; // in blocks
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for (auto chunk : blob.chunks) {
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total_size += chunk.size;
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}
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assert(total_size > 0);
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value->resize(total_size * block_size_);
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value->resize(blob.Size() * block_size_);
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uint64_t offset = 0; // in bytes, not blocks
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for (auto chunk : blob.chunks) {
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@ -250,13 +195,23 @@ Status BlobStore::Get(const Blob& blob,
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}
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Status BlobStore::Delete(const Blob& blob) {
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MutexLock l(&free_list_mutex_);
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return free_list_.Free(blob);
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}
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Status BlobStore::Sync() {
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ReadLock l(&buckets_mutex_);
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for (size_t i = 0; i < buckets_.size(); ++i) {
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Status s = buckets_[i].get()->Sync();
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if (!s.ok()) {
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return s;
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}
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}
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return Status::OK();
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}
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Status BlobStore::Allocate(uint32_t blocks, Blob* blob) {
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// TODO we don't currently support fragmented blobs
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MutexLock l(&allocate_mutex_);
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assert(blocks <= blocks_per_bucket_);
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MutexLock l(&free_list_mutex_);
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Status s;
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s = free_list_.Allocate(blocks, blob);
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@ -271,7 +226,9 @@ Status BlobStore::Allocate(uint32_t blocks, Blob* blob) {
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return s;
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}
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// called with free_list_mutex_ held
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Status BlobStore::CreateNewBucket() {
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WriteLock l(&buckets_mutex_);
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int new_bucket_id;
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new_bucket_id = buckets_.size();
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buckets_.push_back(unique_ptr<RandomRWFile>());
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@ -10,6 +10,7 @@
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#include "util/coding.h"
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#include <list>
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#include <deque>
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#include <cstdint>
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#include <iostream>
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#include <stdexcept>
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@ -26,16 +27,6 @@ struct BlobChunk {
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BlobChunk(uint32_t bucket_id, uint32_t offset, uint32_t size) :
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bucket_id(bucket_id), offset(offset), size(size) {}
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bool operator <= (const BlobChunk& chunk) const {
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if (bucket_id != chunk.bucket_id) {
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return bucket_id < chunk.bucket_id;
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}
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if (offset != chunk.offset) {
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return offset < chunk.offset;
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}
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return true;
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}
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// returns true if it's immediately before chunk
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bool ImmediatelyBefore(const BlobChunk& chunk) const;
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// returns true if chunks overlap
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@ -63,15 +54,26 @@ struct Blob {
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chunks.push_back(BlobChunk(bucket_id, offset, size));
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}
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uint32_t Size() const { // in blocks
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uint32_t ret = 0;
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for (auto chunk : chunks) {
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ret += chunk.size;
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}
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assert(ret > 0);
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return ret;
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}
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// bucket_id, offset, size
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std::vector<BlobChunk> chunks;
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};
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// Keeps a list of free chunks
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// NOT thread-safe. Externally synchronized
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class FreeList {
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public:
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FreeList ();
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~FreeList();
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FreeList() :
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free_blocks_(0) {}
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~FreeList() {}
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// Allocates a a blob. Stores the allocated blob in
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// 'blob'. Returns non-OK status if it failed to allocate.
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@ -85,12 +87,8 @@ class FreeList {
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bool Overlap(const Blob &blob) const;
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private:
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struct FreeChunk {
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BlobChunk chunk;
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FreeChunk* next;
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};
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FreeChunk* free_chunks_list_;
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std::deque<BlobChunk> fifo_free_chunks_;
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uint32_t free_blocks_;
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mutable port::Mutex mutex_;
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};
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@ -111,17 +109,19 @@ class BlobStore {
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Env* env);
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~BlobStore();
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// Allocates space for size bytes (rounded up to be multiple of
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// block size) and writes size bytes from value to a backing store.
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// Allocates space for value.size bytes (rounded up to be multiple of
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// block size) and writes value.size bytes from value.data to a backing store.
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// Sets Blob blob that can than be used for addressing the
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// stored value. Returns non-OK status on error.
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Status Put(const char* value, uint64_t size, Blob* blob);
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Status Put(const Slice& value, Blob* blob);
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// Value needs to have enough space to store all the loaded stuff.
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// This function is thread safe!
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Status Get(const Blob& blob, std::string* value) const;
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// Frees the blob for reuse, but does not delete the data
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// on the backing store.
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Status Delete(const Blob& blob);
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// Sync all opened files that are modified
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Status Sync();
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private:
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const std::string directory_;
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@ -132,10 +132,12 @@ class BlobStore {
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const uint32_t blocks_per_bucket_;
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Env* env_;
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EnvOptions storage_options_;
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// protected by free_list_mutex_
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FreeList free_list_;
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mutable port::Mutex free_list_mutex_;
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// protected by buckets mutex
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std::vector<unique_ptr<RandomRWFile>> buckets_;
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mutable port::Mutex allocate_mutex_;
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mutable port::RWMutex buckets_mutex_;
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// Calls FreeList allocate. If free list can't allocate
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// new blob, creates new bucket and tries again
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@ -144,7 +146,6 @@ class BlobStore {
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// Creates a new backing store and adds all the blocks
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// from the new backing store to the free list
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// NOT thread-safe, call with lock held
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Status CreateNewBucket();
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};
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@ -44,7 +44,7 @@ TEST(BlobStoreTest, SanityTest) {
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// put string of size 170
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test::RandomString(&random, 170, &buf);
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Blob r1;
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ASSERT_OK(blob_store.Put(buf.data(), 170, &r1));
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ASSERT_OK(blob_store.Put(Slice(buf), &r1));
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// use the first file
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for (size_t i = 0; i < r1.chunks.size(); ++i) {
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ASSERT_EQ(r1.chunks[0].bucket_id, 0u);
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@ -53,7 +53,7 @@ TEST(BlobStoreTest, SanityTest) {
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// put string of size 30
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test::RandomString(&random, 30, &buf);
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Blob r2;
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ASSERT_OK(blob_store.Put(buf.data(), 30, &r2));
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ASSERT_OK(blob_store.Put(Slice(buf), &r2));
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// use the first file
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for (size_t i = 0; i < r2.chunks.size(); ++i) {
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ASSERT_EQ(r2.chunks[0].bucket_id, 0u);
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@ -65,7 +65,7 @@ TEST(BlobStoreTest, SanityTest) {
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// put a string of size 100
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test::RandomString(&random, 100, &buf);
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Blob r3;
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ASSERT_OK(blob_store.Put(buf.data(), 100, &r3));
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ASSERT_OK(blob_store.Put(Slice(buf), &r3));
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// use the first file
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for (size_t i = 0; i < r3.chunks.size(); ++i) {
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ASSERT_EQ(r3.chunks[0].bucket_id, 0u);
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@ -74,7 +74,7 @@ TEST(BlobStoreTest, SanityTest) {
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// put a string of size 70
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test::RandomString(&random, 70, &buf);
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Blob r4;
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ASSERT_OK(blob_store.Put(buf.data(), 70, &r4));
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ASSERT_OK(blob_store.Put(Slice(buf), &r4));
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// use the first file
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for (size_t i = 0; i < r4.chunks.size(); ++i) {
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ASSERT_EQ(r4.chunks[0].bucket_id, 0u);
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@ -83,12 +83,50 @@ TEST(BlobStoreTest, SanityTest) {
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// put a string of size 5
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test::RandomString(&random, 5, &buf);
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Blob r5;
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ASSERT_OK(blob_store.Put(buf.data(), 70, &r5));
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ASSERT_OK(blob_store.Put(Slice(buf), &r5));
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// now you get to use the second file
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for (size_t i = 0; i < r5.chunks.size(); ++i) {
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ASSERT_EQ(r5.chunks[0].bucket_id, 1u);
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}
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}
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TEST(BlobStoreTest, FragmentedChunksTest) {
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const uint64_t block_size = 10;
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const uint32_t blocks_per_file = 20;
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Random random(5);
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BlobStore blob_store(test::TmpDir() + "/blob_store_test",
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block_size,
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blocks_per_file,
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Env::Default());
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string buf;
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vector <Blob> r(4);
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// put 4 strings of size 50
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for (int k = 0; k < 4; ++k) {
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test::RandomString(&random, 50, &buf);
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ASSERT_OK(blob_store.Put(Slice(buf), &r[k]));
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// use the first file
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for (size_t i = 0; i < r[k].chunks.size(); ++i) {
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ASSERT_EQ(r[k].chunks[0].bucket_id, 0u);
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}
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}
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// delete the first and third
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ASSERT_OK(blob_store.Delete(r[0]));
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ASSERT_OK(blob_store.Delete(r[2]));
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// put string of size 100. it should reuse space that we deleting
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// by deleting first and third strings of size 50
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test::RandomString(&random, 100, &buf);
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Blob r2;
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ASSERT_OK(blob_store.Put(Slice(buf), &r2));
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// use the first file
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for (size_t i = 0; i < r2.chunks.size(); ++i) {
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ASSERT_EQ(r2.chunks[0].bucket_id, 0u);
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}
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}
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TEST(BlobStoreTest, CreateAndStoreTest) {
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@ -111,7 +149,7 @@ TEST(BlobStoreTest, CreateAndStoreTest) {
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int string_size = size_blocks * block_size - (rand() % block_size);
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test::RandomString(&random, string_size, &buf);
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Blob r;
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ASSERT_OK(blob_store.Put(buf.data(), string_size, &r));
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ASSERT_OK(blob_store.Put(Slice(buf), &r));
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ranges.push_back(make_pair(r, buf));
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} else if (decision == 3) {
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int ti = rand() % ranges.size();
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@ -124,6 +162,7 @@ TEST(BlobStoreTest, CreateAndStoreTest) {
|
||||
ranges.erase(ranges.begin() + ti);
|
||||
}
|
||||
}
|
||||
ASSERT_OK(blob_store.Sync());
|
||||
}
|
||||
|
||||
} // namespace rocksdb
|
||||
|
Loading…
Reference in New Issue
Block a user