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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include <vespa/storage/bucketdb/bucketdatabase.h>
#include <memory>
namespace storage::distributor {
class BucketSpaceDistributionContext;
class DistributorBucketSpaceRepo;
/**
* An "operation routing snapshot" is intended to provide a stable means of computing
* bucket routing targets and performing database lookups for a particular bucket space
* in a potentially multi-threaded setting. When using multiple threads, both the current
* cluster/distribution state as well as the underlying bucket database may change
* independent of each other when observed from any other thread than the main distributor
* thread. Additionally, the bucket management system may operate with separate read-only
* databases during state transitions, complicating things further.
*
* By using an OperationRoutingSnapshot, a caller gets a consistent view of the world
* that stays valid throughout the operation's life time.
*
* Note that holding the DB read guard should be done for as short a time as possible to
* avoid elevated memory usage caused by data stores not being able to free on-hold items.
*/
class OperationRoutingSnapshot {
std::shared_ptr<const BucketSpaceDistributionContext> _context;
std::shared_ptr<BucketDatabase::ReadGuard> _read_guard;
const DistributorBucketSpaceRepo* _bucket_space_repo;
public:
OperationRoutingSnapshot(std::shared_ptr<const BucketSpaceDistributionContext> context,
std::shared_ptr<BucketDatabase::ReadGuard> read_guard,
const DistributorBucketSpaceRepo* bucket_space_repo);
static OperationRoutingSnapshot make_not_routable_in_state(std::shared_ptr<const BucketSpaceDistributionContext> context);
static OperationRoutingSnapshot make_routable_with_guard(std::shared_ptr<const BucketSpaceDistributionContext> context,
std::shared_ptr<BucketDatabase::ReadGuard> read_guard,
const DistributorBucketSpaceRepo& bucket_space_repo);
OperationRoutingSnapshot(const OperationRoutingSnapshot&) noexcept = default;
OperationRoutingSnapshot& operator=(const OperationRoutingSnapshot&) noexcept = default;
OperationRoutingSnapshot(OperationRoutingSnapshot&&) noexcept = default;
OperationRoutingSnapshot& operator=(OperationRoutingSnapshot&&) noexcept = default;
~OperationRoutingSnapshot();
const BucketSpaceDistributionContext& context() const noexcept { return *_context; }
std::shared_ptr<BucketDatabase::ReadGuard> steal_read_guard() noexcept {
return std::move(_read_guard);
}
bool is_routable() const noexcept {
return (_read_guard.get() != nullptr);
}
const DistributorBucketSpaceRepo* bucket_space_repo() const noexcept {
return _bucket_space_repo;
}
};
}
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