0e71867dfe
This optimizes the way in which the mempool oprhan map is limited in the same way the server block manager maps were previously optimized. Previously the code would read a cryptographically random value large enough to construct a hash, find the first entry larger than that value, and evict it. That approach is quite inefficient and could easily become a bottleneck when processing transactions due to the need to read from a source such as /dev/urandom and all of the subsequent hash comparisons. Luckily, strong cryptographic randomness is not needed here. The primary intent of limiting the maps is to control memory usage with a secondary concern of making it difficult for adversaries to force eviction of specific entries. Consequently, this changes the code to make use of the pseudorandom iteration order of Go's maps along with the preimage resistance of the hashing function to provide the desired functionality. It has previously been discussed that the specific pseudorandom iteration order is not guaranteed by the Go spec even though in practice that is how it is implemented. This is not a concern however because even if the specific compiler doesn't implement that, the preimage resistance of the hashing function alone is enough. The following is a before and after comparison of the function for both speed and memory allocations: benchmark old ns/op new ns/op delta ---------------------------------------------------------------- BenchmarkLimitNumOrphans 3727 243 -93.48% benchmark old allocs new allocs delta ----------------------------------------------------------------- BenchmarkLimitNumOrphans 4 0 -100.00% |
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| .. | ||
| doc.go | ||
| error.go | ||
| log.go | ||
| mempool.go | ||
| mempool_test.go | ||
| policy.go | ||
| policy_test.go | ||
| README.md | ||
mempool
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(https://travis-ci.org/btcsuite/btcd) ![ISC License]
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(http://godoc.org/github.com/btcsuite/btcd/mempool)
Package mempool provides a policy-enforced pool of unmined bitcoin transactions.
A key responsbility of the bitcoin network is mining user-generated transactions into blocks. In order to facilitate this, the mining process relies on having a readily-available source of transactions to include in a block that is being solved.
At a high level, this package satisfies that requirement by providing an in-memory pool of fully validated transactions that can also optionally be further filtered based upon a configurable policy.
One of the policy configuration options controls whether or not "standard" transactions are accepted. In essence, a "standard" transaction is one that satisfies a fairly strict set of requirements that are largley intended to help provide fair use of the system to all users. It is important to note that what is considered a "standard" transaction changes over time. For some insight, at the time of this writing, an example of some of the criteria that are required for a transaction to be considered standard are that it is of the most-recently supported version, finalized, does not exceed a specific size, and only consists of specific script forms.
Since this package does not deal with other bitcoin specifics such as network communication and transaction relay, it returns a list of transactions that were accepted which gives the caller a high level of flexibility in how they want to proceed. Typically, this will involve things such as relaying the transactions to other peers on the network and notifying the mining process that new transactions are available.
This package has intentionally been designed so it can be used as a standalone package for any projects needing the ability create an in-memory pool of bitcoin transactions that are not only valid by consensus rules, but also adhere to a configurable policy.
Feature Overview
The following is a quick overview of the major features. It is not intended to be an exhaustive list.
- Maintain a pool of fully validated transactions
- Reject non-fully-spent duplicate transactions
- Reject coinbase transactions
- Reject double spends (both from the chain and other transactions in pool)
- Reject invalid transactions according to the network consensus rules
- Full script execution and validation with signature cache support
- Individual transaction query support
- Orphan transaction support (transactions that spend from unknown outputs)
- Configurable limits (see transaction acceptance policy)
- Automatic addition of orphan transactions that are no longer orphans as new transactions are added to the pool
- Individual orphan transaction query support
- Configurable transaction acceptance policy
- Option to accept or reject standard transactions
- Option to accept or reject transactions based on priority calculations
- Rate limiting of low-fee and free transactions
- Non-zero fee threshold
- Max signature operations per transaction
- Max orphan transaction size
- Max number of orphan transactions allowed
- Additional metadata tracking for each transaction
- Timestamp when the transaction was added to the pool
- Most recent block height when the transaction was added to the pool
- The fee the transaction pays
- The starting priority for the transaction
- Manual control of transaction removal
- Recursive removal of all dependent transactions
Installation and Updating
$ go get -u github.com/btcsuite/btcd/mempool
License
Package mempool is licensed under the copyfree ISC License.