3547f21f89
This makes the mempool an internal package such that it will no longer be an exported module. The only place its functionality is really needed is for the internal implementation of dcrd itself and thus having an unnecessary exported module significantly increases the maintenance burden. This is part of the overall effort to reduce the total number of modules and eventually get to the point it will be possible to follow semver for the root module. It is worth noting that there are a few constants, which will be listed below, that were exported from this module that callers might have previously relied upon. However, due to previous discussions about the goal of removing the module, a code search has revealed that there are no known callers that still rely on them. The aforementioned constants are: - MaxStandardTxSize - DefaultMinRelayTxFee - BaseStandardVerifyFlags Overview of the major changes: - Move the following files from mempool -> internal/mempool: - README.md - doc.go - error.go - log.go - mempool.go - mempool_test.go - policy.go - policy_test.go - Remove mempool/go.mod and mempool/go.sum - Make the README.md and doc.go files match the new reality - Update all import paths in the repository accordingly - Remove the dependency from the root go.mod - Run go mod tidy on all modules
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mempool
Package mempool provides a policy-enforced pool of unmined Decred transactions.
A key responsibility of the Decred network is mining transactions – regular transactions and stake 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.
The Policy configuration options has flags that control whether or not "standard" transactions and old votes are accepted into the mempool. In essence, a "standard" transaction is one that satisfies a fairly strict set of requirements that are largely intended to help provide fair use of the system to all users. It is important to note that what is considered to be a "standard" transaction changes over time as policy and consensus rules evolve. 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 Decred 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.
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
- Stake transaction support (ticket purchases, votes and revocations)
- Option to accept or reject old votes
- 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
License
Package mempool is licensed under the copyfree ISC License.