2018-06-15 22:56:26 -07:00
|
|
|
|
# WAL
|
|
|
|
|
|
|
|
|
|
|
|
Consensus module writes every message to the WAL (write-ahead log).
|
|
|
|
|
|
|
|
|
|
|
|
It also issues fsync syscall through
|
|
|
|
|
|
[File#Sync](https://golang.org/pkg/os/#File.Sync) for messages signed by this
|
|
|
|
|
|
node (to prevent double signing).
|
|
|
|
|
|
|
|
|
|
|
|
Under the hood, it uses
|
|
|
|
|
|
[autofile.Group](https://godoc.org/github.com/tendermint/tmlibs/autofile#Group),
|
|
|
|
|
|
which rotates files when those get too big (> 10MB).
|
|
|
|
|
|
|
|
|
|
|
|
The total maximum size is 1GB. We only need the latest block and the block before it,
|
|
|
|
|
|
but if the former is dragging on across many rounds, we want all those rounds.
|
|
|
|
|
|
|
|
|
|
|
|
## Replay
|
|
|
|
|
|
|
|
|
|
|
|
Consensus module will replay all the messages of the last height written to WAL
|
|
|
|
|
|
before a crash (if such occurs).
|
|
|
|
|
|
|
|
|
|
|
|
The private validator may try to sign messages during replay because it runs
|
|
|
|
|
|
somewhat autonomously and does not know about replay process.
|
|
|
|
|
|
|
|
|
|
|
|
For example, if we got all the way to precommit in the WAL and then crash,
|
|
|
|
|
|
after we replay the proposal message, the private validator will try to sign a
|
|
|
|
|
|
prevote. But it will fail. That's ok because we’ll see the prevote later in the
|
|
|
|
|
|
WAL. Then it will go to precommit, and that time it will work because the
|
|
|
|
|
|
private validator contains the `LastSignBytes` and then we’ll replay the
|
|
|
|
|
|
precommit from the WAL.
|
|
|
|
|
|
|
2018-08-07 18:40:11 -04:00
|
|
|
|
Make sure to read about [WAL corruption](../../../tendermint-core/running-in-production.md#wal-corruption)
|
2018-06-15 22:56:26 -07:00
|
|
|
|
and recovery strategies.
|
