error itself is not enough since it only signals if there were any
errors. Either (types.SignedHeader) or (success bool) is needed to
indicate the status of the operation. Returning a header is optimal
since most of the clients will want to get a newly verified header
anyway.
We first introduced auto-update as a separate struct AutoClient, which
was wrapping Client and calling Update periodically.
// AutoClient can auto update itself by fetching headers every N seconds.
type AutoClient struct {
base *Client
updatePeriod time.Duration
quit chan struct{}
trustedHeaders chan *types.SignedHeader
errs chan error
}
// NewAutoClient creates a new client and starts a polling goroutine.
func NewAutoClient(base *Client, updatePeriod time.Duration) *AutoClient {
c := &AutoClient{
base: base,
updatePeriod: updatePeriod,
quit: make(chan struct{}),
trustedHeaders: make(chan *types.SignedHeader),
errs: make(chan error),
}
go c.autoUpdate()
return c
}
// TrustedHeaders returns a channel onto which new trusted headers are posted.
func (c *AutoClient) TrustedHeaders() <-chan *types.SignedHeader {
return c.trustedHeaders
}
// Err returns a channel onto which errors are posted.
func (c *AutoClient) Errs() <-chan error {
return c.errs
}
// Stop stops the client.
func (c *AutoClient) Stop() {
close(c.quit)
}
func (c *AutoClient) autoUpdate() {
ticker := time.NewTicker(c.updatePeriod)
defer ticker.Stop()
for {
select {
case <-ticker.C:
lastTrustedHeight, err := c.base.LastTrustedHeight()
if err != nil {
c.errs <- err
continue
}
if lastTrustedHeight == -1 {
// no headers yet => wait
continue
}
newTrustedHeader, err := c.base.Update(time.Now())
if err != nil {
c.errs <- err
continue
}
if newTrustedHeader != nil {
c.trustedHeaders <- newTrustedHeader
}
case <-c.quit:
return
}
}
}
Later we merged it into the Client itself with the assumption that most clients will want it.
But now I am not sure. Neither IBC nor cosmos/relayer are using it. It increases complexity (Start/Stop methods).
That said, I think it makes sense to remove it until we see a need for it (until we better understand usage behavior). We can always introduce it later 😅. Maybe in the form of AutoClient.
closes: #4455
Verifying backwards checks that the trustedHeader hasn't expired both before and after the loop in case of verifying many headers (a longer operation), but not during the loop itself.
TrustedHeader() no longer checks whether the header saved in the store has expired.
Tests have been updated to reflect the changes
## Commits:
* verify headers backwards out of trust period
* removed expiration check in trusted header func
* modified tests to reflect changes
* wrote new tests for backwards verification
* modified TrustedHeader and TrustedValSet functions
* condensed test functions
* condensed test functions further
* fix build error
* update doc
* add comments
* remove unnecessary declaration
* extract latestHeight check into a separate func
Co-authored-by: Callum Waters <cmwaters19@gmail.com>
* lite2: add Start method
There are few reasons to do that:
1) separation of state and dynamics (some users will want to delay
starting the light client; does not matter we should not allow them
to create a light client object)
2) less important, but some users might not need autoUpdateRoutine and
removeNoLongerTrustedHeadersRoutine routines
* lite2: wait till routines are finished in Stop
because they are started in Start, it feels more natural to wait for
them to finish in Stop.
* lite2: add TrustedValidatorSet func
* lite2: advance to latest header
without any exponential steps
rename autoUpdate to autoUpdateRoutine
* lite2: wait in Cleanup until goroutines finished running
* lite2: move AutoClient into Client
Most of the users will want auto update feature, so it makes sense to
move it into the Client itself, rather than having a separate
abstraction (it makes the code cleaner, but introduces an extra thing
the user will need to learn).
Also, add `FirstTrustedHeight` func to Client to get first trusted height.
* fix db store tests
* separate examples for auto and manual clients
* AutoUpdate tries to update to latest state
NOT 1 header at a time
* fix errors
* lite2: make Logger an option
remove SetLogger func
* fix lite cmd
* lite2: make concurrency assumptions explicit
* fixes after my own review
* no need for nextHeightFn
sequence func will download intermediate headers
* correct comment
Refs #1771
ADR: https://github.com/tendermint/tendermint/blob/master/docs/architecture/adr-044-lite-client-with-weak-subjectivity.md
## Commits:
* add Verifier and VerifyCommitTrusting
* add two more checks
make trustLevel an option
* float32 for trustLevel
* check newHeader time
* started writing lite Client
* unify Verify methods
* ensure h2.Header.bfttime < h1.Header.bfttime + tp
* move trust checks into Verify function
* add more comments
* more docs
* started writing tests
* unbonding period failures
* tests are green
* export ErrNewHeaderTooFarIntoFuture
* make golangci happy
* test for non-adjusted headers
* more precision
* providers and stores
* VerifyHeader and VerifyHeaderAtHeight funcs
* fix compile errors
* remove lastVerifiedHeight, persist new trusted header
* sequential verification
* remove TrustedStore option
* started writing tests for light client
* cover basic cases for linear verification
* bisection tests PASS
* rename BisectingVerification to SkippingVerification
* refactor the code
* add TrustedHeader method
* consolidate sequential verification tests
* consolidate skipping verification tests
* rename trustedVals to trustedNextVals
* start writing docs
* ValidateTrustLevel func and ErrOldHeaderExpired error
* AutoClient and example tests
* fix errors
* update doc
* remove ErrNewHeaderTooFarIntoFuture
This check is unnecessary given existing a) ErrOldHeaderExpired b)
h2.Time > now checks.
* return an error if we're at more recent height
* add comments
* add LastSignedHeaderHeight method to Store
I think it's fine if Store tracks last height
* copy over proxy from old lite package
* make TrustedHeader return latest if height=0
* modify LastSignedHeaderHeight to return an error if no headers exist
* copy over proxy impl
* refactor proxy and start http lite client
* Tx and BlockchainInfo methods
* Block method
* commit method
* code compiles again
* lite client compiles
* extract updateLiteClientIfNeededTo func
* move final parts
* add placeholder for tests
* force usage of lite http client in proxy
* comment out query tests for now
* explicitly mention tp: trusting period
* verify nextVals in VerifyHeader
* refactor bisection
* move the NextValidatorsHash check into updateTrustedHeaderAndVals
+ update the comment
* add ConsensusParams method to RPC client
* add ConsensusParams to rpc/mock/client
* change trustLevel type to a new cmn.Fraction type
+ update SkippingVerification comment
* stress out trustLevel is only used for non-adjusted headers
* fixes after Fede's review
Co-authored-by: Federico Kunze <31522760+fedekunze@users.noreply.github.com>
* compare newHeader with a header from an alternative provider
* save pivot header
Refs https://github.com/tendermint/tendermint/pull/3989#discussion_r349122824
* check header can still be trusted in TrustedHeader
Refs https://github.com/tendermint/tendermint/pull/3989#discussion_r349101424
* lite: update Validators and Block endpoints
- Block no longer contains BlockMeta
- Validators now accept two additional params: page and perPage
* make linter happy
