closes#4469
Improved speed of cleanup by using SignedHeaderAfter instead of TrustedHeader to jump from header to header.
Prune() is now called when a new header and validator set are saved and is a function dealt by the database itself
## Commits:
* prune headers and vals
* modified cleanup and tests
* fixes after my own review
* implement Prune func
* make db ops concurrently safe
* use Iterator in SignedHeaderAfter
we should iterate from height+1, not from the end!
* simplify cleanup
Co-authored-by: Anton Kaliaev <anton.kalyaev@gmail.com>
Before we were storing trustedHeader (height=1) and trustedNextVals
(height=2).
After this change, we will be storing trustedHeader (height=1) and
trustedVals (height=1). This a) simplifies the code b) fixes#4399
inconsistent pairing issue c) gives a relayer access to the current
validator set #4470.
The only downside is more jumps during bisection. If validator set
changes between trustedHeader and the next header (by 2/3 or more), the
light client will be forced to download the next header and check that
2/3+ signed the transition. But we don't expect validator set change too
much and too often, so it's an acceptable compromise.
Closes#4470 and #4399
Closes#4328
When TrustedHeader(height) is called, if the height is less than the trusted height but the header is not in the trusted store then a function finds the previous lowest height with a trusted header and performs a forwards sequential verification to the header of the height that was given. If no error is found it updates the trusted store with the header and validator set for that height and can then return them to the user.
Commits:
* drafted trusted header
* created function to find previous trusted height
* updates missing headers less than the trusted height
* minor cosmetic tweaks
* incorporated suggestions
* lite2: implement Backwards verification
and add SignedHeaderAfter func to Store interface
Refs https://github.com/tendermint/tendermint/issues/4328#issuecomment-581878549
* remove unused method
* write tests
* start with next height in SignedHeaderAfter func
* fix linter errors
* address Callum's comments
Co-authored-by: Anton Kaliaev <anton.kalyaev@gmail.com>
* 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
