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337 lines
10 KiB
337 lines
10 KiB
package http
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import (
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"context"
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"errors"
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"fmt"
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"math/rand"
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"net/url"
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"strings"
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"time"
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"github.com/tendermint/tendermint/light/provider"
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rpcclient "github.com/tendermint/tendermint/rpc/client"
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rpchttp "github.com/tendermint/tendermint/rpc/client/http"
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"github.com/tendermint/tendermint/rpc/coretypes"
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rpctypes "github.com/tendermint/tendermint/rpc/jsonrpc/types"
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"github.com/tendermint/tendermint/types"
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)
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var defaultOptions = Options{
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MaxRetryAttempts: 5,
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Timeout: 5 * time.Second,
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NoBlockThreshold: 5,
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NoResponseThreshold: 5,
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}
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// http provider uses an RPC client to obtain the necessary information.
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type http struct {
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chainID string
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client rpcclient.RemoteClient
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// httt provider heuristics
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// The provider tracks the amount of times that the
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// client doesn't respond. If this exceeds the threshold
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// then the provider will return an unreliable provider error
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noResponseThreshold uint16
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noResponseCount uint16
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// The provider tracks the amount of time the client
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// doesn't have a block. If this exceeds the threshold
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// then the provider will return an unreliable provider error
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noBlockThreshold uint16
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noBlockCount uint16
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// In a single request, the provider attempts multiple times
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// with exponential backoff to reach the client. If this
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// exceeds the maxRetry attempts, this result in a ErrNoResponse
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maxRetryAttempts uint16
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}
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type Options struct {
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// 0 means no retries
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MaxRetryAttempts uint16
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// 0 means no timeout.
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Timeout time.Duration
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// The amount of requests that a client doesn't have the block
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// for before the provider deems the client unreliable
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NoBlockThreshold uint16
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// The amount of requests that a client doesn't respond to
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// before the provider deems the client unreliable
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NoResponseThreshold uint16
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}
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// New creates a HTTP provider, which is using the rpchttp.HTTP client under
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// the hood. If no scheme is provided in the remote URL, http will be used by
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// default. The 5s timeout is used for all requests.
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func New(chainID, remote string) (provider.Provider, error) {
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return NewWithOptions(chainID, remote, defaultOptions)
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}
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// NewWithOptions is an extension to creating a new http provider that allows the addition
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// of a specified timeout and maxRetryAttempts
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func NewWithOptions(chainID, remote string, options Options) (provider.Provider, error) {
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// Ensure URL scheme is set (default HTTP) when not provided.
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if !strings.Contains(remote, "://") {
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remote = "http://" + remote
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}
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httpClient, err := rpchttp.NewWithTimeout(remote, options.Timeout)
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if err != nil {
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return nil, err
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}
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return NewWithClientAndOptions(chainID, httpClient, options), nil
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}
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func NewWithClient(chainID string, client rpcclient.RemoteClient) provider.Provider {
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return NewWithClientAndOptions(chainID, client, defaultOptions)
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}
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// NewWithClient allows you to provide a custom client.
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func NewWithClientAndOptions(chainID string, client rpcclient.RemoteClient, options Options) provider.Provider {
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return &http{
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client: client,
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chainID: chainID,
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maxRetryAttempts: options.MaxRetryAttempts,
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noResponseThreshold: options.NoResponseThreshold,
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noBlockThreshold: options.NoBlockThreshold,
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}
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}
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func (p *http) String() string {
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return fmt.Sprintf("http{%s}", p.client.Remote())
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}
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// LightBlock fetches a LightBlock at the given height and checks the
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// chainID matches.
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func (p *http) LightBlock(ctx context.Context, height int64) (*types.LightBlock, error) {
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h, err := validateHeight(height)
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if err != nil {
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return nil, provider.ErrBadLightBlock{Reason: err}
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}
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sh, err := p.signedHeader(ctx, h)
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if err != nil {
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return nil, err
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}
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if height != 0 && sh.Height != height {
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return nil, provider.ErrBadLightBlock{
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Reason: fmt.Errorf("height %d responded doesn't match height %d requested", sh.Height, height),
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}
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}
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if sh.Header == nil {
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return nil, provider.ErrBadLightBlock{
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Reason: errors.New("returned header is nil unexpectedly"),
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}
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}
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vs, err := p.validatorSet(ctx, &sh.Height)
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if err != nil {
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return nil, err
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}
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lb := &types.LightBlock{
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SignedHeader: sh,
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ValidatorSet: vs,
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}
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err = lb.ValidateBasic(p.chainID)
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if err != nil {
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return nil, provider.ErrBadLightBlock{Reason: err}
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}
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return lb, nil
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}
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// ReportEvidence calls `/broadcast_evidence` endpoint.
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func (p *http) ReportEvidence(ctx context.Context, ev types.Evidence) error {
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_, err := p.client.BroadcastEvidence(ctx, ev)
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return err
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}
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func (p *http) validatorSet(ctx context.Context, height *int64) (*types.ValidatorSet, error) {
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// Since the malicious node could report a massive number of pages, making us
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// spend a considerable time iterating, we restrict the number of pages here.
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// => 10000 validators max
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const maxPages = 100
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var (
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perPage = 100
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vals = []*types.Validator{}
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page = 1
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total = -1
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)
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for len(vals) != total && page <= maxPages {
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// create another for loop to control retries. If p.maxRetryAttempts
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// is negative we will keep repeating.
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attempt := uint16(0)
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for {
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res, err := p.client.Validators(ctx, height, &page, &perPage)
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switch e := err.(type) {
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case nil: // success!! Now we validate the response
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if len(res.Validators) == 0 {
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return nil, provider.ErrBadLightBlock{
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Reason: fmt.Errorf("validator set is empty (height: %d, page: %d, per_page: %d)",
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height, page, perPage),
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}
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}
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if res.Total <= 0 {
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return nil, provider.ErrBadLightBlock{
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Reason: fmt.Errorf("total number of vals is <= 0: %d (height: %d, page: %d, per_page: %d)",
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res.Total, height, page, perPage),
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}
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}
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case *url.Error:
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if e.Timeout() {
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// if we have exceeded retry attempts then return a no response error
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if attempt == p.maxRetryAttempts {
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return nil, p.noResponse()
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}
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attempt++
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// request timed out: we wait and try again with exponential backoff
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time.Sleep(backoffTimeout(attempt))
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continue
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}
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return nil, provider.ErrBadLightBlock{Reason: e}
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case *rpctypes.RPCError:
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// process the rpc error and return the corresponding error to the light client
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return nil, p.parseRPCError(e)
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default:
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// check if the error stems from the context
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if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
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return nil, err
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}
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// If we don't know the error then by default we return an unreliable provider error and
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// terminate the connection with the peer.
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return nil, provider.ErrUnreliableProvider{Reason: e}
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}
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// update the total and increment the page index so we can fetch the
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// next page of validators if need be
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total = res.Total
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vals = append(vals, res.Validators...)
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page++
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break
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}
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}
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valSet, err := types.ValidatorSetFromExistingValidators(vals)
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if err != nil {
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return nil, provider.ErrBadLightBlock{Reason: err}
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}
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return valSet, nil
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}
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func (p *http) signedHeader(ctx context.Context, height *int64) (*types.SignedHeader, error) {
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// create a for loop to control retries. If p.maxRetryAttempts
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// is negative we will keep repeating.
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for attempt := uint16(0); attempt != p.maxRetryAttempts+1; attempt++ {
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commit, err := p.client.Commit(ctx, height)
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switch e := err.(type) {
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case nil: // success!!
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return &commit.SignedHeader, nil
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case *url.Error:
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// check if the request timed out
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if e.Timeout() {
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// we wait and try again with exponential backoff
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time.Sleep(backoffTimeout(attempt))
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continue
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}
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// check if the connection was refused or dropped
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if strings.Contains(e.Error(), "connection refused") {
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return nil, provider.ErrConnectionClosed
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}
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// else, as a catch all, we return the error as a bad light block response
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return nil, provider.ErrBadLightBlock{Reason: e}
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case *rpctypes.RPCError:
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// process the rpc error and return the corresponding error to the light client
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return nil, p.parseRPCError(e)
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default:
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// check if the error stems from the context
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if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
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return nil, err
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}
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// If we don't know the error then by default we return an unreliable provider error and
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// terminate the connection with the peer.
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return nil, provider.ErrUnreliableProvider{Reason: e}
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}
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}
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return nil, p.noResponse()
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}
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func (p *http) noResponse() error {
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p.noResponseCount++
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if p.noResponseCount > p.noResponseThreshold {
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return provider.ErrUnreliableProvider{
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Reason: fmt.Errorf("failed to respond after %d attempts", p.noResponseCount),
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}
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}
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return provider.ErrNoResponse
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}
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func (p *http) noBlock(e error) error {
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p.noBlockCount++
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if p.noBlockCount > p.noBlockThreshold {
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return provider.ErrUnreliableProvider{
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Reason: fmt.Errorf("failed to provide a block after %d attempts", p.noBlockCount),
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}
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}
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return e
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}
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// parseRPCError process the error and return the corresponding error to the light clent
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// NOTE: When an error is sent over the wire it gets "flattened" hence we are unable to use error
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// checking functions like errors.Is() to unwrap the error.
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func (p *http) parseRPCError(e *rpctypes.RPCError) error {
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switch {
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// 1) check if the error indicates that the peer doesn't have the block
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case strings.Contains(e.Data, coretypes.ErrHeightNotAvailable.Error()):
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return p.noBlock(provider.ErrLightBlockNotFound)
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// 2) check if the height requested is too high
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case strings.Contains(e.Data, coretypes.ErrHeightExceedsChainHead.Error()):
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return p.noBlock(provider.ErrHeightTooHigh)
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// 3) check if the provider closed the connection
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case strings.Contains(e.Data, "connection refused"):
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return provider.ErrConnectionClosed
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// 4) else return a generic error
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default:
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return provider.ErrBadLightBlock{Reason: e}
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}
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}
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func validateHeight(height int64) (*int64, error) {
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if height < 0 {
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return nil, fmt.Errorf("expected height >= 0, got height %d", height)
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}
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h := &height
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if height == 0 {
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h = nil
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}
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return h, nil
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}
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// exponential backoff (with jitter)
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// 0.5s -> 2s -> 4.5s -> 8s -> 12.5 with 1s variation
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func backoffTimeout(attempt uint16) time.Duration {
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// nolint:gosec // G404: Use of weak random number generator
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return time.Duration(500*attempt*attempt)*time.Millisecond + time.Duration(rand.Intn(1000))*time.Millisecond
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}
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