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clients.go
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/
clients.go
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// Copyright 2024 Google LLC. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package main
import (
"bytes"
"context"
"encoding/base64"
"errors"
"fmt"
"io"
"math/rand"
"net/http"
"net/url"
"os"
"path/filepath"
"strconv"
"github.com/transparency-dev/serverless-log/api/layout"
"github.com/transparency-dev/serverless-log/client"
"k8s.io/klog/v2"
)
// NewLeafReader creates a LeafReader.
// The next function provides a strategy for which leaves will be read.
// Custom implementations can be passed, or use RandomNextLeaf or MonotonicallyIncreasingNextLeaf.
func NewLeafReader(tracker *client.LogStateTracker, f client.Fetcher, next func(uint64) uint64, bundleSize int, throttle <-chan bool, errchan chan<- error) *LeafReader {
if bundleSize <= 0 {
panic("bundleSize must be > 0")
}
return &LeafReader{
tracker: tracker,
f: f,
next: next,
bundleSize: bundleSize,
throttle: throttle,
errchan: errchan,
}
}
// LeafReader reads leaves from the tree.
type LeafReader struct {
tracker *client.LogStateTracker
f client.Fetcher
next func(uint64) uint64
bundleSize int
throttle <-chan bool
errchan chan<- error
cancel func()
c leafBundleCache
}
// Run runs the log reader. This should be called in a goroutine.
func (r *LeafReader) Run(ctx context.Context) {
if r.cancel != nil {
panic("LeafReader was ran multiple times")
}
ctx, r.cancel = context.WithCancel(ctx)
for {
select {
case <-ctx.Done():
return
case <-r.throttle:
}
size := r.tracker.LatestConsistent.Size
if size == 0 {
continue
}
i := r.next(size)
if i >= size {
continue
}
klog.V(2).Infof("LeafReader getting %d", i)
_, err := r.getLeaf(ctx, i, size)
if err != nil {
r.errchan <- fmt.Errorf("failed to get leaf: %v", err)
}
}
}
// getLeaf fetches the raw contents committed to at a given leaf index.
func (r *LeafReader) getLeaf(ctx context.Context, i uint64, logSize uint64) ([]byte, error) {
if i >= logSize {
return nil, fmt.Errorf("requested leaf %d >= log size %d", i, logSize)
}
if cached, _ := r.c.get(i); cached != nil {
klog.V(2).Infof("Using cached result for index %d", i)
return cached, nil
}
bi := i / uint64(r.bundleSize)
br := uint64(0)
// Check for partial leaf bundle
if bi == logSize/uint64(r.bundleSize) {
br = logSize % uint64(r.bundleSize)
}
p := filepath.Join(layout.SeqPath("", bi))
if br > 0 {
p += fmt.Sprintf(".%d", br)
}
bRaw, err := r.f(ctx, p)
if err != nil {
if errors.Is(err, os.ErrNotExist) {
return nil, fmt.Errorf("leaf index %d not found: %w", i, err)
}
return nil, fmt.Errorf("failed to fetch leaf index %d: %w", i, err)
}
bs := bytes.Split(bRaw, []byte("\n"))
if l := len(bs); uint64(l) <= br {
return nil, fmt.Errorf("huh, short leaf bundle with %d entries, want %d", l, br)
}
r.c = leafBundleCache{
start: bi * uint64(r.bundleSize),
leaves: bs,
}
return r.c.get(i)
}
// Kills this leaf reader at the next opportune moment.
// This function may return before the reader is dead.
func (r *LeafReader) Kill() {
if r.cancel != nil {
r.cancel()
}
}
// leafBundleCache stores the results of the last fetched tile. This allows
// readers that read contiguous blocks of leaves to act more like real
// clients and fetch a tile of 256 leaves once, instead of 256 times.
type leafBundleCache struct {
start uint64
leaves [][]byte
}
func (tc leafBundleCache) get(i uint64) ([]byte, error) {
end := tc.start + uint64(len(tc.leaves))
if i >= tc.start && i < end {
leaf := tc.leaves[i-tc.start]
return base64.StdEncoding.DecodeString(string(leaf))
}
return nil, errors.New("not found")
}
// RandomNextLeaf returns a function that fetches a random leaf available in the tree.
func RandomNextLeaf() func(uint64) uint64 {
return func(size uint64) uint64 {
return uint64(rand.Int63n(int64(size)))
}
}
// MonotonicallyIncreasingNextLeaf returns a function that always wants the next available
// leaf after the one it previously fetched. It starts at leaf 0.
func MonotonicallyIncreasingNextLeaf() func(uint64) uint64 {
var i uint64
return func(size uint64) uint64 {
if i < size {
r := i
i++
return r
}
return size
}
}
// NewLogWriter creates a LogWriter.
// u is the URL of the write endpoint for the log.
// gen is a function that generates new leaves to add.
func NewLogWriter(hc *http.Client, u *url.URL, gen func() []byte, throttle <-chan bool, errchan chan<- error) *LogWriter {
return &LogWriter{
hc: hc,
u: u,
gen: gen,
throttle: throttle,
errchan: errchan,
}
}
// LogWriter writes new leaves to the log that are generated by `gen`.
type LogWriter struct {
hc *http.Client
u *url.URL
gen func() []byte
throttle <-chan bool
errchan chan<- error
cancel func()
}
// Run runs the log writer. This should be called in a goroutine.
func (w *LogWriter) Run(ctx context.Context) {
if w.cancel != nil {
panic("LogWriter was ran multiple times")
}
ctx, w.cancel = context.WithCancel(ctx)
for {
select {
case <-ctx.Done():
return
case <-w.throttle:
}
newLeaf := w.gen()
resp, err := w.hc.Post(w.u.String(), "application/octet-stream", bytes.NewReader(newLeaf))
if err != nil {
w.errchan <- fmt.Errorf("failed to write leaf: %v", err)
continue
}
body, err := io.ReadAll(resp.Body)
_ = resp.Body.Close()
if err != nil {
w.errchan <- fmt.Errorf("failed to read body: %v", err)
continue
}
if resp.StatusCode != http.StatusOK {
w.errchan <- fmt.Errorf("write leaf was not OK. Status code: %d. Body: %q", resp.StatusCode, body)
continue
}
if resp.Request.Method != http.MethodPost {
w.errchan <- fmt.Errorf("write leaf was redirected to %s", resp.Request.URL)
continue
}
parts := bytes.Split(body, []byte("\n"))
index, err := strconv.Atoi(string(parts[0]))
if err != nil {
w.errchan <- fmt.Errorf("write leaf failed to parse response: %v", body)
continue
}
klog.V(2).Infof("Wrote leaf at index %d", index)
}
}
// Kills this writer at the next opportune moment.
// This function may return before the writer is dead.
func (w *LogWriter) Kill() {
if w.cancel != nil {
w.cancel()
}
}