From 559bccccd40d028e412d9f11709ded0250ba6dcd Mon Sep 17 00:00:00 2001
From: Linus Nordberg <linus@nordberg.se>
Date: Tue, 24 May 2022 23:33:38 +0200
Subject: implement primary and secondary role, for replication

---
 internal/node/secondary/secondary.go | 112 +++++++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)
 create mode 100644 internal/node/secondary/secondary.go

(limited to 'internal/node/secondary/secondary.go')

diff --git a/internal/node/secondary/secondary.go b/internal/node/secondary/secondary.go
new file mode 100644
index 0000000..c181420
--- /dev/null
+++ b/internal/node/secondary/secondary.go
@@ -0,0 +1,112 @@
+package secondary
+
+import (
+	"context"
+	"crypto"
+	"fmt"
+	"net/http"
+	"time"
+
+	"git.sigsum.org/log-go/internal/db"
+	"git.sigsum.org/log-go/internal/node/handler"
+	"git.sigsum.org/sigsum-go/pkg/client"
+	"git.sigsum.org/sigsum-go/pkg/log"
+	"git.sigsum.org/sigsum-go/pkg/requests"
+	"git.sigsum.org/sigsum-go/pkg/types"
+)
+
+// Config is a collection of log parameters
+type Config struct {
+	LogID    string        // H(public key), then hex-encoded
+	TreeID   int64         // Merkle tree identifier used by Trillian
+	Prefix   string        // The portion between base URL and st/v0 (may be "")
+	Deadline time.Duration // Deadline used for gRPC requests
+	Interval time.Duration // Signing frequency
+}
+
+// Secondary is an instance of a secondary node
+type Secondary struct {
+	Config
+	PublicHTTPMux   *http.ServeMux
+	InternalHTTPMux *http.ServeMux
+	TrillianClient  db.Client     // provides access to the Trillian backend
+	Signer          crypto.Signer // provides access to Ed25519 private key
+	Primary         client.Client
+}
+
+// Implementing handler.Config
+func (s Secondary) Prefix() string {
+	return s.Config.Prefix
+}
+func (s Secondary) LogID() string {
+	return s.Config.LogID
+}
+func (s Secondary) Deadline() time.Duration {
+	return s.Config.Deadline
+}
+
+func (s Secondary) Run(ctx context.Context) {
+	ticker := time.NewTicker(s.Interval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ticker.C:
+			s.fetchLeavesFromPrimary(ctx)
+		case <-ctx.Done():
+			return
+		}
+	}
+}
+
+// TODO: nit-pick: the internal endpoint is used by primaries to figure out how much can be signed; not cosigned - update name?
+
+func (s Secondary) InternalHTTPHandlers() []handler.Handler {
+	return []handler.Handler{
+		handler.Handler{s, getTreeHeadToCosign, types.EndpointGetTreeHeadToCosign, http.MethodGet},
+	}
+}
+
+func (s Secondary) fetchLeavesFromPrimary(ctx context.Context) {
+	sctx, cancel := context.WithTimeout(ctx, time.Second*10) // FIXME: parameterize 10
+	defer cancel()
+
+	prim, err := s.Primary.GetUnsignedTreeHead(sctx)
+	if err != nil {
+		log.Warning("unable to get tree head from primary: %v", err)
+		return
+	}
+	log.Debug("got tree head from primary, size %d", prim.TreeSize)
+
+	curTH, err := treeHeadFromTrillian(sctx, s.TrillianClient)
+	if err != nil {
+		log.Warning("unable to get tree head from trillian: %v", err)
+		return
+	}
+	var leaves types.Leaves
+	for index := int64(curTH.TreeSize); index < int64(prim.TreeSize); index += int64(len(leaves)) {
+		req := requests.Leaves{
+			StartSize: uint64(index),
+			EndSize:   prim.TreeSize - 1,
+		}
+		leaves, err = s.Primary.GetLeaves(sctx, req)
+		if err != nil {
+			log.Warning("error fetching leaves [%d..%d] from primary: %v", req.StartSize, req.EndSize, err)
+			return
+		}
+		log.Debug("got %d leaves from primary when asking for [%d..%d]", len(leaves), req.StartSize, req.EndSize)
+		if err := s.TrillianClient.AddSequencedLeaves(ctx, leaves, index); err != nil {
+			log.Error("AddSequencedLeaves: %v", err)
+			return
+		}
+	}
+}
+
+func treeHeadFromTrillian(ctx context.Context, trillianClient db.Client) (*types.TreeHead, error) {
+	th, err := trillianClient.GetTreeHead(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("fetching tree head from trillian: %v", err)
+	}
+	log.Debug("got tree head from trillian, size %d", th.TreeSize)
+	return th, nil
+}
-- 
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