feat: add connectioncount check, hash pining and switch to json rpc 2.0 version

Author: gallindic-flare

images/go_chains_hc/Dockerfile

@@ -1,4 +1,4 @@
-FROM golang AS builder
+FROM golang:1.25.5-alpine@sha256:8bbd14091f2c61916134fa6aeb8f76b18693fcb29a39ec6d8be9242c0a7e9260 AS builder
 
 WORKDIR /app
 COPY go.mod ./

images/go_chains_hc/README.md

@@ -12,6 +12,7 @@ On each `/readyz` request, the sidecar runs a configurable set of checks against
 |---|---|---|
 | `blockdownload` | `getblockchaininfo` | Passes when `initialblockdownload` is `false`. Default for all chains. |
 | `txindex` | `getindexinfo` | Passes when `txindex.synced` is `true`. |
+| `connectioncount` | `getconnectioncount` | Passes when the node has at least `MIN_CONNECTIONS` peers. |
 
 ### Environment Variables
 
@@ -20,7 +21,9 @@ On each `/readyz` request, the sidecar runs a configurable set of checks against
 | `NODE_URL` | yes | — | RPC endpoint, e.g. `http://localhost:8332` |
 | `NODE_USER` | no | — | RPC auth username |
 | `NODE_PASS` | no | — | RPC auth password |
-| `CHECKS` | no | `blockdownload` | Comma-separated list of checks to run (blockdownload,txindex) |
+| `CHECKS` | no | `blockdownload` | Comma-separated list of checks to run (`blockdownload, txindex, connectioncount`) |
+| `MIN_CONNECTIONS` | no | `8` | Minimum peer connections required for the `connectioncount` check |
+
 
 ### Running Locally
 

images/go_chains_hc/checks.go

@@ -12,9 +12,12 @@ import (
 
 type Check func(ctx context.Context, client *http.Client, cfg Config) error
 
+const jsonRPCVersion = "2.0"
+
 var registry = map[string]Check{
-	"blockdownload": checkBlockDownload,
-	"txindex":       checkTxIndex,
+	"blockdownload":   checkBlockDownload,
+	"txindex":         checkTxIndex,
+	"connectioncount": checkConnectionCount,
 }
 
 type rpcRequest struct {
@@ -26,7 +29,7 @@ type rpcRequest struct {
 
 func doRPC(ctx context.Context, client *http.Client, cfg Config, method string) (json.RawMessage, error) {
 	logger := slog.Default()
-	body, err := json.Marshal(rpcRequest{JSONRPC: "1.0", ID: "hc", Method: method, Params: []any{}})
+	body, err := json.Marshal(rpcRequest{JSONRPC: jsonRPCVersion, ID: "hc", Method: method, Params: []any{}})
 	if err != nil {
 		return nil, fmt.Errorf("marshal request: %w", err)
 	}
@@ -46,7 +49,7 @@ func doRPC(ctx context.Context, client *http.Client, cfg Config, method string)
 	}
 	defer resp.Body.Close()
 
-	if resp.StatusCode != http.StatusOK {
+	if resp.StatusCode >= http.StatusBadRequest {
 		return nil, fmt.Errorf("node returned HTTP %d", resp.StatusCode)
 	}
 
@@ -117,3 +120,20 @@ func checkTxIndex(ctx context.Context, client *http.Client, cfg Config) error {
 
 	return nil
 }
+
+func checkConnectionCount(ctx context.Context, client *http.Client, cfg Config) error {
+	result, err := doRPC(ctx, client, cfg, "getconnectioncount")
+	if err != nil {
+		return err
+	}
+
+	var count int
+	if err := json.Unmarshal(result, &count); err != nil {
+		return fmt.Errorf("parse getconnectioncount: %w", err)
+	}
+	if count < cfg.MinConnections {
+		return fmt.Errorf("not enough connections: %d < %d", count, cfg.MinConnections)
+	}
+
+	return nil
+}

images/go_chains_hc/main.go

@@ -6,18 +6,22 @@ import (
 	"log/slog"
 	"net/http"
 	"os"
+	"strconv"
 	"strings"
 	"time"
 )
 
 type Config struct {
-	NodeURL  string
-	NodeUser string
-	NodePass string
-	Checks   []string
-	Addr     string
+	NodeURL        string
+	NodeUser       string
+	NodePass       string
+	Checks         []string
+	Addr           string
+	MinConnections int
 }
 
+const MIN_CONNECTIONS = 8
+
 func configFromEnv() (Config, error) {
 	nodeURL := os.Getenv("NODE_URL")
 	if nodeURL == "" {
@@ -35,12 +39,24 @@ func configFromEnv() (Config, error) {
 		}
 	}
 
+	minConns := MIN_CONNECTIONS
+	if raw := os.Getenv("MIN_CONNECTIONS"); raw != "" {
+		n, err := strconv.Atoi(raw)
+
+		if err != nil || n < 0 {
+			return Config{}, fmt.Errorf("MIN_CONNECTIONS must be a non-negative integer")
+		}
+
+		minConns = n
+	}
+
 	return Config{
-		NodeURL:  nodeURL,
-		NodeUser: os.Getenv("NODE_USER"),
-		NodePass: os.Getenv("NODE_PASS"),
-		Checks:   checks,
-		Addr:     ":8080",
+		NodeURL:        nodeURL,
+		NodeUser:       os.Getenv("NODE_USER"),
+		NodePass:       os.Getenv("NODE_PASS"),
+		Checks:         checks,
+		Addr:           ":8080",
+		MinConnections: minConns,
 	}, nil
 }