feat: add stats api, fix pipeline exe

* added cUSD sample filters
* decouple stats from metrics

internal/api/stats.go

@@ -0,0 +1,51 @@
+package api
+
+import (
+	"net/http"
+
+	"github.com/alitto/pond"
+	"github.com/grassrootseconomics/cic-chain-events/internal/syncer"
+	"github.com/labstack/echo/v4"
+	"github.com/zerodha/logf"
+)
+
+type statsResponse struct {
+	HeadCursor            uint64 `json:"headCursor"`
+	LowerBound            uint64 `json:"lowerBound"`
+	MissingBlocks         uint64 `json:"missingBlocks"`
+	WorkerQueueSize       uint64 `json:"workerQueueSize"`
+	WorkerCount           int    `json:"workerCount"`
+	WorkerSuccessfulTasks uint64 `json:"workerSuccessfulTasks"`
+	WorkerFailedTasks     uint64 `json:"workerFailedTasks"`
+}
+
+func StatsHandler(
+	syncerStats *syncer.Stats,
+	poolStats *pond.WorkerPool,
+	logg logf.Logger,
+) func(echo.Context) error {
+	return func(ctx echo.Context) error {
+		headCursor := syncerStats.GetHeadCursor()
+		lowerBound := syncerStats.GetLowerBound()
+
+		stats := statsResponse{
+			HeadCursor:            headCursor,
+			LowerBound:            lowerBound,
+			WorkerCount:           poolStats.RunningWorkers(),
+			WorkerQueueSize:       poolStats.WaitingTasks(),
+			WorkerSuccessfulTasks: poolStats.SuccessfulTasks(),
+			WorkerFailedTasks:     poolStats.FailedTasks(),
+		}
+
+		if headCursor-lowerBound < 10 {
+			stats.MissingBlocks = 0
+		} else {
+			stats.MissingBlocks = headCursor - lowerBound
+		}
+
+		return ctx.JSON(http.StatusOK, okResp{
+			Ok:   true,
+			Data: stats,
+		})
+	}
+}

internal/api/types.go

@@ -0,0 +1,15 @@
+package api
+
+const (
+	INTERNAL_ERROR = "ERR_INTERNAL"
+)
+
+type okResp struct {
+	Ok   bool        `json:"ok"`
+	Data interface{} `json:"data"`
+}
+
+type errResp struct {
+	Ok    bool   `json:"ok"`
+	Error string `json:"error"`
+}