From df2b89b78d67dfcc487a3b832177b2e42e01e58d Mon Sep 17 00:00:00 2001
From: bap2pecs <111917526+bap2pecs@users.noreply.github.com>
Date: Mon, 16 Dec 2024 21:04:31 -0500
Subject: [PATCH] backport: #217 - shouldn't wait SubmissionRetryInterval at
 the first iteration  (#227)

---
 CHANGELOG.md                             |  1 +
 finality-provider/service/fp_instance.go | 92 ++++++++++++------------
 2 files changed, 48 insertions(+), 45 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1080566d..2637c866 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -46,6 +46,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 * [#216](https://github.com/babylonlabs-io/finality-provider/pull/216) Add multiple fpd connecting to one eotsd in e2e tests
 * [#218](https://github.com/babylonlabs-io/finality-provider/pull/218) Prune used merkle proof
 * [#221](https://github.com/babylonlabs-io/finality-provider/pull/221) Cleanup TODOs
+* [#227](https://github.com/babylonlabs-io/finality-provider/pull/227) Fix FP submission loop
 
 ## v0.13.1
 
diff --git a/finality-provider/service/fp_instance.go b/finality-provider/service/fp_instance.go
index 89e3801c..71360687 100644
--- a/finality-provider/service/fp_instance.go
+++ b/finality-provider/service/fp_instance.go
@@ -339,58 +339,60 @@ func (fp *FinalityProviderInstance) retrySubmitSigsUntilFinalized(targetBlocks [
 	var failedCycles uint32
 	targetHeight := targetBlocks[len(targetBlocks)-1].Height
 
-	// we break the for loop if the block is finalized or the signature is successfully submitted
-	// error will be returned if maximum retries have been reached or the query to the consumer chain fails
+	// First iteration happens before the loop
 	for {
-		select {
-		case <-time.After(fp.cfg.SubmissionRetryInterval):
-			// error will be returned if max retries have been reached
-			var res *types.TxResponse
-			var err error
-			res, err = fp.SubmitBatchFinalitySignatures(targetBlocks)
-			if err != nil {
-				fp.logger.Debug(
-					"failed to submit finality signature to the consumer chain",
-					zap.String("pk", fp.GetBtcPkHex()),
-					zap.Uint32("current_failures", failedCycles),
-					zap.Uint64("target_start_height", targetBlocks[0].Height),
-					zap.Uint64("target_end_height", targetHeight),
-					zap.Error(err),
-				)
-
-				if clientcontroller.IsUnrecoverable(err) {
-					return nil, err
-				}
-
-				if clientcontroller.IsExpected(err) {
-					return nil, nil
-				}
+		// Attempt submission immediately
+		// error will be returned if max retries have been reached
+		var res *types.TxResponse
+		var err error
+		res, err = fp.SubmitBatchFinalitySignatures(targetBlocks)
+		if err != nil {
+			fp.logger.Debug(
+				"failed to submit finality signature to the consumer chain",
+				zap.String("pk", fp.GetBtcPkHex()),
+				zap.Uint32("current_failures", failedCycles),
+				zap.Uint64("target_start_height", targetBlocks[0].Height),
+				zap.Uint64("target_end_height", targetHeight),
+				zap.Error(err),
+			)
 
-				failedCycles++
-				if failedCycles > fp.cfg.MaxSubmissionRetries {
-					return nil, fmt.Errorf("reached max failed cycles with err: %w", err)
-				}
-			} else {
-				// the signature has been successfully submitted
-				return res, nil
+			if clientcontroller.IsUnrecoverable(err) {
+				return nil, err
 			}
 
-			// periodically query the index block to be later checked whether it is Finalized
-			finalized, err := fp.checkBlockFinalization(targetHeight)
-			if err != nil {
-				return nil, fmt.Errorf("failed to query block finalization at height %v: %w", targetHeight, err)
-			}
-			if finalized {
-				fp.logger.Debug(
-					"the block is already finalized, skip submission",
-					zap.String("pk", fp.GetBtcPkHex()),
-					zap.Uint64("target_height", targetHeight),
-				)
-				// returning nil here is to safely break the loop
-				// the error still exists
+			if clientcontroller.IsExpected(err) {
 				return nil, nil
 			}
 
+			failedCycles++
+			if failedCycles > fp.cfg.MaxSubmissionRetries {
+				return nil, fmt.Errorf("reached max failed cycles with err: %w", err)
+			}
+		} else {
+			// the signature has been successfully submitted
+			return res, nil
+		}
+
+		// periodically query the index block to be later checked whether it is Finalized
+		finalized, err := fp.checkBlockFinalization(targetHeight)
+		if err != nil {
+			return nil, fmt.Errorf("failed to query block finalization at height %v: %w", targetHeight, err)
+		}
+		if finalized {
+			fp.logger.Debug(
+				"the block is already finalized, skip submission",
+				zap.String("pk", fp.GetBtcPkHex()),
+				zap.Uint64("target_height", targetHeight),
+			)
+			// TODO: returning nil here is to safely break the loop
+			//  the error still exists
+			return nil, nil
+		}
+
+		// Wait for the retry interval
+		select {
+		case <-time.After(fp.cfg.SubmissionRetryInterval):
+			// Continue to next retry iteration
 		case <-fp.quit:
 			fp.logger.Debug("the finality-provider instance is closing", zap.String("pk", fp.GetBtcPkHex()))
 			return nil, ErrFinalityProviderShutDown