From 1f7b1ac9ed94a3626e77edc217f066332e3f10c1 Mon Sep 17 00:00:00 2001
From: Douglas Thrift <dthrift@flexera.com>
Date: Mon, 28 Feb 2022 17:18:36 -0800
Subject: [PATCH] Handle eventual consistency issues with fpt run log output

---
 cmd/fpt/ChangeLog.md |  5 +++--
 cmd/fpt/run.go       | 37 ++++++++++++++++++++-----------------
 2 files changed, 23 insertions(+), 19 deletions(-)

diff --git a/cmd/fpt/ChangeLog.md b/cmd/fpt/ChangeLog.md
index 64a9f4b..63b891c 100644
--- a/cmd/fpt/ChangeLog.md
+++ b/cmd/fpt/ChangeLog.md
@@ -1,6 +1,7 @@
-Unreleased Changes
-------------------
+v1.4.0 / 2022-03-01
+-------------------
 * Add support for `atob` and `btoa` JavaScript Base64 functions in `fpt script`
+* Handle eventual consistency issues with `fpt run` log output which could result in panics
 
 v1.3.0 / 2021-03-01
 -------------------
diff --git a/cmd/fpt/run.go b/cmd/fpt/run.go
index ca6d9e3..c70c9f1 100644
--- a/cmd/fpt/run.go
+++ b/cmd/fpt/run.go
@@ -96,25 +96,28 @@ func policyTemplateRun(ctx context.Context, cli policy.Client, file string, runO
 		}
 		lastStatus = status
 
-		log, logErr := cli.ShowAppliedPolicyLog(ctx, ap.ID, lastEtag)
-		if logErr != nil {
-			// technically the Goa client should not consider 304 an error
-			if strings.Contains(logErr.Error(), "invalid response code 304") {
-				goto checkStatus
+		if !noLog {
+			log, logErr := cli.ShowAppliedPolicyLog(ctx, ap.ID, lastEtag)
+			if logErr != nil {
+				// technically the Goa client should not consider 304 an error
+				if strings.Contains(logErr.Error(), "invalid response code 304") {
+					goto checkStatus
+				}
+				// the log may not be available yet so we retry 404s
+				if gse, ok := logErr.(*goa.ServiceError); ok && gse.Name == "not_found" {
+					goto checkStatus
+				}
+				return logErr
 			}
-			// the log may not be available yet so we retry 404s
-			if gse, ok := logErr.(*goa.ServiceError); ok && gse.Name == "not_found" {
-				goto checkStatus
-			}
-			return logErr
-		}
 
-		if *log.Etag != lastEtag {
-			lastSize := len(lastLog)
-			lastEtag = *log.Etag
-			lastLog = *log.ResponseBody
-			if !noLog {
-				fmt.Print(lastLog[lastSize:])
+			if *log.Etag != lastEtag {
+				lastSize := len(lastLog)
+				lastEtag = *log.Etag
+				// only print new log data (due to eventual consistency issues, a shorter log may be returned)
+				if lastSize <= len(*log.ResponseBody) {
+					lastLog = *log.ResponseBody
+					fmt.Print(lastLog[lastSize:])
+				}
 			}
 		}