From 51dce409149f7137ba20113eaee732324c81dd17 Mon Sep 17 00:00:00 2001
From: Ivan Ilves <ivan.ilves@schibsted.com>
Date: Sun, 29 Apr 2018 10:47:08 +0200
Subject: [PATCH] IMPROVE: Tolerate errors on `Pull` and `Push` actions

As stated in https://github.com/ivanilves/lstags/issues/146
we need to try harder while pulling or pushing Docker images.
---
 api/v1/v1.go      |  4 ++--
 main.go           |  6 +++++-
 util/wait/wait.go | 28 ++++++++++++++++++++++++++++
 3 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/api/v1/v1.go b/api/v1/v1.go
index bb0408a..d399303 100644
--- a/api/v1/v1.go
+++ b/api/v1/v1.go
@@ -300,7 +300,7 @@ func (api *API) PullTags(cn *collection.Collection) error {
 		}(repo, tags, done)
 	}
 
-	return wait.Until(done)
+	return wait.WithTolerance(done)
 }
 
 // PushTags compares images from remote and "push" (usually local) registries,
@@ -357,7 +357,7 @@ func (api *API) PushTags(cn *collection.Collection, push PushConfig) error {
 		}(repo, tags, done)
 	}
 
-	return wait.Until(done)
+	return wait.WithTolerance(done)
 }
 
 func logDebugData(data io.Reader) {
diff --git a/main.go b/main.go
index 78db5bf..8c0a0d5 100644
--- a/main.go
+++ b/main.go
@@ -36,6 +36,8 @@ type Options struct {
 	} `positional-args:"yes" required:"yes"`
 }
 
+var exitCode = 0
+
 var doNotFail = false
 
 func suicide(err error, critical bool) {
@@ -44,6 +46,8 @@ func suicide(err error, critical bool) {
 	if !doNotFail || critical {
 		os.Exit(1)
 	}
+
+	exitCode = 254 // not typical error code, for "git grep" friendliness
 }
 
 func parseFlags() (*Options, error) {
@@ -169,7 +173,7 @@ func main() {
 		}
 
 		if !o.DaemonMode {
-			os.Exit(0)
+			os.Exit(exitCode)
 		}
 
 		fmt.Printf("WAIT: %v\n-\n", o.PollingInterval)
diff --git a/util/wait/wait.go b/util/wait/wait.go
index 6366827..09889e7 100644
--- a/util/wait/wait.go
+++ b/util/wait/wait.go
@@ -1,5 +1,7 @@
 package wait
 
+import "fmt"
+
 // Until iterates over buffered error channel and:
 // * upon receiving non-nil value from the channel, makes an early return with this value
 // * if no non-nil values were received from iteration over the channel, it just returns nil
@@ -21,3 +23,29 @@ func Until(done chan error) error {
 
 	return nil
 }
+
+// WithTolerance is the same as Until, but it does not return immediately on errors
+// rather loops through all channel capacity returning "composite" error in the end.
+func WithTolerance(done chan error) error {
+	var errMessage string
+
+	i := 0
+
+	for err := range done {
+		if err != nil {
+			errMessage = errMessage + err.Error() + "\n"
+		}
+
+		i++
+
+		if i >= cap(done) {
+			close(done)
+		}
+	}
+
+	if len(errMessage) == 0 {
+		return nil
+	}
+
+	return fmt.Errorf(errMessage)
+}