refactor(logtail): have single chan messaging point

pkg/commands/logtail/root.go

@@ -109,7 +109,9 @@ func (c *RootCommand) Exec(_ io.Reader, out io.Writer) error {
 	go c.outputLoop(out)
 
 	// Start tailing the logs.
-	go c.tail(out, failure)
+	go func() {
+		failure <- c.tail(out)
+	}()
 
 	select {
 	case asyncErr := <-failure:
@@ -127,13 +129,16 @@ func (c *RootCommand) Exec(_ io.Reader, out io.Writer) error {
 // Tail starts the virtual tail process. Tail fetches data from the eventbuffer
 // API. It hands off the requested logs to the outputloop for the actual
 // printing.
-func (c *RootCommand) tail(out io.Writer, failure chan<- error) {
+func (c *RootCommand) tail(out io.Writer) error {
 	// Start this with --from and --to if set.
 	curWindow := c.cfg.from
 	toWindow := c.cfg.to
 
 	// Start the loop with an initial address to query.
-	path := makeNewPath(c.cfg.path, curWindow, "", failure)
+	path, err := makeNewPath(c.cfg.path, curWindow, "")
+	if err != nil {
+		return err
+	}
 
 	// lastBatchID keeps the last successfully read Batch.ID in case we need
 	// re-request on failure.
@@ -153,16 +158,14 @@ func (c *RootCommand) tail(out io.Writer, failure chan<- error) {
 			c.Globals.ErrLog.AddWithContext(err, map[string]any{
 				"GET": path,
 			})
-			failure <- fmt.Errorf("unable to create new request: %w", err)
-			return
+			return fmt.Errorf("unable to create new request: %w", err)
 		}
 		req.Header.Add("Fastly-Key", c.token)
 
 		resp, err := c.doReq(req)
 		if err != nil {
 			c.Globals.ErrLog.Add(err)
-			failure <- fmt.Errorf("unable to execute request: %w", err)
-			return
+			return fmt.Errorf("unable to execute request: %w", err)
 		}
 
 		// Check that our request was successful. If the server is
@@ -172,8 +175,7 @@ func (c *RootCommand) tail(out io.Writer, failure chan<- error) {
 			// not valid, give them an error stating this and exit.
 			if resp.StatusCode == http.StatusNotFound &&
 				c.cfg.from != 0 {
-				failure <- fmt.Errorf("specified 'from' time %d not found, either too far in the past or future", c.cfg.from)
-				return
+				return fmt.Errorf("specified 'from' time %d not found, either too far in the past or future", c.cfg.from)
 			}
 
 			// In an effort to clean up the output, do not print on
@@ -198,8 +200,7 @@ func (c *RootCommand) tail(out io.Writer, failure chan<- error) {
 			}
 
 			// Failing at this point is unrecoverable.
-			failure <- fmt.Errorf("unrecoverable error, response code: %d", resp.StatusCode)
-			return
+			return fmt.Errorf("unrecoverable error, response code: %d", resp.StatusCode)
 		}
 
 		// Read and parse response, send batches to the output loop.
@@ -221,7 +222,10 @@ func (c *RootCommand) tail(out io.Writer, failure chan<- error) {
 				// We can't parse the response, attempt to
 				// re-request from the last window & batch.
 				text.Warning(out, "unable to parse response body: %v", err)
-				path = makeNewPath(path, curWindow, lastBatchID, failure)
+				path, err = makeNewPath(path, curWindow, lastBatchID)
+				if err != nil {
+					return err
+				}
 				continue
 			}
 
@@ -250,7 +254,10 @@ func (c *RootCommand) tail(out io.Writer, failure chan<- error) {
 
 			// Something happened in the scanner, re-request the
 			// current batchID.
-			path = makeNewPath(path, curWindow, lastBatchID, failure)
+			path, err = makeNewPath(path, curWindow, lastBatchID)
+			if err != nil {
+				return err
+			}
 			continue
 		}
 
@@ -267,8 +274,12 @@ func (c *RootCommand) tail(out io.Writer, failure chan<- error) {
 		// We do NOT want to specify a batchID, as this
 		// request was successful.
 		lastBatchID = ""
-		path = makeNewPath(path, curWindow, lastBatchID, failure)
+		path, err = makeNewPath(path, curWindow, lastBatchID)
+		if err != nil {
+			return err
+		}
 	}
+	return nil
 }
 
 // adjustTimes adjusts the passed in from and to flags based on the
@@ -530,13 +541,10 @@ func (l *Log) String() string {
 
 // makeNewPath generates a new request path based on current
 // path, window, and batchID.
-func makeNewPath(path string, window int64, batchID string, failure chan<- error) string {
+func makeNewPath(path string, window int64, batchID string) (string, error) {
 	basePath, err := url.Parse(path)
 	if err != nil {
-		// No reasonable way to carry on from an error at this point
-		// and it should never happen, so error & exit.
-		failure <- fmt.Errorf("error generating request URL: %w", err)
-		return ""
+		return "", fmt.Errorf("error generating request URL: %w", err)
 	}
 
 	// Unset anything in the query parameters that might already exist.
@@ -552,7 +560,7 @@ func makeNewPath(path string, window int64, batchID string, failure chan<- error
 	}
 
 	basePath.RawQuery = q.Encode()
-	return basePath.String()
+	return basePath.String(), nil
 }
 
 // splitByReqID splits slices of logs based on RequestID.