[COMMIT seastar master] stall-analyser: gracefully handle empty input

[Commit Bot]

From: Benny Halevy <bha...@scylladb.com>
Committer: Pavel Emelyanov <xe...@scylladb.com>
Branch: master

stall-analyser: gracefully handle empty input

Currently, the tools prints an obscure error
if the input is empty:
```
Traceback (most recent call last):
File "/home/bhalevy/dev/scylla_s3_reloc_server/./seastar//scripts/stall-analyser.py", line 363, in <module>
print_stats(tally, tmin)
^^^^
NameError: name 'tmin' is not defined. Did you mean: 'min'?
```

Instead, print a meaningful error and direct the user
to run stall-analyser.py --help for usage instructions.

Ref https://github.com/scylladb/scylla_s3_reloc_server/pull/103

Signed-off-by: Benny Halevy <bha...@scylladb.com>

Closes scylladb/seastar#2305

---
diff --git a/scripts/stall-analyser.py b/scripts/stall-analyser.py
--- a/scripts/stall-analyser.py
+++ b/scripts/stall-analyser.py
@@ -126,10 +126,16 @@ def __init__(self, resolver: addr2line.BacktraceResolver):
# Each node in the tree contains:
self.count = 0
self.total = 0
- self.nodes = {}
+ self.nodes = dict[str, Node]()
self.tail = Node('')
self.head = Node('')

+ def empty(self):
+ return not self.nodes
+
+ def __bool__(self):
+ return not self.empty()
+
def process_trace(self, trace: list[str], t: int) -> None:
# process each backtrace and insert it to the tree
#
@@ -341,6 +347,7 @@ def main():
resolver = addr2line.BacktraceResolver(executable=args.executable,
concise=not args.full_function_names)
graph = Graph(resolver)
+ tmin = args.minimum or 0
for s in args.file:
if comment.search(s):
continue
@@ -368,11 +375,13 @@ def main():
# ?? ??:0
if address_threshold:
trace = list(dropwhile(lambda addr: int(addr, 0) >= address_threshold, trace))
- tmin = args.minimum or 0
if t >= tmin:
graph.process_trace(trace, t)

try:
+ if not graph:
+ print("No input data found. Please run `stall-analyser.py --help` for usage instruction")
+ sys.exit()
print_command_line_options(args)
print_stats(tally, tmin)
graph.print_graph(args.direction, args.width, args.branch_threshold)