Log view: display any errors in listing the log files

[MetRonnie]

If there is a failure to list the log files, the user should be presented with an error message, not left in the dark.

Check List

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• No tests needed
• No changelog needed

[MetRonnie]

Actually this change still makes sense irrespective of cylc/cylc-uiserver#607

[oliver-sanders]

This doesn't appear to have made any functional difference in my tests:

test 1:

diff --git a/cylc/flow/scripts/cat_log.py b/cylc/flow/scripts/cat_log.py
index e53524cc6..78d1b3b25 100755
--- a/cylc/flow/scripts/cat_log.py
+++ b/cylc/flow/scripts/cat_log.py
@@ -452,6 +452,9 @@ def _main(
     except KeyError:
         mode = options.mode
 
+    # if mode != 'list-dir':
+    sys.exit('foo bar baz')
+
     if tokens and tokens.get('cycle') and not tokens.get('task'):
         print('Please provide a workflow, task or job ID', file=sys.stderr)
         sys.exit(1)

test 2:

diff --git a/cylc/flow/scripts/cat_log.py b/cylc/flow/scripts/cat_log.py
index e53524cc6..17baa6f35 100755
--- a/cylc/flow/scripts/cat_log.py
+++ b/cylc/flow/scripts/cat_log.py
@@ -452,6 +452,9 @@ def _main(
     except KeyError:
         mode = options.mode
 
+    if mode != 'list-dir':
+        sys.exit('foo bar baz')
+
     if tokens and tokens.get('cycle') and not tokens.get('task'):
         print('Please provide a workflow, task or job ID', file=sys.stderr)
         sys.exit(1)

Before (test1: test2):

After (test1: test2):

[MetRonnie]

Try

    if mode == 'list-dir':
        sys.exit('foo bar baz')

[oliver-sanders]

I did, see my first diff.

I can get the list-dir command to fail (with an error logged at the UIS) but no notification of that error in the UI.

[MetRonnie]

Ah sorry, this only applies to network/graphql errors. E.g. try removing the cat_log_files function in cylc/uiserver/resolvers.py: https://github.com/cylc/cylc-uiserver/blob/dfb1ab41c1284444e37170dd50abd76849469459/cylc/uiserver/resolvers.py#L433

[oliver-sanders]

Removing the cat_log_files function will create an internal code error not a network error right? Note GraphQL errors are another form of internal error.

This PR does not appear to assist with diagnosing remote errors, e.g. try creating an SSH error with your config.

This diff introduces a common network error (host not found), but no error is reported in the log view:

diff --git a/cylc/flow/remote.py b/cylc/flow/remote.py
index e0ab7544a..e99903e0a 100644
--- a/cylc/flow/remote.py
+++ b/cylc/flow/remote.py
@@ -289,7 +289,8 @@ def construct_ssh_cmd(
     if stdin is None:
         command.append('-n')
 
-    command.append(host)
+    # command.append(host)
+    command.append('elephant')
 
     # Pass CYLC_VERSION and optionally, CYLC_CONF_PATH & CYLC_UTC through.
     command += ['env', quote(r'CYLC_VERSION=%s' % CYLC_VERSION)]

I think this PR may make sense, but at present I don't think it is helping as we need the UIS to capture and forward these errors which is clearly isn't doing at present. We should get the errors into the schema at the UIS end first, then make sure the log view is displaying them after.

[MetRonnie]

At the moment this PR guards prevents any bug in the UIS code being silent.

We agreed it doesn't make sense to show an error snackbar for non-zero ret code of cat-log in cylc/cylc-uiserver#607:

I realised that there are a few ways cat-log will exit non-zero when navigating in the UI (e.g. navigating to /log/non-exist), so have settled for just logging the stderr and returning an empty list as before

Maybe we should ensure ret code 1 means no files found, and show an error snackbar for any ret code > 1?