ihs: catch NoHostsError

CHANGES.md

@@ -52,6 +52,10 @@ with warning, for scan errors where workflow is stopped.
 [#5199](https://github.com/cylc/cylc-flow/pull/5199) - Fix a problem with
 the consolidation tutorial.
 
+[#5195](https://github.com/cylc/cylc-flow/pull/5195) -
+Fix issue where workflows can fail to shutdown due to unavailable remote
+platforms and make job log retrieval more robust.
+
 -------------------------------------------------------------------------------
 ## __cylc-8.0.3 (<span actions:bind='release-date'>Released 2022-10-17</span>)__
 

cylc/flow/host_select.py

@@ -27,7 +27,11 @@
 
 from cylc.flow import LOG
 from cylc.flow.cfgspec.glbl_cfg import glbl_cfg
-from cylc.flow.exceptions import GlobalConfigError, HostSelectException
+from cylc.flow.exceptions import (
+    GlobalConfigError,
+    HostSelectException,
+    NoHostsError,
+)
 from cylc.flow.hostuserutil import get_fqdn_by_host, is_remote_host
 from cylc.flow.remote import run_cmd, cylc_server_cmd
 from cylc.flow.terminal import parse_dirty_json
@@ -553,7 +557,11 @@ def _get_metrics(hosts, metrics, data=None):
     }
     for host in hosts:
         if is_remote_host(host):
-            proc_map[host] = cylc_server_cmd(cmd, host=host, **kwargs)
+            try:
+                proc_map[host] = cylc_server_cmd(cmd, host=host, **kwargs)
+            except NoHostsError:
+                LOG.warning(f'Could not contact {host}')
+                continue
         else:
             proc_map[host] = run_cmd(['cylc'] + cmd, **kwargs)
 

cylc/flow/network/ssh_client.py

@@ -67,6 +67,8 @@ async def async_request(self, command, args=None, timeout=None):
                     'cylc path': cylc_path,
                     'use login shell': login_sh,
                 }
+                # NOTE: this can not raise NoHostsError
+                # because we have provided the host
                 proc = remote_cylc_cmd(
                     cmd,
                     platform,

cylc/flow/remote.py

@@ -199,6 +199,10 @@ def construct_rsync_over_ssh_cmd(
         platform: contains info relating to platform
         rsync_includes: files and directories to be included in the rsync
 
+    Raises:
+        NoHostsError:
+            If there are no hosts available for the requested platform.
+
     Developer Warning:
         The Cylc Subprocess Pool method ``rsync_255_fail`` relies on
         ``rsync_cmd[0] == 'rsync'``. Please check that changes to this function
@@ -369,6 +373,10 @@ def remote_cylc_cmd(
     Uses the provided platform configuration to construct the command.
 
     For arguments and returns see construct_ssh_cmd and run_cmd.
+
+    Raises:
+        NoHostsError: If the platform is not contactable.
+
     """
     if not host:
         # no host selected => perform host selection from platform config
@@ -405,6 +413,10 @@ def cylc_server_cmd(cmd, host=None, **kwargs):
     with the localhost platform.
 
     For arguments and returns see construct_ssh_cmd and run_cmd.
+
+    Raises:
+        NoHostsError: If the platform is not contactable.
+
     """
     return remote_cylc_cmd(
         cmd,

cylc/flow/scheduler_cli.py

@@ -393,6 +393,8 @@ def _distribute(host, workflow_id_raw, workflow_id):
         cmd.append("--host=localhost")
 
         # Re-invoke the command
+        # NOTE: has the potential to raise NoHostsError, however, this will
+        # most likely have been raised during host-selection
         cylc_server_cmd(cmd, host=host)
         sys.exit(0)
 

cylc/flow/scripts/cat_log.py

@@ -405,6 +405,8 @@ def main(
             # TODO: Add Intelligent Host selection to this
             with suppress(KeyboardInterrupt):
                 # (Ctrl-C while tailing)
+                # NOTE: This will raise NoHostsError if the platform is not
+                # contactable
                 remote_cylc_cmd(
                     cmd,
                     platform,

cylc/flow/scripts/check_versions.py

@@ -44,6 +44,7 @@
 from cylc.flow.cylc_subproc import procopen, PIPE, DEVNULL
 from cylc.flow import __version__ as CYLC_VERSION
 from cylc.flow.config import WorkflowConfig
+from cylc.flow.exceptions import NoHostsError
 from cylc.flow.id_cli import parse_id
 from cylc.flow.platforms import get_platform, get_host_from_platform
 from cylc.flow.remote import construct_ssh_cmd
@@ -101,15 +102,26 @@ def main(_, options: 'Values', *ids) -> None:
         sys.exit(0)
 
     verbose = cylc.flow.flags.verbosity > 0
+    versions = check_versions(platforms, verbose)
+    report_results(platforms, versions, options.error)
 
+
+def check_versions(platforms, verbose):
     # get the cylc version on each platform
     versions = {}
     for platform_name in sorted(platforms):
         platform = get_platform(platform_name)
-        host = get_host_from_platform(
-            platform,
-            bad_hosts=None
-        )
+        try:
+            host = get_host_from_platform(
+                platform,
+                bad_hosts=None
+            )
+        except NoHostsError:
+            print(
+                f'Could not connect to {platform["name"]}',
+                file=sys.stderr
+            )
+            continue
         cmd = construct_ssh_cmd(
             ['version'],
             platform,
@@ -127,7 +139,10 @@ def main(_, options: 'Values', *ids) -> None:
             versions[platform_name] = out.strip()
         else:
             versions[platform_name] = f'ERROR: {err.strip()}'
+    return versions
+
 
+def report_results(platforms, versions, exit_error):
     # report results
     max_len = max((len(platform_name) for platform_name in platforms))
     print(f'{"platform".rjust(max_len)}: cylc version')
@@ -136,7 +151,7 @@ def main(_, options: 'Values', *ids) -> None:
         print(f'{platform_name.rjust(max_len)}: {result}')
     if all((version == CYLC_VERSION for version in versions.values())):
         ret_code = 0
-    elif options.error:
+    elif exit_error:
         ret_code = 1
     else:
         ret_code = 0

cylc/flow/task_events_mgr.py

@@ -39,6 +39,7 @@
 
 from cylc.flow import LOG, LOG_LEVELS
 from cylc.flow.cfgspec.glbl_cfg import glbl_cfg
+from cylc.flow.exceptions import NoHostsError
 from cylc.flow.hostuserutil import get_host, get_user, is_remote_platform
 from cylc.flow.pathutil import (
     get_remote_workflow_run_job_dir,
@@ -935,8 +936,29 @@ def _get_events_conf(self, itask, key, default=None):
 
     def _process_job_logs_retrieval(self, schd, ctx, id_keys):
         """Process retrieval of task job logs from remote user@host."""
+        # get a host to run retrieval on
         platform = get_platform(ctx.platform_name)
-        host = get_host_from_platform(platform, bad_hosts=self.bad_hosts)
+        try:
+            host = get_host_from_platform(platform, bad_hosts=self.bad_hosts)
+        except NoHostsError:
+            # All of the platforms hosts have been found to be uncontactable.
+            # Reset the bad hosts to allow retrieval retry to take place.
+            self.bad_hosts -= set(platform['hosts'])
+            try:
+                # Get a new host and try again.
+                host = get_host_from_platform(
+                    platform,
+                    bad_hosts=self.bad_hosts
+                )
+            except NoHostsError:
+                # We really can't get a host to try on e.g. no hosts
+                # configured (shouldn't happen). Nothing more we can do here,
+                # move onto the next submission retry.
+                for id_key in id_keys:
+                    self.unset_waiting_event_timer(id_key)
+                return
+
+        # construct the retrieval command
         ssh_str = str(platform["ssh command"])
         rsync_str = str(platform["retrieve job logs command"])
         cmd = shlex.split(rsync_str) + ["--rsh=" + ssh_str]
@@ -962,6 +984,8 @@ def _process_job_logs_retrieval(self, schd, ctx, id_keys):
         )
         # Local target
         cmd.append(get_workflow_run_job_dir(schd.workflow) + "/")
+
+        # schedule command
         self.proc_pool.put_command(
             SubProcContext(
                 ctx, cmd, env=dict(os.environ), id_keys=id_keys, host=host

cylc/flow/task_job_mgr.py

@@ -522,9 +522,6 @@ def submit_task_jobs(self, workflow, itasks, curve_auth,
                 cmd, [len(b) for b in itasks_batches])
 
             if remote_mode:
-                host = get_host_from_platform(
-                    platform, bad_hosts=self.task_remote_mgr.bad_hosts
-                )
                 cmd = construct_ssh_cmd(
                     cmd, platform, host
                 )
@@ -944,13 +941,23 @@ def _run_job_cmd(
             cmd.append(get_remote_workflow_run_job_dir(workflow))
             job_log_dirs = []
             host = 'localhost'
+
+            ctx = SubProcContext(cmd_key, cmd, host=host)
             if remote_mode:
-                host = get_host_from_platform(
-                    platform, bad_hosts=self.task_remote_mgr.bad_hosts
-                )
-                cmd = construct_ssh_cmd(
-                    cmd, platform, host
-                )
+                try:
+                    host = get_host_from_platform(
+                        platform, bad_hosts=self.task_remote_mgr.bad_hosts
+                    )
+                    cmd = construct_ssh_cmd(
+                        cmd, platform, host
+                    )
+                except NoHostsError:
+                    ctx.err = f'No available hosts for {platform["name"]}'
+                    callback_255(ctx, workflow, itasks)
+                    continue
+                else:
+                    ctx = SubProcContext(cmd_key, cmd, host=host)
+
             for itask in sorted(itasks, key=lambda task: task.identity):
                 job_log_dirs.append(
                     itask.tokens.duplicate(
@@ -960,9 +967,7 @@ def _run_job_cmd(
             cmd += job_log_dirs
             LOG.debug(f'{cmd_key} for {platform["name"]} on {host}')
             self.proc_pool.put_command(
-                SubProcContext(
-                    cmd_key, cmd, host=host
-                ),
+                ctx,
                 bad_hosts=self.task_remote_mgr.bad_hosts,
                 callback=callback,
                 callback_args=[workflow, itasks],

cylc/flow/task_remote_mgr.py

@@ -245,6 +245,7 @@ def remote_init(
             )
             self.remote_init_map[
                 platform['install target']] = REMOTE_INIT_FAILED
+            # reset the bad hosts to allow remote-init to retry
             self.bad_hosts -= set(platform['hosts'])
             self.ready = True
         else:
@@ -266,6 +267,24 @@ def remote_init(
                 callback_255_args=[platform]
             )
 
+    def construct_remote_tidy_ssh_cmd(
+        self, platform: Dict[str, Any]
+    ) -> Tuple[List[str], str]:
+        """Return a remote-tidy SSH command.
+
+        Rasies:
+            NoHostsError: If the platform is not contactable.
+        """
+        cmd = ['remote-tidy']
+        cmd.extend(verbosity_to_opts(cylc.flow.flags.verbosity))
+        cmd.append(get_install_target_from_platform(platform))
+        cmd.append(get_remote_workflow_run_dir(self.workflow))
+        host = get_host_from_platform(
+            platform, bad_hosts=self.bad_hosts
+        )
+        cmd = construct_ssh_cmd(cmd, platform, host, timeout='10s')
+        return cmd, host
+
     def remote_tidy(self) -> None:
         """Remove workflow contact files and keys from initialised remotes.
 
@@ -274,20 +293,6 @@ def remote_tidy(self) -> None:
         Timeout any incomplete commands after 10 seconds.
         """
         # Issue all SSH commands in parallel
-
-        def construct_remote_tidy_ssh_cmd(
-            platform: Dict[str, Any]
-        ) -> Tuple[List[str], str]:
-            cmd = ['remote-tidy']
-            cmd.extend(verbosity_to_opts(cylc.flow.flags.verbosity))
-            cmd.append(get_install_target_from_platform(platform))
-            cmd.append(get_remote_workflow_run_dir(self.workflow))
-            host = get_host_from_platform(
-                platform, bad_hosts=self.bad_hosts
-            )
-            cmd = construct_ssh_cmd(cmd, platform, host, timeout='10s')
-            return cmd, host
-
         queue: Deque[RemoteTidyQueueTuple] = deque()
         for install_target, message in self.remote_init_map.items():
             if message != REMOTE_FILE_INSTALL_DONE:
@@ -298,7 +303,7 @@ def construct_remote_tidy_ssh_cmd(
                 platform = get_random_platform_for_install_target(
                     install_target
                 )
-                cmd, host = construct_remote_tidy_ssh_cmd(platform)
+                cmd, host = self.construct_remote_tidy_ssh_cmd(platform)
             except (NoHostsError, PlatformLookupError) as exc:
                 LOG.warning(
                     PlatformError(
@@ -332,7 +337,7 @@ def construct_remote_tidy_ssh_cmd(
                 timeout = time() + 10.0
                 self.bad_hosts.add(item.host)
                 try:
-                    retry_cmd, retry_host = construct_remote_tidy_ssh_cmd(
+                    retry_cmd, retry_host = self.construct_remote_tidy_ssh_cmd(
                         item.platform
                     )
                 except (NoHostsError, PlatformLookupError) as exc:

cylc/flow/workflow_files.py

@@ -1077,6 +1077,10 @@ def _remote_clean_cmd(
         platform: Config for the platform on which to remove the workflow.
         rm_dirs: Sub dirs to remove instead of the whole run dir.
         timeout: Number of seconds to wait before cancelling the command.
+
+    Raises:
+        NoHostsError: If the platform is not contactable.
+
     """
     LOG.debug(
         f"Cleaning {reg} on install target: {platform['install target']} "