zuul-stream: Add variable to disable writing streaming files

Upon further discussion we recently found another case of leaking
console streaming files; if the zuul_console is not running on port
19885, or can not be reached, the streaming spool files will still be
leaked.

The prior work in I823156dc2bcae91bd6d9770bd1520aa55ad875b4 has the
receiving side indicate to the zuul_console daemon that it should
remove the spool file.

If this doesn't happen, either because the daemon was never there, or
it is firewalled off, the streaming spool files are left behind.

This modifies the command action plugin to look for a variable
"zuul_console_disable" which will indicate to the library running the
shell/command task not to write out the spool file at all, as it will
not be consumed.

It is expected this would be set at a host level in inventory for
nodes that you know can not or will not have access to zuul_console
daemon.

We already have a mechanism to disable this for commands running in a
loop; we expand this with a new string type.  The advantage of this is
it leaves the library/command.py side basically untouched.

Documentation is updated, and we cover this with a new test.

Change-Id: I0273993c3ece4363098e4bf30bfc4308bb69a8b4

1 files changed, 22 insertions, 6 deletions

diff --git a/doc/source/howtos/nodepool_static.rst b/doc/source/howtos/nodepool_static.rst
index c10672e7b..163497bcf 100644
--- a/doc/source/howtos/nodepool_static.rst
+++ b/doc/source/howtos/nodepool_static.rst
@@ -69,14 +69,30 @@ Log streaming
 The log streaming service enables Zuul to show the live status of
 long-running ``shell`` or ``command`` tasks.  The server side is setup
 by the ``zuul_console:`` task built-in to Zuul's Ansible installation.
-The executor requires the ability to communicate with the job nodes on
-port 19885 for this to work.
+The executor requires the ability to communicate with this server on
+the job nodes via port ``19885`` for this to work.
 
-The log streaming service may leave files on the static node in the
-format ``/tmp/console-<uuid>-<task_id>-<host>.log`` if jobs are
-interrupted.  These may be safely removed after a short period of
-inactivity with a command such as
+The log streaming service spools command output via files on the job
+node in the format ``/tmp/console-<uuid>-<task_id>-<host>.log``.  By
+default, it will clean these files up automatically.
+
+Occasionally, a streaming file may be left if a job is interrupted.
+These may be safely removed after a short period of inactivity with a
+command such as
 
 .. code-block:: shell
 
    find /tmp -maxdepth 1 -name 'console-*-*-<host>.log' -mtime +2 -delete
+
+If the executor is unable to reach port ``19885`` (for example due to
+firewall rules), or the ``zuul_console`` daemon can not be run for
+some other reason, the command to clean these spool files will not be
+processed and they may be left behind; on an ephemeral node this is
+not usually a problem, but on a static node these files will persist.
+
+In this situation, , Zuul can be instructed to not to create any spool
+files for ``shell`` and ``command`` tasks via setting
+``zuul_console_disable: True`` (usually via a global host variable in
+inventory).  Live streaming of ``shell`` and ``command`` calls will of
+course be unavailable in this case, but no spool files will be
+created.