On Mon, Dec 4, 2017 at 12:12 PM Brady Deetz <bdeetz@xxxxxxxxx> wrote:
I'm not sure if this is a bug where ceph incorrectly reports to the user or if this is just a matter of misleading language. Thought I might bring it up in any case.
I under stand that "may require restart" is fairly direct in its ambiguity, but this probably shouldn't be ambiguous without a good technical reason. But, I find "not observed" to be quite misleading. These arg injections are very clearly being observed. Maybe the output should be "not observed by 'component x', change may require restart." But, I'd still like a definitive yes or no for service restarts required by arg injects.
You're right, but unfortunately there is a good technical reason. Or at least one of effort versus payoff.
We are slowly (or, lately, somewhat rapidly) changing things in configuration management within Ceph, but the historical pattern is that we have a giant struct of variables, and when we want a new config option we add a new variable. These are initialized on startup.
Initially, whenever we wanted to access the variables, we just read them directly out of the config struct. Unfortunately, this could be racy in the case where we changed configs while running, and some configs can't be changed live. So we added an "observer" framework, which lets us call specific functions whenever specified config options get changed, and a set of thread-safe accessor functions.
Then we saw people injecting options we know don't take live effect, so we wanted to add a warning. (For instance, you can't change the number of worker shards in the OSD once it's running.) Obviously, we can assume programmatically that any configuration option with an observer will take live effect. But what about places where we still read the value directly out of the config struct while running? Those *do* take effect immediately, but there's no programmatic way to identify them.
We've talked in the past about adding an extra flag which indicates if the config is a live-changed one or not, but it's run up against issues of difficulty and the effort required to track down every option. (Adding yet another "this might not be registered" statement won't help us much, so it basically needs to be done monolithically.) John recently reworked the config options framework and it may be easier to make these changes now, but the effort of auditing every single option remains. :/
Although it could be that even if we don't know for sure, being able to say with certainty that the ten most-common unobserved options *will* take live effect is useful enough on its own. Patches welcome! ;)
-Greg
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I've run into this on osd args as well.
Ceph Luminous 12.2.1 (CentOS 7.4.1708)
[root@mon0 ceph-admin]# ceph --admin-daemon /var/run/ceph/ceph-mon.mon0.asok config show | grep "mon_allow_pool_delete""mon_allow_pool_delete": "false",[root@mon0 ceph-admin]# ceph tell mon.0 injectargs '--mon_allow_pool_delete=true'injectargs:mon_allow_pool_delete = 'true' (not observed, change may require restart)[root@mon0 ceph-admin]# ceph tell mon.1 injectargs '--mon_allow_pool_delete=true'injectargs:mon_allow_pool_delete = 'true' (not observed, change may require restart)[root@mon0 ceph-admin]# ceph tell mon.2 injectargs '--mon_allow_pool_delete=true'injectargs:mon_allow_pool_delete = 'true' (not observed, change may require restart)[root@mon0 ceph-admin]# ceph --admin-daemon /var/run/ceph/ceph-mon.mon0.asok config show | grep "mon_allow_pool_delete""mon_allow_pool_delete": "true",[root@mon0 ceph-admin]# ceph tell mon.0 injectargs '--mon_allow_pool_delete=false'injectargs:mon_allow_pool_delete = 'false' (not observed, change may require restart)[root@mon0 ceph-admin]# ceph tell mon.1 injectargs '--mon_allow_pool_delete=false'injectargs:mon_allow_pool_delete = 'false' (not observed, change may require restart)[root@mon0 ceph-admin]# ceph tell mon.2 injectargs '--mon_allow_pool_delete=false'injectargs:mon_allow_pool_delete = 'false' (not observed, change may require restart)[root@mon0 ceph-admin]# ceph --admin-daemon /var/run/ceph/ceph-mon.mon0.asok config show | grep "mon_allow_pool_delete""mon_allow_pool_delete": "false",Thanks for the hard work, devs!
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