Here are some news from the front of Postgres 10 development, with the highlight of the following commit:
author: Tom Lane <email@example.com>
date: Mon, 2 Jan 2017 21:37:12 -0500
Allow SSL configuration to be updated at SIGHUP.
It is no longer necessary to restart the server to enable, disable,
or reconfigure SSL. Instead, we just create a new SSL_CTX struct
(by re-reading all relevant files) whenever we get SIGHUP. Testing
shows that this is fast enough that it shouldn't be a problem.
In conjunction with that, downgrade the logic that complains about
pg_hba.conf "hostssl" lines when SSL isn't active: now that's just
a warning condition not an error.
An issue that still needs to be addressed is what shall we do with
passphrase-protected server keys? As this stands, the server would
demand the passphrase again on every SIGHUP, which is certainly
impractical. But the case was only barely supported before, so that
does not seem a sufficient reason to hold up committing this patch.
Andreas Karlsson, reviewed by Michael Banck and Michael Paquier
This has been wanted for a long time. In some environments where Postgres is deployed, there could be CA and/or CLR files installed by default, and the user may want to replace them with custom entries. Still, in most cases, the problems to deal with is the replacement of expired keys. In each case, after replacing something that needs a reload of the SSL context, a restart of the instance is necessary to rebuild it properly. Note that while it may be fine for some users to pay the cost of an instance restart, some users caring about availability do not want to have to take down a server, so this new feature is most helpful for many people.
All the SSL parameters are impacted by this upgrade, and they are the following ones:
Note however that there are a couple of things to be aware of:
- On Windows (or builds with EXEC_BACKEND), the new parameters are read at each backend startup. Existing sessions do not have its context updated, and an error in loading the new parameters will cause the connection to fail.
- Entries of pg_hba.conf with hostssl are ignored are ignored if SSL is disabled and a warning is logged to mention that. In previous versions you would get an error if a hostssl entry was found at server start.
- Passphrase key prompt is enabled, but only at server startup, and disactivated at parameter reload to not stuck every backend reloading the SSL context. There could be improvements in this area by using a new GUC parameter that defines command allowing processes to get the passphrase instead of asking it in a tty. Patches are welcome if there is a use case for it. This behavior is described in the following commit. As passphrase support has been rather limited for a long time, being able to reload SSL contexts even without it has a great value.
This is really a nice feature, and I am happy to see this landing as I have been struggling more than once with the downtime that a SSL update induces.