What is High Availability to Postgres? I’ve staked my career on the answer to that question since I first presented an HA stack to Postgres Open in 2012, and I still don’t feel like there’s an acceptable answer. No matter how the HA techniques have advanced since then, there’s always been a nagging suspicion in my mind that something is missing.
But I’m here to say that a bit of research has uncovered an approach that many different Postgres cloud vendors appear to be converging upon.
Maintaining a Postgres database can involve a lot of busywork. This is especially true for more robust architectures that allocate at least one replica for failover purposes. It’s still fairly common for a DBA to create a replica to accommodate emergency or upgrade scenarios, only to have to repeat the process when it came time to revert to the original master system. It’s not safe to simply subscribe the original primary to the newly promoted secondary, so this leaves either creating a new clone, or using rsync to synchronize all of the files first.
This PG Phriday is going to be a bit different. During my trip to Postgres Open this year, I attended a talk I had originally written off as “some Red Hat stuff.” But I saw the word “containers” in the PostgreSQL in Containers at Scale talk and became intrigued. A few days later, I had something of an epiphany: I’ve been wrong about servers for years; we all have.
That’s a pretty bold claim, so it needs some background.
High availability of PostgreSQL databases is incredibly important to me. You might even say it’s a special interest of mine. It’s one reason I’m both excited and saddened by a feature introduced in 9.4. I’m Excited because it’s a feature I plan to make extensive use of, and saddened because it has flown under the radar thus far. It’s not even listed in the What’s new in PostgreSQL 9.4 Wiki page.
As many seasoned DBAs might know, there’s one area that PostgreSQL still manages to be highly aggravating. By this, I mean the role views have in mucking up PostgreSQL dependencies. The part that annoys me personally, is that it doesn’t have to be this way.
Take, for example, what happens if you try to modify a VARCHAR column so that the column length is higher. We’re not changing the type, or dropping the column, or anything overly complicated.
