A friend contacted me today, asking me “What are the best practices for failover with Postgres?” And he mentioned pgpool-II.
Update: added “code review” to the things that we’re doing well below.
There were a couple themes for me from OSCON last week. One is transitions and change. I’ve got a whole slew of thoughts on this, particularly from my experience leaving the management team of Open Source Bridge.
But the other is the importance of doing things badly. In particular, the importance of doing things badly in open source.
Tim Anglade, at about 41:10, says that he thinks the reason why open source companies make money is because open source is kind of shitty (from an interview he did with Cliff Moon last fall). So, on one hand there’s a Money Making Opportunity. Probably not the one that we’d all prefer, but it is what it is.
When he said that, I immediately thought about the other things that we do badly (other than documentation) and the discussions I’d been having with people last week.
Basically, we had a problem in the Postgres community of experienced developers solving every small bug at nearly the moment it was reported. It’s sort of like a cat sitting at the entrance of the only mousehole.
The effect on the code is amazing – we have clearly documented, concise and consistent code. But the effect on the community is that we don’t have mid-level developers, and it is very difficult for inexperienced developers to build up a portfolio of small projects, based on bugs.
I don’t have a ready solution for this problem. And I do not mean this as a criticism of the thousands of hours our core teams have devoted to fixing bugs. We all benefit from the dedication. I am just pointing out that our system had a clear tradeoff – fewer contributors.
What we could do a bit worse (to address the point of this blog post) is lengthen our response time to solving bugs, and let some less experienced developers respond to the bugs queue. This probably involves creating a bug tracker and holding the tension a bit longer on fixes.
Our committers have made efforts toward spreading the load around more – with commitfest – meaning a greater support of code review, with Tom’s recent presentations about the planner, with our wiki-fied Todo list. And there are many more examples of our committers putting real effort into mentoring, tutoring and finding ways of bringing more people in.
The thing that’s missing from all of those efforts, however, is urgency. That’s what bug-fixing is great for. That’s why we have people who remain in operations work even if they hate being woken up at 3am. Urgent work is worthwhile work (mostly).
I’m sure there are other particular areas where we could do things worse, and thus invite more people to contribute. I’ll be thinking about this more in regard to our project event planning, as I think there’s a bit of a disconnect there, and a huge opportunity to involve more people.
I’m reminded again of David Eaves’ talks about how community management is the core competency of open source, not technology. I struggle with that thought every day, but it rings truer the more I try to work on the significant problems facing any particular open source project.
I’m finally getting to blog, and here are a few highlights:
* “Mistakes were made” was a great time. Thank you everyone who shared stories. And those of you who attended, please connect with me – email or whatever, and let’s continue our discussions about failure.
* I have a little bit of editing to do left on the harder, better, faster, stronger slides. Talk ratings have been very high (thank you audience! 🙂 Should have that up tomorrow!
* Not having a booth at OSCON was a real bummer for Postgres. We need to figure out a way to make this happen for us every year.
* Great having the time to connect with old friends in the hallways this week.
* Thanks O’Reilly for supporting our open source community.
* Thanks Google Open Source Programs office for bringing together open source leaders yet again this year for some important conversations.
Thank you everyone from the Postgres community who contributed to the Postgres day just before OSCON. All the speakers and their talks are listed here.
We need to keep having adjunct events like this! I think LCA has it right scheduling Mini-BoFs to provide networking opportunities for the distinct groups. I think OSCON should formalize this next year, and figure out a way of facilitating those groups in a more structured way.
I have another blog post brewing about difficult conversations.. but that’s going to have to wait until after I enjoy the brewers fest!
I’m giving a couple talks at OSCON this year. The first is on Tuesday, 10:40am room C123: Harder, Better, Faster, Stronger: Postgres 9.1. The other is Mistakes were Made, Wednesday at 1:40pm in room D136.
And here are the rest of the talks tagged with PostgreSQL.
Also remember — there’s a PgDay tomorrow at the Oregon Convention Center!
I’m pushing my examples for my 9.1 talk into a github repo. It should be populated with whatever I decide to use for the talk by Monday evening.
Building 9.1 for me on Mac OS X (leopard!) involved the following:
git tag -l | grep REL9_1
git checkout REL9_1_BETA2
./configure --with-perl --with-python --prefix=/opt/pg91beta2 --with-readline
Normal caveats apply – you need X Code of a reasonably recent version, and a bunch of support libraries to make this happen. I haven’t rebuilt from scratch on OS X in a long time, but now I realize that maybe I aught to go through the pain and document this again.
But I digress!
I have a long list of resources for this talk and wanted to share. Probably in the slides for the talk, I’ll provide shortlinks so that people can pull them up and read instead of listening to me 😀
Here’s my links:
- Latest build of documentation for 9.1
- Heikki’s slides about replication
- Common Table Expressions
- Writeable CTE Examples
- Upserting with Writeable CTEs
- Per column collation support examples
- Review of Postgres Extensions effects and usage for end users
- Dimitri’s talk from last year about his work on Extensions
- David Wheeler’s talk (tomorrow!) on building extensions
- User-level overview of KNN Indexing
- Developer overview of KNN Indexes
- Unlogged tables overview with example performance test from depesz
- Robert Haas’ analysis of features and differences between temporary tables and ulogged tables
- SSI wiki page
- My notes from Kevin Grittner’s talk on SSI
- Postgres 9.1 docs on synchronous replication
- Wiki page for synchronous replication
- Developer wiki page about synchronous replication implementation
- Josh Berkus’ Magical Mystery Tour of 9.1 features
And if you’re wondering about the title, I took it from an great Daft Punk song that fans have created some epic videos of:
Thank you all who participated in the PL/Summit. We spent about 5 hours together for discussions about PLs, and then a few more hours at the pub.
The rough notes from the meeting are at:
I put a few TODOs out there based on discussions, and for a reminder to myself to follow up with folks that had good ideas.
Here’s the TODOs:
* Publish code for PL/NULL – Tim
* Make a list of all the boilerplate code – Selena will send email to -hackers about it
* Set up a 1/2 day meeting at the next pgcon – Josh Berkus
* Set up a Skype session in a few months time to go over progress – Selena (Tim, Alvaro agreed to attend)
* Further discussion of DDL triggers – Jan Wieck
* Further discussion of permission system – Steve Singer
* Further discussion of per-statement config parameters for things like timezone – Jan Urbanski
So, we’re at the Pub and doing “create a billion tables” time trials with Jan Urbanski using Python and Josh Berkus using Perl.
We’re also hacking on a test framework the Slony developers have, specifically hacking with Steve Singer. What we discovered is that sync rep doesn’t wait for a WAL segment to be *replayed* before it returns. In the pg_stat_replication table, we see sent_location, write_location and flush_location synchronized, but not replay_location.
This makes sense from a database perspective, but may be surprising behavior for application developers. There are patches out there (according to what I just heard from Bernd) to make synchronous replication wait for replay on the slave, but it’s not certain when that will be committed. It definitely won’t be part of version 9.1.
I just wrote up configuration details from a database administrator’s perspective, and am planning on doing some additional work to make a highly condensed configuration tutorial for our main docs. We definitely need to explain this more clearly for users, who might be thinking of it more from an application perspective.
On behalf of the Postgres Open organizing committee, I’m pleased to share this announcement:
Postgres Open 2011, a conference for data innovators focused on disruption of the database industry through PostgreSQL, will take place September 14-16, 2011 at Chicago’s Westin Michigan Avenue hotel.
“PostgreSQL’s consistent addition of new features and enhancements, while remaining focused on reliability and performance, has provided myYearbook a solid foundation to create new and innovative applications,” said Gavin Roy, CTO at myYearbook. “We are looking forward to the Postgres Open Conference as a venue to share, network, and learn innovative ways to leverage Postgres in our environment.”
Postgres Open, a community-organized, non-profit conference, addresses the breadth of PostgreSQL usage, from core database system design to enterprise database use. Inviting entrepreneurs and technologists on the leading edge of data management, the conference will focus on open source database innovation and changes in the database market. Postgres Open includes regular talks, keynotes and hands-on tutorials.
The theme of the inaugural conference is “disruption of the database industry”. Topics will include new features in the latest version of PostgreSQL, use cases, product offerings and important announcements. Invited talks and presentations will cover many of the innovations in version 9.1, such as nearest-neighbor indexing, serializable snapshot isolation, and transaction-controlled synchronous replication. Vendors will also be announcing and demonstrating new products and services to enhance and extend PostgreSQL.
Postgres Open 2011’s main program (September 15-16) will be preceded by a day of intensive, half-day tutorials.
The Call For Papers for Postgres Open will open in late May.
Our program committee includes:
Robert Haas, Major Contributor, PostgreSQL committer,
Josh Berkus, Core Team member,
Greg Smith, Major Contributor to PostgreSQL and author of High
Performance PostgreSQL 9.0,
Gavin Roy, CTO of MyYearbook.com and
Selena Deckelmann, Major Contributor to PostgreSQL.
For information concerning sponsorship, please send email to firstname.lastname@example.org for a copy of our prospectus.
Yesterday, I spent my morning at the Clustering summit, catching up on what the cluster hackers have been up to for the last year. I was lucky enough to sit next to Jan Wieck and Kevin Grittner. You may remember Kevin from his work on serializable snapshot isolation.
There were some pretty awesome side conversations about where folks think work needs to be done next, and conflict resolution for multi- (or many-) master setups.
I gave a quick update on Bucardo 5, which had an alpha release last week, supports many-master and has has experimental support for non-Postgres targets. The first two targets are text and MongoDB.
The Postgres project has given the generic name “binary replication” to all the features like WAL shipping, streaming replication and synchronous replication. Simon Riggs also gave his update on these features at the Clustering Summit today. He observed that the 9.1 release is the culmination of 7 years of work on replication subsystems. Simon pointed out that synchronous replication is the best, and most obvious, use case for the binary replication at the core of Postgres. And also pointed out that he was quite pleased with the ultimate design.
For the afternoon, I spent some time with folks on the infrastructure team, giving Magnus well-deserved congratulations for his induction into -core, and meeting up with folks from all over at the Royal Oak and Keg, a reasonable steakhouse in town.
Looking forward to the developers meeting today!
I wrote my review of synchronous replication over on Emma’s Tech blog (It’ll probably be published mid-day Tuesday). I’m visiting Ottawa this year on behalf of Emma, one of many great sponsors of Postgres’ yearly international developer conference, pgCon.
This week will be packed for me – attending the Clustering summit, the developers meeting, presenting about Emma’s database systems, leading the lightning talks, and of course attending the many parties this week.
Because we are spread so far around the globe, pgCon is often our one chance to get together and really dig into problems in-person.
And, I’m pulling together our first ever Procedural Language summit. With the new extension system, over 30 procedural languages implemented, and a ton of new features being added to existing PLs, I thought it was time PL developers should come together and have a chat. I’ve still got a few details to work out before Saturday (sorry all that RSVP’d – final agenda coming soon!).
I’m hoping to also have another, unrelated, announcement this Wednesday. Hopefully all the details come together!
Anyway, with that cliffhanger, I’m off to get a good night’s rest before the clustering summit tomorrow.
Postgres released version 9.1 beta 1 today! This is a preview of 9.1, predicted to be available in the next 2-3 months, not a bugfix release for earlier versions of Postgres.
PostgreSQL 9.1 contains a huge volume of new features, possibly more any single release of PostgreSQL before. These features also include several innovations which PostgreSQL is the first database system to have. The most anticipated features in this version include:
- Synchronous Replication
- Per-column collations for multilingual databases
- Unlogged Fast Tables
- K-Nearest-Neighbor Indexing
- Serializable Snapshot Isolation
- Writeable Common Table Expressions
- SE-Linux Integration
- SQL/MED attached tables
The PostgreSQL project now depends on you to test 9.1beta1 in order have a rapid and bug-free 9.1 release. If you are able to help with testing version 9.1, please see the Beta Testing HOWTO
If you’d like to grab a copy of the latest from git, here is a quick set of instructions to compile 9.1beta1 from the git repo:
git checkout REL9_1_BETA1 ./configure --prefix=/opt/pg9.1beta1 make sudo make install
And then to create a database:
/opt/pg9.1beta1/bin/initdb -D mytestdb /opt/pg9.1beta1/bin/pg_ctl -D mytestdb start
For a preview of features coming this fall, check out Depesz’s blog.