Thread: PG Sharding

PG Sharding

From

Matej

Date:

29 January 2018, 20:34:18

Hi Everyone.

We are looking at a rather large fin-tech installation. But as scalability requirements are high we look at sharding of-course.

I have looked at many sources for Postgresql sharding, but we are a little confused as to shared with schema or databases or both.

So far our understanding:

SCHEMA.

PROS:

- seems native to PG

- backup seems easier

- connection pooling seems easier, as you can use same connection between shard.

CONS:

- schema changes seems litlle more complicated

- heard of backup and maintenance problems

- also some caching problems.

DATABASE:

PROS:

- schema changes litlle easier

- backup and administration seems more robust

CONS:

- heard of vacuum problems

- connection pooling is hard, as 100 shards would mean 100 pools

So what is actually the right approach? If anyone could shed some light on my issue.

Thanks

Re: PG Sharding

From

Melvin Davidson

Date:

29 January 2018, 20:44:45

On Mon, Jan 29, 2018 at 9:34 AM, Matej <gmatej@gmail.com> wrote:

Hi Everyone.

We are looking at a rather large fin-tech installation. But as scalability requirements are high we look at sharding of-course.

I have looked at many sources for Postgresql sharding, but we are a little confused as to shared with schema or databases or both.

So far our understanding:

SCHEMA.

PROS:
- seems native to PG
- backup seems easier
- connection pooling seems easier, as you can use same connection between shard.

CONS:
- schema changes seems litlle more complicated
- heard of backup and maintenance problems
- also some caching problems.

DATABASE:

PROS:
- schema changes litlle easier
- backup and administration seems more robust

CONS:
- heard of vacuum problems
- connection pooling is hard, as 100 shards would mean 100 pools

So what is actually the right approach? If anyone could shed some light on my issue.

Thanks

You might also want to consider GridSQL. IIRC it was originally developed by EnterpriseDB. I saw a demo of it a few years ago and it was quite impressive,

but I've had no interaction with it since, so you will have to judge for yourself.

https://sourceforge.net/projects/gridsql/?source=navbar

Melvin Davidson
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.

Re: PG Sharding

From

Thomas Boussekey

Date:

29 January 2018, 21:15:34

Hello,

Facing the same situation, I'm considering 3 solutions:

- Sharding with postgres_xl (waiting for a Pg10 release)

- Sharding with citusdata (Release 7.2, compatible with Pg10 and pg_partman, seems interesting)

- Partitioning with PG 10 native partitioning or pg_partman

With colleagues, we have tested the 3 scenarios.

Sharding looks interesting, but you have to apprehend its behaviour in case of node loss, or cross-node queries.

Thomas

2018-01-29 15:44 GMT+01:00 Melvin Davidson <melvin6925@gmail.com>:

On Mon, Jan 29, 2018 at 9:34 AM, Matej <gmatej@gmail.com> wrote:
Hi Everyone.

We are looking at a rather large fin-tech installation. But as scalability requirements are high we look at sharding of-course.

I have looked at many sources for Postgresql sharding, but we are a little confused as to shared with schema or databases or both.

So far our understanding:

SCHEMA.

PROS:
- seems native to PG
- backup seems easier
- connection pooling seems easier, as you can use same connection between shard.

CONS:
- schema changes seems litlle more complicated
- heard of backup and maintenance problems
- also some caching problems.

DATABASE:

PROS:
- schema changes litlle easier
- backup and administration seems more robust

CONS:
- heard of vacuum problems
- connection pooling is hard, as 100 shards would mean 100 pools

So what is actually the right approach? If anyone could shed some light on my issue.

Thanks

You might also want to consider GridSQL. IIRC it was originally developed by EnterpriseDB. I saw a demo of it a few years ago and it was quite impressive,
but I've had no interaction with it since, so you will have to judge for yourself.

https://sourceforge.net/projects/gridsql/?source=navbar

--
Melvin Davidson
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.

Re: PG Sharding

From

Matej

Date:

29 January 2018, 21:49:19

Hi Thomas.

Thanks.

Also looked at those solutions:

- PGXL Am a ltille afraid we would be the test dummies. Did not hear of many production installs.

- Citus seems heavily limited scalability vise, because of the master node design.

Regarding partitioning we are considering ourselves pg_pathman. Was hoping on PG10 partitioning but currently not really many changes performance vise.

Overall we are still considering manual APP/sharding as this seems to be the most scalable approach which least added latency. The builtin solutions seems to introduce extra lag and I am afraid of what to do when something goes wrong. then it's not a black box anymore and you have to study the details.

For node loss we plan a master -slave setup, and there will not be so many cross shard queries.

Matej

2018-01-29 16:15 GMT+01:00 Thomas Boussekey <thomas.boussekey@gmail.com>:

Hello,

Facing the same situation, I'm considering 3 solutions:
- Sharding with postgres_xl (waiting for a Pg10 release)
- Sharding with citusdata (Release 7.2, compatible with Pg10 and pg_partman, seems interesting)
- Partitioning with PG 10 native partitioning or pg_partman

With colleagues, we have tested the 3 scenarios.
Sharding looks interesting, but you have to apprehend its behaviour in case of node loss, or cross-node queries.

Thomas

2018-01-29 15:44 GMT+01:00 Melvin Davidson <melvin6925@gmail.com>:

On Mon, Jan 29, 2018 at 9:34 AM, Matej <gmatej@gmail.com> wrote:
Hi Everyone.

We are looking at a rather large fin-tech installation. But as scalability requirements are high we look at sharding of-course.

I have looked at many sources for Postgresql sharding, but we are a little confused as to shared with schema or databases or both.

So far our understanding:

SCHEMA.

PROS:
- seems native to PG
- backup seems easier
- connection pooling seems easier, as you can use same connection between shard.

CONS:
- schema changes seems litlle more complicated
- heard of backup and maintenance problems
- also some caching problems.

DATABASE:

PROS:
- schema changes litlle easier
- backup and administration seems more robust

CONS:
- heard of vacuum problems
- connection pooling is hard, as 100 shards would mean 100 pools

So what is actually the right approach? If anyone could shed some light on my issue.

Thanks

You might also want to consider GridSQL. IIRC it was originally developed by EnterpriseDB. I saw a demo of it a few years ago and it was quite impressive,
but I've had no interaction with it since, so you will have to judge for yourself.

https://sourceforge.net/projects/gridsql/?source=navbar

--
Melvin Davidson
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.

Re: PG Sharding

From

Thomas Boussekey

Date:

29 January 2018, 22:01:03

Hello Matej,

I found some interesting implementation of postgres_XL at TenCent(WeChat) and Javelin. You can find video capture of conferences of IT people from these companies. Moreover, I attended to PgConf.eu at Warsaw in October, and The ESA (European Space Agency) made a lightning talk on their Gaïa project using a 8-datanode cluster.

I agree with you about the SPOF for the master on the citusdata architecture. Yet, implementation is very easy, and it's an extension in Pg10! But I had to fire many foreign into my data model to be able to install my tables into citusdata.

2 years ago, I was looking for a partitioning extension, pg_partman was mature, whereas pg_pathman was in version 0.4 and many issues in their github were written in Cyrillic, and I'm French ;-)... So I had a closer look at pg_partman.

I'm using pg_partman in production now.

2018-01-29 16:49 GMT+01:00 Matej <gmatej@gmail.com>:

Hi Thomas.

Thanks.

Also looked at those solutions:
- PGXL Am a ltille afraid we would be the test dummies. Did not hear of many production installs.
- Citus seems heavily limited scalability vise, because of the master node design.

Regarding partitioning we are considering ourselves pg_pathman. Was hoping on PG10 partitioning but currently not really many changes performance vise.

Overall we are still considering manual APP/sharding as this seems to be the most scalable approach which least added latency. The builtin solutions seems to introduce extra lag and I am afraid of what to do when something goes wrong. then it's not a black box anymore and you have to study the details.

For node loss we plan a master -slave setup, and there will not be so many cross shard queries.

BR
Matej

2018-01-29 16:15 GMT+01:00 Thomas Boussekey <thomas.boussekey@gmail.com>:
Hello,

Facing the same situation, I'm considering 3 solutions:
- Sharding with postgres_xl (waiting for a Pg10 release)
- Sharding with citusdata (Release 7.2, compatible with Pg10 and pg_partman, seems interesting)
- Partitioning with PG 10 native partitioning or pg_partman

With colleagues, we have tested the 3 scenarios.
Sharding looks interesting, but you have to apprehend its behaviour in case of node loss, or cross-node queries.

Thomas

2018-01-29 15:44 GMT+01:00 Melvin Davidson <melvin6925@gmail.com>:

On Mon, Jan 29, 2018 at 9:34 AM, Matej <gmatej@gmail.com> wrote:
Hi Everyone.

We are looking at a rather large fin-tech installation. But as scalability requirements are high we look at sharding of-course.

I have looked at many sources for Postgresql sharding, but we are a little confused as to shared with schema or databases or both.

So far our understanding:

SCHEMA.

PROS:
- seems native to PG
- backup seems easier
- connection pooling seems easier, as you can use same connection between shard.

CONS:
- schema changes seems litlle more complicated
- heard of backup and maintenance problems
- also some caching problems.

DATABASE:

PROS:
- schema changes litlle easier
- backup and administration seems more robust

CONS:
- heard of vacuum problems
- connection pooling is hard, as 100 shards would mean 100 pools

So what is actually the right approach? If anyone could shed some light on my issue.

Thanks

You might also want to consider GridSQL. IIRC it was originally developed by EnterpriseDB. I saw a demo of it a few years ago and it was quite impressive,
but I've had no interaction with it since, so you will have to judge for yourself.

https://sourceforge.net/projects/gridsql/?source=navbar

--
Melvin Davidson
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.

Re: PG Sharding

From

Konstantin Gredeskoul

Date:

29 January 2018, 22:16:22

When I worked at Wanelo, we built a sharded data store for a giant join table with 4B records and growing. We too could not find any generic sharding solution at the level of postgresql, and after some research decided to implement it in the application.

As it was written in ruby, here are some resources to point out:

https://github.com/taskrabbit/makara

https://github.com/wanelo/sequel-schema-sharding

The service used Sequel gem (not active record from Rails) and has been working very stable for us. I’m not sure if your project is in ruby or not, but wanted to give it a shout.

Another good resource is this ActivityFeed library, which relies on pluggable backends to support very high write to maintain precomputed activity feeds for each user using Redis. I’m a bit fan of moving things out of postgresql that don’t have to be there :)

https://github.com/kigster/simple-feed

Best,

Konstantin

Konstantin Gredeskoul

https://kig.re/

https://reinvent.one/

(415) 265-1054

From: Matej <gmatej@gmail.com>
Sent: Monday, January 29, 2018 7:49:19 AM
To: Thomas Boussekey
Cc: Melvin Davidson; pgsql-general@lists.postgresql.org
Subject: Re: PG Sharding

Hi Thomas.

Thanks.

Also looked at those solutions:

- PGXL Am a ltille afraid we would be the test dummies. Did not hear of many production installs.

- Citus seems heavily limited scalability vise, because of the master node design.

Regarding partitioning we are considering ourselves pg_pathman. Was hoping on PG10 partitioning but currently not really many changes performance vise.

For node loss we plan a master -slave setup, and there will not be so many cross shard queries.

Matej

2018-01-29 16:15 GMT+01:00 Thomas Boussekey <thomas.boussekey@gmail.com>:

Hello,

Facing the same situation, I'm considering 3 solutions:
- Sharding with postgres_xl (waiting for a Pg10 release)
- Sharding with citusdata (Release 7.2, compatible with Pg10 and pg_partman, seems interesting)
- Partitioning with PG 10 native partitioning or pg_partman

With colleagues, we have tested the 3 scenarios.
Sharding looks interesting, but you have to apprehend its behaviour in case of node loss, or cross-node queries.

Thomas

2018-01-29 15:44 GMT+01:00 Melvin Davidson <melvin6925@gmail.com>:

On Mon, Jan 29, 2018 at 9:34 AM, Matej <gmatej@gmail.com> wrote:
Hi Everyone.

We are looking at a rather large fin-tech installation. But as scalability requirements are high we look at sharding of-course.

I have looked at many sources for Postgresql sharding, but we are a little confused as to shared with schema or databases or both.

So far our understanding:

SCHEMA.

PROS:
- seems native to PG
- backup seems easier
- connection pooling seems easier, as you can use same connection between shard.

CONS:
- schema changes seems litlle more complicated
- heard of backup and maintenance problems
- also some caching problems.

DATABASE:

PROS:
- schema changes litlle easier
- backup and administration seems more robust

CONS:
- heard of vacuum problems
- connection pooling is hard, as 100 shards would mean 100 pools

So what is actually the right approach? If anyone could shed some light on my issue.

Thanks

You might also want to consider GridSQL. IIRC it was originally developed by EnterpriseDB. I saw a demo of it a few years ago and it was quite impressive,
but I've had no interaction with it since, so you will have to judge for yourself.

https://sourceforge.net/projects/gridsql/?source=navbar

--
Melvin Davidson
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.

Re: PG Sharding

From

Rakesh Kumar

Date:

29 January 2018, 22:50:46


> On Jan 29, 2018, at 09:34 , Matej <gmatej@gmail.com> wrote:
>
> Hi Everyone.
>
> We are looking at a rather large fin-tech installation. But as scalability requirements are high we look at sharding
of-course. 
>
> I have looked at many sources for Postgresql sharding, but we are a little confused as to shared with schema or
databasesor both.  
>
>
> So far our understanding:
>
> SCHEMA.
>
> PROS:
> - seems native to PG
> - backup seems easier
> - connection pooling seems easier, as you can use same connection between shard.
>
> CONS:
> - schema changes seems litlle more complicated
> - heard of backup and maintenance problems
> - also some caching  problems.
>
> DATABASE:
>
> PROS:
> - schema changes litlle easier
> - backup and administration seems more robust
>
> CONS:
> - heard of vacuum problems
> - connection pooling is hard, as 100 shards would mean 100 pools
>
>
> So what is actually the right approach? If anyone could  shed some light on my issue.

From your description it seems your requirement is more of multi tenancy in a non distributed env, rather than
distributedSharding env.

Re: PG Sharding

From

Matej

Date:

30 January 2018, 14:47:26

We are looking for multi tenancy but at scale. That's why the sharding and partitioning. It depends how you look at the distributed part.

Matej

29. jan. 2018 17.50 je oseba "Rakesh Kumar" <rakeshkumar464@aol.com> napisala:

> On Jan 29, 2018, at 09:34 , Matej <gmatej@gmail.com> wrote:
>
> Hi Everyone.
>
> We are looking at a rather large fin-tech installation. But as scalability requirements are high we look at sharding of-course.
>
> I have looked at many sources for Postgresql sharding, but we are a little confused as to shared with schema or databases or both.
>
>
> So far our understanding:
>
> SCHEMA.
>
> PROS:
> - seems native to PG
> - backup seems easier
> - connection pooling seems easier, as you can use same connection between shard.
>
> CONS:
> - schema changes seems litlle more complicated
> - heard of backup and maintenance problems
> - also some caching problems.
>
> DATABASE:
>
> PROS:
> - schema changes litlle easier
> - backup and administration seems more robust
>
> CONS:
> - heard of vacuum problems
> - connection pooling is hard, as 100 shards would mean 100 pools
>
>
> So what is actually the right approach? If anyone could shed some light on my issue.

From your description it seems your requirement is more of multi tenancy in a non distributed env, rather than distributed Sharding env.

Re: PG Sharding

From

Rakesh Kumar

Date:

30 January 2018, 17:05:12

>We are looking for multi tenancy but at scale. That's why the sharding and partitioning. It depends how you look at the distributed part.

Citusdb.

Re: PG Sharding

From

Matej

Date:

30 January 2018, 17:18:54

As already said. It's missing 2 level sharding and is restricted with SPOF.

Matej

2018-01-30 12:05 GMT+01:00 Rakesh Kumar <rakeshkumar464@aol.com>:

>We are looking for multi tenancy but at scale. That's why the sharding and partitioning. It depends how you look at the distributed part.

Citusdb.

Re: PG Sharding

From

Thomas Boussekey

Date:

30 January 2018, 20:26:17

Using citusdb enterprise, you can replicate the table shards.

Here is the link to the documentation:
https://docs.citusdata.com/en/v7.2/reference/user_defined_functions.html#replicate-table-shards

Regards,

Thomas

2018-01-30 12:18 GMT+01:00 Matej <gmatej@gmail.com>:

As already said. It's missing 2 level sharding and is restricted with SPOF.

BR

Matej

2018-01-30 12:05 GMT+01:00 Rakesh Kumar <rakeshkumar464@aol.com>:

>We are looking for multi tenancy but at scale. That's why the sharding and partitioning. It depends how you look at the distributed part.

Citusdb.

Re: PG Sharding

From

Matej

Date:

31 January 2018, 17:59:57

Thanks Thomas.

Still fancying the manual approach litlle bit more.

Will probably go with 8 database and 32 schema per machine. This way, will keep in limits for administration tools as well as autovacuum, also will be ready for connection pooling, as 8 databases is not to much.

This will give us 256 shard per machine, but will be tunable. The lower number will also prevent to much memory/disk fragmentation and with this bad cache hit ratios.

Will also use monthly partitioning per shard, to reduce the change of big tables forming.

Thanks everyone.

2018-01-30 15:26 GMT+01:00 Thomas Boussekey <thomas.boussekey@gmail.com>:

Using citusdb enterprise, you can replicate the table shards.

Here is the link to the documentation:
https://docs.citusdata.com/en/v7.2/reference/user_defined_functions.html#replicate-table-shards

Regards,
Thomas

2018-01-30 12:18 GMT+01:00 Matej <gmatej@gmail.com>:
As already said. It's missing 2 level sharding and is restricted with SPOF.

BR

Matej

2018-01-30 12:05 GMT+01:00 Rakesh Kumar <rakeshkumar464@aol.com>:

>We are looking for multi tenancy but at scale. That's why the sharding and partitioning. It depends how you look at the distributed part.

Citusdb.

Re: PG Sharding

From

Steven Lembark

Date:

01 February 2018, 09:48:22

On Mon, 29 Jan 2018 15:34:18 +0100
Matej <gmatej@gmail.com> wrote:

> Hi Everyone.
> 
> We are looking at a rather large fin-tech installation. But as
> scalability requirements are high we look at sharding of-course.
> 
> I have looked at many sources for Postgresql sharding, but we are a
> little confused as to shared with schema or databases or both.

Suggest looking at the Xreme Data product. It is a parallel,
shared-nothing implementation of PG that should solve your
needs rather nicely.

You can see a description of their product at
https://xtremedata.com/

Happy scaling :-)



-- 
Steven Lembark                                       1505 National Ave
Workhorse Computing                                 Rockford, IL 61103
lembark@wrkhors.com                                    +1 888 359 3508

Re: PG Sharding

From

Dan Wierenga

Date:

02 February 2018, 00:01:17

On Wed, Jan 31, 2018 at 7:48 PM, Steven Lembark <lembark@wrkhors.com> wrote:

On Mon, 29 Jan 2018 15:34:18 +0100
Matej <gmatej@gmail.com> wrote:

> Hi Everyone.
>
> We are looking at a rather large fin-tech installation. But as
> scalability requirements are high we look at sharding of-course.
>
> I have looked at many sources for Postgresql sharding, but we are a
> little confused as to shared with schema or databases or both.

Suggest looking at the Xreme Data product. It is a parallel,
shared-nothing implementation of PG that should solve your
needs rather nicely.

You can see a description of their product at
https://xtremedata.com/

Happy scaling :-)

Having been a production DBA for both the DBX (XtremeData) and the Greenplum MPP database platforms, IMO Greenplum is far superior to DBX. Issues with the GP master node being a single point of failure are solved by a secondary master node and automatic failover technology e.g. keepalived.

But, it sounds like the OP is not really looking for the kind of scale that an MPP solution provides, but rather the kind of scale that is typically solved by a service-orchestration suite. I don't think that "a rather large fin-tech installation" with "high scalability requirements" is really enough detail to give a recommendation on orchestration software.

-dan

Re: PG Sharding

From

Matej

Date:

02 February 2018, 15:50:17

I thought that this kind of solution had high latency and bad OLTP capabilities (low trans/second)? Analytics is not a high priority.

2018-02-01 19:01 GMT+01:00 Dan Wierenga <dwierenga@gmail.com>:

On Wed, Jan 31, 2018 at 7:48 PM, Steven Lembark <lembark@wrkhors.com> wrote:
On Mon, 29 Jan 2018 15:34:18 +0100
Matej <gmatej@gmail.com> wrote:

> Hi Everyone.
>
> We are looking at a rather large fin-tech installation. But as
> scalability requirements are high we look at sharding of-course.
>
> I have looked at many sources for Postgresql sharding, but we are a
> little confused as to shared with schema or databases or both.

Suggest looking at the Xreme Data product. It is a parallel,
shared-nothing implementation of PG that should solve your
needs rather nicely.

You can see a description of their product at
https://xtremedata.com/

Happy scaling :-)

Having been a production DBA for both the DBX (XtremeData) and the Greenplum MPP database platforms, IMO Greenplum is far superior to DBX. Issues with the GP master node being a single point of failure are solved by a secondary master node and automatic failover technology e.g. keepalived.

But, it sounds like the OP is not really looking for the kind of scale that an MPP solution provides, but rather the kind of scale that is typically solved by a service-orchestration suite. I don't think that "a rather large fin-tech installation" with "high scalability requirements" is really enough detail to give a recommendation on orchestration software.

-dan