Jepsen Disputes MongoDB's Data Consistency Claims • Hacker News Board

Re: Jepsen Disputes MongoDB's Data Consistency Claims

#91

Post by ceocoder » Sat, May 23, 2020, 9:27 PM UTC

thomascgalvin wrote: post #53

You can tell a lot about a developer by their preferred database. * Mongo: I like things easy, even if easy is dangerous. I probably write Javascript exclusively * MySQL: I don't like to rock the boat, and MySQL is available everywhere * PostgreSQL: I'm not afraid of the command line * H2: My company can't afford a database admin, so I embedded the database in our application (I have actually done this) * SQLite: I'm…

This might be a stupid question, but surely no one thinks of RabbigMQ as a database right? I’ve used it from 2012 to 2018 extensively, including using things like shovels to build hub spoke topologies, however not once did I think of it as anything but a message broker.

Did I miss something huge?

Re: Jepsen Disputes MongoDB's Data Consistency Claims

#92

Post by robocat » Sat, May 23, 2020, 9:30 PM UTC

Thaxll wrote: post #76

castorp wrote: post #61

Earlier quoted context omitted.

> MySQL and PG are not truly consistent per default, they don't fsync every writes. Postgres most certainly does fsync by default. It's tru, you can disable it, but there is a big warning about "may corrupt your database" in the config file.

No PG does not fsync every writes, more details here: https://dba.stackexchange.com/questions/254069/how-often-doe... My point is people complain about MongoDB are the one not using it most likely, MongoDB is very different from 10 years ago. I like to remind people that PG did not have an official replication system 10years ago and as of today is still behind MySQL. No DB is perfect, it's about tradeof.

“PG writes out and syncs the accumulated WAL (= Transaction log) records at each transaction commit [snip] It also syncs at the end of each WAL file (16MB by default). The wal_writer process also wakes up occasionally and writes out and syncs the WAL.“

So PG keeps data consistent by default - unlike MongoDB.

> MySQL and PG are not truly consistent per default, they don't fsync every writes. MongoDB explains that pretty well [links]

Where in those MongoDB doc links is there anything about MySQL or PG?

Re: Jepsen Disputes MongoDB's Data Consistency Claims

#93

Post by ceocoder » Sat, May 23, 2020, 9:31 PM UTC

wzy wrote: post #90

threeseed wrote: post #57

Earlier quoted context omitted.

And you can tell a lot about a developer when they post comments like this. Almost none of is remotely accurate e.g. RabbitMQ isn't even a database.

I can't believe the one item that was so obviously added as a joke went right over head. It may be good idea to take a break from the computer and find something less stressful to do.

Perhaps that’s because some other message brokers are now being touted as databases[0][1], I remember seeing a thread about it on HN couple of days ago.

[0] https://www.confluent.io/blog/okay-store-data-apache-kafka/

[1] https://dzone.com/articles/is-apache-kafka-a-database-the-20...

Re: Jepsen Disputes MongoDB's Data Consistency Claims

#94

Post by henryfjordan » Sat, May 23, 2020, 9:33 PM UTC

ceocoder wrote: post #91

thomascgalvin wrote: post #53

You can tell a lot about a developer by their preferred database. * Mongo: I like things easy, even if easy is dangerous. I probably write Javascript exclusively * MySQL: I don't like to rock the boat, and MySQL is available everywhere * PostgreSQL: I'm not afraid of the command line * H2: My company can't afford a database admin, so I embedded the database in our application (I have actually done this) * SQLite: I'm…

This might be a stupid question, but surely no one thinks of RabbigMQ as a database right? I’ve used it from 2012 to 2018 extensively, including using things like shovels to build hub spoke topologies, however not once did I think of it as anything but a message broker. Did I miss something huge?

RabbitMQ stores your data, right? Then it's a database! That's pretty much all it takes. A flat file, memory-store, SQL DB, Document store, any of them can be databases if that's where you stick your data!

But also no, RabbitMQ and Kafka and the like are clearly message buses and though they might also technically qualify as a DB it would be a poor descriptor.

Re: Jepsen Disputes MongoDB's Data Consistency Claims

#95

Post by IggleSniggle » Sat, May 23, 2020, 9:36 PM UTC

hartator wrote: post #34

toomuchtodo wrote: post #19

Earlier quoted context omitted.

Why not use PostgreSQL instead? It supports a JSON document data type natively. It also has exceptional stewardship as an open source project. Mongo should never be a first choice, but a last choice for edge cases.

> Why not use PostgreSQL instead? It supports a JSON document data type natively. Yes, that's the thing, it's just a field type. It's not really that different than dumping your JSON in a TEXT column. MongoDB is fun because it's truly JSON - BSON - so you don't have to run migrations, you can store complex documents, and have a more object oriented way of storing your data than SQL.

This is so not true that it hurts. Postgres jsonb is highly queryable.

Re: Jepsen Disputes MongoDB's Data Consistency Claims

#96

Post by ceocoder » Sat, May 23, 2020, 9:40 PM UTC

henryfjordan wrote: post #94

ceocoder wrote: post #91

Earlier quoted context omitted.

This might be a stupid question, but surely no one thinks of RabbigMQ as a database right? I’ve used it from 2012 to 2018 extensively, including using things like shovels to build hub spoke topologies, however not once did I think of it as anything but a message broker. Did I miss something huge?

RabbitMQ stores your data, right? Then it's a database! That's pretty much all it takes. A flat file, memory-store, SQL DB, Document store, any of them can be databases if that's where you stick your data! But also no, RabbitMQ and Kafka and the like are clearly message buses and though they might also technically qualify as a DB it would be a poor descriptor.

Ah I see, we are going with “well technically it stores something therefore it is database joke”. Now I’m fully onboard :)

Back when I worked in LA my CTO used to joke that most places use Microsoft Outlook as a database and Excel as BI tool.

Re: Jepsen Disputes MongoDB's Data Consistency Claims

#97

Post by calcifer » Sat, May 23, 2020, 9:47 PM UTC

gigatexal wrote: post #86

Typical HN posts of late hating on Javascript and MongoDB from database elitists -- the thing is there's a tool for a job and as engineers we need to figure out what tool best suits our use cases. It could very well be a NoSQL database such as Mongo or a relational one like Postgres or MySQL.

> the thing is there's a tool for a job

Really? Which job do you belive needs a "maybe store some of this data, sometimes" kind of database?

Re: Jepsen Disputes MongoDB's Data Consistency Claims

#98

Post by goatinaboat » Sat, May 23, 2020, 9:47 PM UTC

ceocoder wrote: post #96

henryfjordan wrote: post #94

Earlier quoted context omitted.

RabbitMQ stores your data, right? Then it's a database! That's pretty much all it takes. A flat file, memory-store, SQL DB, Document store, any of them can be databases if that's where you stick your data! But also no, RabbitMQ and Kafka and the like are clearly message buses and though they might also technically qualify as a DB it would be a poor descriptor.

Ah I see, we are going with “well technically it stores something therefore it is database joke”. Now I’m fully onboard :) Back when I worked in LA my CTO used to joke that most places use Microsoft Outlook as a database and Excel as BI tool.

well technically it stores something therefore it is database joke

Confluent, the company behind Kafka, are 100% serious about Kafka being a database. It is however a far better database than MongoDB.

Re: Jepsen Disputes MongoDB's Data Consistency Claims

#99

Post by VWWHFSfQ » Sat, May 23, 2020, 9:49 PM UTC

ForHackernews wrote: post #83

1123581321 wrote: post #70

Earlier quoted context omitted.

As someone who chose MySQL and provides direction to developers who really like Postgres, and who also uses Postgres for fun, I do find myself having to both defend MySQL as a prudent option and convince them that I know anything at all about Postgres or computer science. :)

I've heard MySQL (well, MariaDB, really) has improved a lot in recent years, but I still can't imagine why I'd ever choose it over Postgres for a professional project. Is there any reason? It used to be that bargain basement shared-hosting providers would only give you a LAMP stack, so it was MySQL or nothing. But if you're on RDS, Postgres every time for my money.

mysql's admin tools are still far superior than what's available for postgres

Re: Jepsen Disputes MongoDB's Data Consistency Claims

#100

Post by gopalv » Sat, May 23, 2020, 9:52 PM UTC

henryfjordan wrote: post #94

ceocoder wrote: post #91

Earlier quoted context omitted.

This might be a stupid question, but surely no one thinks of RabbigMQ as a database right? I’ve used it from 2012 to 2018 extensively, including using things like shovels to build hub spoke topologies, however not once did I think of it as anything but a message broker. Did I miss something huge?

RabbitMQ stores your data, right? Then it's a database! That's pretty much all it takes. A flat file, memory-store, SQL DB, Document store, any of them can be databases if that's where you stick your data! But also no, RabbitMQ and Kafka and the like are clearly message buses and though they might also technically qualify as a DB it would be a poor descriptor.

> Kafka and the like are clearly message buses and though they might also technically qualify as a DB

ksqldb is actually a database on top of this.

The thing is that they have an incrementally updated materialized view that is the table, while the event stream is similar to a WAL ("ahead of write logs?" in this case).

Because eventually you can't just go over your entire history for every query.