4 ms·

I'm bashing it because it oversimplifies the problem and claims to be a solution that doesn't address the irreducibility of the problem. It's great for a host

by ballard 13y ago

I'm bashing it because it oversimplifies the problem and claims to be a solution that doesn't address the irreducibility of the problem. It's great for a host file but scp can do that. It doesn't coordinate the transition of services to other states. Puppet does an incredible amount of work (dependency satisfaction) to get things where you want them to be. Configuration management is as much management order of operations as well as what files should contain what. There's not much separating the two because you have to usually change them between states. Chef does this to, but in a simpler way. Cfengine was a past attempt, but is really complicated double work of what runs on a server and what runs on a managed node.

rdtsc 13y ago
> It doesn't coordinate the transition of services to other states. Can you be more specific? So to co-ordinate transitions what else would it need -- multi-key transactions? Surely you have good reason to jump in and criticize it so sharply...
- ballard 13y ago
  Configuration management transactions. Puppet has the notion of stages. Yes because it's marketing an unproven technology as a solution when better things already exist. Someone I know from (OpsCode||Puppet) even further the recommendation of zk as basically the only proven consistent KVS. A better approach should be to do what other cloud shops have done and ship ZK appliances. Pushing new tech on customers is using them to beta test unproven tech, which is reinventing the wheel and risky.
nl 13y ago
I'm not sure what problem you think etcd is attempting to solve, but if your solution involvs Puppet or Chef then it isn't surprising you find etcd isn't sufficient for your purposes. etcd is a highly available configuration store. That's all. It's designed for applications to use to store configuration, so they can be started & stopped without relying on file based storage. Generally speaking these applications have to be coded to use etcd (which is completely different to Chef/Puppet, which are Ops tools). Sure, you could do something to write etcd values to a file, and then have them used by any program, but that misses the point. Your criticisms are so completely irrelevant they aren't even wrong.
- uniclaude 13y ago
  No bashing against etcd from me, but can you point me to a reason why a regular database wouldn't work for this type of thing? High availability, throughput and data storage seem to fit into what a database is made for.
  - nl 13y ago
    The HTTP based interface[1] is designed specifically for configuration data and is easily callable from shell scripts as well as form programs. Something like CouchDB is roughly comparable in that sense, but that has pretty different design goals. [1] https://github.com/coreos/etcd/blob/master/Documentation/api.md https://github.com/coreos/etcd/blob/master/Documentation/api...
  - vidarh 13y ago
    You'd think so, but most RDBMS's are a lot of work to set up in a way that provides the kind of consistency guarantees and availability that a configuration store like this does. E.g. take Postgres. You can't connect to the slaves and write, so your client will need to know how to identify which server is currently the master. And if the master fails, you need to implement a leadership election method, promote the chosen slave, and resync your other slaves from the new master. Before you know it you've reimplemented the configuration store with a different data storage mechanism. There's very little intersection between the typical RDBMS and a configuration store like this.
    - uniclaude 13y ago
      Well, even with your point there are a couple reasons why I could imagine databases making sense here. One is that you might already have people used to deal with them in a highly available manner in your team. HA with Postgres is not exactly an area of research anymore. Most people already using Postgres in their stack know about tools like pgbouncer. Another one is that there are other databases, like Riak, that can talk http and have those problems solved. I am here more trying to understand the features that would make one pick etcd over an higly available database. Thanks for taking the time to explain.
vidarh 13y ago
> It doesn't coordinate the transition of services to other states. It's not intended to. It is way outside the scope. But you can easily coordinate transitions on top of Etcd by waiting on key changes. > Configuration management is as much management order of operations as well as what files should contain what. Outside of scope. Nothing stops you from using a configuration management engine like Puppet and triggering it on state changes by waiting for Etcd keys. It'd be trivial. Or use something other than Etcd if those are your needs. But those are not my needs. For my configuration needs there are exactly no places where I have any interest in the complexity of Puppet, but plenty of places where being able to easily set and query configuration values via a simple REST api that's trivially to access even from a bash script is nice. You're right that scp can do that. But then you're suddenly in the job of maintaining hairy scripts to push out config changes and ensure they are in sync. So Etcd provides a solution that provides that synchronization without the complexity of far more featureful solutions. To me, that is a feature. You seem to try to evaluate a handsaw as if it was a chainsaw and give it bad marks for being cumbersome to cut down trees with. Not all of us want to cut down trees.
- ballard 13y ago
  Trying to cast an argument as a strawman with a strawman is pretty weak. You've also admitted that it's an incomplete solution. But What's worse is that people are going to buy this and quickly they'll have to scrap it when it gets out of sync, deadlocks or can't handle more than 8 boxes.
  - vidarh 13y ago
    > Trying to cast an argument as a strawman with a strawman is pretty weak. I've not presented a strawman. I've pointed out to you that people have different needs. I don't need, nor want what Puppet provides, and Etcd does not claim to provide what Puppet provides. I do, however want what Etcd provides. > You've also admitted that it's an incomplete solution In the sense that a car is an incomplete solution if you need a space shuttle. Yet the car is still more practical if you want to drive on a road. > But What's worse is that people are going to buy this and quickly they'll have to scrap it when it gets out of sync, deadlocks or can't handle more than 8 boxes. What basis do you have for that claim?

by ballard 13y ago

rdtsc 13y ago

> It doesn't coordinate the transition of services to other states. Can you be more specific? So to co-ordinate transitions what else would it need -- multi-key transactions? Surely you have good reason to jump in and criticize it so sharply...

ballard 13y ago
Configuration management transactions. Puppet has the notion of stages. Yes because it's marketing an unproven technology as a solution when better things already exist. Someone I know from (OpsCode||Puppet) even further the recommendation of zk as basically the only proven consistent KVS. A better approach should be to do what other cloud shops have done and ship ZK appliances. Pushing new tech on customers is using them to beta test unproven tech, which is reinventing the wheel and risky.

nl 13y ago

I'm not sure what problem you think etcd is attempting to solve, but if your solution involvs Puppet or Chef then it isn't surprising you find etcd isn't sufficient for your purposes. etcd is a highly available configuration store. That's all. It's designed for applications to use to store configuration, so they can be started & stopped without relying on file based storage. Generally speaking these applications have to be coded to use etcd (which is completely different to Chef/Puppet, which are Ops tools). Sure, you could do something to write etcd values to a file, and then have them used by any program, but that misses the point. Your criticisms are so completely irrelevant they aren't even wrong.

uniclaude 13y ago
No bashing against etcd from me, but can you point me to a reason why a regular database wouldn't work for this type of thing? High availability, throughput and data storage seem to fit into what a database is made for.
- nl 13y ago
  The HTTP based interface[1] is designed specifically for configuration data and is easily callable from shell scripts as well as form programs. Something like CouchDB is roughly comparable in that sense, but that has pretty different design goals. [1] https://github.com/coreos/etcd/blob/master/Documentation/api.md https://github.com/coreos/etcd/blob/master/Documentation/api...
- vidarh 13y ago
  You'd think so, but most RDBMS's are a lot of work to set up in a way that provides the kind of consistency guarantees and availability that a configuration store like this does. E.g. take Postgres. You can't connect to the slaves and write, so your client will need to know how to identify which server is currently the master. And if the master fails, you need to implement a leadership election method, promote the chosen slave, and resync your other slaves from the new master. Before you know it you've reimplemented the configuration store with a different data storage mechanism. There's very little intersection between the typical RDBMS and a configuration store like this.
  - uniclaude 13y ago
    Well, even with your point there are a couple reasons why I could imagine databases making sense here. One is that you might already have people used to deal with them in a highly available manner in your team. HA with Postgres is not exactly an area of research anymore. Most people already using Postgres in their stack know about tools like pgbouncer. Another one is that there are other databases, like Riak, that can talk http and have those problems solved. I am here more trying to understand the features that would make one pick etcd over an higly available database. Thanks for taking the time to explain.

vidarh 13y ago

> It doesn't coordinate the transition of services to other states. It's not intended to. It is way outside the scope. But you can easily coordinate transitions on top of Etcd by waiting on key changes. > Configuration management is as much management order of operations as well as what files should contain what. Outside of scope. Nothing stops you from using a configuration management engine like Puppet and triggering it on state changes by waiting for Etcd keys. It'd be trivial. Or use something other than Etcd if those are your needs. But those are not my needs. For my configuration needs there are exactly no places where I have any interest in the complexity of Puppet, but plenty of places where being able to easily set and query configuration values via a simple REST api that's trivially to access even from a bash script is nice. You're right that scp can do that. But then you're suddenly in the job of maintaining hairy scripts to push out config changes and ensure they are in sync. So Etcd provides a solution that provides that synchronization without the complexity of far more featureful solutions. To me, that is a feature. You seem to try to evaluate a handsaw as if it was a chainsaw and give it bad marks for being cumbersome to cut down trees with. Not all of us want to cut down trees.

ballard 13y ago
Trying to cast an argument as a strawman with a strawman is pretty weak. You've also admitted that it's an incomplete solution. But What's worse is that people are going to buy this and quickly they'll have to scrap it when it gets out of sync, deadlocks or can't handle more than 8 boxes.
- vidarh 13y ago
  > Trying to cast an argument as a strawman with a strawman is pretty weak. I've not presented a strawman. I've pointed out to you that people have different needs. I don't need, nor want what Puppet provides, and Etcd does not claim to provide what Puppet provides. I do, however want what Etcd provides. > You've also admitted that it's an incomplete solution In the sense that a car is an incomplete solution if you need a space shuttle. Yet the car is still more practical if you want to drive on a road. > But What's worse is that people are going to buy this and quickly they'll have to scrap it when it gets out of sync, deadlocks or can't handle more than 8 boxes. What basis do you have for that claim?