What anti-pattern are you mocking me for exactly?
Sean Durity From: daemeon reiydelle [mailto:daeme...@gmail.com] Sent: Tuesday, February 23, 2016 11:21 AM To: user@cassandra.apache.org Subject: RE: Restart Cassandra automatically Cassandra nodes do not go down "for no reason". They are not stateless. I would like to thank you for this marvelous example of a wonderful antipattern. Absolutely fantastic. Thank you! I am not being a satirical smartass. I sometimes am challenged by clients in my presentations about sre best practices around c*, hadoop, and elk on the grounds that "noone would ever do this in production". Now I have objective proof! Daemeon sent from my mobile Daemeon C.M. Reiydelle USA 415.501.0198 London +44.0.20.8144.9872 On Feb 23, 2016 7:53 AM, <sean_r_dur...@homedepot.com<mailto:sean_r_dur...@homedepot.com>> wrote: Yes, I can see the potential problem in theory. However, we never do your #2. Generally, we don’t have unused spare hardware. We just fix the host that is down and run repairs. (Side note: while I have seen nodes fight it out over who owns a particular token in earlier versions, it seems that 1.2+ doesn’t allow that to happen as easily. The second node will just not come up.) For most of our use cases, I would agree with your Coli Conjecture. Sean Durity From: Robert Coli [mailto:rc...@eventbrite.com<mailto:rc...@eventbrite.com>] Sent: Tuesday, February 09, 2016 4:41 PM To: user@cassandra.apache.org<mailto:user@cassandra.apache.org> Subject: Re: Restart Cassandra automatically On Tue, Feb 9, 2016 at 6:20 AM, <sean_r_dur...@homedepot.com<mailto:sean_r_dur...@homedepot.com>> wrote: Call me naïve, but we do use an in-house built program for keeping nodes started (based on a flag-check). The program is something that was written for all kinds of daemon processes here, not Cassandra specifically. The basic idea is that is runs a status check. If that fails, and the flag is set, start Cassandra. In my opinion, it has helped more than hurt us – especially with the very fragile 1.1 releases that were prone to heap problems. Ok, you're naïve.. ;P But seriously, think of this scenario : 1) Node A, responsible for range A-M, goes down due to hardware failure of a disk in a RAID 2) Node B is put into service and is made responsible for A-M 3) Months pass 4) Node A comes back up, announces that it is responsible for A-M, and the cluster agrees Consistency is now permanently broken for any involved rows. Why doesn't it (usually) matter? It's not so much that you are naïve but that you are providing still more support for the Coli Conjecture : "If you are using a distributed database you probably do not care about consistency, even if you think you do." You have repeatedly chosen Availability over Consistency and it has never had a negative impact on your actual application. =Rob ________________________________ The information in this Internet Email is confidential and may be legally privileged. It is intended solely for the addressee. Access to this Email by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution or any action taken or omitted to be taken in reliance on it, is prohibited and may be unlawful. When addressed to our clients any opinions or advice contained in this Email are subject to the terms and conditions expressed in any applicable governing The Home Depot terms of business or client engagement letter. The Home Depot disclaims all responsibility and liability for the accuracy and content of this attachment and for any damages or losses arising from any inaccuracies, errors, viruses, e.g., worms, trojan horses, etc., or other items of a destructive nature, which may be contained in this attachment and shall not be liable for direct, indirect, consequential or special damages in connection with this e-mail message or its attachment. ________________________________ The information in this Internet Email is confidential and may be legally privileged. It is intended solely for the addressee. Access to this Email by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution or any action taken or omitted to be taken in reliance on it, is prohibited and may be unlawful. When addressed to our clients any opinions or advice contained in this Email are subject to the terms and conditions expressed in any applicable governing The Home Depot terms of business or client engagement letter. The Home Depot disclaims all responsibility and liability for the accuracy and content of this attachment and for any damages or losses arising from any inaccuracies, errors, viruses, e.g., worms, trojan horses, etc., or other items of a destructive nature, which may be contained in this attachment and shall not be liable for direct, indirect, consequential or special damages in connection with this e-mail message or its attachment.
