HN Explorer

Ask HN: would you use a shared memcached hosted on popular VPS sites?

7 points by ritonlajoie ↗ HN
Hi HNers.

I wondered what are is your opinion on something that might be useful for VPS users. Take Linode as an example: the traffic between linode VPS is free inside the same datacenter.

Regarding memcache, when you need another memcached node, you would need to pay another VPS, only for the RAM. On Linode the ram cost is exactly 25.6 MB/$ no matter the plan you choose.

Imagine a service that would let you rent a shared memcached server for, say, 5 dollar to access a (max) 400MB memcached. Each memcached server would be limited to, say, 10 users. You would then have access to potentialy tens of MB from a fast memcached near your existing VPS at Linode.

This memcached would be shared: you would need to have unique keys, prefixed, for example, by a unique string. You could not store sensitive data on it, as anyone could read/destroy your cache, but depending on your application, that could not be a problem for you. I hear you, you are thinking : but that's not useable! What if everyong is deleting my cache the whole time ? Well, I answer you : there must be a way to avoid that ! SASL is one answer. That's not the question right now as I'm just thinking about the interest of people in such a thing.

Would you use such a service ? How much are you willing to pay to have access to such a memcached shared instance?

Thanks for taking the time to reply ! Contact me on #startups (nick henri) if you want to chat :)

ps: the goals would be to have many memcached servers in the different linode datacenters, as well as EC2, slicehost, etc..

14 comments

[ 3.6 ms ] story [ 39.9 ms ] thread
tptacek
I'd have grave concerns about the security/integrity of data I stored in such a thing. People tend to store low-value data in memcache without realizing that corrupting it allows attackers to hijack user sessions.

What is the value of sharing a memcached instance? If all you're selling is memory, why not just run multiple memcacheds?

ritonlajoie
Well, the thing is that today if you want a memcache on Linode, you need to rent another node. A linode 512MB is 20$/month.

But what If i only need 100MB of memcached, and I don't want to pay 20$/month for that ?

Sure, one could sell memcached memory, with many instances per linode node. But my question is more about getting super-lower memcached for not critical data (if people put sessions in it, they misuse the service, they take their risks..). By sharing the bucket with people, can you afford to pay 5$/month for a part of a 400MB bucket ?

mooism2
Can you not run multiple memcached instances on the same node? Wouldn't this lower the cost just as much?
ritonlajoie
you can, but then it's like partitionned. I'm not sure people would pay for 50 or 100MB memcached near their VPS. That's another question.
petervandijck
I'd try it out, yes. Preferably simply priced, low enough for me not to have to consider running it myself (which is easy enough as well). I think Amazon let's you price something like this through them and the bill is just part of your aws bill? That would work for me.
jmathai
It's an interesting idea to consider. Assuming that it is reliable and secure I would be interested. If Lonode offered it, for example - because I trust them enough.

Instead of having to worry about adding a new memcache host I'd also love if you could handle it on your end. If all of a sudden I need a crapton of memory my mcahe would "expand". I'd get charged for that crapton.

Just some ideas brainstorming.

jmathai
Another idea would be to have really good reports so I can see cache misses, num of reads, num of writes etc. Having that in a nice we GUI would be great.

Basically, make it easy for me to optimize my cache store:).

moe
Sorry, makes no sense to me.

If your app needs a memcached instance then those $20 bucks are likely a rounding error on the hosting bill either way.

And If you just want one for testing then a tiny <50M memcached on the local instance will carry you a long way.

Even ignoring the glaring security and technical concerns, I just don't see a use-case for this.

ritonlajoie
on heroku they offer highly priced memcache.They offer 5mb for free,thats enough for me to think there is a usecase (at the time of my thoughts..)
drdaeman
IMHO technically memcached is best when used locally on LAN, not somewhere on the 'net where latency is high and security is less strict - and memcached has neither encryption nor secure authentication support.
ritonlajoie
Well thats why i am saying that.About having these memcache running in the internal linode network
mahmud
People with scalability problems that need to use memcached don't usually worry about RAM costs, or for that matter host on a VPS.
rograndom
You can limit each memcached instance to only accept connections from a single IP address or a range of IPs. That would clear up a lot of the security concerns. Maybe instead of having everyone share the 400mb, you could rent 50/100mb chunks.