Evaluating Memcached for our site. Looking for advice.

[Ben Manes]

1. Are there tools that exist to help analyze which queries should be  cached?
- I would imagine a StatsPack report would be useful.  

2. What exists  to monitoring and analyze for cache performance on a daily basis?
- DB stats, Memcached stats, as well as local cache stats if they are backed by the remote cache.

3. What level of effort was required to integrate memcached into the application?
- It depends.  For us (Rearden Commerce), we also migrated from Apache Commons caches to Ehcache as well as did some code cleanups.  But the raw integration wasn't too bad.

4. What was the support overhead from a time and expertise standpoint to maintain this?
- N/A.  We haven't deployed yet, though its been code-complete for a while.  I'd doubt it adds much overhead.  Mostly just planning for the operations team during releases, etc.

5. Are there any issues or problems in integrating and deploying the cache that are non-obvious or particularly time consuming?
- Depending on the use-case, integration can require a decent chunk of concurrency analysis (particularly regarding how stale data is treated).  Also, you should consider what happens when converting expensive select-* operations if the cache servers go down.  Such as do you get the missing key values one-by-one (assuming a single cache server went down) or fall-back to the complex query?  You probably need to re-optimize these situations if previously a lot of work went into making them perform well.

6.
- 

7. Are there any hardware requirements for the cache servers or specific hardware that perform much better in a highly loaded environment? (Perhaps specific NICs that do better then others)
- I don't know specifics, but you may find Building Scalable Web Sites and Scalable Internet Architectures good references.  I've heard that its pretty light on the CPU utilization, but you probably want to optimize the TCP/IP connection for this type of activity.


----- Original Message ----
From: Jason Gross <jphgross at gmail.com>
To: memcached at lists.danga.com
Sent: Friday, October 19, 2007 12:19:53 PM
Subject: Evaluating Memcached for our site. Looking for advice.


I am evaluating memcached for our web farm and wanted to poll this  
list for some experience in designing, deploying and maintaining it.  
Specifically I want to analyze the overhead from a development /  
resource and maintenance standpoint so that I can properly plan this  
effort. Would anyone on this list be willing to share their  
experience with deploying memcached?

The site I am working on is a social networking site that users can  
upload individual products which other users can comment on, purchase  
etc. The site is growing quite rapidly and is beginning to show  
significant slowdowns during peak periods. I have a decent  
understanding of what memcached provides and feel that its compelling  
enough to give it a try as there are a significant amount of database  
queries on each page load. I'd be interested in any feedback but have  
some specific questions below of what I am looking for.

1. Are there tools that exist to help analyze which queries should be  
cached?

2. What exists  to monitoring and analyze for cache performance on a  
daily basis?

3. What level of effort was required to integrate memcached into the  
application?

4. What was the support overhead from a time and expertise standpoint  
to maintain this?

5. Are there any issues or problems in integrating and deploying the  
cache that are non-obvious or particularly time consuming?

7. Are there any hardware requirements for the cache servers or  
specific hardware that perform much better in a highly loaded  
environment? (Perhaps specific NICs that do better then others)

Thanks!
-Jason





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