Slow-Actions is great tool for determining the slow areas of a rails application. Since it is built on a rails log parser, it can be used for many other things. For example, here is some standard output from slow-actions when you want to know the speed of different user sessions within a specific date range:

slow-actions log/development.log --sessions --start-date=2009-03-01 --end-date=2009-04-01
           Cost    Average Max
+ ece0e17b48a5fe0fc766fa42f199fb66 (51 entries, 58% Error)
| Total:   2883.262 732.948 3100.00
| Render:  0.00000 0.00000 0.00000
| DB:      55.8220 14.1900 99.0000 

+ e1181ad94b34b41aff2a74ee62d5fb57 (10 entries, 30% Error)
| Total:   1563.912 676.276 1426.00
| Render:  0.00000 0.00000 0.00000
| DB:      14.5350 6.28500 19.0000 

+ 867bc340e6d65e673f29c57189feaf2b (133 entries, 0% Error)
| Total:   1083.138 221.450 386.000
| Render:  0.00000 0.00000 0.00000
| DB:      44.2030 9.03700 90.0000 

Etc...

Now, if we grep for “entries” we get a line for each session:

slow-actions log/development.log --sessions --start-date=2009-03-01 --end-date=2009-04-01 | grep entries
+ ece0e17b48a5fe0fc766fa42f199fb66 (51 entries, 58% Error)
+ e1181ad94b34b41aff2a74ee62d5fb57 (10 entries, 30% Error)
+ 867bc340e6d65e673f29c57189feaf2b (133 entries, 0% Error)
+ 99b39c7a9af55fc01056b5f127dc4c98 (75 entries, 0% Error)
+ 6ee15c4f3bc804ac68e9e868d9c3f7e6 (14 entries, 0% Error)
+ 80928c25c83590c4f89b91f8d4c8896d (9 entries, 0% Error)
+ c78cfa1cb086b3f473015b212ca3da11 (12 entries, 0% Error)
+ 48cd02cf6544493077c84eb16821bda2 (3 entries, 66% Error)
+ ac027817dcf87d473efb54cd737b2a80 (2 entries, 0% Error)
+ dff2ca2678852b06bbb6c7ca0a85b0a9 (1 entries, 0% Error)
+ 08ed3bc031c23bd3b2572ef7ce60d066 (1 entries, 0% Error)

Pipe that to word count, and we have the number of unique sessions within a specified time period:

slow-actions log/development.log --sessions --start-date=2009-03-01 --end-date=2009-04-01 | grep entries | wc -l
11

On a 54m log file, that takes only 0.761s!