Right now BenchmarkCleaner allocates hundreds of strings on every request with an exception. This patch moves those strings to be generated at boot once and re-used.
## Bench Methods
I took a modified form of CodeTriage https://github.com/schneems/codetriage-ko1-test-app/blob/master/perf.rake and ran given rake tasks with and without the patch to BacktraceCleaner.
I made an endpoint results in exception
```
def index
raise “foo"
end
```
The gem `memory_profiler` was used to capture objects allocated for a single request. Then `benchmark/ips` was used to test the speed of the patch.
You will see that we use less objects and the code becomes measurably faster with this patch.
## With patch:
Memory for one request:
```
Total allocated 7441
Total retained 37
```
Requests per second:
```
Calculating -------------------------------------
ips 4 i/100ms
-------------------------------------------------
ips 43.0 (±4.7%) i/s - 216 in 5.037733s
```
## Without patch:
Memory used for one request:
```
Total allocated 11599
Total retained 35
```
Requests per second:
```
Calculating -------------------------------------
ips 3 i/100ms
-------------------------------------------------
ips 39.4 (±7.6%) i/s - 198 in 5.052783s
```
## Analysis
The patch is faster:
```
(43.0 - 39.4 ) / 39.4 * 100
# => 9 # % ~ speed bump
```
It also allocates less objects:
```
11599 - 7441
# => 4158
```
These strings are allocated on __EVERY SINGLE REQUEST__. This patch saves us 4158 objects __PER REQUEST__ with exception.
Faster errors == Faster applications
Add a prefix argument to filter_backtrace_with_cleaning so it has
the same arity as test/unit's filter_backtrace.
Signed-off-by: David Heinemeier Hansson <david@loudthinking.com>
