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Overview

rtime is a passive TCP response time analysis tool. It watches traffic to and from a specified port and measures the time elapsed from an incoming request to the outgoing response. It periodically prints out a report on the number and response time of these requests.

Major Functionality

The functionality is best explained with an example. To watch MySQL’s traffic on port 3306,

# rtime --port 3306 --iterations 2
        ts count     sum    max  min  avg  med stdev 95_max 95_avg 95_med 95_stdev 99_max 99_avg 99_med 99_stdev
1274149776   123  812928 128193 1293 6609 6003   182  11023   5012   4938      102  83223   6038   5832      138
1274149786  1829 1929823 122933 1391 1055 5823   198  12293   5219   5023      130  67230   5829   5223      132

The columns are as follows. Except for the first two columns, everything is measured in microseconds, and pertains to the sample gathered during the time since the last line was printed.

• ts is the Unix timestamp at the end of the period.
• count is how many requests were captured during the period.
• sum is the total response time (referred to as R after this, again, in microseconds).
• max is the maximum R.
• min is the minimum R.
• avg is the total divided by the count.
• med is the median — the middle of the sorted list.
• stdev is the sample standard deviation.
• 95_max, 95_avg, 95_med, 95_stdev are the respective metrics over the population with the largest 5% discarded.
• 99_max and similar are over the population with the largest 1% discarded.

Options

• —port which port to watch
• —interval (default 10) how often, in seconds, to print a line
• —iterations (default 1) how many reports to print out; 0 means infinity