Understanding the graphite response (datapoint) for a summarize query for last 24 hours

Request:

http://example.com:8081/render?format=json&target=summarize(stats.development.com.xxx.operation.yyy.*.*.rate, "24hours", "sum", true)&from=-24hours&tz=UTC

Response:

[{"datapoints":[[0.1,1386198900]],"target":"summarize(stats.development.com.xxx.operation.yyy.5.4.rate, "24hours", "sum", true)"}]

What I wanted was the summary of last 24hours for the stat provided in query.

Can you please interpret "datapoint" for me?
What does "0.1" mean? What is its logarithmic scale?
What does 1386198900 mean?

Solution

[{
  "datapoints" : 
              [[0.1,1386198900]], 
  "target":
              "summarize(stats.development.com.xxx.operation.yyy.5.4.rate, "24hours", "sum", true)"
}]

Here, datapoints sent to the metric stats.development.com.xxx.operation.yyy.5.4.rate, when numerically summed on a 24 hour basis, is 0.1 for the epoch 1386198900, which is the system's way of saying Wed, 04 Dec 2013 23:15:00 GMT. The logarithmic scale is not involved here.

Consider the following example-

You create a metric- website.about-us-page.hits and start sending data every 10 seconds-

1386198900: 3
1386198910: 23
1386198920: 12
1386198930: 1
1386198940: 0
1386198950: 180
1386198960: 12

This URL API request to graphite- target=summarize(stats.website.about-us-page.hits, "20seconds", "sum", true) will return something like-

[{
  "datapoints" : 
              [[26,1386198900]], // sum of first two points
              [[13,1386198920]], // sum of next two points
              [[180,1386198940]],
              [[12,1386198960]], 
  "target":
              "summarize(stats.website.about-us-page.hits, "20seconds", "sum", true)"
}]

summarize() basically helps you see the data in different granularity. Like in cases when you need to know day-wise or hour-wise traffic, rather than on a 10s basis.