Add metrics to measure processing time

[masa213f]

Add metrics to measure the processing time of cluster-manager goroutines.
It may be helpful with performance tuning.

Name	Type
moco_cluster_processing_time_seconds	histogram

With this change, the moco-controller will expose the following metrics.

$ curl -sS localhost:8080/metrics | grep processing_time
# HELP moco_cluster_processing_time_seconds The length of time in seconds processing the cluster
# TYPE moco_cluster_processing_time_seconds histogram
moco_cluster_processing_time_seconds_bucket{name="cluster1",namespace="foo",le="0.1"} 7
moco_cluster_processing_time_seconds_bucket{name="cluster1",namespace="foo",le="0.25"} 19
moco_cluster_processing_time_seconds_bucket{name="cluster1",namespace="foo",le="0.5"} 19
moco_cluster_processing_time_seconds_bucket{name="cluster1",namespace="foo",le="0.75"} 19
moco_cluster_processing_time_seconds_bucket{name="cluster1",namespace="foo",le="1"} 19
moco_cluster_processing_time_seconds_bucket{name="cluster1",namespace="foo",le="2.5"} 19
moco_cluster_processing_time_seconds_bucket{name="cluster1",namespace="foo",le="5"} 19
moco_cluster_processing_time_seconds_bucket{name="cluster1",namespace="foo",le="7.5"} 19
moco_cluster_processing_time_seconds_bucket{name="cluster1",namespace="foo",le="10"} 23
moco_cluster_processing_time_seconds_bucket{name="cluster1",namespace="foo",le="20"} 23
moco_cluster_processing_time_seconds_bucket{name="cluster1",namespace="foo",le="30"} 23
moco_cluster_processing_time_seconds_bucket{name="cluster1",namespace="foo",le="+Inf"} 23
moco_cluster_processing_time_seconds_sum{name="cluster1",namespace="foo"} 38.11477838000001
moco_cluster_processing_time_seconds_count{name="cluster1",namespace="foo"} 23
moco_cluster_processing_time_seconds_bucket{name="cluster2",namespace="bar",le="0.1"} 11
moco_cluster_processing_time_seconds_bucket{name="cluster2",namespace="bar",le="0.25"} 65
moco_cluster_processing_time_seconds_bucket{name="cluster2",namespace="bar",le="0.5"} 65
moco_cluster_processing_time_seconds_bucket{name="cluster2",namespace="bar",le="0.75"} 66
moco_cluster_processing_time_seconds_bucket{name="cluster2",namespace="bar",le="1"} 66
moco_cluster_processing_time_seconds_bucket{name="cluster2",namespace="bar",le="2.5"} 66
moco_cluster_processing_time_seconds_bucket{name="cluster2",namespace="bar",le="5"} 66
moco_cluster_processing_time_seconds_bucket{name="cluster2",namespace="bar",le="7.5"} 66
moco_cluster_processing_time_seconds_bucket{name="cluster2",namespace="bar",le="10"} 73
moco_cluster_processing_time_seconds_bucket{name="cluster2",namespace="bar",le="20"} 73
moco_cluster_processing_time_seconds_bucket{name="cluster2",namespace="bar",le="30"} 73
moco_cluster_processing_time_seconds_bucket{name="cluster2",namespace="bar",le="+Inf"} 73
moco_cluster_processing_time_seconds_sum{name="cluster2",namespace="bar"} 70.92830542099993
moco_cluster_processing_time_seconds_count{name="cluster2",namespace="bar"} 73

Signed-off-by: Masayuki Ishii masa213f@gmail.com