feature: add request handling statistics for pouch daemon

[allencloud]

Signed-off-by: Allen Sun allensun.shl@alibaba-inc.com

Ⅰ. Describe what this PR did

When called by upper systems, pouch daemon bears lots of requests there. Then what is the dealing status of all these request is a quite important dimension for evaluate whether the daemon deals them very well.

For the API layers, we plan to provide a brand new API endpoint:

GET /stats

It returns ResponseStats:

// ResponseStats ResponseStats contains all request handling result in daemon including 2xx3xx response number, 4xx and 5xx number.
// swagger:model ResponseStats

type ResponseStats struct {

	// all requests number handled by daemon no matter success or failure.
	AllRequests uint64 `json:"AllRequests,omitempty"`

	// all response number returned by daemon which is 4xx status code.
	Req4xxCount uint64 `json:"Req4xxCount,omitempty"`

	// all response number returned by daemon which is 5xx status code.
	Req5xxCount uint64 `json:"Req5xxCount,omitempty"`

	// all response number returned by daemon which is 2xx or 3xx status code.
	Req2xx3xxCount uint64 `json:"req2xx3xxCount,omitempty"`
}

If the pouchd restarts, then all the data will start from 0.

Ⅱ. Does this pull request fix one issue?

none

Ⅲ. Describe how you did it

none

Ⅳ. Describe how to verify it

none

Ⅴ. Special notes for reviews

[codecov-io]

Codecov Report

Merging #2037 into master will increase coverage by 38.6%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2037      +/-   ##
==========================================
+ Coverage   23.47%   62.08%   +38.6%     
==========================================
  Files         180      200      +20     
  Lines       15860    15547     -313     
==========================================
+ Hits         3723     9652    +5929     
+ Misses      11860     4677    -7183     
- Partials      277     1218     +941

Flag	Coverage Δ
#criv1alpha1test	33.74% <12.5%> (?)
#criv1alpha2test	34.25% <12.5%> (?)
#integrationtest	38.54% <100%> (?)
#unittest	21.98% <0%> (-1.5%)	⬇️

Impacted Files	Coverage Δ
apis/server/router.go	92.3% <100%> (+92.3%)	⬆️
apis/opts/portbindings.go	0% <0%> (-80.96%)	⬇️
storage/volume/driver/fake_driver.go	0% <0%> (-50%)	⬇️
storage/volume/types/volume_util.go	16.44% <0%> (-46.06%)	⬇️
apis/opts/spec_annotation.go	60% <0%> (-40%)	⬇️
daemon/logger/syslog/syslog.go	25% <0%> (-37.07%)	⬇️
storage/volume/core_util.go	10.34% <0%> (-32.52%)	⬇️
apis/opts/memory_swap.go	81.81% <0%> (-18.19%)	⬇️
storage/volume/driver/proxy.go	53.42% <0%> (-13.7%)	⬇️
storage/volume/driver/driver.go	44.96% <0%> (-13.24%)	⬇️
... and 169 more

[allencloud]

I think we need to review the API very carefully. @HusterWan @fuweid

[pouchrobot]

ping @allencloud
Conflict happens after merging a previous commit.
Please rebase the branch against master and push it back again. Thanks a lot.

[fuweid]

will reopen it if we need it.

cc @allencloud