Modularize the whole thing (#16)

* Use channels, add a metric router, split up configuration and use extended version of Influx line protocol internally

* Use central timer for collectors and router. Add expressions to router

* Add expression to router config

* Update entry points

* Start with README

* Update README for CCMetric

* Formatting

* Update README.md

* Add README for MultiChanTicker

* Add README for MultiChanTicker

* Update README.md

* Add README to metric router

* Update main README

* Remove SinkEntity type

* Update README for sinks

* Update go files

* Update README for receivers

* Update collectors README

* Update collectors README

* Use seperate page per collector

* Fix for tempstat page

* Add docs for customcmd collector

* Add docs for ipmistat collector

* Add docs for topprocs collector

* Update customCmdMetric.md

* Use seconds when calculating LIKWID metrics

* Add IB metrics ib_recv_pkts and ib_xmit_pkts

* Drop domain part of host name

* Updated to latest stable version of likwid

* Define source code dependencies in Makefile

* Add GPFS / IBM Spectrum Scale collector

* Add vet and staticcheck make targets

* Add vet and staticcheck make targets

* Avoid go vet warning:
struct field tag `json:"..., omitempty"` not compatible with reflect.StructTag.Get: suspicious space in struct tag value
struct field tag `json:"...", omitempty` not compatible with reflect.StructTag.Get: key:"value" pairs not separated by spaces

* Add sample collector to README.md

* Add CPU frequency collector

* Avoid staticcheck warning: redundant return statement

* Avoid staticcheck warning: unnecessary assignment to the blank identifier

* Simplified code

* Add CPUFreqCollectorCpuinfo
a metric collector to measure the current frequency of the CPUs
as obtained from /proc/cpuinfo
Only measure on the first hyperthread

* Add collector for NFS clients

* Move publication of metrics into Flush() for NatsSink

* Update GitHub actions

* Refactoring

* Avoid vet warning: Println arg list ends with redundant newline

* Avoid vet warning struct field commands has json tag but is not exported

* Avoid vet warning: return copies lock value.

* Corrected typo

* Refactoring

* Add go sources in internal/...

* Bad separator in Makefile

* Fix Infiniband collector

Co-authored-by: Holger Obermaier <40787752+ho-ob@users.noreply.github.com>

collectors/memstatMetric.md

@@ -0,0 +1,27 @@
+
+## `memstat` collector
+
+```json
+  "memstat": {
+    "exclude_metrics": [
+      "mem_used"
+    ]
+  }
+```
+
+The `memstat` collector reads data from `/proc/meminfo` and outputs a handful **node** metrics. If a metric is not required, it can be excluded from forwarding it to the sink.
+
+
+Metrics:
+* `mem_total`
+* `mem_sreclaimable`
+* `mem_slab`
+* `mem_free`
+* `mem_buffers`
+* `mem_cached`
+* `mem_available`
+* `mem_shared`
+* `swap_total`
+* `swap_free`
+* `mem_used` = `mem_total` - (`mem_free` + `mem_buffers` + `mem_cached`)
+