Add jenkins input plugin (#4289)

plugins/inputs/jenkins/README.md

@@ -0,0 +1,96 @@
+# Jenkins Plugin
+
+The jenkins plugin gathers information about the nodes and jobs running in a jenkins instance.
+
+This plugin does not require a plugin on jenkins and it makes use of Jenkins API to retrieve all the information needed.
+
+### Configuration:
+
+```toml
+  ## The Jenkins URL
+  url = "http://my-jenkins-instance:8080"
+  #  username = "admin"
+  #  password = "admin"
+
+  ## Set response_timeout
+  response_timeout = "5s"
+
+  ## Optional SSL Config
+  #  ssl_ca = /path/to/cafile
+  #  ssl_cert = /path/to/certfile
+  #  ssl_key = /path/to/keyfile
+  ## Use SSL but skip chain & host verification
+  #  insecure_skip_verify = false
+
+  ## Optional Max Job Build Age filter
+  ## Default 1 hour, ignore builds older than max_build_age
+  #  max_build_age = "1h"
+
+  ## Optional Sub Job Depth filter
+  ## Jenkins can have unlimited layer of sub jobs
+  ## This config will limit the layers of pulling, default value 0 means
+  ## unlimited pulling until no more sub jobs
+  #  max_subjob_depth = 0
+
+  ## Optional Sub Job Per Layer
+  ## In workflow-multibranch-plugin, each branch will be created as a sub job.
+  ## This config will limit to call only the lasted branches in each layer,
+  ## empty will use default value 10
+  #  max_subjob_per_layer = 10
+
+  ## Jobs to exclude from gathering
+  #  job_exclude = [ "job1", "job2/subjob1/subjob2", "job3/*"]
+
+  ## Nodes to exclude from gathering
+  #  node_exclude = [ "node1", "node2" ]
+
+  ## Worker pool for jenkins plugin only
+  ## Empty this field will use default value 5
+  #  max_connections = 5
+```
+
+### Metrics:
+
+- jenkins_node
+  - tags:
+    - arch
+    - disk_path
+    - temp_path
+    - node_name
+    - status ("online", "offline")
+  - fields:
+    - disk_available
+    - temp_available
+    - memory_available
+    - memory_total
+    - swap_available
+    - swap_total
+    - response_time
+
+- jenkins_job
+  - tags:
+    - name
+    - parents
+    - result
+  - fields:
+    - duration
+    - result_code (0 = SUCCESS, 1 = FAILURE, 2 = NOT_BUILD, 3 = UNSTABLE, 4 = ABORTED)
+
+### Sample Queries:
+
+```
+SELECT mean("memory_available") AS "mean_memory_available", mean("memory_total") AS "mean_memory_total", mean("temp_available") AS "mean_temp_available" FROM "jenkins_node" WHERE time > now() - 15m GROUP BY time(:interval:) FILL(null)
+```
+
+```
+SELECT mean("duration") AS "mean_duration" FROM "jenkins_job" WHERE time > now() - 24h GROUP BY time(:interval:) FILL(null)
+```
+
+### Example Output:
+
+```
+$ ./telegraf --config telegraf.conf --input-filter jenkins --test
+jenkins_node,arch=Linux\ (amd64),disk_path=/var/jenkins_home,temp_path=/tmp,host=myhost,node_name=master swap_total=4294963200,memory_available=586711040,memory_total=6089498624,status=online,response_time=1000i,disk_available=152392036352,temp_available=152392036352,swap_available=3503263744 1516031535000000000
+jenkins_job,host=myhost,name=JOB1,parents=apps/br1,result=SUCCESS duration=2831i,result_code=0i 1516026630000000000
+jenkins_job,host=myhost,name=JOB2,parents=apps/br2,result=SUCCESS duration=2285i,result_code=0i 1516027230000000000
+```