Add tomcat input plugin (#3112)

plugins/inputs/tomcat/README.md

@@ -0,0 +1,73 @@
+# Tomcat Input Plugin
+
+The Tomcat plugin collects statistics available from the tomcat manager status page from the `http://<host>/manager/status/all?XML=true URL.`
+(`XML=true` will return only xml data). See the [Tomcat documentation](https://tomcat.apache.org/tomcat-9.0-doc/manager-howto.html#Server_Status) for details of these statistics.
+
+### Configuration:
+
+```toml
+# A Telegraf plugin to collect tomcat metrics.
+[[inputs.tomcat]]
+  # A Tomcat status URI to gather stats.
+  # Default is "http://127.0.0.1:8080/manager/status/all?XML=true".
+  url = "http://127.0.0.1:8080/manager/status/all?XML=true"
+  # Credentials for status URI.
+  # Default is tomcat/s3cret.
+  username = "tomcat"
+  password = "s3cret"
+```
+
+### Measurements & Fields:
+
+- tomcat\_jvm\_memory
+    - free
+    - total
+    - max
+- tomcat\_jvm\_memorypool
+  - max\_threads
+  - current\_thread\_count
+  - current\_threads\_busy
+  - max\_time
+  - processing\_time
+  - request\_count
+  - error\_count
+  - bytes\_received
+  - bytes\_sent
+- tomcat\_connector
+  - max\_threads
+  - current\_thread\_count
+  - current\_thread\_busy
+  - max\_time
+  - processing\_time
+  - request\_count
+  - error\_count
+  - bytes\_received
+  - bytes\_sent
+
+### Tags:
+
+- tomcat\_jvm\_memorypool has the following tags:
+  - name
+  - type
+- tomcat\_connector
+  - name
+
+### Sample Queries:
+
+TODO
+
+### Example Output:
+
+```
+$ ./telegraf -config telegraf.conf -input-filter tomcat -test
+* Plugin: tomcat, Collection 1
+> tomcat_jvm_memory,host=N8-MBP free=20014352i,max=127729664i,total=41459712i 1474663361000000000
+> tomcat_jvm_memorypool,host=N8-MBP,name=Eden\ Space,type=Heap\ memory committed=11534336i,init=2228224i,max=35258368i,used=1941200i 1474663361000000000
+> tomcat_jvm_memorypool,host=N8-MBP,name=Survivor\ Space,type=Heap\ memory committed=1376256i,init=262144i,max=4390912i,used=1376248i 1474663361000000000
+> tomcat_jvm_memorypool,host=N8-MBP,name=Tenured\ Gen,type=Heap\ memory committed=28549120i,init=5636096i,max=88080384i,used=18127912i 1474663361000000000
+> tomcat_jvm_memorypool,host=N8-MBP,name=Code\ Cache,type=Non-heap\ memory committed=6946816i,init=2555904i,max=251658240i,used=6406528i 1474663361000000000
+> tomcat_jvm_memorypool,host=N8-MBP,name=Compressed\ Class\ Space,type=Non-heap\ memory committed=1966080i,init=0i,max=1073741824i,used=1816120i 1474663361000000000
+> tomcat_jvm_memorypool,host=N8-MBP,name=Metaspace,type=Non-heap\ memory committed=18219008i,init=0i,max=-1i,used=17559376i 1474663361000000000
+> tomcat_connector,host=N8-MBP,name=ajp-bio-8009 bytes_received=0i,bytes_sent=0i,current_thread_count=0i,current_threads_busy=0i,error_count=0i,max_threads=200i,max_time=0i,processing_time=0i,request_count=0i 1474663361000000000
+> tomcat_connector,host=N8-MBP,name=http-bio-8080 bytes_received=0i,bytes_sent=86435i,current_thread_count=10i,current_threads_busy=1i,error_count=2i,max_threads=200i,max_time=167i,processing_time=245i,request_count=15i 1474663361000000000
+```