Update changelog

(cherry picked from commit d900a35839170e30ddf28b855611e2c5aec99343)

CHANGELOG.md

@@ -1,3 +1,17 @@
+## v1.18.2 [2021-04-28]
+
+#### Bugfixes
+
+  - [#9160](https://github.com/influxdata/telegraf/pull/9160) `processors.converter` Add support for large hexadecimal strings
+  - [#9195](https://github.com/influxdata/telegraf/pull/9195) `inputs.apcupsd` Fix apcupsd 'ALARMDEL' bug via forked repo
+  - [#9110](https://github.com/influxdata/telegraf/pull/9110) `parsers.json` Make JSON format compatible with nulls
+  - [#9128](https://github.com/influxdata/telegraf/pull/9128) `inputs.nfsclient` Fix nfsclient ops map to allow collection of metrics other than read and write
+  - [#8917](https://github.com/influxdata/telegraf/pull/8917) `inputs.snmp` Log snmpv3 auth failures
+  - [#8892](https://github.com/influxdata/telegraf/pull/8892) `common.shim` Accept larger inputs from scanner
+  - [#9045](https://github.com/influxdata/telegraf/pull/9045) `inputs.vsphere` Add MetricLookback setting to handle reporting delays in vCenter 6.7 and later
+  - [#9026](https://github.com/influxdata/telegraf/pull/9026) `outputs.sumologic` Carbon2 serializer: sanitize metric name
+  - [#9086](https://github.com/influxdata/telegraf/pull/9086) `inputs.opcua` Fix error handling
+
 ## v1.18.1 [2021-04-07]
 
 #### Bugfixes

etc/telegraf.conf

@@ -8164,6 +8164,12 @@
 #   # custom_attribute_include = []
 #   # custom_attribute_exclude = ["*"]
 #
+#   ## The number of vSphere 5 minute metric collection cycles to look back for non-realtime metrics. In
+#   ## some versions (6.7, 7.0 and possible more), certain metrics, such as cluster metrics, may be reported
+#   ## with a significant delay (>30min). If this happens, try increasing this number. Please note that increasing
+#   ## it too much may cause performance issues.
+#   # metric_lookback = 3
+#
 #   ## Optional SSL Config
 #   # ssl_ca = "/path/to/cafile"
 #   # ssl_cert = "/path/to/certfile"