docs: Clarify how to use a client with InfluxDB 1.8 (#35)

CHANGELOG.md

@@ -1,8 +1,13 @@
 ## 1.3.0 [unreleased]
 
 ### Features
+
 1. [#32](https://github.com/influxdata/influxdb-client-ruby/pull/32): Checks the health of a running InfluxDB instance by querying the /health
 
+### Documentation
+
+1. [#35](https://github.com/influxdata/influxdb-client-ruby/pull/35): Clarify how to use a client with InfluxDB 1.8
+
 ## 1.2.0 [2020-03-13]
 
 ### Features
@@ -13,7 +18,7 @@
 ### Security
 1. [#29](https://github.com/influxdata/influxdb-client-ruby/pull/29): Upgrade rake to version 12.3.3 - [CVE-2020-8130](https://github.com/advisories/GHSA-jppv-gw3r-w3q8)
 
-### Bugs
+### Bug Fixes
 1. [#22](https://github.com/influxdata/influxdb-client-ruby/pull/22): Fixed batch write
 1. [#28](https://github.com/influxdata/influxdb-client-ruby/pull/28): Correctly parse CSV where multiple results include multiple tables
 1. [#30](https://github.com/influxdata/influxdb-client-ruby/pull/30): Send Content-Type headers

README.md

@@ -10,7 +10,7 @@
 
 This repository contains the reference Ruby client for the InfluxDB 2.0.
 
-#### Note: Use this client library with InfluxDB 2.x and InfluxDB 1.8+. For connecting to InfluxDB 1.7 or earlier instances, use the [influxdb-ruby](https://github.com/influxdata/influxdb-ruby) client library.
+#### Note: Use this client library with InfluxDB 2.x and InfluxDB 1.8+ ([see details](#influxdb-18-api-compatibility)). For connecting to InfluxDB 1.7 or earlier instances, use the [influxdb-ruby](https://github.com/influxdata/influxdb-ruby) client library.
 
 ## Installation
 
@@ -237,6 +237,20 @@ The time range could be specified as:
 
 Server availability can be checked using the `client.health` method. That is equivalent of the [influx ping](https://v2.docs.influxdata.com/v2.0/reference/cli/influx/ping/).
 
+### InfluxDB 1.8 API compatibility
+
+[InfluxDB 1.8.0 introduced forward compatibility APIs](https://docs.influxdata.com/influxdb/latest/tools/api/#influxdb-2-0-api-compatibility-endpoints) for InfluxDB 2.0. This allow you to easily move from InfluxDB 1.x to InfluxDB 2.0 Cloud or open source.
+
+The following forward compatible APIs are available:
+
+| API | Endpoint | Description |
+|:----------|:----------|:----------|
+| [query_api.rb](lib/influxdb2/client/query_api.rb) | [/api/v2/query](https://docs.influxdata.com/influxdb/latest/tools/api/#api-v2-query-http-endpoint) | Query data in InfluxDB 1.8.0+ using the InfluxDB 2.0 API and [Flux](https://docs.influxdata.com/flux/latest/) _(endpoint should be enabled by [`flux-enabled` option](https://docs.influxdata.com/influxdb/latest/administration/config/#flux-enabled-false))_  |
+| [write_api.rb](lib/influxdb2/client/write_api.rb) | [/api/v2/write](https://docs.influxdata.com/influxdb/latest/tools/api/#api-v2-write-http-endpoint) | Write data to InfluxDB 1.8.0+ using the InfluxDB 2.0 API |
+| [health_api.rb](lib/influxdb2/client/health_api.rb) | [/health](https://docs.influxdata.com/influxdb/latest/tools/api/#health-http-endpoint) | Check the health of your InfluxDB instance |    
+
+For detail info see [InfluxDB 1.8 example](examples/influxdb_18_example.rb).
+
 ## Local tests
 
 ```

examples/influxdb_18_example.rb

@@ -0,0 +1,35 @@
+$LOAD_PATH.unshift File.expand_path('../lib', __dir__)
+require 'influxdb2/client'
+
+username = 'username'
+password = 'password'
+
+database = 'telegraf'
+retention_policy = 'autogen'
+
+bucket = "#{database}/#{retention_policy}"
+
+client = InfluxDB2::Client.new('http://localhost:8086',
+                               "#{username}:#{password}",
+                               bucket: bucket,
+                               org: '-',
+                               use_ssl: false,
+                               precision: InfluxDB2::WritePrecision::NANOSECOND)
+
+puts '*** Write Points ***'
+
+write_api = client.create_write_api
+point = InfluxDB2::Point.new(name: 'mem')
+                        .add_tag('host', 'host1')
+                        .add_field('used_percent', 21.43234543)
+puts point.to_line_protocol
+write_api.write(data: point)
+
+puts '*** Query Points ***'
+
+query_api = client.create_query_api
+query = "from(bucket: \"#{bucket}\") |> range(start: -1h)"
+result = query_api.query(query: query)
+result[0].records.each { |record| puts "#{record.time} #{record.measurement}: #{record.field} #{record.value}" }
+
+client.close!