GitHub-Issue#2778: Added README for CloudWatch Logs Sink (#3101)

* Adding README

Signed-off-by: Marcos Gonzalez Mayedo <[email protected]>

* Added README to sink

Signed-off-by: Marcos Gonzalez Mayedo <[email protected]>

* Added PluginFunctionality to README

Signed-off-by: Marcos Gonzalez Mayedo <[email protected]>

* Update data-prepper-plugins/cloudwatch-logs/README.md

Co-authored-by: Mark Kuhn <[email protected]>
Signed-off-by: Marcos Gonzalez Mayedo <[email protected]>

* Update data-prepper-plugins/cloudwatch-logs/README.md

Co-authored-by: Mark Kuhn <[email protected]>
Signed-off-by: Marcos Gonzalez Mayedo <[email protected]>

* Added fixes to configuration in README and example id

Signed-off-by: Marcos Gonzalez Mayedo <[email protected]>

* Added extra info in plugin functionality

Signed-off-by: Marcos Gonzalez Mayedo <[email protected]>

---------

Signed-off-by: Marcos Gonzalez Mayedo <[email protected]>
Signed-off-by: Marcos Gonzalez Mayedo <[email protected]>
Co-authored-by: Marcos Gonzalez Mayedo <[email protected]>
Co-authored-by: Mark Kuhn <[email protected]>

data-prepper-plugins/cloudwatch-logs/README.md

@@ -0,0 +1,83 @@
+# CloudWatch Logs Sink
+
+This Data Prepper sink allows the sending of log data to CloudWatch Logs via a CloudWatchLogsClient.
+
+## Usages
+
+The CloudWatch Logs sink should be configured as part of Data Prepper pipeline yaml file.
+
+## Configuration Options
+
+```
+pipeline:
+  ...
+  sink:
+    - cloudwatch_logs:
+        aws:
+          region: us-east-1
+          sts_role_arn: arn:aws:iam::123456789012:role/Data-Prepper
+          sts_header_overrides:
+            custom_header: ...
+            custom_header2: ...
+            ...
+          sts_external_id: 123ABC
+        log_group: sample_group
+        log_stream: sample_stream
+        buffer_type: in_memory
+        threshold:
+          batch_size: 10000
+          max_event_size: 256kb
+          max_request_size: 1mb
+          retry_count: 5
+          back_off_time: 500ms
+```
+
+## AWS Configuration
+
+- `region` (Optional) : A string representing the AWS region to use for credentials. Defaults to [standard SDK behavior to determine the region](https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/region-selection.html).
+
+- `sts_role_arn` (Optional) : A string representing AWS STS role to assume for requests to CloudWatchLogs. which will use the [standard SDK behavior for credentials](https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/credentials.html).
+
+- `sts_header_overrides` (Optional) : A string map representing different custom headers that can be added.
+
+- `sts_external_id` (Optional) : A string representing the external ID to attach to AssumeRole requests. Referenced here: [how to use external ID](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_create_for-user_externalid.html)
+
+## Threshold Configuration
+
+- `batch_size` (Optional) : An integer value that indicates how many events we hold until we make a call to CloudWatch Logs. Defaults to 25. (Min = 1, Max = 10000)
+
+- `max_event_size` (Optional) : A string representing the max size in bytes of the allowed events. Defaults to "256kb". (Min = "1b", Max = "256kb")
+
+- `max_request_size` (Optional) : A string representing the count or size of bytes we hold until we make a call to CloudWatch Logs. Default is "1mb". (Min = "1b", Max = "1mb")
+
+- `retry_count` (Optional) : An integer value that indicates the number of retries we make when encountering errors sending logs to CloudWatch Logs. Defaults to 5. (Min = 1, Max = 15)
+
+- `log_send_interval` (Optional) : A string representing the amount of time in seconds between making requests. Defaults to "60s". (Min = "5s", Max = "300s") 
+
+- `back_off_time` (Optional) : A string representing the amount of time in milliseconds between errored transmission re-attempts. Defaults to "500ms". (Min = "500ms", Max = "1000ms")
+
+## Buffer Type Configuration
+
+- `buffer_type` (Optional) : A string representing the type of buffer to use to hold onto events. Currently only supports `in_memory`.
+
+## Plugin Functionality
+The cloudwatch_logs sink plugin uses credentials to establish a client to CloudWatch Logs. It currently uses the current system timestamp for publishing and implements an exponential back off strategy
+for retransmission.
+
+The cloudwatch_logs sink plugin also adds an overhead of 26 bytes added to each event message. This is done by the AWS SDK when formatting the API call to CloudWatch Logs. This must be considered when setting custom
+threshold parameters.
+## Metrics
+
+### Counters
+
+* `cloudWatchLogsEventsSucceeded` - The number of log events successfully published to CloudWatch Logs.
+* `cloudWatchLogsEventsFailed` - The number of log events failed while publishing to CloudWatch Logs.
+* `cloudWatchLogsRequestsSucceeded` - The number of log requests successfully made to CloudWatch Logs.
+* `cloudWatchLogsRequestsFailed` - The number of log requests failed to reach CloudWatch Logs.
+
+## Developer Guide
+
+This plugin is compatible with Java 11. See below
+
+- [CONTRIBUTING](https://github.com/opensearch-project/data-prepper/blob/main/CONTRIBUTING.md)
+- [monitoring](https://github.com/opensearch-project/data-prepper/blob/main/docs/monitoring.md)