I have published an InfoQ news post about AWS's expansion of log based CloudWatch metrics and alarms to JSON formatted logs and API events:
Shortly after releasing the AWS CloudTrail Processing Library (CPL), Amazon Web Services has also integrated AWS CloudTrail with Amazon CloudWatch Logs to enable alarms and respective "notifications from CloudWatch, triggered by specific API activity captured by CloudTrail". The implied support for monitoring JSON-formatted logs has recently been officially released as well.
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Continue reading the full post in Amazon CloudWatch Supports JSON Logs and Integrates AWS CloudTrail.