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Amazon CloudWatch Logs
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Example: Count Log Events

The simplest type of log event monitoring is to count the number of log events that occur. You might want to do this to keep a count of all events, to create a "heartbeat" style monitor or just to practice creating metric filters.

In the following CLI example, a metric filter called MyAppAccessCount is applied to the log group MyApp/access.log to create the metric EventCount in the CloudWatch namespace MyNamespace. The filter is configured to match any log event content and to increment the metric by "1".

To create a metric filter using the CloudWatch console

  1. Open the CloudWatch console at https://console.aws.amazon.com/cloudwatch/.

  2. In the navigation pane, choose Logs.

  3. In the contents pane, select a log group, and then choose Create Metric Filter.

  4. On the Define Logs Metric Filter screen, leave Filter Pattern blank.

  5. Choose Assign Metric, and then on the Create Metric Filter and Assign a Metric screen, for Filter Name, type EventCount.

  6. Under Metric Details, for Metric Namespace, type MyNameSpace.

  7. For Metric Name, type MyAppEventCount.

  8. Choose Show advanced metric settings and confirm that Metric Value is 1. This specifies that the count is incremented by 1 for every log event.

  9. For Default Value type 0, and then choose Create Filter. Specifying a default value ensures that data is reported even during periods when no log events occur, preventing spotty metrics where data sometimes does not exist.

To create a metric filter using the AWS CLI

At a command prompt, run the following command:

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aws logs put-metric-filter \ --log-group-name MyApp/access.log \ --filter-name EventCount \ --filter-pattern "" \ --metric-transformations \ metricName=MyAppEventCount,metricNamespace=MyNamespace,metricValue=1,defaultValue=0

You can test this new policy by posting any event data. You should see data points published to the metric MyAppAccessEventCount.

To post event data using the AWS CLI

At a command prompt, run the following command:

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aws logs put-log-events \ --log-group-name MyApp/access.log --log-stream-name TestStream1 \ --log-events \ timestamp=1394793518000,message="Test event 1" \ timestamp=1394793518000,message="Test event 2" \ timestamp=1394793528000,message="This message also contains an Error"