Supported logs and discovered fields

CloudWatch Logs Insights supports different log types. For every log that's sent to Amazon CloudWatch Logs, CloudWatch Logs Insights automatically generates five system fields:

• @message contains the raw unparsed log event. This is the equivalent to the message field in InputLogevent.

• @timestamp contains the event timestamp in the log event's timestamp field. This is the equivalent to the timestamp field in InputLogevent.

• @ingestionTime contains the time when CloudWatch Logs received the log event.

• @logStream contains the name of the log stream that the log event was added to. Log streams group logs through the same process that generated them.

• @log is a log group identifier in the form of account-id:log-group-name. When querying multiple log groups, this can be useful to identify which log group a particular event belongs to.

CloudWatch Logs Insights inserts the @ symbol at the start of fields that it generates.

For many log types, CloudWatch Logs also automatically discovers the log fields contained in the logs. These automatic discovery fields are shown in the following table.

For other types of logs with fields that CloudWatch Logs Insights doesn't automatically discover, you can use the parse command to extract and create ephemeral fields for use in that query. For more information, see CloudWatch Logs Insights query syntax.

If the name of a discovered log field starts with the @ character, CloudWatch Logs Insights displays it with an additional @ appended to the beginning. For example, if a log field name is @example.com, this field name is displayed as @@example.com.

Log type	Discovered log fields
Amazon VPC flow logs	@timestamp, @logStream, @message, accountId, endTime, interfaceId, logStatus, startTime, version, action, bytes, dstAddr, dstPort, packets, protocol, srcAddr, srcPort
Route 53 logs	@timestamp, @logStream, @message, edgeLocation, hostZoneId, protocol, queryName, queryTimestamp, queryType, resolverIp, responseCode, version
Lambda logs	@timestamp, @logStream, @message, @requestId, @duration, @billedDuration, @type, @maxMemoryUsed, @memorySize If a Lambda log line contains an X-Ray trace ID, it also includes the following fields: @xrayTraceId and @xraySegmentId. CloudWatch Logs Insights automatically discovers log fields in Lambda logs, but only for the first embedded JSON fragment in each log event. If a Lambda log event contains multiple JSON fragments, you can parse and extract the log fields by using the parse command. For more information, see Fields in JSON logs.
CloudTrail logs Logs in JSON format	For more information, see Fields in JSON logs.
Other log types	@timestamp, @ingestionTime, @logStream, @message, @log.

Fields in JSON logs

With CloudWatch Logs Insights, you use dot notation to represent JSON fields. This section contains an example JSON event and code snippet that show how you can access JSON fields using dot notation.

Example: JSON event

{
    "eventVersion": "1.0",
    "userIdentity": {
        "type": "IAMUser",
        "principalId": "EX_PRINCIPAL_ID",
        "arn": "arn: aws: iam: : 123456789012: user/Alice",
        "accessKeyId": "EXAMPLE_KEY_ID",
        "accountId": "123456789012",
        "userName": "Alice"
    },
    "eventTime": "2014-03-06T21: 22: 54Z",
    "eventSource": "ec2.amazonaws.com",
    "eventName": "StartInstances",
    "awsRegion": "us-east-2",
    "sourceIPAddress": "205.251.233.176",
    "userAgent": "ec2-api-tools1.6.12.2",
    "requestParameters": {
        "instancesSet": {
            "items": [
                {
                    "instanceId": "i-abcde123"
                }
            ]
        }
    },
    "responseElements": {
        "instancesSet": {
            "items": [
                {
                    "instanceId": "i-abcde123",
                    "currentState": {
                        "code": 0,
                        "name": "pending"
                    },
                    "previousState": {
                        "code": 80,
                        "name": "stopped"
                    }
                }
            ]
        }
    }
}

The example JSON event contains an object that's named userIdentity. userIdentity contains a field that's named type. To represent value of type using dot notation, you use userIdentity.type.

The example JSON event contains arrays that flatten to lists of nested field names and values. To represent the value of instanceId for the first item in requestParameters.instancesSet, you use requestParameters.instancesSet.items.0.instanceId. The number 0 that's placed before the field instanceID refers to the position of values for the field items. The following example contains a code snippet that shows how you can access nested JSON fields in a JSON log event.

Example: Query

fields @timestamp, @message
| filter requestParameters.instancesSet.items.0.instanceId="i-abcde123"
| sort @timestamp desc

The code snippet shows a query that uses dot notation with the filter command to access the value of the nested JSON field instanceId. The query filters on messages where the value of instanceId equals "i-abcde123" and returns all of the log events that contain the specified value.

Note

CloudWatch Logs Insights can extract a maximum of 200 log event fields from a JSON log. For additional fields that aren't extracted, you can use the parse command to extract the fields from the raw unparsed log event in the message field. For more information about the parse command, see Query syntax in the Amazon CloudWatch User Guide.