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StartLiveTailCommand
Starts a Live Tail streaming session for one or more log groups. A Live Tail session returns a stream of log events that have been recently ingested in the log groups. For more information, see Use Live Tail to view logs in near real time .
The response to this operation is a response stream, over which the server sends live log events and the client receives them.
The following objects are sent over the stream:
-
A single LiveTailSessionStart object is sent at the start of the session.
-
Every second, a LiveTailSessionUpdate object is sent. Each of these objects contains an array of the actual log events.
If no new log events were ingested in the past second, the
LiveTailSessionUpdate
object will contain an empty array.The array of log events contained in a
LiveTailSessionUpdate
can include as many as 500 log events. If the number of log events matching the request exceeds 500 per second, the log events are sampled down to 500 log events to be included in eachLiveTailSessionUpdate
object.If your client consumes the log events slower than the server produces them, CloudWatch Logs buffers up to 10
LiveTailSessionUpdate
events or 5000 log events, after which it starts dropping the oldest events. -
A SessionStreamingException object is returned if an unknown error occurs on the server side.
-
A SessionTimeoutException object is returned when the session times out, after it has been kept open for three hours.
The StartLiveTail
API routes requests to streaming-logs.Region.amazonaws.com
using SDK host prefix injection. VPC endpoint support is not available for this API.
You can end a session before it times out by closing the session stream or by closing the client that is receiving the stream. The session also ends if the established connection between the client and the server breaks.
For examples of using an SDK to start a Live Tail session, see Start a Live Tail session using an Amazon Web Services SDK .
Example Syntax
Use a bare-bones client and the command you need to make an API call.
import { CloudWatchLogsClient, StartLiveTailCommand } from "@aws-sdk/client-cloudwatch-logs"; // ES Modules import
// const { CloudWatchLogsClient, StartLiveTailCommand } = require("@aws-sdk/client-cloudwatch-logs"); // CommonJS import
const client = new CloudWatchLogsClient(config);
const input = { // StartLiveTailRequest
logGroupIdentifiers: [ // StartLiveTailLogGroupIdentifiers // required
"STRING_VALUE",
],
logStreamNames: [ // InputLogStreamNames
"STRING_VALUE",
],
logStreamNamePrefixes: [
"STRING_VALUE",
],
logEventFilterPattern: "STRING_VALUE",
};
const command = new StartLiveTailCommand(input);
const response = await client.send(command);
// { // StartLiveTailResponse
// responseStream: { // StartLiveTailResponseStream Union: only one key present
// sessionStart: { // LiveTailSessionStart
// requestId: "STRING_VALUE",
// sessionId: "STRING_VALUE",
// logGroupIdentifiers: [ // StartLiveTailLogGroupIdentifiers
// "STRING_VALUE",
// ],
// logStreamNames: [ // InputLogStreamNames
// "STRING_VALUE",
// ],
// logStreamNamePrefixes: [
// "STRING_VALUE",
// ],
// logEventFilterPattern: "STRING_VALUE",
// },
// sessionUpdate: { // LiveTailSessionUpdate
// sessionMetadata: { // LiveTailSessionMetadata
// sampled: true || false,
// },
// sessionResults: [ // LiveTailSessionResults
// { // LiveTailSessionLogEvent
// logStreamName: "STRING_VALUE",
// logGroupIdentifier: "STRING_VALUE",
// message: "STRING_VALUE",
// timestamp: Number("long"),
// ingestionTime: Number("long"),
// },
// ],
// },
// SessionTimeoutException: { // SessionTimeoutException
// message: "STRING_VALUE",
// },
// SessionStreamingException: { // SessionStreamingException
// message: "STRING_VALUE",
// },
// },
// };
StartLiveTailCommand Input
Parameter | Type | Description |
---|
Parameter | Type | Description |
---|---|---|
logGroupIdentifiers Required | string[] | undefined | An array where each item in the array is a log group to include in the Live Tail session. Specify each log group by its ARN. If you specify an ARN, the ARN can't end with an asterisk (*). You can include up to 10 log groups. |
logEventFilterPattern | string | undefined | An optional pattern to use to filter the results to include only log events that match the pattern. For example, a filter pattern of Regular expression filter patterns are supported. For more information about filter pattern syntax, see Filter and Pattern Syntax . |
logStreamNamePrefixes | string[] | undefined | If you specify this parameter, then only log events in the log streams that have names that start with the prefixes that you specify here are included in the Live Tail session. If you specify this field, you can't also specify the You can specify this parameter only if you specify only one log group in |
logStreamNames | string[] | undefined | If you specify this parameter, then only log events in the log streams that you specify here are included in the Live Tail session. If you specify this field, you can't also specify the You can specify this parameter only if you specify only one log group in |
StartLiveTailCommand Output
Parameter | Type | Description |
---|
Parameter | Type | Description |
---|---|---|
$metadata Required | ResponseMetadata | Metadata pertaining to this request. |
responseStream | AsyncIterable<StartLiveTailResponseStream> | undefined | An object that includes the stream returned by your request. It can include both log events and exceptions. |
Throws
Name | Fault | Details |
---|
Name | Fault | Details |
---|---|---|
AccessDeniedException | client | You don't have sufficient permissions to perform this action. |
InvalidOperationException | client | The operation is not valid on the specified resource. |
InvalidParameterException | client | A parameter is specified incorrectly. |
LimitExceededException | client | You have reached the maximum number of resources that can be created. |
ResourceNotFoundException | client | The specified resource does not exist. |
CloudWatchLogsServiceException | Base exception class for all service exceptions from CloudWatchLogs service. |