# Access logs for your Application Load Balancer Elastic Load Balancing provides access logs that capture detailed information about requests sent to your load balancer. Each log contains information such as the time the request was received, the client's IP address, latencies, request paths, and server responses. You can use these access logs to analyze traffic patterns and troubleshoot issues. Access logs is an optional feature of Elastic Load Balancing that is disabled by default. After you enable access logs for your load balancer, Elastic Load Balancing captures the logs and stores them in the Amazon S3 bucket that you specify as compressed files. You can disable access logs at any time. You are charged storage costs for Amazon S3, but not charged for the bandwidth used by Elastic Load Balancing to send log files to Amazon S3. For more information about storage costs, see [Amazon S3 pricing](https://aws.amazon.com/s3/pricing/). **Topics** + [Access log files](#access-log-file-format) + [Access log entries](#access-log-entry-format) + [Example log entries](#access-log-entry-examples) + [Configure log delivery notifications](#access-log-event-notifications) + [Processing access log files](#log-processing-tools) + [Enable access logs](enable-access-logging.md) + [Disable access logs](disable-access-logging.md) ## Access log files Elastic Load Balancing publishes a log file for each load balancer node every 5 minutes. Log delivery is eventually consistent. The load balancer can deliver multiple logs for the same period. This usually happens if the site has high traffic. The file names of the access logs use the following format: ``` bucket[/prefix]/AWSLogs/aws-account-id/elasticloadbalancing/region/yyyy/mm/dd/aws-account-id_elasticloadbalancing_region_app.load-balancer-id_end-time_ip-address_random-string.log.gz ``` *bucket* The name of the S3 bucket. *prefix* (Optional) The prefix (logical hierarchy) for the bucket. The prefix that you specify must not include the string `AWSLogs`. For more information, see [Organizing objects using prefixes](https://docs.aws.amazon.com/AmazonS3/latest/userguide/using-prefixes.html). `AWSLogs` We add the portion of the file name starting with `AWSLogs` after the bucket name and optional prefix that you specify. *aws-account-id* The AWS account ID of the owner. *region* The Region for your load balancer and S3 bucket. *yyyy*/*mm*/*dd* The date that the log was delivered. *load-balancer-id* The resource ID of the load balancer. If the resource ID contains any forward slashes (/), they are replaced with periods (.). *end-time* The date and time that the logging interval ended. For example, an end time of 20140215T2340Z contains entries for requests made between 23:35 and 23:40 in UTC or Zulu time. *ip-address* The IP address of the load balancer node that handled the request. For an internal load balancer, this is a private IP address. *random-string* A system-generated random string. The following is an example log file name with a prefix: ``` s3://amzn-s3-demo-logging-bucket/logging-prefix/AWSLogs/123456789012/elasticloadbalancing/us-east-2/2022/05/01/123456789012_elasticloadbalancing_us-east-2_app.my-loadbalancer.1234567890abcdef_20220215T2340Z_172.160.001.192_20sg8hgm.log.gz ``` The following is an example log file name without a prefix: ``` s3://amzn-s3-demo-logging-bucket/AWSLogs/123456789012/elasticloadbalancing/us-east-2/2022/05/01/123456789012_elasticloadbalancing_us-east-2_app.my-loadbalancer.1234567890abcdef_20220215T2340Z_172.160.001.192_20sg8hgm.log.gz ``` You can store your log files in your bucket for as long as you want, but you can also define Amazon S3 lifecycle rules to archive or delete log files automatically. For more information, see [Object lifecycle management](https://docs.aws.amazon.com/AmazonS3/latest/userguide/object-lifecycle-mgmt.html) in the *Amazon S3 User Guide*. ## Access log entries Elastic Load Balancing logs requests sent to the load balancer, including requests that never made it to the targets. For example, if a client sends a malformed request, or there are no healthy targets to respond to the request, the request is still logged. Each log entry contains the details of a single request (or connection in the case of WebSockets) made to the load balancer. For WebSockets, an entry is written only after the connection is closed. If the upgraded connection can't be established, the entry is the same as for an HTTP or HTTPS request. **Important** Elastic Load Balancing logs requests on a best-effort basis. We recommend that you use access logs to understand the nature of the requests, not as a complete accounting of all requests. **Topics** + [Syntax](#access-log-entry-syntax) + [Actions taken](#actions-taken) + [Classification reasons](#classification-reasons) + [Error reason codes](#error-reason-codes) + [Transform status codes](#transform-status-codes) ### Syntax The following table describes the fields of an access log entry, in order. All fields are delimited by spaces. When we add a new field, we add it to the end of the log entry. As we prepare to release a new field, you might see an additional trailing "-" before the field is released. Ensure that you configure log parsing to stop after the last documented field, and update log parsing after we release a new field. | Field (position) | Description | | --- | --- | | type (1) | The type of request or connection. The possible values are as follows (ignore any other values): [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/elasticloadbalancing/latest/application/load-balancer-access-logs.html) | | time (2) | The time when the load balancer generated a response to the client, in ISO 8601 format. For WebSockets, this is the time when the connection is closed. | | elb (3) | The resource ID of the load balancer. If you are parsing access log entries, note that resources IDs can contain forward slashes (/). | | client:port (4) | The IP address and port of the requesting client. If there is a proxy in front of the load balancer, this field contains the IP address of the proxy. | | target:port (5) | The IP address and port of the target that processed this request. If the client didn't send a full request, the load balancer can't dispatch the request to a target, and this value is set to -. If the target is a Lambda function, this value is set to -. If the request is blocked by AWS WAF, this value is set to -. | | request\$1processing\$1time (6) | The total time elapsed (in seconds, with millisecond precision) from the time the load balancer received the request until the time it sent the request to a target. This value is set to -1 if the load balancer can't dispatch the request to a target. This can happen if the target closes the connection before the idle timeout or if the client sends a malformed request. This value can also be set to -1 if a TCP connection cannot be established with the target before reaching the 10-second TCP connection timeout. If AWS WAF is enabled for your Application Load Balancer or the target type is a Lambda function, the time it takes for the client to send the required data for POST requests is counted towards `request_processing_time`. | | target\$1processing\$1time (7) | The total time elapsed (in seconds, with millisecond precision) from the time the load balancer sent the request to a target until the target started to send the response headers. This value is set to -1 if the load balancer can't dispatch the request to a target. This can happen if the target closes the connection before the idle timeout or if the client sends a malformed request. This value can also be set to -1 if the registered target does not respond before the idle timeout. If AWS WAF is not enabled for your Application Load Balancer, the time it takes for the client to send the required data for POST requests is counted towards `target_processing_time`. | | response\$1processing\$1time (8) | The total time elapsed (in seconds, with millisecond precision) from the time the load balancer received the response header from the target until it started to send the response to the client. This includes both the queuing time at the load balancer and the connection acquisition time from the load balancer to the client. This value is set to -1 if the load balancer doesn't receive a response from a target. This can happen if the target closes the connection before the idle timeout or if the client sends a malformed request. | | elb\$1status\$1code (9) | The status code of the response generated by the load balancer, fixed response rule, or AWS WAF custom response code for Block actions. | | target\$1status\$1code (10) | The status code of the response from the target. This value is recorded only if a connection was established to the target and the target sent a response. Otherwise, it is set to -. | | received\$1bytes (11) | The size of the request, in bytes, received from the client (requester). For HTTP requests, this includes the headers. For WebSockets, this is the total number of bytes received from the client on the connection. | | sent\$1bytes (12) | The size of the response, in bytes, sent to the client (requester). For HTTP requests, this includes the response headers and body. For WebSockets, this is the total number of bytes sent to the client on the connection. The TCP headers and TLS handshake payload are not included in `sent_bytes`. Therefore `sent_bytes` won't match `DataTransfer-Out-Bytes` in AWS Cost Explorer. | | "request\$1line" (13) | The request line from the client, enclosed in double quotes and logged using the following format: HTTP method \$1 protocol://host:port/uri \$1 HTTP version. The load balancer preserves the URL sent by the client, as is, when recording the request URI. It does not set the content type for the access log file. When you process this field, consider how the client sent the URL. | | "user\$1agent" (14) | A User-Agent string that identifies the client that originated the request, enclosed in double quotes. The string consists of one or more product identifiers, product[/version]. If the string is longer than 8 KB, it is truncated. | | ssl\$1cipher (15) | [HTTPS listener] The SSL cipher. This value is set to - if the listener is not an HTTPS listener. | | ssl\$1protocol (16) | [HTTPS listener] The SSL protocol. This value is set to - if the listener is not an HTTPS listener. | | target\$1group\$1arn (17) | The Amazon Resource Name (ARN) of the target group. | | "trace\$1id" (18) | The contents of the **X-Amzn-Trace-Id** header, enclosed in double quotes. | | "domain\$1name" (19) | [HTTPS listener] The SNI domain provided by the client during the TLS handshake, enclosed in double quotes. This value is set to - if the client doesn't support SNI or the domain doesn't match a certificate and the default certificate is presented to the client. | | "chosen\$1cert\$1arn" (20) | [HTTPS listener] The ARN of the certificate presented to the client, enclosed in double quotes. This value is set to `session-reused` if the session is reused. This value is set to - if the listener is not an HTTPS listener. | | matched\$1rule\$1priority (21) | The priority value of the rule that matched the request. If a rule matched, this is a value from 1 to 50,000. If no rule matched and the default action was taken, this value is set to 0. If an error occurs during rules evaluation, it is set to -1. For any other error, it is set to -. | | request\$1creation\$1time (22) | The time when the load balancer received the request from the client, in ISO 8601 format. | | "actions\$1executed" (23) | The actions taken when processing the request, enclosed in double quotes. This value is a comma-separated list that can include the values described in [Actions taken](#actions-taken). If no action was taken, such as for a malformed request, this value is set to -. | | "redirect\$1url" (24) | The URL of the redirect target for the location header of the HTTP response, enclosed in double quotes. If no redirect actions were taken, this value is set to -. | | "error\$1reason" (25) | The error reason code, enclosed in double quotes. If the request failed, this is one of the error codes described in [Error reason codes](#error-reason-codes). If the actions taken do not include an authenticate action or the target is not a Lambda function, this value is set to -. | | "target:port\$1list" (26) | A space-delimited list of IP addresses and ports for the targets that processed this request, enclosed in double quotes. Currently, this list can contain one item and it matches the target:port field. If the client didn't send a full request, the load balancer can't dispatch the request to a target, and this value is set to -. If the target is a Lambda function, this value is set to -. If the request is blocked by AWS WAF, this value is set to -. | | "target\$1status\$1code\$1list" (27) | A space-delimited list of status codes from the responses of the targets, enclosed in double quotes. Currently, this list can contain one item and it matches the target\$1status\$1code field. This value is recorded only if a connection was established to the target and the target sent a response. Otherwise, it is set to -. | | "classification" (28) | The classification for desync mitigation, enclosed in double quotes. If the request does not comply with RFC 7230, the possible values are Acceptable, Ambiguous, and Severe. If the request complies with RFC 7230, this value is set to -. | | "classification\$1reason" (29) | The classification reason code, enclosed in double quotes. If the request does not comply with RFC 7230, this is one of the classification codes described in [Classification reasons](#classification-reasons). If the request complies with RFC 7230, this value is set to -. | | conn\$1trace\$1id (30) | The connection traceability ID is a **unique opaque ID** used to identify each connection. After a connection is established with a client, subsequent requests from this client will contain this ID in their respective access log entries. This ID acts as a foreign key to create a link between the connection and access logs. | | "transformed\$1host" (31) | The host header after it is modified by a host header rewrite transform. If any of the following are true, this value is set to -. [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/elasticloadbalancing/latest/application/load-balancer-access-logs.html) | | "transformed\$1uri" (32) | The URI after it is modified by a URL rewrite transform. If any of the following are true, this value is set to -. [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/elasticloadbalancing/latest/application/load-balancer-access-logs.html) | | "request\$1transform\$1status" (33) | The status of the rewrite transform. If no rewrite transform was applied, this value is set to -. Otherwise, this value is one of the status values described in [Transform status codes](#transform-status-codes). | ### Actions taken The load balancer stores the actions that it takes in the actions\$1executed field of the access log. + `authenticate` — The load balancer validated the session, authenticated the user, and added the user information to the request headers, as specified by the rule configuration. + `fixed-response` — The load balancer issued a fixed response, as specified by the rule configuration. + `forward` — The load balancer forwarded the request to a target, as specified by the rule configuration. + `redirect` — The load balancer redirected the request to another URL, as specified by the rule configuration. + `rewrite` — The load balancer rewrote the request URL, as specified by the rule configuration. + `waf` — The load balancer forwarded the request to AWS WAF to determine whether the request should be forwarded to the target. If this is the final action, AWS WAF determined that the request should be rejected. By default, requests rejected by AWS WAF will be logged as "403" in the `elb_status_code` field. When AWS WAF is configured to reject requests with a Custom Response Code, the `elb_status_code` field will reflect the configured response code. + `waf-failed` — The load balancer attempted to forward the request to AWS WAF, but this process failed. ### Classification reasons If a request does not comply with RFC 7230, the load balancer stores one of the following codes in the classification\$1reason field of the access log. For more information, see [Desync mitigation mode](edit-load-balancer-attributes.md#desync-mitigation-mode). | Code | Description | Classification | | --- | --- | --- | | `AmbiguousUri` | The request URI contains control characters. | Ambiguous | | `BadContentLength` | The Content-Length header contains a value that cannot be parsed or is not a valid number. | Severe | | `BadHeader` | A header contains a null character or carriage return. | Severe | | `BadTransferEncoding` | The Transfer-Encoding header contains a bad value. | Severe | | `BadUri` | The request URI contains a null character or carriage return. | Severe | | `BadMethod` | The request method is malformed. | Severe | | `BadVersion` | The request version is malformed. | Severe | | `BothTeClPresent` | The request contains both a Transfer-Encoding header and a Content-Length header. | Ambiguous | | `DuplicateContentLength` | There are multiple Content-Length headers with the same value. | Ambiguous | | `EmptyHeader` | A header is empty or there is a line with only spaces. | Ambiguous | | `GetHeadZeroContentLength` | There is a Content-Length header with a value of 0 for a GET or HEAD request. | Acceptable | | `MultipleContentLength` | There are multiple Content-Length headers with different values. | Severe | | `MultipleTransferEncodingChunked` | There are multiple Transfer-Encoding: chunked headers. | Severe | | `NonCompliantHeader` | A header contains a non-ASCII or control character. | Acceptable | | `NonCompliantVersion` | The request version contains a bad value. | Acceptable | | `SpaceInUri` | The request URI contains a space that is not URL encoded. | Acceptable | | `SuspiciousHeader` | There is a header that can be normalized to Transfer-Encoding or Content-Length using common text normalization techniques. | Ambiguous | | `SuspiciousTeClPresent` | The request contains both a Transfer-Encoding header and a Content-Length header, with at least one of them being suspicious. | Severe | | `UndefinedContentLengthSemantics` | There is a Content-Length header defined for a GET or HEAD request. | Ambiguous | | `UndefinedTransferEncodingSemantics` | There is a Transfer-Encoding header defined for a GET or HEAD request. | Ambiguous | ### Error reason codes If the load balancer cannot complete an authenticate action, the load balancer stores one of the following reason codes in the error\$1reason field of the access log. The load balancer also increments the corresponding CloudWatch metric. For more information, see [Authenticate users using an Application Load Balancer](listener-authenticate-users.md). | Code | Description | Metric | | --- | --- | --- | | `AuthInvalidCookie` | The authentication cookie is not valid. | `ELBAuthFailure` | | `AuthInvalidGrantError` | The authorization grant code from the token endpoint is not valid. | `ELBAuthFailure` | | `AuthInvalidIdToken` | The ID token is not valid. | `ELBAuthFailure` | | `AuthInvalidStateParam` | The state parameter is not valid. | `ELBAuthFailure` | | `AuthInvalidTokenResponse` | The response from the token endpoint is not valid. | `ELBAuthFailure` | | `AuthInvalidUserinfoResponse` | The response from the user info endpoint is not valid. | `ELBAuthFailure` | | `AuthMissingCodeParam` | The authentication response from the authorization endpoint is missing a query parameter named 'code'. | `ELBAuthFailure` | | `AuthMissingHostHeader` | The authentication response from the authorization endpoint is missing a host header field. | `ELBAuthError` | | `AuthMissingStateParam` | The authentication response from the authorization endpoint is missing a query parameter named 'state'. | `ELBAuthFailure` | | `AuthTokenEpRequestFailed` | There is an error response (non-2XX) from the token endpoint. | `ELBAuthError` | | `AuthTokenEpRequestTimeout` | The load balancer is unable to communicate with the token endpoint, or the token endpoint is not responding within 5 seconds. | `ELBAuthError` | | `AuthUnhandledException` | The load balancer encountered an unhandled exception. | `ELBAuthError` | | `AuthUserinfoEpRequestFailed` | There is an error response (non-2XX) from the IdP user info endpoint. | `ELBAuthError` | | `AuthUserinfoEpRequestTimeout` | The load balancer is unable to communicate with the IdP user info endpoint, or the user info endpoint is not responding within 5 seconds. | `ELBAuthError` | | `AuthUserinfoResponseSizeExceeded` | The size of the claims returned by the IdP exceeded 11K bytes. | `ELBAuthUserClaimsSizeExceeded` | If the load balancer cannot complete an jwt-validation action, the load balancer stores one of the following reason codes in the error\$1reason field of the access log. The load balancer also increments the corresponding CloudWatch metric. For more information, see [Verify JWTs using an Application Load Balancer](listener-verify-jwt.md). | Code | Description | Metric | | --- | --- | --- | | `JWTHeaderNotPresent` | Request does not contain Authorization header. | `JWTValidationFailureCount` | | `JWTRequestFormatInvalid` | Token in request is malformed or missing mandatory parts (header, payload, or signature), Header does not contain "Bearer " prefix, Header contains a different auth type like "Basic ", Authorization header is present but token is not present, if there are multiple tokens present in the request | `JWTValidationFailureCount` | | `JWKSRequestTimeout` | The load balancer is unable to communicate with the JWKS endpoint, or the JWKS endpoint is not responding within 5 seconds. | `JWTValidationFailureCount` | | `JWKSResponseSizeExceeded` | The size of the response returned by the JWKS endpoint exceeds 150KB or the number of keys returned by the JWKS endpoint exceeds 10. | `JWTValidationFailureCount` | | `JWKSRequestFailed` | There is an error response (non-2XX) from the JWKS endpoint. | `JWTValidationFailureCount` | | `JWKSResponseInvalid` | JWKS response has one or more of the following problems: Non-JSON format, Invalid characters, Invalid JWKS format, Missing/invalid mandatory JWKS attributes, Public key has unsupported algorithm, the public key could not be converted to a decoding key, public key size was not 2K. | `JWTValidationFailureCount` | | `JWTSignatureValidationError` | Failed to validate token signature for any reason including signature does not match, Token is signed with an unsupported algorithm, The KID in the token is not present in the JWKS endpoint. | `JWTValidationFailureCount` | | `JWTClaimNotPresent` | JWT in the client request does not contain a claim which is required for validation | `JWTValidationFailureCount` | | `JWTClaimFormatInvalid` | The format of the claim’s value in the JWT does not match the format specified in the configuration | `JWTValidationFailureCount` | | `JWTClaimValueInvalid` | The value of the claim in the JWT is invalid. | `JWTValidationFailureCount` | | `JWTValidationInternalError` | The load balancer encountered an unexpected error while validating the JWT in the client request. | `JWTValidationFailureCount` | If a request to a weighted target group fails, the load balancer stores one of the following error codes in the error\$1reason field of the access log. | Code | Description | | --- | --- | | `AWSALBTGCookieInvalid` | The AWSALBTG cookie, which is used with weighted target groups, is not valid. For example, the load balancer returns this error when cookie values are URL encoded. | | `WeightedTargetGroupsUnhandledException` | The load balancer encountered an unhandled exception. | If a request to a Lambda function fails, the load balancer stores one of the following reason codes in the error\$1reason field of the access log. The load balancer also increments the corresponding CloudWatch metric. For more information, see the Lambda [Invoke](https://docs.aws.amazon.com/lambda/latest/api/API_Invoke.html) action. | Code | Description | Metric | | --- | --- | --- | | `LambdaAccessDenied` | The load balancer did not have permission to invoke the Lambda function. | `LambdaUserError` | | `LambdaBadRequest` | Lambda invocation failed because the client request headers or body did not contain only UTF-8 characters. | `LambdaUserError` | | `LambdaConnectionError` | The load balancer cannot connect to Lambda. | `LambdaInternalError` | | `LambdaConnectionTimeout` | An attempt to connect to Lambda timed out. | `LambdaInternalError` | | `LambdaEC2AccessDeniedException` | Amazon EC2 denied access to Lambda during function initialization. | `LambdaUserError` | | `LambdaEC2ThrottledException` | Amazon EC2 throttled Lambda during function initialization. | `LambdaUserError` | | `LambdaEC2UnexpectedException` | Amazon EC2 encountered an unexpected exception during function initialization. | `LambdaUserError` | | `LambdaENILimitReachedException` | Lambda couldn't create a network interface in the VPC specified in the configuration of the Lambda function because the limit for network interfaces was exceeded. | `LambdaUserError` | | `LambdaInvalidResponse` | The response from the Lambda function is malformed or is missing required fields. | `LambdaUserError` | | `LambdaInvalidRuntimeException` | The specified version of the Lambda runtime is not supported. | `LambdaUserError` | | `LambdaInvalidSecurityGroupIDException` | The security group ID specified in the configuration of the Lambda function is not valid. | `LambdaUserError` | | `LambdaInvalidSubnetIDException` | The subnet ID specified in the configuration of the Lambda function is not valid. | `LambdaUserError` | | `LambdaInvalidZipFileException` | Lambda could not unzip the specified function zip file. | `LambdaUserError` | | `LambdaKMSAccessDeniedException` | Lambda could not decrypt environment variables because access to the KMS key was denied. Check the KMS permissions of the Lambda function. | `LambdaUserError` | | `LambdaKMSDisabledException` | Lambda could not decrypt environment variables because the specified KMS key is disabled. Check the KMS key settings of the Lambda function. | `LambdaUserError` | | `LambdaKMSInvalidStateException` | Lambda could not decrypt environment variables because the state of the KMS key is not valid. Check the KMS key settings of the Lambda function. | `LambdaUserError` | | `LambdaKMSNotFoundException` | Lambda could not decrypt environment variables because the KMS key was not found. Check the KMS key settings of the Lambda function. | `LambdaUserError` | | `LambdaRequestTooLarge` | The size of the request body exceeded 1 MB. | `LambdaUserError` | | `LambdaResourceNotFound` | The Lambda function could not be found. | `LambdaUserError` | | `LambdaResponseTooLarge` | The size of the response exceeded 1 MB. | `LambdaUserError` | | `LambdaServiceException` | Lambda encountered an internal error. | `LambdaInternalError` | | `LambdaSubnetIPAddressLimitReachedException` | Lambda could not set up VPC access for the Lambda function because one or more subnets have no available IP addresses. | `LambdaUserError` | | `LambdaThrottling` | The Lambda function was throttled because there were too many requests. | `LambdaUserError` | | `LambdaUnhandled` | The Lambda function encountered an unhandled exception. | `LambdaUserError` | | `LambdaUnhandledException` | The load balancer encountered an unhandled exception. | `LambdaInternalError` | | `LambdaWebsocketNotSupported` | WebSockets are not supported with Lambda. | `LambdaUserError` | If the load balancer encounters an error when forwarding requests to AWS WAF, it stores one of the following error codes in the error\$1reason field of the access log. | Code | Description | | --- | --- | | `WAFConnectionError` | The load balancer cannot connect to AWS WAF. | | `WAFConnectionTimeout` | The connection to AWS WAF timed out. | | `WAFResponseReadTimeout` | A request to AWS WAF timed out. | | `WAFServiceError` | AWS WAF returned a 5XX error. | | `WAFUnhandledException` | The load balancer encountered an unhandled exception. | ### Transform status codes | Code | Description | | --- | --- | | `TransformBufferTooSmall` | The rewrite transform failed because the result exceeded the size of an internal buffer. Try to make the regular expression less complex. | | `TransformCompileError` | The compilation of the regular expression failed. | | `TransformCompileTooBig` | The compiled regular expression was too large. Try to make the regular expression less complex. | | `TransformInvalidHost` | The host header rewrite transform failed because the resulting host is not valid. | | `TransformInvalidPath` | The URL rewrite transform failed because the resulting path is not valid. | | `TransformRegexSyntaxError` | The regular expression contained a syntax error. | | `TransformReplaceError` | The transform replacement failed. | | `TransformSuccess` | The rewrite transform completed successfully. | ## Example log entries The following are example log entries. Note that the example text appears on multiple lines only to make them easier to read. **Example HTTP Entry** The following is an example log entry for an HTTP listener (port 80 to port 80): ``` http 2018-07-02T22:23:00.186641Z app/my-loadbalancer/50dc6c495c0c9188 192.168.131.39:2817 10.0.0.1:80 0.000 0.001 0.000 200 200 34 366 "GET http://www.example.com:80/ HTTP/1.1" "curl/7.46.0" - - arn:aws:elasticloadbalancing:us-east-2:123456789012:targetgroup/my-targets/73e2d6bc24d8a067 "Root=1-58337262-36d228ad5d99923122bbe354" "-" "-" 0 2018-07-02T22:22:48.364000Z "forward" "-" "-" "10.0.0.1:80" "200" "-" "-" TID_1234abcd5678ef90 "-" "-" "-" ``` **Example HTTPS Entry** The following is an example log entry for an HTTPS listener (port 443 to port 80): ``` https 2018-07-02T22:23:00.186641Z app/my-loadbalancer/50dc6c495c0c9188 192.168.131.39:2817 10.0.0.1:80 0.086 0.048 0.037 200 200 0 57 "GET https://www.example.com:443/ HTTP/1.1" "curl/7.46.0" ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 arn:aws:elasticloadbalancing:us-east-2:123456789012:targetgroup/my-targets/73e2d6bc24d8a067 "Root=1-58337281-1d84f3d73c47ec4e58577259" "www.example.com" "arn:aws:acm:us-east-2:123456789012:certificate/12345678-1234-1234-1234-123456789012" 1 2018-07-02T22:22:48.364000Z "authenticate,forward" "-" "-" "10.0.0.1:80" "200" "-" "-" TID_1234abcd5678ef90 "m.example.com" "-" "TransformSuccess" ``` **Example HTTP/2 Entry** The following is an example log entry for an HTTP/2 stream. ``` h2 2018-07-02T22:23:00.186641Z app/my-loadbalancer/50dc6c495c0c9188 10.0.1.252:48160 10.0.0.66:9000 0.000 0.002 0.000 200 200 5 257 "GET https://10.0.2.105:773/ HTTP/2.0" "curl/7.46.0" ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 arn:aws:elasticloadbalancing:us-east-2:123456789012:targetgroup/my-targets/73e2d6bc24d8a067 "Root=1-58337327-72bd00b0343d75b906739c42" "-" "-" 1 2018-07-02T22:22:48.364000Z "redirect" "https://example.com:80/" "-" "10.0.0.66:9000" "200" "-" "-" TID_1234abcd5678ef90 "-" "-" "-" ``` **Example WebSockets Entry** The following is an example log entry for a WebSockets connection. ``` ws 2018-07-02T22:23:00.186641Z app/my-loadbalancer/50dc6c495c0c9188 10.0.0.140:40914 10.0.1.192:8010 0.001 0.003 0.000 101 101 218 587 "GET http://10.0.0.30:80/ HTTP/1.1" "-" - - arn:aws:elasticloadbalancing:us-east-2:123456789012:targetgroup/my-targets/73e2d6bc24d8a067 "Root=1-58337364-23a8c76965a2ef7629b185e3" "-" "-" 1 2018-07-02T22:22:48.364000Z "forward" "-" "-" "10.0.1.192:8010" "101" "-" "-" TID_1234abcd5678ef90 "-" "-" "-" ``` **Example Secured WebSockets Entry** The following is an example log entry for a secured WebSockets connection. ``` wss 2018-07-02T22:23:00.186641Z app/my-loadbalancer/50dc6c495c0c9188 10.0.0.140:44244 10.0.0.171:8010 0.000 0.001 0.000 101 101 218 786 "GET https://10.0.0.30:443/ HTTP/1.1" "-" ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 arn:aws:elasticloadbalancing:us-west-2:123456789012:targetgroup/my-targets/73e2d6bc24d8a067 "Root=1-58337364-23a8c76965a2ef7629b185e3" "-" "-" 1 2018-07-02T22:22:48.364000Z "forward" "-" "-" "10.0.0.171:8010" "101" "-" "-" TID_1234abcd5678ef90 "-" "-" "-" ``` **Example Entries for Lambda Functions** The following is an example log entry for a request to a Lambda function that succeeded: ``` http 2018-11-30T22:23:00.186641Z app/my-loadbalancer/50dc6c495c0c9188 192.168.131.39:2817 - 0.000 0.001 0.000 200 200 34 366 "GET http://www.example.com:80/ HTTP/1.1" "curl/7.46.0" - - arn:aws:elasticloadbalancing:us-east-2:123456789012:targetgroup/my-targets/73e2d6bc24d8a067 "Root=1-58337364-23a8c76965a2ef7629b185e3" "-" "-" 0 2018-11-30T22:22:48.364000Z "forward" "-" "-" "-" "-" "-" "-" TID_1234abcd5678ef90 "-" "-" "-" ``` The following is an example log entry for a request to a Lambda function that failed: ``` http 2018-11-30T22:23:00.186641Z app/my-loadbalancer/50dc6c495c0c9188 192.168.131.39:2817 - 0.000 0.001 0.000 502 - 34 366 "GET http://www.example.com:80/ HTTP/1.1" "curl/7.46.0" - - arn:aws:elasticloadbalancing:us-east-2:123456789012:targetgroup/my-targets/73e2d6bc24d8a067 "Root=1-58337364-23a8c76965a2ef7629b185e3" "-" "-" 0 2018-11-30T22:22:48.364000Z "forward" "-" "LambdaInvalidResponse" "-" "-" "-" "-" TID_1234abcd5678ef90 "-" "-" "-" ``` ## Configure log delivery notifications To receive notifications when Elastic Load Balancing delivers logs to your S3 bucket, use Amazon S3 Event Notifications. Elastic Load Balancing uses [PutObject](https://docs.aws.amazon.com/AmazonS3/latest/API/API_PutObject.html), [CreateMultipartUpload](https://docs.aws.amazon.com/AmazonS3/latest/API/API_CreateMultipartUpload.html), and [POST Object](https://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectPOST.html) to deliver logs to Amazon S3. To ensure that you receive all log delivery notifications, include all of these object creation events in your configuration. For more information, see [Amazon S3 Event Notifications](https://docs.aws.amazon.com/AmazonS3/latest/userguide/EventNotifications.html) in the *Amazon Simple Storage Service User Guide*. ## Processing access log files The access log files are compressed. If you download the files, you must uncompress them to view the information. If there is a lot of demand on your website, your load balancer can generate log files with gigabytes of data. You might not be able to process such a large amount of data using line-by-line processing. Therefore, you might have to use analytical tools that provide parallel processing solutions. For example, you can use the following analytical tools to analyze and process access logs: + Amazon Athena is an interactive query service that makes it easy to analyze data in Amazon S3 using standard SQL. For more information, see [Querying Application Load Balancer logs](https://docs.aws.amazon.com/athena/latest/ug/application-load-balancer-logs.html) in the *Amazon Athena User Guide*. + [Loggly](https://documentation.solarwinds.com/en/success_center/loggly/content/admin/s3-ingestion-auto.htm) + [Splunk](https://splunk.github.io/splunk-add-on-for-amazon-web-services/) + [Sumo logic](https://www.sumologic.com/application/elb/) # Enable access logs for your Application Load Balancer When you enable access logs for your load balancer, you must specify the name of the S3 bucket where the load balancer will store the logs. The bucket must have a bucket policy that grants Elastic Load Balancing permission to write to the bucket. **Topics** + [Step 1: Create an S3 bucket](#access-log-create-bucket) + [Step 2: Attach a policy to your S3 bucket](#attach-bucket-policy) + [Step 3: Configure access logs](#enable-access-logs) + [Step 4: Verify bucket permissions](#verify-bucket-permissions) + [Troubleshooting](#bucket-permissions-troubleshooting) ## Step 1: Create an S3 bucket When you enable access logs, you must specify an S3 bucket for the access logs. You can use an existing bucket, or create a bucket specifically for access logs. The bucket must meet the following requirements. **Requirements** + The bucket must be located in the same Region as the load balancer. The bucket and the load balancer can be owned by different accounts. + The only server-side encryption option that's supported is Amazon S3-managed keys (SSE-S3). For more information, see [Amazon S3-managed encryption keys (SSE-S3)](https://docs.aws.amazon.com/AmazonS3/latest/userguide/UsingServerSideEncryption.html). **To create an S3 bucket using the Amazon S3 console** 1. Open the Amazon S3 console at [https://console.aws.amazon.com/s3/](https://console.aws.amazon.com/s3/). 1. Choose **Create bucket**. 1. On the **Create bucket** page, do the following: 1. For **Bucket name**, enter a name for your bucket. This name must be unique across all existing bucket names in Amazon S3. In some Regions, there might be additional restrictions on bucket names. For more information, see [Bucket restrictions and limitations](https://docs.aws.amazon.com/AmazonS3/latest/userguide/BucketRestrictions.html) in the *Amazon S3 User Guide*. 1. For **AWS Region**, select the Region where you created your load balancer. 1. For **Default encryption**, choose **Amazon S3-managed keys (SSE-S3)**. 1. Choose **Create bucket**. ## Step 2: Attach a policy to your S3 bucket Your S3 bucket must have a bucket policy that grants Elastic Load Balancing permission to write the access logs to the bucket. Bucket policies are a collection of JSON statements written in the access policy language to define access permissions for your bucket. Each statement includes information about a single permission and contains a series of elements. If you're using an existing bucket that already has an attached policy, you can add the statement for Elastic Load Balancing access logs to the policy. If you do so, we recommend that you evaluate the resulting set of permissions to ensure that they are appropriate for the users that need access to the bucket for access logs. ### Bucket policy This policy grants permissions to the log delivery service. **** ``` { "Version":"2012-10-17", "Statement": [ { "Effect": "Allow", "Principal": { "Service": "logdelivery.elasticloadbalancing.amazonaws.com" }, "Action": "s3:PutObject", "Resource": "arn:aws:s3:::amzn-s3-demo-bucket/prefix/AWSLogs/123456789012/*" } ] } ``` For `Resource`, enter the ARN of the location for the access logs, using the format shown in the example policy. Always include the account ID of the account with the load balancer in the resource path of the S3 bucket ARN. This ensures that only load balancers from the specified account can write access logs to the S3 bucket. The ARN that you specify depends on whether you plan to include a prefix when you enable access logs in [step 3](#enable-access-logs). **Example S3 bucket ARN with a prefix** The S3 bucket name is amzn-s3-demo-logging-bucket and the prefix is logging-prefix. ``` arn:aws:s3:::amzn-s3-demo-logging-bucket/logging-prefix/AWSLogs/123456789012/* ``` **AWS GovCloud (US)** – The following example uses the ARN syntax for the AWS GovCloud (US) Regions. ``` arn:aws-us-gov:s3:::amzn-s3-demo-logging-bucket/logging-prefix/AWSLogs/123456789012/* ``` **Example S3 bucket ARN with no prefix** The S3 bucket name is amzn-s3-demo-logging-bucket. There is no prefix portion in the S3 bucket ARN. ``` arn:aws:s3:::amzn-s3-demo-logging-bucket/AWSLogs/123456789012/* ``` **AWS GovCloud (US)** – The following example uses the ARN syntax for the AWS GovCloud (US) Regions. ``` arn:aws-us-gov:s3:::amzn-s3-demo-logging-bucket/AWSLogs/123456789012/* ``` ### Legacy bucket policy Previously, for Regions available before August 2022, we required a policy that granted permissions to an Elastic Load Balancing account that was specific to the Region. This legacy policy is still supported, but we recommend that you replace it with the newer policy above. If you prefer to keep using the legacy policy, which is not shown here, you can. For reference, here are the IDs of the Elastic Load Balancing accounts to specify in `Principal` in the legacy policy. Note that Regions that are not in this list do not support the legacy policy. + US East (N. Virginia) – 127311923021 + US East (Ohio) – 033677994240 + US West (N. California) – 027434742980 + US West (Oregon) – 797873946194 + Africa (Cape Town) – 098369216593 + Asia Pacific (Hong Kong) – 754344448648 + Asia Pacific (Jakarta) – 589379963580 + Asia Pacific (Mumbai) – 718504428378 + Asia Pacific (Osaka) – 383597477331 + Asia Pacific (Seoul) – 600734575887 + Asia Pacific (Singapore) – 114774131450 + Asia Pacific (Sydney) – 783225319266 + Asia Pacific (Tokyo) – 582318560864 + Canada (Central) – 985666609251 + Europe (Frankfurt) – 054676820928 + Europe (Ireland) – 156460612806 + Europe (London) – 652711504416 + Europe (Milan) – 635631232127 + Europe (Paris) – 009996457667 + Europe (Stockholm) – 897822967062 + Middle East (Bahrain) – 076674570225 + South America (São Paulo) – 507241528517 + AWS GovCloud (US-East) – 190560391635 + AWS GovCloud (US-West) – 048591011584 ### Outposts Zones The following policy grants permissions to the specified log delivery service. Use this policy for load balancers in Outposts Zones. ``` { "Effect": "Allow", "Principal": { "Service": "logdelivery.elb.amazonaws.com" }, "Action": "s3:PutObject", "Resource": "arn:aws:s3:::amzn-s3-demo-bucket/prefix/AWSLogs/123456789012/*", "Condition": { "StringEquals": { "s3:x-amz-acl": "bucket-owner-full-control" } } } ``` For `Resource`, enter the ARN of the location for the access logs, using the format shown in the example policy. Always include the account ID of the account with the load balancer in the resource path of the S3 bucket ARN. This ensures that only load balancers from the specified account can write access logs to the S3 bucket. The S3 bucket ARN that you specify depends on whether you plan to include a prefix when you enable access logs in [step 3](#enable-access-logs). **Example S3 bucket ARN with a prefix** The S3 bucket name is amzn-s3-demo-logging-bucket and the prefix is logging-prefix. ``` arn:aws:s3:::amzn-s3-demo-logging-bucket/logging-prefix/AWSLogs/123456789012/* ``` **Example S3 bucket ARN with no prefix** The S3 bucket name is amzn-s3-demo-logging-bucket. There is no prefix portion in the S3 bucket ARN. ``` arn:aws:s3:::amzn-s3-demo-logging-bucket/AWSLogs/123456789012/* ``` ### Security best practices + Use the full resource path, including the account ID portion of the S3 bucket ARN. Don't use wildcards (\$1) in the account ID portion of the S3 bucket ARN. ``` "Resource": "arn:aws:s3:::amzn-s3-demo-bucket/prefix/AWSLogs/123456789012/*" ``` + Use `aws:SourceArn` to ensure that only load balancers from the specified Region and account can use your bucket. ``` "Condition": { "ArnLike": { "aws:SourceArn": "arn:aws:elasticloadbalancing:region:123456789012:loadbalancer/*" } } ``` + Use `aws:SourceOrgId` with `aws:SourceArn` to ensure that only load balancers from the specified organization can use your bucket. ``` "Condition": { "StringEquals": { "aws:SourceOrgId": "o-1234567890" }, "ArnLike": { "aws:SourceArn": "arn:aws:elasticloadbalancing:*:*:loadbalancer/*" } } ``` + If you have a `Deny` statement to prevent access to service principals except those explicitly allowed, be sure to add `logdelivery.elasticloadbalancing.amazonaws.com` to the list of allowed service principals. For example, if you used the `aws:PrincipalServiceNamesList` condition, add `logdelivery.elasticloadbalancing.amazonaws.com` as follows: ``` { "Effect": "Deny", "Principal": "*", "Condition": { "StringNotEqualsIfExists": { "aws:PrincipalServiceNamesList": [ "logdelivery.elasticloadbalancing.amazonaws.com", "service.amazonaws.com" ] } } } ``` If you used the `NotPrincipal` element, add `logdelivery.elasticloadbalancing.amazonaws.com` as follows. Note that we recommend that you use the `aws:PrincipalServiceName` or `aws:PrincipalServiceNamesList` condition key to explicitly allow service principals instead of using the `NotPrincipal` element. For more information, see [NotPrincipal](https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements_notprincipal.html). ``` { "Effect": "Deny", "NotPrincipal": { "Service": [ "logdelivery.elasticloadbalancing.amazonaws.com", "service.amazonaws.com" ] } }, ``` After you create your bucket policy, use an Amazon S3 interface, such as the Amazon S3 console or AWS CLI commands, to attach your bucket policy to your S3 bucket. ------ #### [ Console ] **To attach your bucket policy to your S3 bucket** 1. Open the Amazon S3 console at [https://console.aws.amazon.com/s3/](https://console.aws.amazon.com/s3/). 1. Select the name of the bucket to open its details page. 1. Choose **Permissions** and then choose **Bucket policy**, **Edit**. 1. Update the bucket policy to grant the required permissions. 1. Choose **Save changes**. ------ #### [ AWS CLI ] **To attach your bucket policy to your S3 bucket** Use the [put-bucket-policy](https://docs.aws.amazon.com/cli/latest/reference/s3api/put-bucket-policy.html) command. In this example, the bucket policy was saved to the specified .json file. ``` aws s3api put-bucket-policy \ --bucket amzn-s3-demo-bucket \ --policy file://access-log-policy.json ``` ------ ## Step 3: Configure access logs Use the following procedure to configure access logs to capture request information and deliver log files to your S3 bucket. **Requirements** The bucket must meet the requirements described in [step 1](#access-log-create-bucket), and you must attach a bucket policy as described in [step 2](#attach-bucket-policy). If you include a prefix, it must not include the string "AWSLogs". **To manage the S3 bucket for your access logs** Be sure to disable access logs before you delete the bucket that you configured for access logs. Otherwise, if there is a new bucket with the same name and the required bucket policy but created in an AWS account that you don't own, Elastic Load Balancing could write the access logs for your load balancer to this new bucket. ------ #### [ Console ] **To enable access logs** 1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/). 1. In the navigation pane, choose **Load Balancers**. 1. Select the name of your load balancer to open its details page. 1. On the **Attributes** tab, choose **Edit**. 1. For **Monitoring**, turn on **Access logs**. 1. For **S3 URI**, enter the S3 URI for your log files. The URI that you specify depends on whether you're using a prefix. + URI with a prefix: s3://*amzn-s3-demo-logging-bucket*/*logging-prefix* + URI without a prefix: s3://*amzn-s3-demo-logging-bucket* 1. Choose **Save changes**. ------ #### [ AWS CLI ] **To enable access logs** Use the [modify-load-balancer-attributes](https://docs.aws.amazon.com/cli/latest/reference/elbv2/modify-load-balancer-attributes.html) command with the related attributes. ``` aws elbv2 modify-load-balancer-attributes \ --load-balancer-arn load-balancer-arn \ --attributes \ Key=access_logs.s3.enabled,Value=true \ Key=access_logs.s3.bucket,Value=amzn-s3-demo-logging-bucket \ Key=access_logs.s3.prefix,Value=logging-prefix ``` ------ #### [ CloudFormation ] **To enable access logs** Update the [AWS::ElasticLoadBalancingV2::LoadBalancer](https://docs.aws.amazon.com/AWSCloudFormation/latest/TemplateReference/aws-resource-elasticloadbalancingv2-loadbalancer.html) resource to include the related attributes. ``` Resources: myLoadBalancer: Type: 'AWS::ElasticLoadBalancingV2::LoadBalancer' Properties: Name: my-alb Type: application Scheme: internal Subnets: - !Ref subnet-AZ1 - !Ref subnet-AZ2 SecurityGroups: - !Ref mySecurityGroup LoadBalancerAttributes: - Key: "access_logs.s3.enabled" Value: "true" - Key: "access_logs.s3.bucket" Value: "amzn-s3-demo-logging-bucket" - Key: "access_logs.s3.prefix" Value: "logging-prefix" ``` ------ ## Step 4: Verify bucket permissions After access logs are enabled for your load balancer, Elastic Load Balancing validates the S3 bucket and creates a test file to ensure that the bucket policy specifies the required permissions. You can use the Amazon S3 console to verify that the test file was created. The test file is not an actual access log file; it doesn't contain example records. **To verify a test file was created in your bucket using the Amazon S3 console** 1. Open the Amazon S3 console at [https://console.aws.amazon.com/s3/](https://console.aws.amazon.com/s3/). 1. Select the name of the bucket that you specified for access logs. 1. Navigate to the test file, `ELBAccessLogTestFile`. The location depends on whether you're using a prefix. + Location with a prefix: *amzn-s3-demo-logging-bucket*/*logging-prefix*/AWSLogs/*123456789012*/ELBAccessLogTestFile + Location without a prefix: *amzn-s3-demo-logging-bucket*/AWSLogs/*123456789012*/ELBAccessLogTestFile ## Troubleshooting If you receive an access denied error, the following are possible causes: + The bucket policy does not grant Elastic Load Balancing permission to write access logs to the bucket. Verify that you are using the correct bucket policy for the Region. Verify that the resource ARN uses the same bucket name that you specified when you enabled access logs. Verify that the resource ARN does not include a prefix if you did not specify a prefix when you enabled access logs. + The bucket uses an unsupported server-side encryption option. The bucket must use Amazon S3-managed keys (SSE-S3). # Disable access logs for your Application Load Balancer You can disable access logs for your load balancer at any time. After you disable access logs, your access logs remain in your S3 bucket until you delete them. For more information, see [Creating, configuring, and working with S3 buckets](https://docs.aws.amazon.com/AmazonS3/latest/userguide/creating-buckets-s3.html) in the *Amazon S3 User Guide*. ------ #### [ Console ] **To disable access logs** 1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/). 1. In the navigation pane, choose **Load Balancers**. 1. Select the name of your load balancer to open its details page. 1. On the **Attributes** tab, choose **Edit**. 1. For **Monitoring**, turn off **Access logs**. 1. Choose **Save changes**. ------ #### [ AWS CLI ] **To disable access logs** Use the [modify-load-balancer-attributes](https://docs.aws.amazon.com/cli/latest/reference/elbv2/modify-load-balancer-attributes.html) command. ``` aws elbv2 modify-load-balancer-attributes \ --load-balancer-arn load-balancer-arn \ --attributes Key=access_logs.s3.enabled,Value=false ``` ------