access logs

• You can enable access logs for you ALB from the attributes panel. it is disabled by default
• Logs will be sent to s3, so resource policy have to be updated

{
  "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/*"
    }
  ]
}

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

• Here are the access logs entries
• It is for UNDERSTANDING but not for ALL ACCOUNTING

Here are the actions

• authenticate 
• fixed-response — Rule
• forward — Rule
• redirect — Rule.
• 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.

Field	Description
type	The type of request or connection. The possible values are as follows (ignore any other values): - http — HTTP - https — HTTP over TLS - h2 — HTTP/2 over TLS - grpcs— gRPC over TLS - ws — WebSockets - wss — WebSockets over TLS
time	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	The resource ID of the load balancer. If you are parsing access log entries, note that resources IDs can contain forward slashes (/).
client:port	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	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_processing_time	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_processing_time	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_processing_time	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_status_code	The status code of the response generated by the load balancer, fixed response rule, or AWS WAF custom response code for Block actions.
target_status_code	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_bytes	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_bytes	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 counted, and have no correlation to DataTransfer-Out-Bytes in AWS Cost Explorer.
”request”	The request line from the client, enclosed in double quotes and logged using the following format: HTTP method + protocol://host:port/uri + 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_agent”	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_cipher	[HTTPS listener] The SSL cipher. This value is set to - if the listener is not an HTTPS listener.
ssl_protocol	[HTTPS listener] The SSL protocol. This value is set to - if the listener is not an HTTPS listener.
target_group_arn	The Amazon Resource Name (ARN) of the target group.
”trace_id”	The contents of the X-Amzn-Trace-Id header, enclosed in double quotes.
”domain_name”	[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_cert_arn”	[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_rule_priority	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_creation_time	The time when the load balancer received the request from the client, in ISO 8601 format.
”actions_executed”	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. If no action was taken, such as for a malformed request, this value is set to -.
“redirect_url”	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_reason”	The error reason code, enclosed in double quotes. If the request failed, this is one of the error codes described in 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_list”	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_status_code_list”	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_status_code 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”	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_reason”	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. If the request complies with RFC 7230, this value is set to -.
/conn_trace_id	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.