You can configure CloudFront to create log files that contain detailed information about every user request that CloudFront receives. These access logs are available for both web and RTMP distributions. If you enable logging, you can also specify the Amazon S3 bucket that you want CloudFront to save files in.
How Logging Works
The following diagram shows how CloudFront logs information about requests for your objects.
How CloudFront Logs Information About Requests for Your Objects
In this diagram, you have two websites, A and B, and two corresponding CloudFront distributions. Users request your objects using URLs that are associated with your distributions.
CloudFront routes each request to the appropriate edge location.
CloudFront writes data about each request to a log file specific to that distribution. In this example, information about requests related to Distribution A goes into a log file just for Distribution A, and information about requests related to Distribution B goes into a log file just for Distribution B.
CloudFront periodically saves the log file for a distribution in the Amazon S3 bucket that you specified when you enabled logging. CloudFront then starts saving information about subsequent requests in a new log file for the distribution.
Each entry in a log file gives details about a single request. For more information about log file format, see Log File Format.
Choosing an Amazon S3 Bucket for Your Access Logs
When you enable logging for a distribution, you specify the Amazon S3 bucket that you want CloudFront to store log files in. If you're using Amazon S3 as your origin, we recommend that you do not use the same bucket for your log files; using a separate bucket simplifies maintenance.
You can store the log files for multiple distributions in the same bucket. When you enable logging, you can specify an optional prefix for the file names, so you can keep track of which log files are associated with which distributions.
If no users access your content during a given hour, you don't receive any log files for that hour.
Amazon S3 Permissions Required to Access Your Log Files
Your AWS account must have Amazon S3
FULL_CONTROL permission for the bucket that you specify for log files.
If you're the bucket owner, your account has this permission by default. If you're not, the bucket owner must
update the access control list (ACL) for the bucket to grant your AWS account
When you enable logging, CloudFront automatically updates the ACL for the bucket to give the awsdatafeeds account
FULL_CONTROL permission. This account writes log files to the bucket.
If you update the ACL for the bucket to remove permissions for the awsdatafeeds account, CloudFront updates the ACL again the next time the awsdatafeeds account needs to write a log file to your log bucket.
In addition to the ACL on the bucket, there's an ACL on each log file. The bucket owner has
FULL_CONTROL permission on each log file, the distribution owner (if different from the bucket owner)
has no permission, and the awsdatafeeds account has read and write permissions.
If you disable logging, CloudFront doesn't delete the ACLs for either the bucket or the log files. If you want, you can do that yourself.
File Name Format
The name of each log file that CloudFront saves in your Amazon S3 bucket uses the following file name format:
The date and time are in Coordinated Universal time (UTC).
For example, if your bucket name is
mylogs, your prefix is
myprefix/, and your distribution ID is
EMLARXS9EXAMPLE, your file names look similar to this:
When you enable logging for a distribution, you can specify an optional prefix for the file names, so you can
keep track of which log files are associated with which distributions. If you include a value for the log file prefix
and your prefix doesn't include a
/, CloudFront adds one automatically. If your value does include a
CloudFront doesn't add another one.
The .gz at the end of the file name indicates that CloudFront has compressed the log file using gzip.
Timing of Log File Delivery
CloudFront delivers access logs for a distribution up to several times an hour. In general, a log file contains information about the requests that CloudFront received during a given time period. CloudFront usually delivers the log file for that time period to your Amazon S3 bucket within an hour of the events that appear in the log. Note, however, that some or all log file entries for a time period can sometimes be delayed by up to 24 hours. When log entries are delayed, CloudFront saves them in a log file for which the file name includes the date and time of the period in which the requests occurred, not the date and time when the file was delivered.
When creating a log file, CloudFront consolidates information for your distribution from all of the edge locations that received requests for your objects during the time period that the log file covers.
CloudFront can save more than one file for a time period depending on how many requests CloudFront receives for the objects associated with a distribution.
CloudFront begins to reliably deliver access logs about four hours after you enable logging. You might get a few access logs before that time.
If no users request your objects during the time period, you don't receive any log files for that period.
Analyzing Access Logs
Because you can receive multiple access logs an hour, we recommend that you combine all the log files you receive for a given period into one file. You can then analyze the data for that period more quickly and accurately.
We recommend that you use the logs to understand the nature of the requests for your content, not as a complete accounting of all requests. CloudFront delivers access logs on a best-effort basis. The log entry for a particular request might be delivered long after the request was actually processed and, in rare cases, a log entry might not be delivered at all. When a log entry is omitted from access logs, the number of entries in the access logs won't match the usage that appears in the AWS usage and billing reports.
For more information about CloudFront access logs, including recommendations for tools that you can use to analyze access logs, see Using CloudFront Logging.
Editing Your Logging Settings
You can enable or disable logging, change the Amazon S3 bucket where your logs are stored, and change the prefix for log files by using the CloudFront console or the CloudFront API. Your changes to logging settings take effect within 12 hours.
For more information, see the following topics:
Updating a web or an RTMP distribution using the CloudFront console: Listing, Viewing, and Updating CloudFront Distributions.
Updating a web distribution using the CloudFront API: PUT Distribution Config in the Amazon CloudFront API Reference.
Updating an RTMP distribution using the CloudFront API: PUT Streaming Distribution Config in the Amazon CloudFront API Reference.
To use the CloudFront API to change access log settings for web distributions, you must use the 2009-04-02 or later version of the API. To use the CloudFront API to change access log settings for RTMP distributions, you must use the 2010-05-01 or later version of the API.
Deleting Log Files from an Amazon S3 Bucket
CloudFront does not automatically delete log files from your Amazon S3 bucket. For information about deleting log files from an Amazon S3 bucket, see the following topics:
Log File Format
Each entry in a log file gives details about a single user request. The log files for web and for RTMP distributions are not identical, but they share the following characteristics:
Use the W3C extended log file format. (For more information, go to http://www.w3.org/TR/WD-logfile.html.)
Contain tab-separated values.
Contain records that are not necessarily in chronological order.
Contain two header lines: one with the file-format version, and another that lists the W3C fields included in each record.
Substitute URL-encoded equivalents for spaces and non-standard characters in field values.
These non-standard characters consist of all ASCII codes below 32 and above 127, plus the characters in the following table. The URL encoding standard is RFC 1738. For more information, go to http://www.ietf.org/rfc/rfc1738.txt.
Web Distribution Log File Format
The log file for a web distribution includes the following fields in the listed order.
|Field Number||Field Name||Description|
|1||date||The date on which the event occurred in the format |
|2||time||The time when the CloudFront server finished responding to the request (in UTC), for example, |
|3||x-edge-location||The edge location that served the request. Each edge location is identified by a three-letter code and an arbitrarily assigned number, for example, DFW3. The three-letter code typically corresponds with the International Air Transport Association airport code for an airport near the edge location. (These abbreviations might change in the future.) For a list of edge locations, see the Amazon CloudFront detail page, http://aws.amazon.com/cloudfront.|
|4||sc-bytes||The total number of bytes that CloudFront served to the viewer in response to the request, including headers, for example,
|5||c-ip||The IP address of the viewer that made the request, for example, |
|6||cs-method||The HTTP access method: |
|7||cs(Host)||The domain name of the CloudFront distribution, for example, |
|8||cs-uri-stem||The portion of the URI that identifies the path and object, for example, |
One of the following values:
|10||cs(Referer)||The name of the domain that originated the request. Common referrers include search engines, other websites that link directly to your objects, and your own website.|
|11||cs(User-Agent)||The value of the |
The query string portion of the URI, if any. When a URI doesn't contain a query string, the value of
For more information, see Configuring CloudFront to Cache Based on Query String Parameters.
The cookie header in the request, including name-value pairs and the associated attributes.
If you enable cookie logging, CloudFront logs the cookies in all requests regardless of which cookies you choose to
forward to the origin: none, all, or a whitelist of cookie names. When a request doesn't include a cookie header,
the value of
For more information about cookies, see Configuring CloudFront to Cache Objects Based on Cookies.
How CloudFront classified the response after the last byte left the edge location. In some cases, the result type
can change between the time that CloudFront is ready to send the response and the time that CloudFront has finished sending the response.
For example, in HTTP streaming, suppose CloudFront finds a segment in the edge cache. The value of
Possible values include:
|15||x-edge-request-id||An encrypted string that uniquely identifies a request.|
The value that the viewer included in the
|17||cs-protocol||The protocol that the viewer specified in the request, either |
|18||cs-bytes||The number of bytes of data that the viewer included in the request (client to server bytes), including headers.|
|19||time-taken||The number of seconds between the time that a CloudFront edge server receives a viewer's request and the time that CloudFront writes the last byte of the response to the edge server's output queue as measured on the server. From the perspective of the viewer, the total time to get the full object will be longer than this value due to network latency and TCP buffering.|
If the viewer used an HTTP proxy or a load balancer to send the request, the value of
If the viewer did not use an HTTP proxy or a load balancer, the value of
Possible values include the following:
Possible values include the following:
How CloudFront classified the response just before returning the response to the viewer. See also
Possible values include:
Question marks (?) in URLs and query strings are not included in the log.
The following is an example log file for a web distribution:
#Version: 1.0 #Fields: date time x-edge-location sc-bytes c-ip cs-method cs(Host) cs-uri-stem sc-status cs(Referer) cs(User-Agent) cs-uri-query cs(Cookie) x-edge-result-type x-edge-request-id x-host-header cs-protocol cs-bytes time-taken x-forwarded-for ssl-protocol ssl-cipher x-edge-response-result-type 2014-05-23 01:13:11 FRA2 182 192.0.2.10 GET d111111abcdef8.cloudfront.net /view/my/file.html 200 www.displaymyfiles.com Mozilla/4.0%20(compatible;%20MSIE%205.0b1;%20Mac_PowerPC) - zip=98101 RefreshHit MRVMF7KydIvxMWfJIglgwHQwZsbG2IhRJ07sn9AkKUFSHS9EXAMPLE== d111111abcdef8.cloudfront.net http - 0.001 - - - RefreshHit 2014-05-23 01:13:12 LAX1 2390282 192.0.2.202 GET d111111abcdef8.cloudfront.net /soundtrack/happy.mp3 304 www.unknownsingers.com Mozilla/4.0%20(compatible;%20MSIE%207.0;%20Windows%20NT%205.1) a=b&c=d zip=50158 Hit xGN7KWpVEmB9Dp7ctcVFQC4E-nrcOcEKS3QyAez--06dV7TEXAMPLE== d111111abcdef8.cloudfront.net http - 0.002 - - - Hit
RTMP Distribution Log File Format
Each record in an RTMP access log represents a playback event, for example, connect, play, pause, stop,
disconnect, and so on. As a result, CloudFront generates multiple log records each time a viewer watches a video.
To relate log records that stem from the same stream ID, use the
Some fields have values for all events, and some have values only for Play, Stop, Pause, Unpause, and Seek events. Usually, when the log file contains a hyphen (-) for a field, the field isn't relevant for the corresponding event.
The following table describes the fields that are present in each record in the RTMP distribution log file, regardless of the type of event. The fields appear in the log in the order listed.
|Field Number||Field Name||Description|
|1||date||The date on which the event occurred in the format yyyy-mm-dd, for example, 2014-05-23. The date and time are in Coordinated Universal Time (UTC).|
|2||time||The time when the server received the request (in UTC), for example, 01:42:39.|
|3||x-edge-location||The edge location where the playback event occurred. Each edge location is identified by a three-letter code and an arbitrarily assigned number, for example, DFW3. The three-letter code typically corresponds with the International Air Transport Association airport code for an airport near the edge location. (These abbreviations might change in the future.) For a list of edge locations, see the Amazon CloudFront detail page, http://aws.amazon.com/cloudfront.|
|4||c-ip||Client IP, for example, 192.0.2.183.|
|5||x-event||The event type. This is a Connect, Disconnect, Play, Stop, Pause, Unpause, or Seek event.|
|6||sc-bytes||The running total number of bytes sent from the server to the client, up to the time of the event.|
|7||x-cf-status||A code indicating the status of the event. Currently, "OK" is the only value for this field. New functionality in the future could require new status codes.|
An opaque string identifier that can be used to differentiate clients.
This value is unique for each connection.
|9||cs-uri-stem||The stem portion of the URI, including the application and the application instance. This is sometimes referred
to as the FMS connect string. For example, |
|10||cs-uri-query||The query string portion of the URI that is included on the connect string.|
|11||c-referrer||The URI of the referrer.|
|12||x-page-url||The URL of the page from which the SWF is linked.|
|13||c-user-agent||The value of the |
The following fields usually have values only for Play, Stop, Pause, Unpause, and Seek events. For other events, they contain a single hyphen (-). These fields appear in the log after the fields in the preceding table and in the order listed.
|x-sname||The stream name.|
|x-sname-query||The stream query string, if any.|
|x-file-ext||The stream type, for example, FLV.|
|x-sid||The stream ID. This is a unique integer identifier for the connection.|
Question marks (?) in URLs and query strings are not included in the log.
The following is an example of a log file for an RTMP distribution:
#Version: 1.0 #Fields: date time x-edge-location c-ip x-event sc-bytes x-cf-status x-cf-client-id cs-uri-stem cs-uri-query c-referrer x-page-url c-user-agent x-sname x-sname-query x-file-ext x-sid 2010-03-12 23:51:20 SEA4 192.0.2.147 connect 2014 OK bfd8a98bee0840d9b871b7f6ade9908f rtmp://shqshne4jdp4b6.cloudfront.net/cfx/st key=value http://player.longtailvideo.com/player.swf http://www.longtailvideo.com/support/jw-player-setup-wizard?example=204 LNX%2010,0,32,18 - - - - 2010-03-12 23:51:21 SEA4 192.0.2.222 play 3914 OK bfd8a98bee0840d9b871b7f6ade9908f rtmp://shqshne4jdp4b6.cloudfront.net/cfx/st key=value http://player.longtailvideo.com/player.swf http://www.longtailvideo.com/support/jw-player-setup-wizard?example=204 LNX%2010,0,32,18 myvideo p=2&q=4 flv 1 2010-03-12 23:53:44 SEA4 192.0.2.4 stop 323914 OK bfd8a98bee0840d9b871b7f6ade9908f rtmp://shqshne4jdp4b6.cloudfront.net/cfx/st key=value http://player.longtailvideo.com/player.swf http://www.longtailvideo.com/support/jw-player-setup-wizard?example=204 LNX%2010,0,32,18 dir/other/myvideo p=2&q=4 flv 1 2010-03-12 23:53:44 SEA4 192.0.2.103 play 8783724 OK bfd8a98bee0840d9b871b7f6ade9908f rtmp://shqshne4jdp4b6.cloudfront.net/cfx/st key=value http://player.longtailvideo.com/player.swf http://www.longtailvideo.com/support/jw-player-setup-wizard?example=204 LNX%2010,0,32,18 dir/favs/myothervideo p=42&q=14 mp4 2 2010-03-12 23:56:21 SEA4 192.0.2.199 stop 429822014 OK bfd8a98bee0840d9b871b7f6ade9908f rtmp://shqshne4jdp4b6.cloudfront.net/cfx/st key=value http://player.longtailvideo.com/player.swf http://www.longtailvideo.com/support/jw-player-setup-wizard?example=204 LNX%2010,0,32,18 dir/favs/myothervideo p=42&q=14 mp4 2 2010-03-12 23:59:44 SEA4 192.0.2.14 disconnect 429824092 OK bfd8a98bee0840d9b871b7f6ade9908f rtmp://shqshne4jdp4b6.cloudfront.net/cfx/st key=value http://player.longtailvideo.com/player.swf http://www.longtailvideo.com/support/jw-player-setup-wizard?example=204 LNX%2010,0,32,18 - - - -
Charges for Access Logs
Access logging is an optional feature of CloudFront. There is no extra charge for enabling access logging. However, you accrue the usual Amazon S3 charges for storing and accessing the files on Amazon S3 (you can delete them at any time). For more information about charges for CloudFront, see CloudFront Reports.