Understanding Acquia log analysis

One of Acquia's internal monitoring tools performs a log analysis of recent traffic to your website, allowing the Support team to determine if there have been changes to your website's traffic patterns, or your website's response to them, by breaking down per-hour traffic reports into a table.

Acquia Support will sometimes provide this output to customers to help them understand what changes took place, and when. The output file may appear densely packed with information; this article can help you to interpret its contents.

Data structure

Here's an example of what the output might look like:

Date/Time          #Reqs   Avg(s)  Max(s)  #>5s  HTTP:2XX  3XX   4XX   403   404   5XX
28/Jul/2015:10:XX  40817   0.20    13.66   37    33413     1430  5974  690   5284  0
28/Jul/2015:11:XX  41395   0.24    47.05   125   34743     1490  5158  1168  3990  1
28/Jul/2015:12:XX  52454   0.21    13.02   82    44709     2097  5637  827   4810  9
28/Jul/2015:13:XX  60165   0.20    15.08   54    51330     2393  6439  868   5571  3
28/Jul/2015:14:XX  71464   0.23    10.43   29    62365     2997  6090  824   5266  11
28/Jul/2015:15:XX  92274   0.26    10.25   116   81635     3777  6857  889   5968  4

In the previous list, each line represents the compilation of an hour's requests. Every column in this line provides information about the traffic seen in this hour.

Column Description
#Reqs The total number of requests this hour. A larger number can indicate a traffic spike.
Avg(s) The average, in seconds, of how long each request took to complete. A larger number would indicate an hour where your website's instances struggled to keep up with demand.
Max(s) The maximum number of seconds the longest request took to complete in this hour.
#>5s How many requests in this hour took more than five seconds to complete.
HTTP:2XX The number of requests this hour that responded with a 2XX HTTP response code, indicating that the request was received and handled successfully. Higher numbers in this column are better.
3XX The number of requests this hour that responded with a 3XX HTTP response code, indicating a good request, but requiring some kind of redirection to complete.
4XX The number of requests this hour that responded with a 4XX HTTP response code, which typically indicates a problem (potentially client-side). Two specific 4XX-level response codes are are broken out separately in the following columns.
403 Forbidden. The request was a valid request, but the server is refusing to respond to it.
404 Not Found. The requested resource does not exist.
5XX The server has encountered an error.

For more information about HTTP status codes, see List of HTTP status codes.

What to look for

When reading this report, Acquia looks for many things, including:

  • Did the number of requests spike upward?
  • Did the average response time spike upward?
  • What requests take a tremendously long time to complete?
  • Did the overall ratio between 2XX/3XX/4XX/5XX responses change?
  • Are there a great deal of 5XX requests?
  • Does the ratio between good (2XX / 3XX) traffic and traffic returning 404 warrant a fix to the underlying cause of the 404s or the usage of the Fast 404 module to lessen their effect?

Acquia Support will generally make recommendations and point out where problems may be based on these statistics. By analyzing when and how the data changed, and comparing it to events that may have taken place at that time (such as code deploys, media campaigns, or news events), you can use this information to help understand where you may need to look to make optimization changes to your website.

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