Full content is available from Wiki, this seems to be an essential extract, from our POV. Many will not understand some, or all of it, I’m struggling myself, but our problems seem well illustrated in this copy.-
Load limits[edit]
A web server (program) has defined load limits, because it can handle only a limited number of concurrent client connections (usually between 2 and 80,000, by default between 500 and 1,000) per
IP address (and TCP port) and it can serve only a certain maximum number of
requests per second (RPS, also known as
queries per second or QPS) depending on:
- its own settings,
- the HTTP request type,
- whether the content is static or dynamic,
- whether the content is cached, and
- the hardware and software limitations of the OS of the computer on which the web server runs.
When a web server is near to or over its limit, it becomes unresponsive.
Causes of overload[edit]
At any time web servers can be overloaded due to:
- Excess legitimate web traffic. Thousands or even millions of clients connecting to the web site in a short interval, e.g., Slashdot effect;
-
Distributed Denial of Service attacks. A denial-of-service attack (DoS attack) or distributed denial-of-service attack (DDoS attack) is an attempt to make a computer or network resource unavailable to its intended users;
-
Computer worms that sometimes cause abnormal traffic because of millions of infected computers (not coordinated among them)
-
XSS viruses can cause high traffic because of millions of infected browsers or web servers;
-
Internet bots Traffic not filtered/limited on large web sites with very few resources (bandwidth, etc.);
-
Internet (network) slowdowns, so that client requests are served more slowly and the number of connections increases so much that server limits are reached;
- Web servers (computers) partial unavailability. This can happen because of required or urgent maintenance or upgrade, hardware or software failures, back-end (e.g., database) failures, etc.; in these cases the remaining web servers get too much traffic and become overloaded.
Symptoms of overload[edit]
The symptoms of an overloaded web server are:
- Requests are served with (possibly long) delays (from 1 second to a few hundred seconds).
- The web server returns an HTTP error code, such as 500, 502, 503, 504, 408, or even 404, which is inappropriate for an overload condition.
- The web server refuses or resets (interrupts) TCP connections before it returns any content.
- In very rare cases, the web server returns only a part of the requested content. This behavior can be considered a bug, even if it usually arises as a symptom of overload.
Interesting to note that Error codes are described as 'inappropriate for an overload condition'!
I think that means 404 is technically inappropriate, since it indicates that a connection has been made but the server can’t handle it. I have had that today, but I have also been getting 503, which is the actual overload error code.
I don’t usually worry about delays serving the response when posting, or loading times, but today is the worst I can remember.
Problem is of course that it avalanches because people just try to reload the page, so the server gets multiple hits.
Which looks like exactly what you’ve done John? It’s a right Royal PITA I spent quite a while reloading images on another thread about my car, deleting blank image boxes, copying from postimage over to the forum only to get 404 and 503 messages? The disappearing images were the fault of postimage to be fair, but I can’t get the images to reload? Oh well. ![]()
Barrie
Which looks like exactly what you’ve done John? It’s a right Royal PITA I spent quite a while reloading images on another thread about my car, deleting blank image boxes, copying from postimage over to the forum only to get 404 and 503 messages? The disappearing images were the fault of postimage to be fair, but I can’t get the images to reload? Oh well. ![]()
Barrie
Should we all stop using the forum for 7 days and allow the techy peeps to resolve the issues?
Is that feasible?
Grant
Should we all stop using the forum for 7 days and allow the techy peeps to resolve the issues?
Is that feasible?
Grant
Particularly bad at the moment, more 404s than you can shake a stick at.
Forum index page shows 54 user online in the last five minutes.
Can anybody explain that?
I’ve had problems in the early hours too so how can it be due to too much load on the server?
Seems to remember all this was being discussed at a high level meeting a few weeks back.
Did anything come of those discussions?
![]()
Particularly bad at the moment, more 404s than you can shake a stick at.
Forum index page shows 54 user online in the last five minutes.
Can anybody explain that?
I’ve had problems in the early hours too so how can it be due to too much load on the server?
Seems to remember all this was being discussed at a high level meeting a few weeks back.
Did anything come of those discussions?
![]()
In trying to reply to an email notification on another thread about the site performance, it has taken me EIGHT attempts to get this far. Three server lockouts, two 503 errors, two 404 errors and finally this page loaded after waiting 112.833 seconds.
Anyone who comes on and tries to defend that performance should have a real hard look in a mirror.
Every post seems to get a doppelganger.![]()
![]()