The arrows in the left most represent incoming request stream. Do we assume that this request is coming all at once ? or that requests are coming in different time intervals ?
The second set of blue dotted arrows are kind of misleading (to me at least). It makes me assume that what ever comes into the server (load balancer) is forwarded as it is to the web server. If that's the case, Does the load balancer guarantee that the web servers will always have equal amounts of work? Does it have to remember anything to decide ?
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rokhinip
Requests to a site can be made simultaneously by multiple users or over different time intervals. The latter case is trivial to handle and so mainly consider the case of multiple simultaneous requests as represented by the left most blue arrows. The second set of blue arrows are not misleading because the requests coming into the site are directly forwarded to the web-servers through the load balancer.
As evidenced by the name, the load balancer simply determines which web server should service a request. The heavy lifting and computation is done by the web server. The load balancer doesn't guarantee equal amounts of work because it cannot know beforehand about the amount of work for each request. Moreover, this is also dependent on the way each web server further splits up the work amongst the worker processes. It can however, use some heuristics to possibly estimate the work load of each web server.
How the load balancer decides to allocate requests to web servers is analogous to asking how any kind of scheduling mechanism works. In this case, there is presumably some querying about the resource availability of each web server. There might also be information in the incoming request which indicates how long it could take (like we do in our homework) and the load balancer might use this information to influence its scheduling policy.
I think an interesting parallel is that of how ISPC tasks are run. We can think of each request to the site here as being 1 ISPC task. Each ISPC task is handled in any order and by any core, much like the requests here are handled in any order (according to the scheduling policy of the load balancer) and by any web server. And finally, the allocation of an ISPC task to a worker/core is dependent on resource availability and busyness of workers and presumably, those factors also come into play here.
The arrows in the left most represent incoming request stream. Do we assume that this request is coming all at once ? or that requests are coming in different time intervals ? The second set of blue dotted arrows are kind of misleading (to me at least). It makes me assume that what ever comes into the server (load balancer) is forwarded as it is to the web server. If that's the case, Does the load balancer guarantee that the web servers will always have equal amounts of work? Does it have to remember anything to decide ?
This comment was marked helpful 0 times.
Requests to a site can be made simultaneously by multiple users or over different time intervals. The latter case is trivial to handle and so mainly consider the case of multiple simultaneous requests as represented by the left most blue arrows. The second set of blue arrows are not misleading because the requests coming into the site are directly forwarded to the web-servers through the load balancer.
As evidenced by the name, the load balancer simply determines which web server should service a request. The heavy lifting and computation is done by the web server. The load balancer doesn't guarantee equal amounts of work because it cannot know beforehand about the amount of work for each request. Moreover, this is also dependent on the way each web server further splits up the work amongst the worker processes. It can however, use some heuristics to possibly estimate the work load of each web server.
How the load balancer decides to allocate requests to web servers is analogous to asking how any kind of scheduling mechanism works. In this case, there is presumably some querying about the resource availability of each web server. There might also be information in the incoming request which indicates how long it could take (like we do in our homework) and the load balancer might use this information to influence its scheduling policy.
I think an interesting parallel is that of how ISPC tasks are run. We can think of each request to the site here as being 1 ISPC task. Each ISPC task is handled in any order and by any core, much like the requests here are handled in any order (according to the scheduling policy of the load balancer) and by any web server. And finally, the allocation of an ISPC task to a worker/core is dependent on resource availability and busyness of workers and presumably, those factors also come into play here.
This comment was marked helpful 0 times.