Why do multiple RPC calls in GWT significantly slow response time?_问答_开发者

I'm testing a Google Web Toolkit application and having some performance issue with multiple RPC calls. The structure of the app is:

User submits a query
Initial query is serviced by a single server-side servlet
Once initial reply received, multiple components ar开发者_如何转开发e subsequently updated by iterating over each component and calling an update method, passing it the results of the initial query
Each component's update method does some work on the data passed to it, in addition to potentially calling other server-side services
On success of these calls, the component is updated in the UI.

With the initial query service and 1 component (effectively running sequentially), response time is fast. However, adding any other components (e.g initial query service + 2 components, these 2 components calling asynchronously) hugely impacts the response time.

Is there any way to improve / rectify this?

Example: (IQS = initial query, C1 = component 1, C2 = component 2, C1S = comp. 1 service, C2S = component 2 service)

Initial Query + 1 component

IQS, returned - propagating results, 1297273015477
C1, Sending server request,1297273015477
C1S, Sending back..., 1297273016486
C1, Receiving Complete, 1297273016522 (total time from initial call - 1045ms)

Initial Query + 2 components

IQS, returned - propagating results, 1297272667185
C1, Sending server request,1297272667185
C2, Sending server request,1297272668132
C1S, Sending back..., 1297272668723 
C2S, Sending back..., 1297272669371
C1, Back at client to process, 1297272671077 (total time from initial call - 3892ms)
C2, Back at client to process, 1297272674518 (total time from initial call - 6386ms)

Thanks in advance.

Paul

I think you need to make your analysis more fine grained: in the data provided you have established that the client started the 2nd component call and got a response back 6386ms later. Some of this was

Going over the wire
Being received at the server
Processed at the server (this could be broken down, as well).
Sent back over the wire.

The GWT-RPC service really only has to do with 1 and 4. Do you know how long each step takes?

Well, I think your problem is not directly related to GWT. Because , I have used multiple rpc calls at same time, my application performance did not degraded.I think that you may have server side synchronization issues.

The overhead of http with cookies, and the sequencing of some of these (rather than firing all the request when the user is switching to another part of the application) is part of the reason why they seem to slow things down. E.G. A user requests a page, once that page's widgets are in place they fire requests for the data they're supposed to show, possibly making decisions to add more widgets based on that data (but hopefully passing the data into those widgets).

You might be looking for some tools that help you to create batched rpc calls like: gwt-dispatch. I don't think there's anything automatic.

A low-tech way to get more information is to put basic timing logging into every RPC to see how long they take. Create a new Date() at the top, subtract its ms from a new Date()'s ms at the end, print it to stdout or use Log.info() or whatever.

For something more industrial strength I used the "SpringSource tc" combined with Chrome's Speed Tracer in order to get a full stack view of what calls were taking what amount of time, and what was actually able to happen in parallel. Not trivial to set up but once I did I was able to zero in on the real issues (in my case it was getting tons of unnecessary information from Hibernate queries) very quickly.

Here's the basic info we used:

Download the tc Server Developer Edition (free) http://www.springsource.com/products/tc-server-developer-edition-preview

NOTE: Do not even THINK about installing in a directory structure that has spaces.....

Installing tc Server: Main Steps http://static.springsource.com/projects/tc-server/2.1/getting-started/html/ch06s02.html#install-developer-edition

Viewing Spring Insight Data In Google Speed Tracer http://static.springsource.com/projects/tc-server/2.0/devedition/html/ch04s04.html

url is now localhost:8080 instead of the old port address for the other installation of tomcat.

One more detail, you'll need to make a .war file and deploy that to the tomcat directory. (You're not getting perf data on dev mode, but rather a local GWT compiled release)

-- Andrew @ learnvc.com