Hi again.
On this list, it is customary (and requested) to respond in-line and not "top
post".
See : http://tomcat.apache.org/lists.html#tomcat-users, item #6.
It makes it easier to follow the conversation, as opposed to having to scroll back and
forth to find out what you are commenting on.
On 18.04.2017 16:58, Chris Gamache wrote:
Excellent information. Thank you!
Is there a way to create a split point where sendFile will handle files of
certain mime types (or all mime-types except for an exclusion list of mime
types) and/or of certain sizes while compression will handle files of other
mime-types and/or certain sizes?
Both settings have a minimum file size that engages their mechanism but to
set up a division of labor I would think we would need all of
include/exclude and max/min for both sendfile() and compression. Again, I
could be missing something obvious by staring at the problem too long.
As you have probably already found out from the extensive and exquisitely written on-line
tomcat documentation, there do not seem to exist such fine-tuned parameters available in
the standard tomcat Connectors.
If you want this type of control, /and/ you can more or less determine the kind of
response you want to send by examining the request URL, I would have a look at a servlet
filter such as URLRewrite (http://tuckey.org/urlrewrite/), which could examine the request
and determine to which specific response-generating servlet it should dispatch the call.
In that servlet you can then decide yourself to compress or not the output, and/or to use
sendfile.
@André and the rest of the listserv, In your opinions-- thinking about the
web site consumer's experience, and having to choose either send sendfile()
or compression-- is the juice worth the squeeze so-to-speak keeping
sendfile() and sending uncompressed files, or is the better choice to
enable compression at the expense of direct static file access and save
bandwidth?
I think that this is a question to which you are the only one who can provide the right
answer, because "it depends" on a lot of factors that are specific to your application,
your mix of documents, your bandwidth availability and cost, the requirements of your
clients etc..
On Tue, Apr 18, 2017 at 9:08 AM, André Warnier (tomcat) <a...@ice-sa.com>
wrote:
On 18.04.2017 14:50, Chris Gamache wrote:
Using tomcat 8.0.43 ...
I'm grappling with GZip compression options. Historically, I've used a
custom GZip filter and that's been fine for the most part. If the file
being served is under 50K the filter would compress it in memory and send
it out. If the file is over 50K, it would connect the OutputStream to a
GZipOutputStream rather than compressing the whole thing in memory and
then
sending it out from there. When that happens it doesn't send a
Content-Length header. This is fine for most browsers. Safari has a
problem
with this and will decline to receive the file. In looking at the GZip
filter I've been using, it's kind-of naive-- there must be a more
intelligent compression option built into tomcat by now, right?
To enable compression, I set `compression="on"` in my <Connector/> element
in my server.xml file. There is on sticking point-- if sendFile is
available (asynchronous file-sending by the DefaultServlet using NIO) it
will trump compression by default. I can turn off sendFile, and browsers
report that they are receiving compressed files. So it seems like an
all-or-nothing situation where compression and sendFile are mutually
exclusive. There are minimum file size settings for both options, but no
max file size settings so I can't say "use sendFile for files under 50K
and
compression for files above 50K" because sendFile will always trump
compression.
I think the idea of sending out static files asynchronously is fantastic..
I
also want my pages to load faster by sending less data.
I figure the smart people who work on tomcat know a whole lot more about
this stuff than I do. They must have had a reason to prioritize sendFile
over compression, or the expert tomcat administrators have figured out a
way to balance the two.
Maybe I've been staring at the problem too long, but I can't figure it
out.
So, is it advisable turn of sendFile to engage compression? Or, is there a
combination of settings that will let me best use them both?
For what it's worth :
sendfile() is a way by which the (web) application can just point the OS
to a static file on disk, and say "send this". And the sendfile logic in
the OS takes care of the rest, in the most efficient way possible for that
OS, and the call returns ok to your application right away, even possibly
before the sendfile() action has completed.
The sticky point here is "a static file on disk".
So if you want to send back a gzipped file, then the only solution is to
first create that gzipped version as a file on disk, and then use
sendfile() on that gzipped version.
And then, presumably, you'd want to "clean up" these gzipped versions at
some point.
Which cannot happen right after you have called sendfile(), because you do
not really know when it will be done actually sending the file.
So it is not really a "priority" issue, it is that these are different
things, and that sendfile() really only works on a file, not on dynamic
output from a webapp.
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