Re: Macro caching and other caching

Whoops, was misreading the API. It's actually that tempTemplateName
variable.

On Tue, Jul 31, 2012 at 11:21 AM, Bradley Wagner <
[email protected]> wrote:

> A StringWriter:
>
> String template = ... the string containing the dynamic template to
> generate ...
> // Get a template as stream.
> StringWriter writer = new StringWriter();
> StringReader reader = new StringReader(template);
> // create a temporary template name
> String tempTemplateName = "velocityTransform-" +
> System.currentTimeMillis();
>
> // ask Velocity to evaluate it.
> VelocityEngine engine = getEngine();
> boolean success = engine.evaluate(context, writer, tempTemplateName,
> reader);
>
> if (!success)
> {
>     LOG.debug("Velocity could not evaluate template with content: \n" +
> template);
>     return null;
> }
> LOG.debug("Velocity successfully evaluted template with content: \n" +
> template);
> String strResult = writer.getBuffer().toString();
> return strResult;
>
> On Tue, Jul 31, 2012 at 11:10 AM, Nathan Bubna <[email protected]> wrote:
>
>> What do you use for logTag (template name) when you are using evaluate()?
>>
>> On Tue, Jul 31, 2012 at 8:01 AM, Bradley Wagner
>> <[email protected]> wrote:
>> > Doing both. In the other case we're using a classpath resource loader to
>> > evaluate templates like this:
>> >
>> > VelocityContext = ... a context that we're building each time ...
>> > VelocityEngine engine = ... our single engine ...
>> > Template template = engine.getTemplate(templatePath);
>> > StringWriter writer = new StringWriter();
>> > template.merge(context, writer);
>> >
>> > However, we only have 7 of those static templates in our whole system.
>> >
>> > On Tue, Jul 31, 2012 at 10:52 AM, Nathan Bubna <[email protected]>
>> wrote:
>> >>
>> >> And you're sure you're only using VelocityEngine.evaluate?  Not
>> >> loading templates through the resource loader?  Or are you doing both?
>> >>
>> >> On Mon, Jul 30, 2012 at 2:51 PM, Bradley Wagner
>> >> <[email protected]> wrote:
>> >> > Nathan,
>> >> >
>> >> > Tokens are referenced by
>> >> > org.apache.velocity.runtime.parser.node.ASTReference which seem to be
>> >> > referenced by arrays of
>> org.apache.velocity.runtime.parser.node.Nodes.
>> >> > Most
>> >> > of the classes referencing these things are AST classes in the
>> >> > org.apache.velocity.runtime.parser.node package.
>> >> >
>> >> > Here's our properties file:
>> >> >
>> >> > runtime.log.logsystem.class =
>> >> >
>> >> >
>> org.apache.velocity.runtime.log.Log4JLogChute,org.apache.velocity.runtime.log.AvalonLogSystem
>> >> >
>> >> >
>> runtime.log.logsystem.log4j.logger=com.hannonhill.cascade.velocity.VelocityEngine
>> >> >
>> >> > runtime.log.error.stacktrace = false
>> >> > runtime.log.warn.stacktrace = false
>> >> > runtime.log.info.stacktrace = false
>> >> > runtime.log.invalid.reference = true
>> >> >
>> >> > input.encoding=UTF-8
>> >> > output.encoding=UTF-8
>> >> >
>> >> > directive.foreach.counter.name = velocityCount
>> >> > directive.foreach.counter.initial.value = 1
>> >> >
>> >> > resource.loader = class
>> >> >
>> >> > class.resource.loader.description = Velocity Classpath Resource
>> Loader
>> >> > class.resource.loader.class =
>> >> > org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader
>> >> >
>> >> > velocimacro.permissions.allow.inline.local.scope = true
>> >> >
>> >> > Thanks!
>> >> > Bradley
>> >> >
>> >> > On Mon, Jul 30, 2012 at 4:47 PM, Nathan Bubna <[email protected]>
>> wrote:
>> >> >>
>> >> >> On Mon, Jul 30, 2012 at 1:30 PM, Bradley Wagner
>> >> >> <[email protected]> wrote:
>> >> >> > Thanks for the input.
>> >> >> >
>> >> >> > What we're seeing is that Velocity seems to be holding on to a lot
>> >> >> > of org.apache.velocity.runtime.parser.Token objects (around 5
>> >> >> > million).
>> >> >> > We
>> >> >> > allow people to write arbitrary Velocity templates in our system
>> and
>> >> >> > are
>> >> >> > evaluating them with:
>> >> >> >
>> >> >> > VelocityEngine.evaluate(Context context, Writer writer, String
>> >> >> > logTag,
>> >> >> > Reader reader)
>> >> >> >
>> >> >> > I was under the impression that Templates evaluated this way are
>> >> >> > inherently
>> >> >> > not cacheable. Is that the case? If that's not true, is there a
>> way
>> >> >> > to
>> >> >> > control the cache Velocity is using for these?
>> >> >>
>> >> >> me too.  just out of curiosity, what properties are you using for
>> >> >> configuration?  and can you tell any more about what class is
>> holding
>> >> >> onto those Tokens?
>> >> >>
>> >> >> > On Thu, Jul 19, 2012 at 10:26 AM, Alex Fedotov <[email protected]>
>> >> >> > wrote:
>> >> >> >
>> >> >> >> I think that Velocity has one global hash table for macros from
>> the
>> >> >> >> *.vm
>> >> >> >> libraries and that is more or less static for the life time of
>> the
>> >> >> >> Velocity
>> >> >> >> engine.
>> >> >> >>
>> >> >> >> I wish there there was a mechanism to control the list of the
>> *.vm
>> >> >> >> files
>> >> >> >> and their order of lookup for each individual merge (thread).
>> This
>> >> >> >> would
>> >> >> >> facilitate macro overloads based on the context.
>> >> >> >> Unfortunately this feature is not available.
>> >> >> >>
>> >> >> >> I think the 1.7 behavior is (more or less):
>> >> >> >>
>> >> >> >> When template reference is found (i.e. #parse("x")) it is
>> looked-up
>> >> >> >> in
>> >> >> >> the
>> >> >> >> resource cache and if found there (with all the expiration
>> checks,
>> >> >> >> etc.)
>> >> >> >> the parsed AST tree is used.
>> >> >> >> If not found the template is loaded from the file, actually
>> parsed
>> >> >> >> and
>> >> >> >> put
>> >> >> >> into the cache. During the actual parsing process the macros that
>> >> >> >> are
>> >> >> >> defined in the template are put into the macro manager cache
>> which
>> >> >> >> is
>> >> >> >> organized as:
>> >> >> >> "defining template name (name space)" => "macro name" => AST
>> macro
>> >> >> >> code
>> >> >> >> The AST is then rendered in the current context running #parse.
>> >> >> >>
>> >> >> >> When the time comes to call a macro there is a lookup process
>> which
>> >> >> >> can
>> >> >> >> be
>> >> >> >> influenced by some props, but the most general case is:
>> >> >> >>
>> >> >> >> 1. Lookup in the global *.vm files, if found use that.
>> >> >> >> 2. Lookup in the same "name space" that calls the macro, if found
>> >> >> >> use
>> >> >> >> that.
>> >> >> >> 3. Going back through the "list" of the #parse-d templates
>> lookup in
>> >> >> >> each
>> >> >> >> name space on the stack.
>> >> >> >>
>> >> >> >> The stack can be actually very long too, for example
>> >> >> >>
>> >> >> >> #foreach($templ in [1..5])
>> >> >> >>   #parse("${templ}.vtl")
>> >> >> >> #end
>> >> >> >>
>> >> >> >> #mymacro()
>> >> >> >>
>> >> >> >> The lookup list here would contain:
>> >> >> >>
>> >> >> >> 1.vtl, 2.vtl, 3.vtl, 4.vtl, 5.vtl
>> >> >> >>
>> >> >> >> This is true even for cases where the name is the same:
>> >> >> >>
>> >> >> >> #foreach($item in [1..5])
>> >> >> >>   #parse('item.vtl')
>> >> >> >> #end
>> >> >> >>
>> >> >> >> The lookup list here would contain:
>> >> >> >>
>> >> >> >> item.vtl, item.vtl, item.vtl, item.vtl, item.vtl
>> >> >> >>
>> >> >> >> There is no attempt to optimize the lookup list and collapse the
>> >> >> >> duplicates.
>> >> >> >>
>> >> >> >> Unfortunately 1.7 also had some nasty concurrency bugs there that
>> >> >> >> had
>> >> >> >> to do
>> >> >> >> with clearing the name space of all the macros and repopulating
>> it
>> >> >> >> again on
>> >> >> >> each parse which did not work at all with multiple threads.
>> >> >> >> One thread could clear the name space while another was doing a
>> >> >> >> lookup,
>> >> >> >> etc.
>> >> >> >>
>> >> >> >> I think there was an effort to redesign that part in 2.0, but I
>> have
>> >> >> >> not
>> >> >> >> looked at that yet.
>> >> >> >>
>> >> >> >> Alex
>> >> >> >>
>> >> >> >> On Wed, Jul 18, 2012 at 5:42 PM, Bradley Wagner <
>> >> >> >> [email protected]> wrote:
>> >> >> >>
>> >> >> >> > Hi,
>> >> >> >> >
>> >> >> >> > We recently made some changes to our software to use just a
>> single
>> >> >> >> > VelocityEngine as per recommendations on this group.
>> >> >> >> >
>> >> >> >> > We ran into an issue where macros were all of the sudden being
>> >> >> >> > shared
>> >> >> >> > across template renders because we had not
>> >> >> >> > specified: velocimacro.permissions.allow.inline.local.scope =
>> >> >> >> > true.
>> >> >> >> > However, we also had not ever turned on caching in our props
>> file
>> >> >> >> > with: class.resource.loader.cache = true.
>> >> >> >> >
>> >> >> >> > Does this mean that macros are cached separately from whatever
>> is
>> >> >> >> > being
>> >> >> >> > cached in the class.resource.loader.cache cache? Is there any
>> way
>> >> >> >> > to
>> >> >> >> > control that caching or is just using this property the
>> >> >> >> > way: velocimacro.permissions.allow.inline.local.scope = true
>> >> >> >> >
>> >> >> >> > One side effect of our recent changes is that the app seems to
>> >> >> >> > have
>> >> >> >> > an
>> >> >> >> > increased mem footprint. We're not *sure* it can be attributed
>> to
>> >> >> >> velocity
>> >> >> >> > but I was trying to see what kinds of things Velocity could be
>> >> >> >> > hanging on
>> >> >> >> > to and how much memory they might be taking up.
>> >> >> >> >
>> >> >> >> > Thanks!
>> >> >> >> >
>> >> >> >>
>> >> >
>> >> >
>> >
>> >
>>
>
>