view roundup/cgi/TAL/TALParser.py @ 6565:2c2dbfc332ba

Try to handle multiple connections better. The session database is a hot spot. When multiple requests (e.g. 20) come in at the same time session database contention can get great. The original code didn't retry session database access when the open failed. This resulted in errors at the client. The second pass delayed 0.01 seconds and retried. It was better but we still had multiple second stalls. I think the first request got in, everybody else backed up and then retried at the same time. Again they stepped on each other. With logging I would see many counters go all the way to low single digits or to -1 indicating falure. This pass uses randomint to generate delays from 0-.125 seconds in 5ms increments. This performs better in testing. I rarely saw a counter less than 13 (2 failed retries). Current logging starts after 6 failures and counts down until success or failure.
author John Rouillard <rouilj@ieee.org>
date Thu, 16 Dec 2021 20:02:00 -0500
parents 23b8e6067f7c
children
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##############################################################################
#
# Copyright (c) 2001, 2002 Zope Corporation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.0 (ZPL).  A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
##############################################################################
"""
Parse XML and compile to TALInterpreter intermediate code.
"""

from .XMLParser import XMLParser
from .TALDefs import XML_NS, ZOPE_I18N_NS, ZOPE_METAL_NS, ZOPE_TAL_NS
from .TALGenerator import TALGenerator

class TALParser(XMLParser):

    ordered_attributes = 1

    def __init__(self, gen=None): # Override
        XMLParser.__init__(self)
        if gen is None:
            gen = TALGenerator()
        self.gen = gen
        self.nsStack = []
        self.nsDict = {XML_NS: 'xml'}
        self.nsNew = []

    def getCode(self):
        return self.gen.getCode()

    def getWarnings(self):
        return ()

    def StartNamespaceDeclHandler(self, prefix, uri):
        self.nsStack.append(self.nsDict.copy())
        self.nsDict[uri] = prefix
        self.nsNew.append((prefix, uri))

    def EndNamespaceDeclHandler(self, prefix):
        self.nsDict = self.nsStack.pop()

    def StartElementHandler(self, name, attrs):
        if self.ordered_attributes:
            # attrs is a list of alternating names and values
            attrlist = []
            for i in range(0, len(attrs), 2):
                key = attrs[i]
                value = attrs[i+1]
                attrlist.append((key, value))
        else:
            # attrs is a dict of {name: value}
            attrlist = sorted(attrs.items()) # Sorted for definiteness
        name, attrlist, taldict, metaldict, i18ndict \
              = self.process_ns(name, attrlist)
        attrlist = self.xmlnsattrs() + attrlist
        self.gen.emitStartElement(name, attrlist, taldict, metaldict, i18ndict)

    def process_ns(self, name, attrlist):
        taldict = {}
        metaldict = {}
        i18ndict = {}
        fixedattrlist = []
        name, namebase, namens = self.fixname(name)
        for key, value in attrlist:
            key, keybase, keyns = self.fixname(key)
            ns = keyns or namens # default to tag namespace
            item = key, value
            if ns == 'metal':
                metaldict[keybase] = value
                item = item + ("metal",)
            elif ns == 'tal':
                taldict[keybase] = value
                item = item + ("tal",)
            elif ns == 'i18n':
                assert 0, "dealing with i18n: " + repr((keybase, value))
                i18ndict[keybase] = value
                item = item + ('i18n',)
            fixedattrlist.append(item)
        if namens in ('metal', 'tal', 'i18n'):
            taldict['tal tag'] = namens
        return name, fixedattrlist, taldict, metaldict, i18ndict

    def xmlnsattrs(self):
        newlist = []
        for prefix, uri in self.nsNew:
            if prefix:
                key = "xmlns:" + prefix
            else:
                key = "xmlns"
            if uri in (ZOPE_METAL_NS, ZOPE_TAL_NS, ZOPE_I18N_NS):
                item = (key, uri, "xmlns")
            else:
                item = (key, uri)
            newlist.append(item)
        self.nsNew = []
        return newlist

    def fixname(self, name):
        if ' ' in name:
            uri, name = name.split(' ')
            prefix = self.nsDict[uri]
            prefixed = name
            if prefix:
                prefixed = "%s:%s" % (prefix, name)
            ns = 'x'
            if uri == ZOPE_TAL_NS:
                ns = 'tal'
            elif uri == ZOPE_METAL_NS:
                ns = 'metal'
            elif uri == ZOPE_I18N_NS:
                ns = 'i18n'
            return (prefixed, name, ns)
        return (name, name, None)

    def EndElementHandler(self, name):
        name = self.fixname(name)[0]
        self.gen.emitEndElement(name)

    def DefaultHandler(self, text):
        self.gen.emitRawText(text)

def test():
    import sys
    p = TALParser()
    file = "tests/input/test01.xml"
    if sys.argv[1:]:
        file = sys.argv[1]
    p.parseFile(file)
    program, macros = p.getCode()
    from .TALInterpreter import TALInterpreter
    from .DummyEngine import DummyEngine
    engine = DummyEngine(macros)
    TALInterpreter(program, macros, engine, sys.stdout, wrap=0)()

if __name__ == "__main__":
    test()

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