a main problem when crawling is long waiting time cuased by crawl-delay
values from robots.txt entries. that attribute is not supported by
google and interpreted by yandex and bing in different ways. In large
crawls there is always one host which blocks the whole crawl with
extreme large values. YaCy now still obeys crawl-delay but limits them
to 10 seconds.
Additionally the blocking logic when loading new robots.txt was analyzed
and a deadlock was removed. Furthermore the construction of new queue
lists was redesigned and it was ensured that always a large list of
different hosts for host-balancing is provided for the loader.
For finer control over which parsed documents can trigger an addition of
their links to the crawl stack, complementary to the existing crawl
depth parameter.
New "Media Type detection" section in the advanced crawl start page
allow to choose between :
- not loading URLs with unknown or unsupported file extension without
checking the actual Media Type (relying Content-Type header for now).
This was the old default behavior, faster, but not really accurate.
- always cross check URL file extension against the actual Media Type.
This lets properly parse URLs ending with an apparently odd file
extension, but which have actually a supported Media Type such as
text/html.
Sample URLs with misleading file extensions added as documentation in
the crawl start page.
fixes issue #244
When using the 'From Link-List of URL' as a crawl start, with lists in
the order of one or more thousands of links, the failreason_s Solr field
maximum size (32kb) was exceeded by the string representation of the URL
must-match filter when a crawl URL was rejected because not matching.
This makes possbile to set up much more advanced document crawl filters,
by filtering on one or more document indexed fields before inserting in
the index.
Initializing Thread names using the Thread constructor parameter is
faster as it already sets a thread name even if no customized one is
given, while an additional call to the Thread.setName() function
internally do synchronized access, eventually runs access check on the
security manager and performs a native call.
Profiling a running YaCy server revealed that the total processing time
spent on Thread.setName() for a typical p2p search was in the range of
seconds.
Required for proper operation when the default system locale is Turkish,
as dottless and dotted i characters have specific case conversion rules
in this language.
When a crawl is started, a new field to exclude content from scraping is
available. The field can be identified with the class name of div tags.
All text contained in such a div tag where the configured class name(s)
match are not indexed, while the remaining page is indexed.
Using a Reentrant lock instead of the intrinsic synchronization lock
permits limiting the blocking time to acquire a lock.
Useful on a very busy Cache concurrently accessed by many threads : when
the time to acquire a lock is too high, getting/storing content on the
cache becomes inefficient, and it is then better to fall back to loading
remote resources.
Illustrated by the CacheTest stress test and some traces reported in
mantis 751 ( http://mantis.tokeek.de/view.php?id=751 )
Shutdown was hanging in CrawlQueues.close() at
this.workerQueue.put(POISON_REQUEST) when config value
crawler.MaxActiveThreads was greater than 200.
Revealed by "Collision" Threads dumps in mantis 689
(http://mantis.tokeek.de/view.php?id=689#c1312)
Fixed consistency between this.worker.length and this.workerQueue
capacity, and made the process more reliable using non-blocking offer()
function.
Even after network switch, ErroCache was still holding a reference to
the previous Solr cores, thus becoming useless until next YaCy restart.
Initial error cache filling with recent errors from the index was also
missing after the swtich.
If remote crawl option is not activated, skip init of remoteCrawlJob to save the resources of queue and ideling thread.
Deploy of the remoteCrawlJob deferred on activation of the option.
to support the new time parser and search functions in YaCy a high
precision detection of date and time on the day is necessary. That
requires that the time zone of the document content and the time zone of
the user, doing a search, is detected. The time zone of the search
request is done automatically using the browsers time zone offset which
is delivered to the search request automatically and invisible to the
user. The time zone for the content of web pages cannot be detected
automatically and must be an attribute of crawl starts. The advanced
crawl start now provides an input field to set the time zone in minutes
as an offset number. All parsers must get a time zone offset passed, so
this required the change of the parser java api. A lot of other changes
had been made which corrects the wrong handling of dates in YaCy which
was to add a correction based on the time zone of the server. Now no
correction is added and all dates in YaCy are UTC/GMT time zone, a
normalized time zone for all peers.
- date navigation
The date is taken from the CONTENT of the documents / web pages, NOT
from a date submitted in the context of metadata (i.e. http header or
html head form). This makes it possible to search for documents in the
future, i.e. when documents contain event descriptions for future
events.
The date is written to an index field which is now enabled by default.
All documents are scanned for contained date mentions.
To visualize the dates for a specific search results, a histogram
showing the number of documents for each day is displayed. To render
these histograms the morris.js library is used. Morris.js requires also
raphael.js which is now also integrated in YaCy.
The histogram is now also displayed in the index browser by default.
To select a specific range from a search result, the following modifiers
had been introduced:
from:<date>
to:<date>
These modifiers can be used separately (i.e. only 'from' or only 'to')
to describe an open interval or combined to have a closed interval. Both
dates are inclusive. To select a specific single date only, use the
'to:' - modifier.
The histogram shows blue and green lines; the green lines denot weekend
days (saturday and sunday).
Clicking on bars in the histogram has the following reaction:
1st click: add a from:<date> modifier for the date of the bar
2nd click: add a to:<date> modifier for the date of the bar
3rd click: remove from and date modifier and set a on:<date> for the bar
When the on:<date> modifier is used, the histogram shows an unlimited
time period. This makes it possible to click again (4th click) which is
then interpreted as a 1st click again (sets a from modifier).
The display feature is NOT switched on by default; to switch it on use
the /ConfigSearchPage_p.html servlet.
given css class and extends a given vocabulary with a term consisting
with the text content of the html class tag. Additionally, the term is
included into the semantic facet of the document. This allows the
creation of faceted search to documents without the pre-creation of
vocabularies; instead, the vocabulary is created on-the-fly, possibly
for use in other crawls. If any of the term scraping for a specific
vocabulary is successful on a document, this vocabulary is excluded for
auto-annotation on the page.
To use this feature, do the following:
- create a vocabulary on /Vocabulary_p.html (if not existent)
- in /CrawlStartExpert.html you will now see the vocabularies as column
in a table. The second column provides text fields where you can name
the class of html entities where the literal of the corresponding
vocabulary shall be scraped out
- when doing a search, you will see the content of the scraped fields in
a navigation facet for the given vocabulary
Michael Peter Christen