Many non-blocking "java.nio.file.NoSuchFileException" traces with
warning log level can be logged by Solr, especially when heavily
crawling. This is issue is known from Solr 5.x but still unresolved with
Solr 6.x ( https://issues.apache.org/jira/browse/SOLR-9120 )
Consequently upgraded to "SEVERE" the default log level of the related
internal Solr class.
See also mantis 727 ( http://mantis.tokeek.de/view.php?id=727 )
This organizes all urls to be loaded in separate queues for each host.
Each host separates the crawl depth into it's own queue. The primary
rule for urls taken from any queue is, that the crawl depth is minimal.
This produces a crawl depth which is identical to the clickdepth.
Furthermorem the crawl is able to create a much better balancing over
all hosts which is fair to all hosts that are in the queue.
This process will create a very large number of files for wide crawls in
the QUEUES folder: for each host a directory, for each crawl depth a
file inside the directory. A crawl with maxdepth = 4 will be able to
create 10.000s of files. To be able to use that many file readers, it
was necessary to implement a new index data structure which opens the
file only if an access is wanted (OnDemandOpenFileIndex). The usage of
such on-demand file reader shall prevent that the number of file
pointers is over the system limit, which is usually about 10.000 open
files. Some parts of YaCy had to be adopted to handle the crawl depth
number correctly. The logging and the IndexCreateQueues servlet had to
be adopted to show the crawl queues differently, because the host name
is attached to the port on the host to differentiate between http,
https, and ftp services.
- transformed log lines to String before they are stored because the
storage space is about 1:250 (45kb for one line before transformation,
180 bytes afterwards)
- this saves up to 10MB RAM so we can increase the number of lines to
1000 again.
log4j-over-slf4j is there. From slf4j all loggings are routed to the jdk
logger. Now all loggings are consistently done to the jdk logger.
- added some lines to the logging properties to suppress many solr
logging statements. The number of the logging entries had already become
a performance issue, therefore removing these from the log should
increase performance.
title_count_i, title_chars_val, title_words_val
description_count_i, description_chars_val, description_words_val
- added many asserts to ensure data type correctness from YaCy to Solr
and vice versa
- made many fixes according to new findings from these asserts (!)
