Hi Lewis, The results of TRACE level logging will give you messages from the various system components according to whatever those developers thought relevant for exposing from the application. Assembling the HTrace spans from a single trace will give you something similar, but structured according to the major boundaries within the system. The original intention is for tracing a single request through multiple RPC's across multiple systems. At the very least, you'd see these boundary points and the amount of time spent in each component. Each component's developers are free to use the HTrace API to attach "annotations" to their trace spans. These annotations are arbitrary messages, accompanied by timestamps, included by the whims of the projects' developers.
I guess the big difference is that trace spans collected by HTrace are a bit more structured than simple log messages. There's a parent-child relationship between spans, and this hierarchy exists across threads within a process and across processes within a distributed application. Maybe someone else can do a better job explaining... -n On Thu, Feb 26, 2015 at 12:57 PM, Lewis John Mcgibbney < [email protected]> wrote: > Hi Folks, > Right now we are able to initiate TRACE within Log4j file in Nutch 2.X [0]. > Nutch 2.X offer storage abstraction for storage of Webpage and Host data > through use of Apache Gora. > Gora backend support includes > > - Apache Avro 1.7.6 > - Apache Hadoop 1.2.1 and 2.5.2 > - Apache HBase 0.98.8-hadoop2 > - Apache Cassandra 2.0.2 > - Apache Solr 4.10.3 > - MongoDB 2.6.X > - Apache Accumlo 1.5.1 > > Parts of the Nutch 2.X search stack include Nutch, Gora, optionally Solr > and/or Elastic Search for indexing context and optionally Hadoop for > running it all on. > > As a developer of Nutch and Gora am very keen to see a more verbose tracing > mechanism (potentially with some visualization) for debugging our search > stack deployments. Can I please kick off conversation on what the > difference and benefits of H Trace are over log4j TRACE level logging. > > Once I understand the above, I would like to obtain advice on the > integration points for having HTrace as the tracing mechanism for the stack > I describe above. > Thanks > Lewis > > [0] https://github.com/apache/nutch/blob/2.x/conf/log4j.properties > -- > *Lewis* >
