Hi Hiran, ... to answer the questions...
> What is the plugin's life cycle? Is there one plugin instance per > server? One per URL? One per thread? Or one in total? There is a single instance per plugin and task (a Java process running Nutch). In local mode (not running in a distributed manner on a Hadoop cluster), this means there is a single instance of every plugin. So the Fetcher job holds one single instance of every protocol plugin. > This scope defines whether I can make use of local variables, or > instance fields. Yes, you can use instance fields, e.g. to pool connections. > Or is there some other mechanism where a plugin could > store data that should survive across the getProtocolOutput calls? No. > Could a plugin define which scope it wants to be in? No. Keep in mind that most methods, for example, getProtocolOutput, need to be thread-safe. That is they might be called concurrently from multiple Fetcher threads. Best, Sebastian
