1. A method of processing log data, comprising: determining a parser definition associated with a set of log data; compiling the parser definition to create an instance of a parser to parse the set of log data, wherein the parser has a hierarchical structure comprising a plurality of hierarchically related nodes, each of at least a subset of said nodes having associated therewith one or more actors each configured to parse data associated with that node; and sending at least a portion of the set of log data to the parser instance prior to compilation of said parser instance being completed; wherein a first node of said parser instance is configured to receive and parse log data associated with the first node even if compilation of the parser definition has not been completed with respect to a second node of said parser instance.