1. A computer-implemented method for facilitating log stream processing in a distributed program execution service, comprising: under control of one or more computer systems configured with executable instructions, provisioning at least one virtual computer system instance in the distributed program execution service; provisioning at least one log stream in the distributed program execution service, access to the log stream made available to said at least one virtual computer system instance through a file-oriented interface; provisioning, in the distributed program execution service, a set of log stream processing agents arranged according to a log stream processing graph as determined at least in part by at least one interaction with a provisioning interface of the distributed program execution service, a plurality of the set of log stream processing agents being associated with at least one input log stream and at least one output log stream and the log stream processing graph determining when an output log stream of a first log stream processing agent of the set of log stream processing agents is an input log stream of a second log stream processing agent of the set of log stream processing agents; receiving a plurality of log records into the log stream through the file-oriented interface and streaming the plurality of log records in the log stream to at least one of the set of log stream processing agents; processing the log stream in real-time with the set of log stream processing agents in accordance with the log stream processing graph, the processing responsive to reconfigurations of at least the log stream, the set of log stream processing agents, and the log stream processing graph as determined at least in part by at least one interaction with the provisioning interface of the distributed program execution service; and storing an output of at least one of the set of log stream processing agents for inspection.