WAL data grows forever even though data is delivered in E2E

With a heavy enough write load, it appears that the E2E agent WAL will get into a state where data just gets constantly shuffled around between the various directories / states (e.g. writing, logged, sending, sent). When this happens, the WAL directories grow indefinitely until the disk is exhausted, no matter how much data caused the problem.

To reproduce:

• Use the supplied config (or something similar).
• Write to the agent source at a rate of > 1MB/s for a short burst (using something like the provided generator below).
• Note that data is delivered to the collectorSink but the agent WAL manager constantly grows the data.

The config:

n1 : execStream("tail -F datafile") | agentE2ESink("host", 12345);
n2 : collectorSource(12345) | collectorSink("file://...", "n2-");

Generator:

perl -e 'while (1) { print $i++, "\n"; }' >> datafile

This looks and smells just like FLUME-430. I haven't yet examined the WAL or destination data for duplicates / missing events.