hc000 reports that under moderate load from multiple concurrent web clients
with pcp 3.11.3 (bintray?) on ubuntu, pmwebd intermittently reports "IPC
protocol failure" errors, breaking connections. A -Dpdu type log indicates
considerable traffic. It is suspicious that the trace ends with a pmXmitPDU
FETCH followed by a pmGetPDU: PMNS_IDS. (Note that the pmapi subset of pmwebd
is single-threaded, but maintains distinct pmapi contexts for web clients.)
[10995]pmXmitPDU: PMNS_NAMES fd=8 len=52
000: 34 700e 10 18000000 0 1000000 17000000 6b736964
008: 7665642e 6165722e 61725f64 74636177 7e657669
[10995]pmGetPDU: PMNS_IDS fd=8 len=24 from=0
000: 18 700d 0 1000000 1000000 2e00000f
[10995]pmXmitPDU: PMNS_NAMES fd=8 len=52
000: 34 700e 10 19000000 0 1000000 18000000 6b736964
008: 7665642e 6972772e 725f6574 63617761 65766974
[10995]pmGetPDU: PMNS_IDS fd=8 len=24 from=0
000: 18 700d 0 1000000 1000000 4800000f
[10995]pmXmitPDU: FETCH fd=8 len=164
000: a4 7003 10 10000000 0 0 22000000 6004000
008: 1004000 1600000f 1400000f 2000000f 200000f f 208000f 8000f
016: c000f 80c000f 14c000f 64c000f 84c000f 10c000f 90c000f 3d38000f
024: 40d4000f 25d4000f 3dd4000f 3fd4000f 504000f 104000f 204000f 404000f
032: 1070000f 1170000f d00000f 400000f 500000f 2600000f 2700000f 2e00000f
040: 4800000f
[10995]pmGetPDU: PMNS_IDS fd=8 len=24 from=0
000: 18 700d 0 1000000 1000000 4900000f
[Tue Jul 26 20:29:22] pmwebd(10995): [135.28.59.140:53515] pmFetch failed: IPC
protocol failure