foolscap: "an inbound callRemote ... failed" log entries include all arguments

[daira]

For example:

allmydata.storage.backends.cloud.cloud_common.CloudError: ("try 1 failed: PUT object ('shares/oh/ohcac6xn5ot7hxwfcstdeqcf4e/0.16624',) {}", '')
]
03:53:03.778 L23 []#87614 an inbound callRemote that we [n4zt] executed (on behalf of someone else, TubID uzie) failed
03:53:03.778 L10 []#87615  reqID=66831, rref=<allmydata.storage.bucket.BucketWriter object at 0x3bf6b50>, methname=RIBucketWriter.write
03:53:03.792 L10 []#87616  args=[8716681284L, '<VERY long string>']
03:53:03.792 L10 []#87617  kwargs={}
03:53:03.792 L10 []#87618  the LOCAL failure was: [...]

Note that in this case the cloud backend has avoided logging the data that we attempted to write, but foolscap has logged it, causing a temporary memory leak, and possibly resulting in performance problems when argument strings are large.

In other cases, logging the arguments of remote operations may leak secrets into the log (see also #562 and related tickets).

[daira]

Also filed against foolscap as ​http://foolscap.lothar.com/trac/ticket/205.