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TritonDataCenter / mdb_v8

postmortem debugging for Node.js and other V8-based programs
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CTRL+C of ::findjsobjects, followed by ::findjsobjects reports only some objects #91

Closed jordanhendricks closed 7 years ago

jordanhendricks commented 7 years ago

I was debugging a core file on a Manta object. I was running version 1.1 of mdb and version 3.14.5.11 of mdb_v8:

jhendricks@manta # mdb $MANTA_INPUT_FILE
Loading modules: [ libumem.so.1 libc.so.1 ld.so.1 ]
> ::version
mdb 1.1
> ::load v8
mdb_v8 version: 1.1.4 (release, from 3a6fad0)
V8 version: 3.14.5.11
Autoconfigured V8 support from target
C++ symbol demangling enabled

While running a ::findjsobjects on the core, I ran CTRL+C. I then ran ::findjsobjects again, expecting it to restart, or at least error. Instead, it produced some output:

> ::findjsobjects
^C
> ::findjsobjects
  OBJECT #OBJECTS   #PROPS CONSTRUCTOR: PROPS
80bfdfcd        2       44 Array
80bf8415        1       60 IncomingMessage: _readableState, readable, ...
80bf0595        1       11 Object: authorization, x-forwarded-for, date, ...
80becc0d        2       32 ServerResponse: domain, _events, _maxListeners, ...
80becba5        1       34 IncomingMessage: _readableState, readable, ...
80be9cbd        1        3 Object: ...
80be2931        2        2 TypeError: arguments, type
80bdf6fd        1        3 Object: scheme, params, signingString
80bdb741        1        6 Object: writeQueueSize, owner, onread, reading, ...
80bda495        1        9 Key: type, parts, part, comment, source, ...
80bd41d5        1        4 Object: methods, name, params, spec
80bd40f1        1       28 Socket: _connecting, _handle, _readableState, ...
80bd40d5        1        4 Domain: domain, _events, _maxListeners, members
80bd11b9        2        7 Object: type, uuid, login, groups, ...
80bd1169        2        2 Object: roles, account
80bc8a7d        1       19 Socket: _connecting, _handle, _readableState, ...
80bc8791        2       24 FastMessageDecoder: _readableState, readable, ...
80bc8761        2        9 FastMessageEncoder: _readableState, readable, ...
80bc86e5        1       22 Socket: _connecting, _handle, _readableState, ...
80bc8639        1       15 FastConnection: domain, _events, _maxListeners, ...
80bc7b59        3       25 CueBallClaimHandle: ch_claimTimeout, ch_pool, ...
80bc6939        1       21 Socket: _connecting, _handle, _readableState, ...
80bc5079        7       28 Socket: _connecting, _handle, _readableState, ...
80bc4d79        1        3 Object: host, port, servername
80b8a5ed        4        1 Object: op
80b899e5       17        2 Object: metadata, parentMetadata
80b88f59       30        4 Object: op, metadata, etag, shard
80b8832d       17        4 Object: operations, successes, ndone, nerrors
80b873b5       34        5 Object: func, funcname, status, err, result
80b87325       32        2 Object: key, requestId
80b858f5       34        3 Object: op, metadata, etag
80b84869       30        1 Object: uuids
80b80401        2        3 Object: err, key, requestId
80b80101       32        2 Object: req_id, noCache
80b78865        4        2 Object: accept-encoding, accept
80b74165        4        1 Object: headers
>

After discussion with @davepacheco, we determined ::findjsobjects would have simply stopped running after the user CTRL-C. This means that this list is an incomplete set of objects in the file, which is quite confusing to the user, given that it happily printed objects.

::findjsobjects should report an error in this case. One way to do this is to set a flag indicating whether the operation is done. If that flag isn't set, the operation should report an error.

davepacheco commented 7 years ago

I've got this fixed in a change that's wrapped up with #88 and #44.