[mythtv-commits] Ticket #13404: QT5: QFileInfo is not registered to QMetaType at startup anymore

Sat Feb 9 13:21:47 UTC 2019

#13404: QT5: QFileInfo is not registered to QMetaType at startup anymore
----------------------------------+--------------------------
     Reporter:  rcrdnalor         |      Owner:  (none)
         Type:  Patch - Bug Fix   |     Status:  new
     Priority:  minor             |  Milestone:  needs_triage
    Component:  MythTV - General  |    Version:  v29-fixes
     Severity:  medium            |   Keywords:
Ticket locked:  0                 |
----------------------------------+--------------------------
 QT5: QFileInfo is not a registered QMetaType at startup anymore

 When I use the Services API to retrieve a preview on a freshly booted
 backend,
 I get an empty xml file, if it is run straight after start of mythbackend:

 {{{
 wget -O preview.png http://<be-
 address>:6544/Content/GetPreviewImage?RecordedId=<n>
 }}}

 The preview.png looks like an xml file holding the xml body only:

 {{{
 $ cat ./preview.png
 <?xml version="1.0" encoding="UTF-8"?><></>
 }}}

 The second attempt works as expected and returns a valid preview.png

 Note: This causes missing icons or thumbnails in MythWeb:

 Missing previews in MythWeb:
 {{{
 https://code.mythtv.org/trac/ticket/10707#comment:10
 https://code.mythtv.org/trac/ticket/10707#comment:11
 }}}

 Missing Channel Icons in MythWeb:
 {{{
 https://lists.gt.net/mythtv/users/620286
 https://forum.mythtv.org/viewtopic.php?f=6&t=2578&p=12580&hilit=icon#p12580
 }}}

 Every mornig, when I fire up MythWeb, I get these missing thumbnails.
 MythWeb causes the httpworker of mythtv to spawn multiple threads at the
 same time,
 therefore, the first 5 or 6 previews are corrupt.

 The reason for this is that in the file 'servicehost.cpp', the
 method 'QVariant MethodInfo::Invoke' tries to get the !MetaType-index of
 'QFileInfo'
 at line 81:

 {{{
 int nRetIdx = QMetaType::type( m_oMethod.typeName() );
 }}}

 but QFileInfo is not registered to QMetaType at this time.

 Note: After the first call, the type gets registered, because the
 Content Service 'QFileInfo Content::!GetPreviewImage' is actually called.

 Below the log excerpt with the applied path
 (01_add_logging_to_methodinfo_invoke.patch)
 for more verbosity. The log is done using the following loglevels:
 'general:err,http:debug'

 {{{
  I CoreContext httpserver.cpp:466 (HttpWorker) HttpWorker(9): New
 connection
  I HttpServer9 httprequest.cpp:1140 (GetParameters) sParams:
 'RecordedId=10'
  I HttpServer9 httprequest.cpp:1332 (ParseRequest) (Request Header)
 accept: */*
  I HttpServer9 httprequest.cpp:1332 (ParseRequest) (Request Header)
 accept-encoding: identity
  I HttpServer9 httprequest.cpp:1332 (ParseRequest) (Request Header)
 connection: Keep-Alive
  I HttpServer9 httprequest.cpp:1332 (ParseRequest) (Request Header) host:
 A.B.C.D:6544
  I HttpServer9 httprequest.cpp:1332 (ParseRequest) (Request Header) user-
 agent: Wget/1.19.4 (linux-gnu)
  I HttpServer9 httprequest.cpp:1644 (ExtractMethodFromURL)
 ExtractMethodFromURL(end) : GetPreviewImage : /Content
  D HttpServer9 httpserver.cpp:376 (DelegateRequest) m_sBaseUrl: /Content
  I HttpServer9 servicehost.cpp:325 (ProcessRequest)
 ServiceHost::ProcessRequest: GetPreviewImage : GET
 /Content/GetPreviewImage?RecordedId=10 HTTP/1.1
  D HttpServer9 servicehost.cpp:85 (Invoke) MethodInfo::Invoke: nRetIndx is
 '0' and type is 'QFileInfo'.
  I HttpServer9 httprequest.cpp:369 (SendResponse)
 HTTPRequest::SendResponse(xml/html) () :200 OK -> W.X.Y.Z: 8
  D HttpServer9 httprequest.cpp:419 (SendResponse) Reponse Content Length:
 44
  D HttpServer9 httprequest.cpp:450 (SendResponse) Response header size:
 400 bytes
  W HttpServer9 httpserver.cpp:645 (run) HttpWorker(9): Error The remote
 host closed the connection (1)
  I HttpServer9 httpserver.cpp:693 (run) HttpWorker(9): Connection -1
 closed. 1 requests were handled
  I CoreContext housekeeper.cpp:725 (Run) Queueing HouseKeeperTask
 'DBCleanup'.
  I CoreContext housekeeper.cpp:725 (Run) Queueing HouseKeeperTask
 'JobQueueRecover'.
  I CoreContext housekeeper.cpp:725 (Run) Queueing HouseKeeperTask
 'LogClean'.
 ....
  I CoreContext httpserver.cpp:466 (HttpWorker) HttpWorker(58): New
 connection
  I HttpServer58 httprequest.cpp:1140 (GetParameters) sParams:
 'RecordedId=10'
  I HttpServer58 httprequest.cpp:1332 (ParseRequest) (Request Header)
 accept: */*
  I HttpServer58 httprequest.cpp:1332 (ParseRequest) (Request Header)
 accept-encoding: identity
  I HttpServer58 httprequest.cpp:1332 (ParseRequest) (Request Header)
 connection: Keep-Alive
  I HttpServer58 httprequest.cpp:1332 (ParseRequest) (Request Header) host:
 A.B.C.D:6544
  I HttpServer58 httprequest.cpp:1332 (ParseRequest) (Request Header) user-
 agent: Wget/1.19.4 (linux-gnu)
  I HttpServer58 httprequest.cpp:1644 (ExtractMethodFromURL)
 ExtractMethodFromURL(end) : GetPreviewImage : /Content
  D HttpServer58 httpserver.cpp:376 (DelegateRequest) m_sBaseUrl: /Content
  I HttpServer58 servicehost.cpp:325 (ProcessRequest)
 ServiceHost::ProcessRequest: GetPreviewImage : GET
 /Content/GetPreviewImage?RecordedId=10 HTTP/1.1
  D HttpServer58 servicehost.cpp:85 (Invoke) MethodInfo::Invoke: nRetIndx
 is '1178' and type is 'QFileInfo'.
  I HttpServer58 httprequest.cpp:358 (SendResponse)
 HTTPRequest::SendResponse( File ) :200 OK -> W.X.Y.Z:
  I HttpServer58 httprequest.cpp:503 (SendResponseFile) SendResponseFile (
 /mnt/data01/my_data01/recordings/3006_20180804082700.mkv.png )
  I HttpServer58 httprequest.cpp:1128 (TestMimeType)
 HTTPRequest::TestMimeType(/mnt/data01/my_data01/recordings/3006_20180804082700.mkv.png)
 - type is image/png
  D HttpServer58 httprequest.cpp:611 (SendResponseFile) Response header
 size: 471 bytes
  W HttpServer58 httpserver.cpp:645 (run) HttpWorker(58): Error The remote
 host closed the connection (1)
  I HttpServer58 httpserver.cpp:693 (run) HttpWorker(58): Connection -1
 closed. 1 requests were handled
 }}}

 These stanzas indicate that something went wrong:
 {{{
 MethodInfo::Invoke: nRetIndx is '0' and type is 'QFileInfo'.
 HTTPRequest::SendResponse(xml/html) () :200 OK -> W.X.Y.Z: 8"
 }}}

 Analysis:

 Up to fixes/29, the 'QFileInfo' type was registered to 'QMetaType',
 but only for QT4:

 See File 'libs/libmythservicecontracts/service.h' from branch fixes/29:

 {{{
 #if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
 Q_DECLARE_METATYPE( QFileInfo )
 inline Service::Service(QObject *parent) : QObject(parent)
 {
     qRegisterMetaType< QFileInfo >();
 }
 #else
 inline Service::Service(QObject *parent) : QObject(parent) {}
 #endif
 }}}

 This explains, that this bug is not visible in fixes/0.27 (QT4)
 and is a regression since v28 (QT5).

 For QT5, it is not necessary anymore to declare the metatype,
 because this is already done in in the header file of <QFileInfo>,
 but registering 'QFileInfo' seems to be necessary for MythTV Services.

 See attached patches 02_register_qfileinfo_at_startup_v29.patch
 and 02_register_qfileinfo_at_startup_v30_master.patch

 The patch for master is compile time tested, only.

 Enclosed the mythtv version (mythtv_version.txt).

-- 
Ticket URL: <https://code.mythtv.org/trac/ticket/13404>
MythTV <http://www.mythtv.org>
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