qgsfileutils: add method to know if we are close to the limit of simu…

…ltaneously opened files (refs #43620)
qgis · Sep 23, 2021 · d69d8e5 · d69d8e5
1 parent 80d7014
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diff --git a/python/core/auto_generated/qgsfileutils.sip.in b/python/core/auto_generated/qgsfileutils.sip.in
@@ -181,6 +181,8 @@ desired.
 .. versionadded:: 3.22
 %End
 
+
+
 };
 
 /************************************************************************

diff --git a/src/core/qgsfileutils.cpp b/src/core/qgsfileutils.cpp
@@ -26,6 +26,12 @@
 #include <QSet>
 #include <QDirIterator>
 
+#ifdef Q_OS_UNIX
+// For getrlimit()
+#include <sys/resource.h>
+#include <sys/time.h>
+#endif
+
 #ifdef MSVC
 #include <Windows.h>
 #include <ShlObj.h>
@@ -462,3 +468,36 @@ bool QgsFileUtils::renameDataset( const QString &oldPath, const QString &newPath
 
   return res;
 }
+
+int QgsFileUtils::openedFileLimit()
+{
+#ifdef Q_OS_UNIX
+  struct rlimit rescLimit;
+  if ( getrlimit( RLIMIT_NOFILE, &rescLimit ) == 0 )
+  {
+    return rescLimit.rlim_cur;
+  }
+#endif
+  return -1;
+}
+
+int QgsFileUtils::openedFileCount()
+{
+#ifdef Q_OS_LINUX
+  int res = static_cast<int>( QDir( "/proc/self/fd" ).entryList().size() );
+  if ( res == 0 )
+    res = -1;
+  return res;
+#else
+  return -1;
+#endif
+}
+
+bool QgsFileUtils::isCloseToLimitOfOpenedFiles( int filesToBeOpened )
+{
+  const int nFileLimit = QgsFileUtils::openedFileLimit();
+  const int nFileCount = QgsFileUtils::openedFileCount();
+  // We need some margin as Qt will crash if it cannot create some file descriptors
+  constexpr int SOME_MARGIN = 20;
+  return nFileCount > 0 && nFileLimit > 0 && nFileCount + filesToBeOpened > nFileLimit - SOME_MARGIN;
+}
diff --git a/src/core/qgsfileutils.h b/src/core/qgsfileutils.h
@@ -180,6 +180,40 @@ class CORE_EXPORT QgsFileUtils
      */
     static bool renameDataset( const QString &oldPath, const QString &newPath, QString &error SIP_OUT, Qgis::FileOperationFlags flags = Qgis::FileOperationFlag::IncludeMetadataFile | Qgis::FileOperationFlag::IncludeStyleFile );
 
+    /**
+     * Returns the limit of simultaneously opened files by the process.
+     *
+     * Currently only implemented on Unix.
+     *
+     * \returns Limit, or -1 if unknown.
+     * \note not available in Python bindings
+     * \since QGIS 3.22
+     */
+    static int openedFileLimit() SIP_SKIP;
+
+    /**
+     * Returns the number of currently opened files by the process.
+     *
+     * Currently only implemented on Linux.
+     *
+     * \returns Number of files, or -1 if unknown
+     * \note not available in Python bindings
+     * \since QGIS 3.22
+     */
+    static int openedFileCount() SIP_SKIP;
+
+    /**
+     * Returns whether when opening new file(s) will reach, or nearly reach,
+     * the limit of simultaneously opened files by the process.
+     *
+     * Currently only implemented on Linux.
+     *
+     * \param filesToBeOpened Number of files that will be opened.
+     * \returns true if close to the limit, or false if not, or unknown.
+     * \note not available in Python bindings
+     * \since QGIS 3.22
+     */
+    static bool isCloseToLimitOfOpenedFiles( int filesToBeOpened = 1 ) SIP_SKIP;
 };
 
 #endif // QGSFILEUTILS_H