HPCC-33043 Ensure blob storage files are completely written before being read

dali/base/dadfs.cpp

@@ -3779,6 +3779,47 @@ protected: friend class CDistributedFilePart;
         clusters.kill();
     }
 
+    //Ensure that enough time has passed from when the file was last modified for reads to be consistent
+    //Important for blob storage or remote, geographically synchronized storage
+    void checkWriteSync()
+    {
+        time_t modifiedTime = 0;
+        time_t now = 0;
+
+        Owned<IPropertyTreeIterator> iter = root->getElements("Cluster");
+        ForEach(*iter)
+        {
+            const char * name = iter->query().queryProp("@name");
+            unsigned marginMs = getWriteSyncMarginMs(name);
+            if (marginMs)
+            {
+                if (0 == modifiedTime)
+                {
+                    CDateTime modified;
+                    if (!getModificationTime(modified))
+                        return;
+                    modifiedTime = modified.getSimple();
+                }
+
+                if (0 == now)
+                    now = time(&now);
+
+                //Round the elapsed time down - so that a change on the last ms of one time period does not count as a whole second of elapsed time
+                //This could be avoided if the modified time was more granular
+                unsigned __int64 elapsedMs = (now - modifiedTime) * 1000;
+                if (elapsedMs >= 1000)
+                    elapsedMs -= 999;
+
+                if (unlikely(elapsedMs < marginMs))
+                {
+                    LOG(MCuserProgress, "Delaying access to %s on %s for %ums to ensure write sync", queryLogicalName(), name, (unsigned)(marginMs - elapsedMs));
+                    MilliSleep(marginMs - elapsedMs);
+                    now = 0; // re-evaluate now - unlikely to actually happen
+                }
+            }
+        }
+    }
+
     bool hasDirPerPart() const
     {
         return FileDescriptorFlags::none != (fileFlags & FileDescriptorFlags::dirperpart);
@@ -8299,6 +8340,7 @@ IDistributedFile *CDistributedFileDirectory::dolookup(CDfsLogicalFileName &_logi
                     }
                     CDistributedFile *ret = new CDistributedFile(this,fcl.detach(),*logicalname,accessMode,user);  // found
                     ret->setSuperOwnerLock(superOwnerLock.detach());
+                    ret->checkWriteSync();
                     return ret;
                 }
                 // now super file

helm/hpcc/values.schema.json

@@ -603,6 +603,11 @@
             "eclwatchVisible": {
               "type": "boolean"
             },
+            "writeSyncMarginMs": {
+              "description": "Time that is required to elapse between writing a file and all read copies to be consistently updated",
+              "type": "integer",
+              "default": 0
+            },
             "components": {},
             "prefix": {},
             "subPath": {},

system/jlib/jfile.cpp

@@ -7911,7 +7911,8 @@ static const std::array<PlaneAttributeInfo, PlaneAttributeCount> planeAttributeI
     { PlaneAttrType::integer, 1024, false, "blockedFileIOKB" },   // enum PlaneAttributeType::BlockedSequentialIO    {0}
     { PlaneAttrType::integer, 1024, false, "blockedRandomIOKB" }, // enum PlaneAttributeType::blockedRandomIOKB      {1}
     { PlaneAttrType::boolean, 0, true, "fileSyncWriteClose" },    // enum PlaneAttributeType::fileSyncWriteClose     {2}
-    { PlaneAttrType::boolean, 0, true, "concurrentWriteSupport" } // enum PlaneAttributeType::concurrentWriteSupport {3}
+    { PlaneAttrType::boolean, 0, true, "concurrentWriteSupport" },// enum PlaneAttributeType::concurrentWriteSupport {3}
+    { PlaneAttrType::integer, 1, false, "writeSyncMarginMs" },    // enum PlaneAttributeType::WriteSyncMarginMs      {4}
 }};
 
 // {prefix, {key1: value1, key2: value2, ...}}
@@ -8089,6 +8090,12 @@ bool getFileSyncWriteCloseEnabled(const char *planeName)
     return 0 != getPlaneAttributeValue(planeName, FileSyncWriteClose, defaultFileSyncWriteCloseEnabled ? 1 : 0);
 }
 
+unsigned getWriteSyncMarginMs(const char * planeName)
+{
+    constexpr unsigned dft = 0;
+    return (unsigned)getPlaneAttributeValue(planeName, WriteSyncMarginMs, dft);
+}
+
 static constexpr bool defaultConcurrentWriteSupport = isContainerized() ? false : true;
 bool getConcurrentWriteSupported(const char *planeName)
 {

system/jlib/jfile.hpp

@@ -744,12 +744,14 @@ extern jlib_decl IPropertyTreeIterator * getRemoteStoragesIterator();
 extern jlib_decl IPropertyTreeIterator * getPlanesIterator(const char * category, const char *name);
 
 extern jlib_decl IFileIO *createBlockedIO(IFileIO *base, size32_t blockSize);
+//MORE: Should use enum class to avoid potential symbol clashes
 enum PlaneAttributeType // remember to update planeAttributeInfo in jfile.cpp
 {
     BlockedSequentialIO,
     BlockedRandomIO,
     FileSyncWriteClose,
     ConcurrentWriteSupport,
+    WriteSyncMarginMs,
     PlaneAttributeCount
 };
 extern jlib_decl const char *getPlaneAttributeString(PlaneAttributeType attr);
@@ -761,6 +763,7 @@ extern jlib_decl size32_t getBlockedFileIOSize(const char *planeName, size32_t d
 extern jlib_decl size32_t getBlockedRandomIOSize(const char *planeName, size32_t defaultSize=0);
 extern jlib_decl bool getFileSyncWriteCloseEnabled(const char *planeName);
 extern jlib_decl bool getConcurrentWriteSupported(const char *planeName);
+extern jlib_decl unsigned getWriteSyncMarginMs(const char * planeName);
 
 //---- Pluggable file type related functions ----------------------------------------------