importSources(): Return either success, error, or no change.

That way we can detect when the import of all layers are no-op (besides
changing last_updated) and exit gracefully.

2 files changed, 53 insertions, 31 deletions

diff --git a/import_source.py b/import_source.py
index c4cb96f..647c79e 100644
--- a/import_source.py
+++ b/import_source.py
@@ -28,6 +28,7 @@ from pathlib import Path
 from datetime import datetime, timedelta, UTC
 from typing import Any, Final, Optional
 import traceback
+from enum import Enum, unique
 from hashlib import sha256
 import struct
 
@@ -435,6 +436,13 @@ def listArchiveMembers(namelist : list[str],
             logging.debug('Ignoring archive member %s', name)
     return members
 
+@unique
+class ImportStatus(Enum):
+    """Return value for importSources(): success, error, or no-change."""
+    IMPORT_SUCCESS = 0
+    IMPORT_ERROR = 1
+    IMPORT_NOCHANGE = 255
+
 # pylint: disable-next=dangerous-default-value
 def importSources(dso : gdal.Dataset, lyr : ogr.Layer,
                   sources : dict[str,Any] = {},
@@ -442,7 +450,7 @@ def importSources(dso : gdal.Dataset, lyr : ogr.Layer,
                   extent : ogr.Geometry|None = None,
                   dsoTransaction : bool = False,
                   lyrcache : ogr.Layer|None = None,
-                  force : bool = False) -> bool:
+                  force : bool = False) -> ImportStatus:
     """Clear lyr and import source layers to it."""
 
     layername = lyr.GetName()
@@ -462,7 +470,7 @@ def importSources(dso : gdal.Dataset, lyr : ogr.Layer,
                         layername)
         lyrTransaction = False
 
-    rv = True
+    rv = ImportStatus.IMPORT_NOCHANGE
     now = datetime.now().astimezone()
     fingerprint = sha256()
     fingerprint_map = fingerprintLayerDefn(fingerprint, lyr)
@@ -482,20 +490,24 @@ def importSources(dso : gdal.Dataset, lyr : ogr.Layer,
         dso.FlushCache()
 
         fingerprint = fingerprint.digest()
-        if lyrcache is not None:
-            if not updateLayerCache(layername=layername,
-                                    cache=lyrcache,
-                                    ds=dso, lyr=lyr,
-                                    force=force,
-                                    lyrTransaction=lyrTransaction,
-                                    last_updated=now,
-                                    fingerprint=fingerprint):
-                if isinstance(lyrTransaction, bool):
-                    # the transaction on lyr was already rolled back
-                    lyrTransaction = False
+        if lyrcache is None:
+            rv = ImportStatus.IMPORT_SUCCESS
+        elif updateLayerCache(layername=layername,
+                              cache=lyrcache,
+                              ds=dso, lyr=lyr,
+                              force=force,
+                              lyrTransaction=lyrTransaction,
+                              last_updated=now,
+                              fingerprint=fingerprint):
+            rv = ImportStatus.IMPORT_SUCCESS
+        else:
+            rv = ImportStatus.IMPORT_NOCHANGE
+            if isinstance(lyrTransaction, bool):
+                # the transaction on lyr was already rolled back
+                lyrTransaction = False
 
     except Exception: # pylint: disable=broad-exception-caught
-        rv = False
+        rv = ImportStatus.IMPORT_ERROR
         if isinstance(lyrTransaction, str):
             query = 'ROLLBACK TO ' + lyrTransaction
             logging.exception('Exception occured within transaction: %s', query)
@@ -523,17 +535,16 @@ def importSources(dso : gdal.Dataset, lyr : ogr.Layer,
             try:
                 dso.ExecuteSQL(query)
             except Exception: # pylint: disable=broad-exception-caught
-                rv = False
+                rv = ImportStatus.IMPORT_ERROR
                 logging.exception('Could not execute SQL: %s', query)
         elif isinstance(lyrTransaction, bool) and lyrTransaction:
             try:
                 if lyr.CommitTransaction() != ogr.OGRERR_NONE:
-                    rv = False
+                    rv = ImportStatus.IMPORT_ERROR
                     logging.error('Could not commit transaction')
             except Exception: # pylint: disable=broad-exception-caught
-                rv = False
+                rv = ImportStatus.IMPORT_ERROR
                 logging.exception('Could not commit transaction on layer "%s"', layername)
-
     return rv
 
 # pylint: disable-next=dangerous-default-value
diff --git a/webmap-import b/webmap-import
index c801b6d..6f514a9 100755
--- a/webmap-import
+++ b/webmap-import
@@ -64,7 +64,8 @@ from import_source import (
     openOutputDS,
     createOutputLayer,
     validateOutputLayer,
-    importSources
+    importSources,
+    ImportStatus
 )
 
 def setFieldIf(cond : bool,
@@ -256,9 +257,8 @@ def processOutputLayer(ds : gdal.Dataset,
                        extent : ogr.Geometry|None = None,
                        dsTransaction : bool = False,
                        lyrcache : ogr.Layer|None = None,
-                       force : bool = False) -> bool:
-    """Process an output layer, and return a boolean indicating whether
-    the import was sucessful (or skipped), or not."""
+                       force : bool = False) -> ImportStatus:
+    """Process an output layer."""
 
     logging.info('Processing output layer "%s"', layername)
     lyr = ds.GetLayerByName(layername)
@@ -274,7 +274,7 @@ def processOutputLayer(ds : gdal.Dataset,
                                 lyrcache=lyrcache,
                                 cachedir=cachedir)):
         logging.info('Output layer "%s" is up to date, skipping', layername)
-        return True
+        return ImportStatus.IMPORT_NOCHANGE
 
     validateOutputLayer(lyr, srs=srs, options=layerdef['create'])
 
@@ -661,15 +661,26 @@ def main() -> NoReturn:
 
     rv = 0
     try:
+        r = ImportStatus.IMPORT_NOCHANGE
         for layername, layerdef in layers.items():
-            if not processOutputLayer(dso, layername, layerdef,
-                                      srs=srs,
-                                      cachedir=cachedir,
-                                      extent=extent,
-                                      dsTransaction=dsoTransaction,
-                                      lyrcache=lyr_cache,
-                                      force=args.force):
+            r0 = processOutputLayer(dso, layername, layerdef,
+                                    srs=srs,
+                                    cachedir=cachedir,
+                                    extent=extent,
+                                    dsTransaction=dsoTransaction,
+                                    lyrcache=lyr_cache,
+                                    force=args.force)
+            if r0 == ImportStatus.IMPORT_ERROR:
                 rv = 1
+                if dsoTransaction:
+                    dsoTransaction = False
+                    logging.debug('Rolling back transaction')
+                    # no need to catch the exception here
+                    if dso.CommitTransaction() != ogr.OGRERR_NONE:
+                        logging.error('Could not rollback transaction')
+            if r == ImportStatus.IMPORT_NOCHANGE and r0 == ImportStatus.IMPORT_SUCCESS:
+                r = ImportStatus.IMPORT_SUCCESS
+        logging.info('result = %s', str(r))
 
         if sourcePathLocks is not None:
             releaseSourcePathLocks(sourcePathLocks)
@@ -682,7 +693,6 @@ def main() -> NoReturn:
                 rv = 1
 
     except Exception: # pylint: disable=broad-exception-caught
-        rv = 1
         if dsoTransaction:
             logging.exception('Exception occured within transaction, rolling back')
             try:
@@ -692,6 +702,7 @@ def main() -> NoReturn:
                 logging.exception('Could not rollback transaction')
         else:
             traceback.print_exc()
+        sys.exit(1)
 
     finally:
         lyr_cache = None