Make sure we don't lose changes if we are interrupted

If we are interrupted after we have fetched changes, but before we
have applied them, then rollback so that we try againt next time.

diff --git a/cookbooks/tile/templates/default/replicate.erb b/cookbooks/tile/templates/default/replicate.erb
index 5d940375bf36e60d6e96a19c5b5692fc6b3e6a1e..e1ecab695d27ba0a68ac8c5b864076713c394207 100644 (file)
--- a/cookbooks/tile/templates/default/replicate.erb
+++ b/cookbooks/tile/templates/default/replicate.erb
@@ -6,12 +6,20 @@
 # Setting to midnight ensures we get conistent data after first run
 # osmosis --read-replication-interval-init
 
 # Setting to midnight ensures we get conistent data after first run
 # osmosis --read-replication-interval-init
 

+# Define exit handler
+function onexit {
+    [ -f state-prev.txt ] && mv state-prev.txt state.txt
+}
+

 # Send output to the log
 exec > /var/log/tile/replicate.log 2>&1
 
 # Change to the replication state directory
 cd /var/lib/replicate
 
 # Send output to the log
 exec > /var/log/tile/replicate.log 2>&1
 
 # Change to the replication state directory
 cd /var/lib/replicate
 

+# Install exit handler
+trap onexit EXIT
+

 # Read in initial state
 . state.txt
 
 # Read in initial state
 . state.txt
 


@@ -21,6 +29,9 @@ do
     # Work out the name of the next file
     file="changes-${sequenceNumber}.osm.gz"
 
     # Work out the name of the next file
     file="changes-${sequenceNumber}.osm.gz"
 

+    # Save state file so we can rollback if an error occurs
+    cp state.txt state-prev.txt
+

     # Fetch the next set of changes
     osmosis --read-replication-interval --simc --write-xml-change file="${file}" compressionMethod="gzip"
 
     # Fetch the next set of changes
     osmosis --read-replication-interval --simc --write-xml-change file="${file}" compressionMethod="gzip"
 


@@ -45,6 +56,9 @@ do
            # Remove file, it will just be an empty changeset
            rm ${file}
 
            # Remove file, it will just be an empty changeset
            rm ${file}
 

+            # No need to rollback now
+            rm state-prev.txt
+

             # Sleep for a short while
            sleep 30
        else
             # Sleep for a short while
            sleep 30
        else


@@ -58,6 +72,9 @@ do
             osm2pgsql --slim --append ${file}
 <% end -%>
 
             osm2pgsql --slim --append ${file}
 <% end -%>
 

+            # No need to rollback now
+            rm state-prev.txt
+

             # Expire tiles which are touched by the changes
             sudo -u www-data /usr/local/bin/expire-tiles ${file} > /dev/null 2>&1 &
        fi
             # Expire tiles which are touched by the changes
             sudo -u www-data /usr/local/bin/expire-tiles ${file} > /dev/null 2>&1 &
        fi