From: Grant Slater <git@firefishy.com>
Date: Thu, 23 Jan 2014 15:27:26 +0000 (+0000)
Subject: Make sure we don't lose changes if we are interrupted
X-Git-Url: https://git.openstreetmap.org/chef.git/commitdiff_plain/af30bf6e1e06bfc20250818d65a8216ca5dce634

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 5d940375b..e1ecab695 100644
--- 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
 
+# 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
 
+# Install exit handler
+trap onexit EXIT
+
 # Read in initial state
 . state.txt
 
@@ -21,6 +29,9 @@ do
     # 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"
 
@@ -45,6 +56,9 @@ do
 	    # 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
@@ -58,6 +72,9 @@ do
             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