fix(zk): Fix zookeper upgrade to 5.5.0 (#511)

Fixes the "logs found but no snapshot" error when upgrading from a
short-lived older version. Fixes #472.

See https://issues.apache.org/jira/browse/ZOOKEEPER-3056.

install.sh

@@ -164,6 +164,16 @@ $dc build --force-rm --parallel
 echo ""
 echo "Docker images built."
 
+
+ZOOKEEPER_LOG_FILE_COUNT=$($dcr zookeeper bash -c 'ls 2>/dev/null -Ubad1 -- /var/lib/zookeeper/log/version-2/* | wc -l | tr -d '[:space:]'')
+ZOOKEEPER_SNAPSHOT_FILE_COUNT=$($dcr zookeeper bash -c 'ls 2>/dev/null -Ubad1 -- /var/lib/zookeeper/data/version-2/* | wc -l | tr -d '[:space:]'')
+# This is a workaround for a ZK upgrade bug: https://issues.apache.org/jira/browse/ZOOKEEPER-3056
+if [ "$ZOOKEEPER_LOG_FILE_COUNT" -gt "0" ] && [ "$ZOOKEEPER_SNAPSHOT_FILE_COUNT" -eq "0" ]; then
+  $dcr -v $(pwd)/zookeeper:/temp zookeeper bash -c 'cp /temp/snapshot.0 /var/lib/zookeeper/data/version-2/snapshot.0'
+  $dc run -e ZOOKEEPER_SNAPSHOT_TRUST_EMPTY=true zookeeper
+fi
+
+
 echo "Bootstrapping and migrating Snuba..."
 $dcr snuba-api bootstrap --force
 echo ""