opt-in to automatic ELB deregister when ELB_LIST=all

Author: wjordan

load-balancing/elb/README.md

@@ -46,5 +46,10 @@ To use these scripts in your own application:
 1. Copy the `.sh` files in this directory into your application source.
 1. Edit your application's `appspec.yml` to run `deregister_from_elb.sh` on the ApplicationStop event,
 and `register_with_elb.sh` on the ApplicationStart event.
+1. If your instance is not  in an Auto Scaling Group,
+edit `common_functions.sh` to set `ELB_LIST` to contain the name(s) of the Elastic Load
+Balancer(s) your deployment group is a part of. Make sure the entries in ELB_LIST are separated by space.
+Alternatively, you can set `ELB_LIST` to `all` to automatically use all load balancers the instance is
+registered to.
 1. Deploy!
 

load-balancing/elb/common_functions.sh

@@ -15,6 +15,7 @@
 
 # ELB_LIST defines which Elastic Load Balancers this instance should be part of.
 # The elements in ELB_LIST should be separated by space.
+# Set to "all" to automatically find all load balancers the instance is registered to.
 ELB_LIST=""
 
 # Under normal circumstances, you shouldn't need to change anything below this line.

load-balancing/elb/deregister_from_elb.sh

@@ -50,8 +50,7 @@ fi
 
 msg "Instance is not part of an ASG, continuing..."
 
-msg "Checking that user set at least one load balancer"
-if test -z "$ELB_LIST"; then
+if [ "${ELB_LIST}" = all ]; then
     msg "Finding all the ELBs that this instance is registered to"
     get_elb_list $INSTANCE_ID
     if [ $? != 0 ]; then
@@ -60,6 +59,11 @@ if test -z "$ELB_LIST"; then
     echo "$ELB_LIST" > /tmp/elblist
 fi
 
+msg "Checking that user set at least one load balancer"
+if test -z "$ELB_LIST"; then
+    error_exit "Must have at least one load balancer to deregister from"
+fi
+
 # Loop through all LBs the user set, and attempt to deregister this instance from them.
 for elb in $ELB_LIST; do
     msg "Checking validity of load balancer named '$elb'"

load-balancing/elb/register_with_elb.sh

@@ -50,8 +50,7 @@ fi
 
 msg "Instance is not part of an ASG, continuing..."
 
-msg "Checking that user set at least one load balancer"
-if test -z "$ELB_LIST"; then
+if [ "${ELB_LIST}" = all ]; then
     if [ -a /tmp/elblist ]; then
         msg "Finding all the ELBs that this instance was previously registered to"
         read ELB_LIST < /tmp/elblist
@@ -61,6 +60,11 @@ if test -z "$ELB_LIST"; then
     fi
 fi
 
+msg "Checking that user set at least one load balancer"
+if test -z "$ELB_LIST"; then
+    error_exit "Must have at least one load balancer to register to"
+fi
+
 # Loop through all LBs the user set, and attempt to register this instance to them.
 for elb in $ELB_LIST; do
     msg "Checking validity of load balancer named '$elb'"