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1 files changed, 117 insertions, 0 deletions

diff --git a/node-admin/scripts/etc-hosts.sh b/node-admin/scripts/etc-hosts.sh
new file mode 100755
index 00000000000..a588d3cc4e6
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+++ b/node-admin/scripts/etc-hosts.sh
@@ -0,0 +1,117 @@
+#!/bin/bash
+# Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+set -e
+
+source "${0%/*}/common.sh"
+
+declare -r HOSTS_FILE=/etc/hosts
+declare -r HOSTS_LINE_SUFFIX=" # Managed by etc-hosts.sh"
+
+function Usage {
+    UsageHelper "$@" <<EOF
+Usage: $SCRIPT_NAME <command> [--num-nodes <num-nodes>]
+Manage Docker container DNS<->IP resolution ($HOSTS_FILE).
+
+Commands:
+  start     Add Docker containers to $HOSTS_FILE
+  stop      Remove Docker containers from $HOSTS_FILE (not implemented)
+  restart   Stop, then start
+
+Options:
+  --num-nodes <num-nodes>
+            Add <num-nodes> hosts instead of the default $DEFAULT_NUM_APP_CONTAINERS.
+EOF
+}
+
+function IsInHostsAlready {
+    local ip="$1"
+    local hostname="$2"
+    local file="$3"
+
+    # TODO: Escape $ip to make sure it's matched as a literal in the regex.
+    local matching_ip_line
+    matching_ip_line=$(grep -E "^$ip[ \\t]" "$file")
+
+    local -i num_ip_lines=0
+    # This 'if' is needed because wc -l <<< "" is 1.
+    if [ -n "$matching_ip_line" ]
+    then
+        num_ip_lines=$(wc -l <<< "$matching_ip_line")
+    fi
+
+    local matching_hostname_line
+    matching_hostname_line=$(grep -E "^[^#]*[ \\t]$hostname(\$|[ \\t])" "$file")
+
+    local -i num_hostname_lines=0
+    # This 'if' is needed because wc -l <<< "" is 1.
+    if [ -n "$matching_hostname_line" ]
+    then
+        num_hostname_lines=$(wc -l <<< "$matching_hostname_line")
+    fi
+
+    if ((num_ip_lines == 1)) && ((num_hostname_lines == 1)) &&
+           [ "$matching_ip_line" == "$matching_hostname_line" ]
+    then
+        return 0
+    elif ((num_ip_lines == 0)) && ((num_hostname_lines == 0))
+    then
+        return 1
+    else
+        Fail "$file contains a conflicting host specification for $hostname/$ip"
+    fi
+}
+
+function AddHost {
+    local ip="$1"
+    local hostname="$2"
+    local file="$3"
+
+    if IsInHostsAlready "$ip" "$hostname" "$file"
+    then
+        return
+    fi
+
+    echo -n "Adding host $hostname ($ip) to $file... "
+    printf "%-11s %s%s\n" "$ip" "$hostname" "$HOSTS_LINE_SUFFIX" >> "$file"
+    echo done
+}
+
+function Stop {
+    # TODO: Remove entries.
+    :
+}
+
+function StartAsRoot {
+    if (($# != 0))
+    then
+        Usage
+    fi
+
+    # May need sudo
+    if [ ! -w "$HOSTS_FILE" ]
+    then
+        Fail "$HOSTS_FILE is not writeable (run script with sudo)"
+    fi
+
+    AddHost "$CONFIG_SERVER_IP" "$CONFIG_SERVER_HOSTNAME" "$HOSTS_FILE"
+
+    local -i index=1
+    for ((; index <= NUM_APP_CONTAINERS; ++index))
+    do
+        local ip="$APP_NETWORK_PREFIX.$index"
+        local container_name="$APP_HOSTNAME_PREFIX$index"
+        AddHost "$ip" "$container_name" "$HOSTS_FILE"
+    done
+}
+
+function Start {
+    if [ "$(id -u)" != 0 ]
+    then
+        sudo "$0" "$@"
+    else
+        StartAsRoot "$@"
+    fi
+}
+
+Main "$@"