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solr/docker/scripts/wait-for-zookeeper.sh

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+#!/bin/bash
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# A helper script to wait for ZooKeeper
+#
+# This script waits for a ZooKeeper master to appear.
+# It repeatedly looks up the name passed as argument
+# in the DNS using getent, and then connects to the
+# ZooKeeper admin port and uses the 'srvr' command to
+# obtain the server's status.
+# You can use this in a Kubernetes init container to
+# delay Solr pods starting until the ZooKeeper service
+# has settled down. Or you could explicitly run this in
+# the Solr container before exec'ing Solr.
+#
+# Inspired by https://github.com/helm/charts/blob/9eba7b1c80990233a68dce48f4a8fe0baf9b7fa5/incubator/solr/templates/statefulset.yaml#L60
+#
+# Usage: wait-for-zookeeper.sh [--max-attempts count] [--wait-seconds seconds] zookeeper-service-name
+#
+# If no argument is provided, but a Solr-style ZK_HOST is set,
+# that will be used. If neither is provided, the default
+# name is 'solr-zookeeper-headless', to match the helm chart.
+
+set -euo pipefail
+
+SCRIPT="$0"
+
+if [[ "${VERBOSE:-}" == "yes" ]]; then
+    set -x
+fi
+
+function usage {
+  echo "$1"
+  echo "Usage: $SCRIPT [--max-attempts count] [--wait-seconds seconds ] zookeeper-service-name"
+  exit 1
+}
+
+TMP_HOSTS="/tmp/hosts.$$"
+TMP_STATUS="/tmp/status.$$"
+
+function cleanup {
+    rm -f $TMP_HOSTS $TMP_STATUS
+}
+
+trap cleanup EXIT
+
+function check_zookeeper {
+    local host=$1
+    local port="${2:-2181}"
+    if ! echo srvr | nc "$host" "$port" > $TMP_STATUS; then
+        echo "Failed to get status from $host"
+        return
+    fi
+    if [ ! -s $TMP_STATUS ]; then
+        echo "No data from $ip"
+        return
+    fi
+    if grep -q 'not currently serving requests' $TMP_STATUS; then
+        echo "Node $ip is not currently serving requests"
+        return
+    fi
+    mode=$(grep "Mode: " $TMP_STATUS | sed 's/Mode: //');
+    if [ -z "$mode" ]; then
+        echo "Cannot determine mode from:"
+        cat $TMP_STATUS
+        return
+    fi
+    echo "Node $ip is a $mode"
+    if [ "$mode" = "leader" ] || [ "$mode" = "standalone" ]; then
+        echo "Done"
+        exit 0
+    fi
+}
+
+max_attempts=120
+wait_seconds=2
+while (( $# > 0 )); do
+  case "$1" in
+   --help)
+     cat <<EOM
+Usage: $SCRIPT [options] zookeeper-service-name
+
+Options:
+  --max-attempts count: number of attempts to check Solr is up. Default: $max_attempts
+  --wait-seconds seconds: number of seconds to wait between attempts. Default: $wait_seconds
+EOM
+     exit 0
+     ;;
+
+   --max-attempts)
+     max_attempts="$2";
+     shift 2;
+     ;;
+
+   --wait-seconds)
+     wait_seconds="$2";
+     shift 2;
+     ;;
+
+   *)
+    if [ -n "${lookup_arg:-}" ]; then
+      usage "Cannot specify multiple zookeeper service names"
+    fi
+    lookup_arg=$1;
+    shift;
+    break;
+    ;;
+
+  esac
+done
+
+grep -q -E '^[0-9]+$' <<<"$max_attempts" || usage "--max-attempts $max_attempts: not a number"
+if (( max_attempts == 0 )); then
+  echo "The --max-attempts argument should be >0"
+  exit 1
+fi
+grep -q -E '^[0-9]+$' <<<"$wait_seconds" || usage "--wait-seconds $wait_seconds: not a number"
+
+if [ -z "${lookup_arg:-}" ]; then
+  if [ -n "$ZK_HOST" ]; then
+    lookup_arg="$ZK_HOST"
+  else
+    lookup_arg=solr-zookeeper-headless
+  fi
+fi
+
+echo "Looking up '$lookup_arg'"
+# split on commas, for when a ZK_HOST string like zoo1:2181,zoo2:2181 is used
+IFS=',' read -ra lookups <<< "$lookup_arg"
+((attempts_left=max_attempts))
+while (( attempts_left > 0 )); do
+  for lookup in "${lookups[@]}"; do
+    if grep -q -E "^\[[0-9].*\]" <<<"$lookup"; then
+      # looks like an IPv6 address, eg [2001:DB8::1] or [2001:DB8::1]:2181
+      # getent does not support the bracket notation, but does support IPv6 addresses
+      host=$(sed -E 's/\[(.*)\].*/\1/' <<<"$lookup")
+      port=$(sed -E 's/^\[(.*)\]:?//' <<<"$lookup")
+    else
+      # IPv4, just split on :
+      IFS=: read -ra split <<<"$lookup"
+      host="${split[0]}"
+      port="${split[1]:-}"
+    fi
+    if [[ "${VERBOSE:-}" == "yes" ]]; then
+      echo "Parsed host=$host port=${port:-}"
+    fi
+    if getent hosts "$host" > $TMP_HOSTS; then
+      while read -r ip hostname ; do
+        echo "${hostname:-}">/dev/null # consume for shellcheck
+        check_zookeeper "$ip" "$port"
+      done <$TMP_HOSTS
+    else
+      echo "Cannot find $lookup yet"
+    fi
+  done
+  (( attempts_left-- ))
+  if (( attempts_left == 0 )); then echo "Still no master found; giving up"
+    exit 1
+  fi
+  sleep "$wait_seconds"
+done
+
+# To test the parsing:
+#  bash scripts/wait-for-zookeeper.sh foo
+#  bash scripts/wait-for-zookeeper.sh 'ZK_HOST=[2001:DB8::1]:2181,[2001:DB8::1],127.0.0.1:2181,127.0.0.2'
+#  ZK_HOST=[2001:DB8::1]:2181,[2001:DB8::1],127.0.0.1:2181,127.0.0.2 bash scripts/wait-for-zookeeper.sh