Replica set example that uses PetSet

3.2/root/usr/bin/run-mongod-pet

@@ -0,0 +1,75 @@
+#!/bin/bash
+#
+# Run mongod in a PetSet-based replica set. See
+# https://github.com/sclorg/mongodb-container/blob/master/examples/petset/README.md
+# for a description of how this is intended to work.
+#
+# Note that this differs from the `run-mongodb-replication` script in at least
+# these aspects:
+# - It does not attempt to remove the host from the replica set configuration
+#   when it is terminating. That is by design, because, in a PetSet, when a
+#   pod/container terminates and is restarted by OpenShift, it will always have
+#   the same hostname. Removing hosts from the configuration affects replica set
+#   elections and can impact the replica set stability.
+# - The original replication example uses MONGODB_INITIAL_REPLICA_COUNT to wait
+#   for a certain number of pods to come up and then initializes the replica set.
+#   This example, instead, initializes the replica set when the first pod starts.
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+source ${CONTAINER_SCRIPTS_PATH}/common.sh
+
+function usage() {
+  echo "You must specify the following environment variables:"
+  echo "  MONGODB_USER"
+  echo "  MONGODB_PASSWORD"
+  echo "  MONGODB_DATABASE"
+  echo "  MONGODB_ADMIN_PASSWORD"
+  echo "  MONGODB_KEYFILE_VALUE"
+  echo "  MONGODB_REPLICA_NAME"
+  echo "Optional variables:"
+  echo "  MONGODB_SERVICE_NAME (default: mongodb)"
+  echo "MongoDB settings:"
+  echo "  MONGODB_NOPREALLOC (default: true)"
+  echo "  MONGODB_SMALLFILES (default: true)"
+  echo "  MONGODB_QUIET (default: true)"
+  exit 1
+}
+
+function cleanup() {
+  echo "=> Shutting down MongoDB server ..."
+  pkill -INT mongod || :
+  wait_for_mongo_down
+  exit 0
+}
+
+trap 'cleanup' SIGINT SIGTERM
+
+# If user provides own config file use it and do not generate new one
+if [ ! -s "${MONGODB_CONFIG_PATH}" ]; then
+  # Generate config file for MongoDB
+  envsubst < "${CONTAINER_SCRIPTS_PATH}/mongodb.conf.template" > "${MONGODB_CONFIG_PATH}"
+fi
+
+if ! [[ -v MONGODB_USER && -v MONGODB_PASSWORD && -v MONGODB_DATABASE && -v MONGODB_ADMIN_PASSWORD && -v MONGODB_KEYFILE_VALUE && -v MONGODB_REPLICA_NAME ]]; then
+  usage
+fi
+
+mongo_common_args="-f ${MONGODB_CONFIG_PATH}"
+
+# Attention: setup_keyfile may modify value of mongo_common_args!
+setup_keyfile
+
+${CONTAINER_SCRIPTS_PATH}/init-petset-replset.sh &
+
+# TODO: capture exit code of `init-petset-replset.sh` and exit with an error if
+# the initialization failed, so that the container will be restarted and the
+# user can gain more visibility that there is a problem in a way other than just
+# inspecting log messages.
+
+# Make sure env variables don't propagate to mongod process.
+unset MONGODB_USER MONGODB_PASSWORD MONGODB_DATABASE MONGODB_ADMIN_PASSWORD
+mongod ${mongo_common_args} --replSet "${MONGODB_REPLICA_NAME}" &
+wait

3.2/root/usr/share/container-scripts/mongodb/common.sh

@@ -259,3 +259,8 @@ function setup_keyfile() {
   chmod 0600 ${MONGODB_KEYFILE_PATH}
   mongo_common_args+=" --keyFile ${MONGODB_KEYFILE_PATH}"
 }
+
+# info prints a message prefixed by date and time.
+function info() {
+  printf "=> [%s] %s\n" "$(date +'%a %b %d %T')" "$*"
+}

3.2/root/usr/share/container-scripts/mongodb/init-petset-replset.sh

@@ -0,0 +1,159 @@
+#!/bin/bash
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+source "${CONTAINER_SCRIPTS_PATH}/common.sh"
+
+# This is a full hostname that will be added to replica set
+# (for example, "replica-2.mongodb.myproject.svc.cluster.local")
+readonly MEMBER_HOST="$(hostname -f)"
+
+# Description of possible statuses: https://docs.mongodb.com/manual/reference/replica-states/
+readonly WAIT_PRIMARY_STATUS='
+  while (rs.status().startupStatus || (rs.status().hasOwnProperty("myState") && rs.status().myState != 1)) {
+    printjson(rs.status());
+    sleep(1000);
+  };
+  printjson(rs.status());
+'
+readonly WAIT_PRIMARY_OR_SECONDARY_STATUS="
+  var mbrs;
+  while (!mbrs || mbrs.length == 0 || !(mbrs[0].state == 1 || mbrs[0].state == 2)) {
+    printjson(rs.status());
+    sleep(1000);
+    mbrs = rs.status().members.filter(function(el) {
+      return el.name.indexOf(\"${MEMBER_HOST}:\") > -1;
+    });
+  };
+  print(mbrs[0].stateStr);
+"
+
+# Outputs available endpoints (hostnames) to stdout.
+# This also includes hostname of the current pod.
+#
+# Uses the following global variables:
+# - MONGODB_SERVICE_NAME (optional, defaults to 'mongodb')
+function find_endpoints() {
+  local service_name="${MONGODB_SERVICE_NAME:-mongodb}"
+
+  # Extract host names from lines like this: "10 33 0 mongodb-2.mongodb.myproject.svc.cluster.local."
+  dig "${service_name}" SRV +search +short | cut -d' ' -f4 | rev | cut -c2- | rev
+}
+
+# TODO: unify this and `mongo_initiate` from common.sh
+# Initializes the replica set configuration. It is safe to call this function if
+# a replica set is already configured.
+#
+# Arguments:
+# - $1: host address[:port]
+#
+# Uses the following global variables:
+# - MONGODB_REPLICA_NAME
+# - MONGODB_ADMIN_PASSWORD
+# - WAIT_PRIMARY_STATUS
+function initiate() {
+  local host="$1"
+
+  if mongo --eval "quit(db.isMaster().setName == '${MONGODB_REPLICA_NAME}' ? 0 : 1)" --quiet; then
+    info "Replica set '${MONGODB_REPLICA_NAME}' already exists, skipping initialization"
+    return
+  fi
+
+  local config="{_id: '${MONGODB_REPLICA_NAME}', members: [{_id: 0, host: '${host}'}]}"
+
+  info "Initiating MongoDB replica using: ${config}"
+  mongo admin --eval "rs.initiate(${config});${WAIT_PRIMARY_STATUS}" --quiet
+
+  info "Creating MongoDB users ..."
+  mongo_create_admin
+  mongo_create_user "-u admin -p ${MONGODB_ADMIN_PASSWORD}"
+
+  info "Successfully initialized replica set"
+}
+
+# Adds a host to the replica set configuration. It is safe to call this function
+# if the host is already in the configuration.
+#
+# Arguments:
+# - $1: host address[:port]
+#
+# Global variables:
+# - MAX_ATTEMPTS
+# - SLEEP_TIME
+# - MONGODB_REPLICA_NAME
+# - MONGODB_ADMIN_PASSWORD
+# - WAIT_PRIMARY_OR_SECONDARY_STATUS
+function add_member() {
+  local host="$1"
+  info "Adding ${host} to replica set ..."
+
+  local script
+  script="
+    for (var i = 0; i < ${MAX_ATTEMPTS}; i++) {
+      var ret = rs.add('${host}');
+      if (ret.ok) {
+        quit(0);
+      }
+      // ignore error if host is already in the configuration
+      if (ret.code == 103) {
+        quit(0);
+      }
+      sleep(${SLEEP_TIME});
+    }
+    printjson(ret);
+    quit(1);
+  "
+
+  # TODO: replace this with a call to `replset_addr` from common.sh, once it returns host names.
+  local endpoints
+  endpoints="$(find_endpoints | paste -s -d,)"
+
+  if [ -z "${endpoints}" ]; then
+    info "ERROR: couldn't add host to replica set!"
+    info "CAUSE: DNS lookup for '${MONGODB_SERVICE_NAME:-mongodb}' returned no results."
+    return 1
+  fi
+
+  local replset_addr
+  replset_addr="${MONGODB_REPLICA_NAME}/${endpoints}"
+
+  if ! mongo admin -u admin -p "${MONGODB_ADMIN_PASSWORD}" --host "${replset_addr}" --eval "${script}" --quiet; then
+    info "ERROR: couldn't add host to replica set!"
+    return 1
+  fi
+
+  info "Successfully added to replica set"
+  info "Waiting for PRIMARY/SECONDARY status ..."
+
+  local rs_status_out
+  rs_status_out="$(mongo admin -u admin -p "${MONGODB_ADMIN_PASSWORD}" --host "${replset_addr}" --eval "${WAIT_PRIMARY_OR_SECONDARY_STATUS}" --quiet || :)"
+
+  if ! echo "${rs_status_out}" | grep -xqs '\(SECONDARY\|PRIMARY\)'; then
+    info "ERROR: failed waiting for PRIMARY/SECONDARY status. Command output was:"
+    echo "${rs_status_out}"
+    echo "==> End of the error output <=="
+    return 1
+  fi
+
+  info "Successfully joined replica set"
+}
+
+info "Waiting for local MongoDB to accept connections ..."
+wait_for_mongo_up &>/dev/null
+
+# PetSet pods are named with a predictable name, following the pattern:
+#   $(petset name)-$(zero-based index)
+# MEMBER_ID is computed by removing the prefix matching "*-", i.e.:
+#  "mongodb-0" -> "0"
+#  "mongodb-1" -> "1"
+#  "mongodb-2" -> "2"
+readonly MEMBER_ID="${HOSTNAME##*-}"
+
+# Initialize replica set only if we're the first member
+if [ "${MEMBER_ID}" = '0' ]; then
+  initiate "${MEMBER_HOST}"
+else
+  add_member "${MEMBER_HOST}"
+fi