Merge pull request #289 from dciabrin/osprh-11488

Improve the failover of galera service

Author: openshift-merge-bot[bot]

templates/galera/bin/mysql_shutdown.sh

@@ -44,5 +44,16 @@ if curl -s --cacert ${CACERT} --header "Content-Type:application/json" --header
     done
 fi
 
-log "Shutting down local galera node"
+log "Initiating orchestrated shutdown of the local galera node"
+
+log "Failover service to another available galera node"
+bash $(dirname $0)/mysql_wsrep_notify.sh --status failover
+
+log "Close all active connections to this local galera node"
+# filter out system and localhost connections, only consider clients with a port in the host field
+# from that point, clients will automatically reconnect to another node
+CLIENTS=$(mysql -uroot -p${DB_ROOT_PASSWORD} -nN -e "select id from information_schema.processlist where host like '%:%';")
+echo -n "$CLIENTS" | tr '\n' ',' | xargs mysqladmin -uroot -p${DB_ROOT_PASSWORD} kill
+
+log "Shutdown local server"
 mysqladmin -uroot -p"${DB_ROOT_PASSWORD}" shutdown

templates/galera/bin/mysql_wsrep_notify.sh

@@ -32,18 +32,26 @@ function log_error() {
 function mysql_get_status {
     local name=$1
     mysql -nNE -uroot -p"${DB_ROOT_PASSWORD}" -e "show status like '${name}';" | tail -1
-    if [ $? != 0 ]; then
-        log_error "could not get value of mysql variable '${name}' (rc=$?)"
-        return 1
-    fi
+    local rc=$?
+    [ $rc = 0 ] || log_error "could not get value of mysql variable '${name}' (rc=$rc)"
+}
+
+function mysql_get_members {
+    mysql -nN -uroot -p"${DB_ROOT_PASSWORD}" -e "select node_name from mysql.wsrep_cluster_members;"
+    local rc=$?
+    [ $rc = 0 ] || log_error "could not get cluster members from mysql' (rc=$rc)"
 }
 
-# Refresh environment variables with the latest WSREP state from mysql
+# When optional script parameters are not provided, set up the environment
+# variables with the latest WSREP state retrieved from mysql
 function mysql_probe_state {
-    UUID=$(mysql_get_status wsrep_gcomm_uuid)
-    PARTITION=$(mysql_get_status wsrep_cluster_status)
-    INDEX=$(mysql_get_status wsrep_local_index)
-    SIZE=$(mysql_get_status wsrep_cluster_size)
+    [ "$1" = "reprobe" ] && unset UUID PARTITION INDEX SIZE MEMBERS
+    : ${UUID=$(mysql_get_status wsrep_gcomm_uuid)}
+    : ${PARTITION=$(mysql_get_status wsrep_cluster_status)}
+    : ${INDEX=$(mysql_get_status wsrep_local_index)}
+    : ${SIZE=$(mysql_get_status wsrep_cluster_size)}
+    : ${MEMBERS=$(mysql_get_members)}
+    [ -n "${UUID}" -a -n "${PARTITION}" -a -n "${INDEX}" -a -n "${SIZE}" -a -n "${MEMBERS}" ]
 }
 
 # REST API call to the k8s API server
@@ -83,12 +91,10 @@ function api_server {
 # Update the service's active endpoint
 # (parse JSON with python3 as we don't have jq in the container image)
 function service_endpoint {
-    local endpoint=$1
-    if [ -n "${endpoint}" ]; then
-        python3 -c 'import json,sys;s=json.load(sys.stdin);s["spec"]["selector"]["statefulset.kubernetes.io/pod-name"]="'${endpoint}'";print(json.dumps(s,indent=2))'
-    else
-        python3 -c 'import json,sys;s=json.load(sys.stdin);s["spec"]["selector"].pop("statefulset.kubernetes.io/pod-name", None);print(json.dumps(s,indent=2))'
-    fi
+    local endpoint="$1"
+    # note: empty endpoint means "block incoming traffic", so the selector must still
+    # be present, otherwise k8s would balance incoming traffic to _any_ available pod.
+    python3 -c 'import json,sys;s=json.load(sys.stdin);s["spec"]["selector"]["statefulset.kubernetes.io/pod-name"]="'${endpoint}'";print(json.dumps(s,indent=2))'
     [ $? == 0 ] || log_error "Could not parse json endpoint (rc=$?)"
 }
 
@@ -123,7 +129,7 @@ function retry {
         retries=$((retries - 1))
         # reprobe mysql state now, as if the cluster state changed since
         # the start of this script, we might not need to retry the action
-        mysql_probe_state
+        mysql_probe_state reprobe
     done
     if [ $rc -ne 0 ]; then
         log_error "Could not run action after ${RETRIES} tries. Stop retrying."
@@ -149,6 +155,11 @@ function reconfigure_service_endpoint {
 
     CURRENT_ENDPOINT=$(echo "$CURRENT_SVC" | parse_output '["spec"]["selector"].get("statefulset.kubernetes.io/pod-name","")')
     [ $? == 0 ] || return 1
+    # do not reconfigure endpoint if unecessary, to avoid client disconnections
+    if [ -n "${CURRENT_ENDPOINT}" ] && echo "$MEMBERS" | grep -q "^${CURRENT_ENDPOINT}\$"; then
+        log "Active endpoint ${CURRENT_ENDPOINT} is still part of the primary partition. Nothing to be done."
+        return 0
+    fi
     if [ "${CURRENT_ENDPOINT}" == "${PODNAME}" ]; then
         log "Node ${PODNAME} is currently the active endpoint for service ${SERVICE}. Nothing to be done."
         return 0
@@ -164,6 +175,39 @@ function reconfigure_service_endpoint {
     return 0
 }
 
+## Failover to another node if we are the current Active endpoint
+function failover_service_endpoint {
+    if [ $PARTITION != "Primary" ]; then
+        log "Node ${PODNAME} is not the Primary partion. Nothing to be done."
+        return 0
+    fi
+
+    CURRENT_SVC=$(api_server GET "$SERVICE")
+    local rc=$?
+    [ $rc == 0 ] || return $rc
+
+    CURRENT_ENDPOINT=$(echo "$CURRENT_SVC" | parse_output '["spec"]["selector"].get("statefulset.kubernetes.io/pod-name","")')
+    [ $? == 0 ] || return 1
+    if [ "${CURRENT_ENDPOINT}" != "${PODNAME}" ]; then
+        log "Node ${PODNAME} is not the active endpoint. Nothing to be done."
+        return 0
+    fi
+    # select the first available node in the primary partition to be the failover endpoint
+    NEW_ENDPOINT=$(echo "$MEMBERS" | grep -v "${PODNAME}" | head -1)
+    if [ -z "${NEW_ENDPOINT}" ]; then
+        log "No other available node to become the active endpoint."
+    fi
+
+    NEW_SVC=$(echo "$CURRENT_SVC" | service_endpoint "$NEW_ENDPOINT")
+    [ $? == 0 ] || return 1
+
+    log "Configuring a new active endpoint for service ${SERVICE}: '${CURRENT_ENDPOINT}' -> '${NEW_ENDPOINT}'"
+    UPDATE_RESULT=$(echo "$NEW_SVC" | api_server PUT "$SERVICE")
+    [ $? == 0 ] || return 1
+
+    return 0
+}
+
 ## Change the Active endpoint from the service
 function remove_service_endpoint {
     CURRENT_SVC=$(api_server GET "$SERVICE")
@@ -194,17 +238,29 @@ function remove_service_endpoint {
 log "called with args: $*"
 
 # Galera always calls script with --status argument
-# All other arguments (uuid,partition,index...) are optional,
-# so get those values by probing mysql directly
-STATUS=""
-PARTITION=""
-INDEX=""
+# All other optional arguments (uuid,partition,index...):
+# UUID: cluster's current UUID
+# MEMBERS: galera node connected to the cluster
+# SIZE: number of nodes in the cluster
+# INDEX: member index in the cluster
+# PARTITION: cluster partition we're in (Primary, Non-primary)
 while [ $# -gt 0 ]; do
     case $1 in
         --status)
             STATUS=$2
             shift;;
-        --uuid|--members|--primary|--index)
+        --members)
+            MEMBERS=$(echo "$2" | tr ',' '\n' | cut -d/ -f2)
+            SIZE=$(echo "$MEMBERS" | wc -l)
+            shift;;
+        --primary)
+            [ "$2" = "yes" ] && PARTITION="Primary"
+            [ "$2" = "no" ] && PARTITION="Non-primary"
+            shift;;
+        --index)
+            INDEX=$2
+            shift;;
+        --uuid)
             shift;;
     esac
     shift
@@ -215,6 +271,15 @@ if [ -z "${STATUS}" ]; then
     exit 1
 fi
 
+# Contition: ask for a failover. This should be called when mysql is running
+if echo "${STATUS}" | grep -i -q -e 'failover'; then
+    mysql_probe_state
+    if [ $? != 0 ]; then
+        log_error "Could not probe missing mysql information. Aborting"
+    fi
+    retry "failover_service_endpoint"
+fi
+
 # Condition: disconnecting -> remove oneself from endpoint if Active
 if echo "${STATUS}" | grep -i -q -e 'disconnecting'; then
     retry "remove_service_endpoint"
@@ -228,6 +293,9 @@ fi
 
 # At this point mysql is started, query missing arguments
 mysql_probe_state
+if [ $? != 0 ]; then
+    log_error "Could not probe missing mysql information. Aborting"
+fi
 
 # Condition: first member of the primary partition -> set as Active endpoint
 if [ $PARTITION = "Primary" -a $SIZE -ge 0 -a "$INDEX" = "0" ]; then