JAVA J2EE 4 U

 #!/bin/bash

# Configuration

PATRONI_API="http://localhost:8008"

MAX_ALLOWED_LAG=1048576  # 1MB lag threshold

# Function to get LSN of a node

get_lsn() {

    local NODE=$1

    curl -s "${PATRONI_API}/cluster" | jq -r ".members[] | select(.name==\"$NODE\") | .xlog_location"

}

# Check if Patroni API is accessible

if ! curl -s "${PATRONI_API}/cluster" &>/dev/null; then

    echo "Error: Unable to reach Patroni API at ${PATRONI_API}"

    exit 1

fi

# Fetch current cluster status

echo "Fetching Patroni cluster status..."

CLUSTER_INFO=$(curl -s "${PATRONI_API}/cluster")

# Extract leader and replicas

LEADER=$(echo "$CLUSTER_INFO" | jq -r '.leader')

REPLICAS=$(echo "$CLUSTER_INFO" | jq -r '.members[] | select(.role=="replica") | .name')

echo "Current Leader: $LEADER"

echo "Available Replicas:"

echo "$REPLICAS"

# Get current LSN for leader

LEADER_LSN=$(get_lsn "$LEADER")

echo "Leader LSN: $LEADER_LSN"

# Prompt user for the target leader

read -p "Enter the target replica to become the new leader: " TARGET

# Validate input

if ! echo "$REPLICAS" | grep -qw "$TARGET"; then

    echo "Error: Invalid replica name. Exiting."

    exit 1

fi

# Get LSN for target replica

TARGET_LSN=$(get_lsn "$TARGET")

echo "Target Replica LSN: $TARGET_LSN"

# Calculate LSN lag

LSN_LAG=$((LEADER_LSN - TARGET_LSN))

echo "LSN Lag: $LSN_LAG bytes"

# Validate RPO threshold

if (( LSN_LAG > MAX_ALLOWED_LAG )); then

    echo "Error: Replica is lagging by more than $MAX_ALLOWED_LAG bytes. Switchover aborted."

    exit 1

fi

# Initiate switchover

echo "Initiating switchover from $LEADER to $TARGET..."

SWITCHOVER_RESPONSE=$(curl -s -X POST "${PATRONI_API}/switchover" -H "Content-Type: application/json" \

    -d "{\"leader\": \"$LEADER\", \"candidate\": \"$TARGET\"}")

# Check result

if echo "$SWITCHOVER_RESPONSE" | jq -e '.error' &>/dev/null; then

    echo "Switchover failed: $(echo "$SWITCHOVER_RESPONSE" | jq -r '.error')"

    exit 1

fi

echo "Switchover successful! $TARGET is now the new leader."