Add cluster.raft.leader.transfer command for graceful leader change (#7819)
* proto: add RaftLeadershipTransfer RPC for forced leader change Add new gRPC RPC and messages for leadership transfer: - RaftLeadershipTransferRequest: optional target_id and target_address - RaftLeadershipTransferResponse: previous_leader and new_leader This enables graceful leadership transfer before master maintenance, reducing errors in filers during planned maintenance windows. Ref: https://github.com/seaweedfs/seaweedfs/issues/7527 * proto: regenerate Go files for RaftLeadershipTransfer Generated from master.proto changes. * master: implement RaftLeadershipTransfer gRPC handler Add gRPC handler for leadership transfer with support for: - Transfer to any eligible follower (when target_id is empty) - Transfer to a specific server (when target_id and target_address are provided) Uses hashicorp/raft LeadershipTransfer() and LeadershipTransferToServer() APIs. Returns the previous and new leader in the response. * shell: add cluster.raft.leader.transfer command Add weed shell command for graceful leadership transfer: - Displays current cluster status before transfer - Supports auto-selection of target (any eligible follower) - Supports targeted transfer with -id and -address flags - Provides clear feedback on success/failure with troubleshooting tips Usage: cluster.raft.leader.transfer cluster.raft.leader.transfer -id <server_id> -address <grpc_address> * master: add unit tests for raft gRPC handlers Add tests covering: - RaftLeadershipTransfer with no raft initialized - RaftLeadershipTransfer with target_id but no address - RaftListClusterServers with no raft initialized - RaftAddServer with no raft initialized - RaftRemoveServer with no raft initialized These tests verify error handling when raft is not configured. * shell: add tests for cluster.raft.leader.transfer command Add tests covering: - Command name and help text validation - HasTag returns false for ResourceHeavy - Validation of -id without -address - Argument parsing with unknown flags * master: clarify that leadership transfer requires -raftHashicorp The default raft implementation (seaweedfs/raft, a goraft fork) does not support graceful leadership transfer. This feature is only available when using hashicorp raft (-raftHashicorp=true). Update error messages and help text to make this requirement clear: - gRPC handler returns specific error for goraft users - Shell command help text notes the requirement - Added test for goraft case * test: use strings.Contains instead of custom helper Replace custom contains/containsHelper functions with the standard library strings.Contains for better maintainability. * shell: return flag parsing errors instead of swallowing them - Return the error from flag.Parse() instead of returning nil - Update test to explicitly assert error for unknown flags * test: document integration test scenarios for Raft leadership transfer Add comments explaining: - Why these unit tests only cover 'Raft not initialized' scenarios - What integration tests should cover (with multi-master cluster) - hashicorp/raft uses concrete types that cannot be easily mocked * fix: address reviewer feedback on tests and leader routing - Remove misleading tests that couldn't properly validate their documented behavior without a real Raft cluster: - TestRaftLeadershipTransfer_GoraftNotSupported - TestRaftLeadershipTransfer_ValidationTargetIdWithoutAddress - Change WithClient(false) to WithClient(true) for RaftLeadershipTransfer RPC to ensure the request is routed to the current leader * Improve cluster.raft.transferLeader command - Rename command from cluster.raft.leader.transfer to cluster.raft.transferLeader - Add symmetric validation: -id and -address must be specified together - Handle case where same leader is re-elected after transfer - Add test for -address without -id validation - Add docker compose file for 5-master raft cluster testing
This commit is contained in:
Chris Lu
144
weed/shell/command_cluster_raft_leader_transfer.go
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144
weed/shell/command_cluster_raft_leader_transfer.go
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package shell
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import (
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"context"
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"flag"
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"fmt"
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"io"
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"time"
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"github.com/seaweedfs/seaweedfs/weed/pb/master_pb"
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)
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func init() {
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Commands = append(Commands, &commandRaftLeaderTransfer{})
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}
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type commandRaftLeaderTransfer struct{}
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func (c *commandRaftLeaderTransfer) Name() string {
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return "cluster.raft.transferLeader"
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}
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func (c *commandRaftLeaderTransfer) Help() string {
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return `transfer raft leadership to another master server
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This command initiates a graceful leadership transfer from the current
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leader to another server. Use this before performing maintenance on
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the current leader to reduce errors in filers and other components.
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Examples:
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# Transfer to any eligible follower (auto-selection)
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cluster.raft.transferLeader
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# Transfer to a specific server
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cluster.raft.transferLeader -id <server_id> -address <server_grpc_address>
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Notes:
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- Requires hashicorp raft (-raftHashicorp=true on master)
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- This command must be sent to the current leader
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- The target server must be a voting member of the raft cluster
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- Use 'cluster.raft.ps' to list available servers and identify the leader
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`
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}
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func (c *commandRaftLeaderTransfer) HasTag(CommandTag) bool {
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return false
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}
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func (c *commandRaftLeaderTransfer) Do(args []string, commandEnv *CommandEnv, writer io.Writer) error {
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leaderTransferCommand := flag.NewFlagSet(c.Name(), flag.ContinueOnError)
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targetId := leaderTransferCommand.String("id", "", "target server id (must be used with -address)")
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targetAddress := leaderTransferCommand.String("address", "", "target server grpc address (must be used with -id)")
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if err := leaderTransferCommand.Parse(args); err != nil {
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return err
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}
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// Validate: id and address must be specified together
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if *targetId != "" && *targetAddress == "" {
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return fmt.Errorf("-address is required when -id is specified")
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}
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if *targetAddress != "" && *targetId == "" {
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return fmt.Errorf("-id is required when -address is specified")
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}
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// First, show current cluster status
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fmt.Fprintf(writer, "Checking current raft cluster status...\n")
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var currentLeader string
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err := commandEnv.MasterClient.WithClient(false, func(client master_pb.SeaweedClient) error {
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ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
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defer cancel()
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resp, err := client.RaftListClusterServers(ctx, &master_pb.RaftListClusterServersRequest{})
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if err != nil {
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return fmt.Errorf("failed to list cluster servers: %v", err)
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}
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if len(resp.ClusterServers) == 0 {
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fmt.Fprintf(writer, "No raft cluster configured (single master mode)\n")
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return fmt.Errorf("leadership transfer not available in single master mode")
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}
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fmt.Fprintf(writer, "Raft cluster has %d servers:\n", len(resp.ClusterServers))
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for _, server := range resp.ClusterServers {
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suffix := ""
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if server.IsLeader {
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suffix = " <- current leader"
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currentLeader = server.Id
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}
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fmt.Fprintf(writer, " %s %s [%s]%s\n", server.Id, server.Address, server.Suffrage, suffix)
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}
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return nil
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})
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if err != nil {
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return err
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}
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if currentLeader == "" {
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return fmt.Errorf("no leader found in cluster")
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}
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// Perform the transfer
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targetDesc := "any eligible follower"
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if *targetId != "" {
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targetDesc = fmt.Sprintf("server %s (%s)", *targetId, *targetAddress)
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}
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fmt.Fprintf(writer, "\nTransferring leadership from %s to %s...\n", currentLeader, targetDesc)
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err = commandEnv.MasterClient.WithClient(true, func(client master_pb.SeaweedClient) error {
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ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
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defer cancel()
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resp, err := client.RaftLeadershipTransfer(ctx, &master_pb.RaftLeadershipTransferRequest{
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TargetId: *targetId,
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TargetAddress: *targetAddress,
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})
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if err != nil {
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return fmt.Errorf("leadership transfer failed: %v", err)
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}
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if resp.PreviousLeader != resp.NewLeader {
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fmt.Fprintf(writer, "Leadership successfully transferred.\n")
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fmt.Fprintf(writer, " Previous leader: %s\n", resp.PreviousLeader)
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fmt.Fprintf(writer, " New leader: %s\n", resp.NewLeader)
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} else {
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fmt.Fprintf(writer, "Leadership transfer initiated, but the same leader was re-elected.\n")
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fmt.Fprintf(writer, " Current leader: %s\n", resp.NewLeader)
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}
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return nil
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})
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if err != nil {
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fmt.Fprintf(writer, "\nLeadership transfer failed: %v\n", err)
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fmt.Fprintf(writer, "\nTroubleshooting:\n")
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fmt.Fprintf(writer, " - Ensure you are connected to the current leader\n")
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fmt.Fprintf(writer, " - Ensure target server is a voting member (use 'cluster.raft.ps')\n")
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fmt.Fprintf(writer, " - Ensure target server is healthy and reachable\n")
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return err
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}
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return nil
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}
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89
weed/shell/command_cluster_raft_leader_transfer_test.go
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89
weed/shell/command_cluster_raft_leader_transfer_test.go
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@@ -0,0 +1,89 @@
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package shell
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import (
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"bytes"
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"strings"
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"testing"
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)
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func TestRaftLeaderTransfer_Name(t *testing.T) {
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cmd := &commandRaftLeaderTransfer{}
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expected := "cluster.raft.transferLeader"
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if cmd.Name() != expected {
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t.Errorf("expected name %q, got %q", expected, cmd.Name())
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}
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}
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func TestRaftLeaderTransfer_Help(t *testing.T) {
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cmd := &commandRaftLeaderTransfer{}
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help := cmd.Help()
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// Verify help text contains key information
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expectedPhrases := []string{
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"transfer raft leadership",
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"cluster.raft.transferLeader",
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"-id",
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"-address",
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"cluster.raft.ps",
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"-raftHashicorp",
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}
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for _, phrase := range expectedPhrases {
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if !strings.Contains(help, phrase) {
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t.Errorf("help text should contain %q", phrase)
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}
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}
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}
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func TestRaftLeaderTransfer_HasTag(t *testing.T) {
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cmd := &commandRaftLeaderTransfer{}
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// The command should not have any special tags
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if cmd.HasTag(ResourceHeavy) {
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t.Error("expected HasTag to return false for ResourceHeavy")
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}
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}
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func TestRaftLeaderTransfer_ValidateTargetIdWithoutAddress(t *testing.T) {
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cmd := &commandRaftLeaderTransfer{}
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var buf bytes.Buffer
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// Create a mock command environment - this will fail because no master client
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// but we can verify argument parsing
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err := cmd.Do([]string{"-id", "test-server"}, nil, &buf)
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// Should fail because -address is required when -id is specified
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if err == nil {
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t.Error("expected error when -id is specified without -address")
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}
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if err != nil && !strings.Contains(err.Error(), "-address is required") {
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t.Errorf("expected error about missing -address, got: %v", err)
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}
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}
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func TestRaftLeaderTransfer_ValidateTargetAddressWithoutId(t *testing.T) {
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cmd := &commandRaftLeaderTransfer{}
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var buf bytes.Buffer
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// Verify argument parsing - address without id should fail
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err := cmd.Do([]string{"-address", "localhost:19333"}, nil, &buf)
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// Should fail because -id is required when -address is specified
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if err == nil {
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t.Error("expected error when -address is specified without -id")
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}
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if err != nil && !strings.Contains(err.Error(), "-id is required") {
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t.Errorf("expected error about missing -id, got: %v", err)
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}
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}
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func TestRaftLeaderTransfer_UnknownFlag(t *testing.T) {
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cmd := &commandRaftLeaderTransfer{}
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var buf bytes.Buffer
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// Unknown flag should return an error
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err := cmd.Do([]string{"-unknown-flag"}, nil, &buf)
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if err == nil {
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t.Error("expected error for unknown flag")
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}
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}
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