nmon/internal/simagent/pool.go

package simagent

import (
	"context"
	"errors"
	"fmt"
	"sync"
)

// Pool hosts many agents in one process, one UDP socket each.
type Pool struct {
	mu     sync.Mutex
	agents []*Agent
}

// Start launches one agent per config and appends them to the pool. If any
// fails, the ones started by this call are closed and the error is returned.
func (p *Pool) Start(ctx context.Context, cfgs []Config) error {
	started := make([]*Agent, 0, len(cfgs))
	for i, c := range cfgs {
		a, err := Start(ctx, c)
		if err != nil {
			for _, s := range started {
				_ = s.Close() // best-effort rollback; the start error is the one to report
			}
			return fmt.Errorf("agent %d: %w", i, err)
		}
		started = append(started, a)
	}
	p.mu.Lock()
	p.agents = append(p.agents, started...)
	p.mu.Unlock()
	return nil
}

// Agents returns the running agents in start order.
func (p *Pool) Agents() []*Agent {
	p.mu.Lock()
	defer p.mu.Unlock()
	return append([]*Agent(nil), p.agents...)
}

// Close stops every agent.
func (p *Pool) Close() error {
	p.mu.Lock()
	agents := p.agents
	p.agents = nil
	p.mu.Unlock()
	var errs []error
	for _, a := range agents {
		errs = append(errs, a.Close())
	}
	return errors.Join(errs...)
}