Make handler context vars backend agnostic (#37)

backends/memory/memory_backend.go

@@ -2,6 +2,7 @@ package memory
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"os"
 	"sync"
@@ -16,7 +17,6 @@ import (
 	"github.com/guregu/null"
 	"github.com/iancoleman/strcase"                          // TODO factor out
 	"github.com/jsuar/go-cron-descriptor/pkg/crondescriptor" // TODO factor out
-	"github.com/pkg/errors"
 	"github.com/robfig/cron"
 	"golang.org/x/exp/slog"
 )
@@ -226,6 +226,10 @@ func (m *MemBackend) start(ctx context.Context, queue string) (err error) {
 				}
 
 				if err != nil {
+					if errors.Is(err, context.Canceled) {
+						return
+					}
+
 					m.logger.Error("job failed", err, "job_id", job.ID)
 					runAfter := internal.CalculateBackoff(job.Retries)
 					job.RunAfter = runAfter
@@ -277,8 +281,7 @@ func (m *MemBackend) scheduleFutureJobs(ctx context.Context, queue string) {
 }
 
 func (m *MemBackend) handleJob(ctx context.Context, job *jobs.Job, h handler.Handler) (err error) {
-	ctxv := handler.CtxVars{Job: job}
-	hctx := handler.WithContext(ctx, ctxv)
+	ctx = handler.WithJobContext(ctx, job)
 
 	// check if the job is being retried and increment retry count accordingly
 	if job.Status != internal.JobStatusNew {
@@ -286,7 +289,7 @@ func (m *MemBackend) handleJob(ctx context.Context, job *jobs.Job, h handler.Han
 	}
 
 	// execute the queue handler of this job
-	err = handler.Exec(hctx, h)
+	err = handler.Exec(ctx, h)
 	if err != nil {
 		job.Error = null.StringFrom(err.Error())
 	}

backends/memory/memory_backend_test.go

@@ -66,7 +66,7 @@ func TestBasicJobProcessing(t *testing.T) {
 	for {
 		select {
 		case <-timeoutTimer:
-			err = errors.New("timed out waiting for job(s)")
+			err = jobs.ErrJobTimeout
 		case <-done:
 			doneCnt++
 		}

backends/postgres/postgres_backend.go

@@ -51,7 +51,10 @@ const (
 	setIdleInTxSessionTimeout = `SET idle_in_transaction_session_timeout = 0`
 )
 
+type contextKey struct{}
+
 var (
+	txCtxVarKey               contextKey
 	ErrCnxString              = errors.New("invalid connecton string: see documentation for valid connection strings")
 	ErrDuplicateJobID         = errors.New("duplicate job id")
 	ErrNoQueue                = errors.New("no queue specified")
@@ -168,16 +171,14 @@ func WithTransactionTimeout(txTimeout int) config.Option {
 
 // txFromContext gets the transaction from a context, if the transaction is already set
 func txFromContext(ctx context.Context) (t pgx.Tx, err error) {
-	if v, ok := ctx.Value(handler.CtxVarsKey).(handler.CtxVars); ok {
-		var tx pgx.Tx
-		var ok bool
-		if tx, ok = v.Tx.(pgx.Tx); !ok {
-			return nil, ErrNoTransactionInContext
-		}
-		return tx, nil
+	var ok bool
+	if t, ok = ctx.Value(txCtxVarKey).(pgx.Tx); ok {
+		return
 	}
 
-	return nil, ErrNoTransactionInContext
+	err = ErrNoTransactionInContext
+
+	return
 }
 
 // initializeDB initializes the tables, types, and indices necessary to operate Neoq
@@ -538,7 +539,11 @@ func (p *PgBackend) updateJob(ctx context.Context, jobErr error) (err error) {
 		_, err = tx.Exec(ctx, qstr, time.Now(), errMsg, status, job.ID)
 	}
 
-	if err == nil && time.Until(runAfter) > 0 {
+	if err != nil {
+		return
+	}
+
+	if time.Until(runAfter) > 0 {
 		p.mu.Lock()
 		p.futureJobs[job.ID] = runAfter
 		p.mu.Unlock()
@@ -733,6 +738,7 @@ func (p *PgBackend) pendingJobs(ctx context.Context, queue string) (jobsCh chan
 // 1. handleJob first creates a transactions inside of which a row lock is acquired for the job to be processed.
 // 2. handleJob secondly calls the handler on the job, and finally updates the job's status
 func (p *PgBackend) handleJob(ctx context.Context, jobID int64, h handler.Handler) (err error) {
+	var job *jobs.Job
 	var tx pgx.Tx
 	conn, err := p.pool.Acquire(ctx)
 	if err != nil {
@@ -746,15 +752,13 @@ func (p *PgBackend) handleJob(ctx context.Context, jobID int64, h handler.Handle
 	}
 	defer func(ctx context.Context) { _ = tx.Rollback(ctx) }(ctx) // rollback has no effect if the transaction has been committed
 
-	ctxv := handler.CtxVars{Tx: tx}
-	var job *jobs.Job
 	job, err = p.getPendingJob(ctx, tx, jobID)
 	if err != nil {
 		return
 	}
 
-	ctxv.Job = job
-	ctx = handler.WithContext(ctx, ctxv)
+	ctx = handler.WithJobContext(ctx, job)
+	ctx = context.WithValue(ctx, txCtxVarKey, tx)
 
 	// check if the job is being retried and increment retry count accordingly
 	if job.Status != internal.JobStatusNew {

backends/postgres/postgres_backend_test.go

@@ -2,7 +2,7 @@ package postgres_test
 
 import (
 	"context"
-	"fmt"
+	"errors"
 	"os"
 	"testing"
 	"time"
@@ -12,8 +12,6 @@ import (
 	"github.com/acaloiaro/neoq/config"
 	"github.com/acaloiaro/neoq/handler"
 	"github.com/acaloiaro/neoq/jobs"
-	"github.com/pkg/errors"
-	"golang.org/x/exp/slog"
 )
 
 var errPeriodicTimeout = errors.New("timed out waiting for periodic job")
@@ -22,9 +20,9 @@ var errPeriodicTimeout = errors.New("timed out waiting for periodic job")
 // most basic configuration.
 func TestBasicJobProcessing(t *testing.T) {
 	queue := "testing"
-	numJobs := 10
-	doneCnt := 0
 	done := make(chan bool)
+	defer close(done)
+
 	var timeoutTimer = time.After(5 * time.Second)
 
 	var connString = os.Getenv("TEST_DATABASE_URL")
@@ -50,35 +48,20 @@ func TestBasicJobProcessing(t *testing.T) {
 		t.Error(err)
 	}
 
-	go func() {
-		for i := 0; i < numJobs; i++ {
-			jid, e := nq.Enqueue(ctx, &jobs.Job{
-				Queue: queue,
-				Payload: map[string]interface{}{
-					"message": fmt.Sprintf("hello world: %d", i),
-				},
-			})
-			if e != nil || jid == jobs.DuplicateJobID {
-				slog.Error("job was not enqueued. either it was duplicate or this error caused it:", e)
-			}
-		}
-	}()
+	jid, e := nq.Enqueue(ctx, &jobs.Job{
+		Queue: queue,
+		Payload: map[string]interface{}{
+			"message": "hello world",
+		},
+	})
+	if e != nil || jid == jobs.DuplicateJobID {
+		t.Error(e)
+	}
 
-	for {
-		select {
-		case <-timeoutTimer:
-			err = errors.New("timed out waiting for job(s)")
-		case <-done:
-			doneCnt++
-		}
-
-		if doneCnt >= numJobs {
-			break
-		}
-
-		if err != nil {
-			break
-		}
+	select {
+	case <-timeoutTimer:
+		err = jobs.ErrJobTimeout
+	case <-done:
 	}
 
 	if err != nil {
@@ -87,6 +70,8 @@ func TestBasicJobProcessing(t *testing.T) {
 }
 
 func TestCron(t *testing.T) {
+	done := make(chan bool, 1)
+	defer close(done)
 	const cron = "* * * * * *"
 	var connString = os.Getenv("TEST_DATABASE_URL")
 	if connString == "" {
@@ -101,7 +86,6 @@ func TestCron(t *testing.T) {
 	}
 	defer nq.Shutdown(ctx)
 
-	var done = make(chan bool)
 	h := handler.New(func(ctx context.Context) (err error) {
 		done <- true
 		return

examples/add_postgres_job/main.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"context"
+	"log"
+	"time"
+
+	"github.com/acaloiaro/neoq"
+	"github.com/acaloiaro/neoq/backends/postgres"
+	"github.com/acaloiaro/neoq/config"
+	"github.com/acaloiaro/neoq/handler"
+	"github.com/acaloiaro/neoq/jobs"
+)
+
+func main() {
+	var done = make(chan bool, 1)
+	const queue = "foobar"
+	ctx := context.Background()
+	nq, err := neoq.New(ctx,
+		config.WithConnectionString("postgres://postgres:postgres@127.0.0.1:5432/neoq"),
+		neoq.WithBackend(postgres.Backend),
+	)
+	if err != nil {
+		log.Fatalf("error initializing postgres backend: %v", err)
+	}
+	defer nq.Shutdown(ctx)
+
+	h := handler.New(func(ctx context.Context) (err error) {
+		var j *jobs.Job
+		time.Sleep(1 * time.Second)
+		j, err = handler.JobFromContext(ctx)
+		log.Println("got job id:", j.ID, "messsage:", j.Payload["message"])
+		done <- true
+		return
+	})
+
+	err = nq.Start(ctx, queue, h)
+	if err != nil {
+		log.Println("error listening to queue", err)
+	}
+
+	// Add a job that will execute 1 hour from now
+	jobID, err := nq.Enqueue(ctx, &jobs.Job{
+		Queue: queue,
+		Payload: map[string]interface{}{
+			"message": "hello, world",
+		},
+	})
+	if err != nil {
+		log.Fatalf("error adding job: %v", err)
+	}
+
+	log.Println("added job:", jobID)
+	<-done
+}

handler/handler.go

@@ -17,10 +17,9 @@ const (
 type contextKey struct{}
 
 var (
-	CtxVarsKey           contextKey
-	ErrContextHasNoJob   = errors.New("context has no Job")
-	ErrNoHandlerForQueue = errors.New("no handler for queue")
-	// TODO this error is here because cyclic imports with neoq
+	JobCtxVarKey           contextKey
+	ErrContextHasNoJob     = errors.New("context has no Job")
+	ErrNoHandlerForQueue   = errors.New("no handler for queue")
 	ErrNoProcessorForQueue = errors.New("no processor configured for queue")
 )
 
@@ -35,16 +34,6 @@ type Handler struct {
 	QueueCapacity int64
 }
 
-// CtxVars are variables passed to every Handler context
-type CtxVars struct {
-	Job *jobs.Job
-	// this is a bit hacky. Tx here contains a pgx.Tx for PgBackend, but because we're in the handlers package, and we don't
-	// want all neoq users to have pgx as a transitive dependency, we store Tx as any, and coerce it to a pgx.Tx inside
-	// the postgres backend
-	// TODO redesign HandlerCtxVars so it doesn't need to include a pgx.Tx
-	Tx any
-}
-
 // Option is function that sets optional configuration for Handlers
 type Option func(w *Handler)
 
@@ -101,9 +90,9 @@ func New(f Func, opts ...Option) (h Handler) {
 	return
 }
 
-// WithContext creates a new context with the job and transaction set
-func WithContext(ctx context.Context, v CtxVars) context.Context {
-	return context.WithValue(ctx, CtxVarsKey, v)
+// WithJobContext creates a new context with the Job set
+func WithJobContext(ctx context.Context, j *jobs.Job) context.Context {
+	return context.WithValue(ctx, JobCtxVarKey, j)
 }
 
 // Exec executes handler functions with a concrete time deadline
@@ -140,9 +129,10 @@ func Exec(ctx context.Context, handler Handler) (err error) {
 }
 
 // JobFromContext fetches the job from a context if the job context variable is already set
-func JobFromContext(ctx context.Context) (*jobs.Job, error) {
-	if v, ok := ctx.Value(CtxVarsKey).(CtxVars); ok {
-		return v.Job, nil
+func JobFromContext(ctx context.Context) (j *jobs.Job, err error) {
+	var ok bool
+	if j, ok = ctx.Value(JobCtxVarKey).(*jobs.Job); ok {
+		return
 	}
 
 	return nil, ErrContextHasNoJob

jobs/jobs.go

@@ -3,6 +3,7 @@ package jobs
 import (
 	"crypto/md5" // nolint: gosec
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"time"
@@ -10,6 +11,10 @@ import (
 	"github.com/guregu/null"
 )
 
+var (
+	ErrJobTimeout = errors.New("timed out waiting for job(s)")
+)
+
 const (
 	DuplicateJobID = -1
 	UnqueuedJobID  = -2