feat: shared pgx-pool #4393
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,64 @@ | ||
| package postgresqlretriever | ||
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| import ( | ||
| "context" | ||
| "sync" | ||
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| "github.com/jackc/pgx/v5/pgxpool" | ||
| ) | ||
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| type poolEntry struct { | ||
| pool *pgxpool.Pool | ||
| refCount int | ||
| } | ||
|
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| var ( | ||
| mu sync.Mutex | ||
| poolMap = make(map[string]*poolEntry) | ||
| ) | ||
|
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| // GetPool returns a pool for a given URI, creating it if needed. | ||
| func GetPool(ctx context.Context, uri string) (*pgxpool.Pool, error) { | ||
| mu.Lock() | ||
| defer mu.Unlock() | ||
|
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| // If already exists, bump refCount | ||
| if entry, ok := poolMap[uri]; ok { | ||
| entry.refCount++ | ||
| return entry.pool, nil | ||
| } | ||
|
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| // Create a new pool | ||
| pool, err := pgxpool.New(ctx, uri) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| if err := pool.Ping(ctx); err != nil { | ||
| pool.Close() | ||
| return nil, err | ||
| } | ||
|
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| poolMap[uri] = &poolEntry{ | ||
| pool: pool, | ||
| refCount: 1, | ||
| } | ||
|
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| return pool, nil | ||
| } | ||
|
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Contributor
There was a problem hiding this comment. The current implementation of To improve this, you can use a double-checked locking pattern. This avoids holding the lock during the potentially long-running pool creation and pinging process. func GetPool(ctx context.Context, uri string) (*pgxpool.Pool, error) {
mu.Lock()
if entry, ok := poolMap[uri]; ok {
entry.refCount++
mu.Unlock()
return entry.pool, nil
}
mu.Unlock()
// Create a new pool outside the lock.
pool, err := pgxpool.New(ctx, uri)
if err != nil {
return nil, err
}
if err := pool.Ping(ctx); err != nil {
pool.Close()
return nil, err
}
mu.Lock()
defer mu.Unlock()
// Re-check if another goroutine created the pool while we were unlocked.
if entry, ok := poolMap[uri]; ok {
pool.Close() // Close the one we just created, it's not needed.
entry.refCount++
return entry.pool, nil
}
poolMap[uri] = &poolEntry{
pool: pool,
refCount: 1,
}
return pool, nil
} |
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| // ReleasePool decreases refCount and closes/removes when it hits zero. | ||
| func ReleasePool(ctx context.Context, uri string) { | ||
|
Contributor
There was a problem hiding this comment. The You will also need to update the call site in func ReleasePool(uri string) { |
||
| mu.Lock() | ||
| defer mu.Unlock() | ||
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| entry, ok := poolMap[uri] | ||
| if !ok { | ||
| return // nothing to do | ||
| } | ||
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| entry.refCount-- | ||
| if entry.refCount <= 0 { | ||
| entry.pool.Close() | ||
| delete(poolMap, uri) | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,85 @@ | ||
| package postgresqlretriever_test | ||
|
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| import ( | ||
| "context" | ||
| "testing" | ||
| "time" | ||
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| "github.com/stretchr/testify/assert" | ||
| "github.com/testcontainers/testcontainers-go" | ||
| "github.com/testcontainers/testcontainers-go/wait" | ||
| rr "github.com/thomaspoignant/go-feature-flag/retriever/postgresqlretriever" | ||
| ) | ||
|
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| func TestGetPool_MultipleURIsAndReuse(t *testing.T) { | ||
|
Contributor
There was a problem hiding this comment. The existing test Please consider adding a new test that calls Here is an example of how you could structure such a test: func TestGetPool_Concurrency(t *testing.T) {
// ... (test container setup)
var wg sync.WaitGroup
numGoroutines := 100
wg.Add(numGoroutines)
var firstPool *pgxpool.Pool
var poolMu sync.Mutex
// Concurrently get the same pool
for i := 0; i < numGoroutines; i++ {
go func() {
defer wg.Done()
pool, err := rr.GetPool(ctx, uri1)
assert.NoError(t, err)
assert.NotNil(t, pool)
poolMu.Lock()
if firstPool == nil {
firstPool = pool
} else {
// Use assert.Same to check for pointer equality
assert.Same(t, firstPool, pool, "All goroutines should get the same pool instance")
}
poolMu.Unlock()
}()
}
wg.Wait()
// Concurrently release the pool
wg.Add(numGoroutines)
for i := 0; i < numGoroutines; i++ {
go func() {
defer wg.Done()
rr.ReleasePool(uri1) // Assuming ctx is removed
}()
}
wg.Wait()
// Verify the pool is closed and can be recreated
recreatedPool, err := rr.GetPool(ctx, uri1)
assert.NoError(t, err)
assert.NotNil(t, recreatedPool)
assert.NotSame(t, firstPool, recreatedPool, "A new pool should be created after all references are released")
rr.ReleasePool(uri1)
} |
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| ctx := context.Background() | ||
|
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| // Setup Container | ||
| req := testcontainers.ContainerRequest{ | ||
| Image: "postgres:15-alpine", | ||
| ExposedPorts: []string{"5432/tcp"}, | ||
| Env: map[string]string{"POSTGRES_PASSWORD": "password"}, | ||
| // This waits until the log says the system is ready, preventing connection errors | ||
| WaitingFor: wait.ForAll( | ||
| wait.ForLog("database system is ready to accept connections").WithStartupTimeout(10*time.Second), | ||
| wait.ForListeningPort("5432/tcp").WithStartupTimeout(10*time.Second), | ||
| ), | ||
| } | ||
|
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| pg, err := testcontainers.GenericContainer(ctx, testcontainers.GenericContainerRequest{ | ||
| ContainerRequest: req, | ||
| Started: true, | ||
| }) | ||
| assert.NoError(t, err) | ||
| defer pg.Terminate(ctx) | ||
|
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| endpoint, err := pg.Endpoint(ctx, "") | ||
| assert.NoError(t, err) | ||
| baseURI := "postgres://postgres:password@" + endpoint + "/postgres?sslmode=disable" | ||
|
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| // Different URIs | ||
| uri1 := baseURI + "&application_name=A" | ||
| uri2 := baseURI + "&application_name=B" | ||
|
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| // First Calls (RefCount = 1) | ||
| pool1a, err := rr.GetPool(ctx, uri1) | ||
| assert.NoError(t, err) | ||
| assert.NotNil(t, pool1a) | ||
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| pool2a, err := rr.GetPool(ctx, uri2) | ||
| assert.NoError(t, err) | ||
| assert.NotNil(t, pool2a) | ||
|
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| // Verify distinct pools | ||
| assert.NotEqual(t, pool1a, pool2a) | ||
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| // Reuse Logic (RefCount = 2 for URI1) | ||
| pool1b, err := rr.GetPool(ctx, uri1) | ||
| assert.NoError(t, err) | ||
| assert.Equal(t, pool1a, pool1b, "Should return exact same pool instance") | ||
|
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| // Release Logic | ||
| // URI1 RefCount: 2 -> 1 | ||
| rr.ReleasePool(ctx, uri1) | ||
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| // URI1 RefCount: 1 -> 0 (Closed & Removed) | ||
| rr.ReleasePool(ctx, uri1) | ||
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| // Recreation Logic | ||
| // URI1 should now create a NEW pool | ||
| pool1c, err := rr.GetPool(ctx, uri1) | ||
| assert.NoError(t, err) | ||
| assert.NotEqual(t, pool1a, pool1c, "Should be a new pool instance after full release") | ||
|
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| // Cleanup new pool | ||
| rr.ReleasePool(ctx, uri1) | ||
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| // URI2 Cleanup verification | ||
| rr.ReleasePool(ctx, uri2) // RefCount -> 0 | ||
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| pool2b, err := rr.GetPool(ctx, uri2) | ||
| assert.NoError(t, err) | ||
| assert.NotEqual(t, pool2a, pool2b, "URI2 should be recreated") | ||
|
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| rr.ReleasePool(ctx, uri2) | ||
| } | ||
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The use of global variables (
muandpoolMap) to implement the singleton pattern for the connection pool is a common approach for shared resources. However, global state can sometimes make testing more complex and introduce implicit dependencies. While acceptable for this specific use case, it's a design choice that should be considered carefully in larger architectures.