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) { | ||
|
Check warning on line 21 in retriever/postgresqlretriever/postgres.go
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| 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 | ||
| } | ||
|
Comment on lines
+21
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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(uri string) { | ||
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| 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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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.