feat: towards decoupling from metrics component - make it optional (#131)

* feat: decouple from metrics component making it optional

* chore: update api

Author: aleortega

README.md

@@ -10,11 +10,12 @@ To create the component you have the option of:
 
 - Supplying any `PoolConfig` options you want. This are related 1:1 with [node-postgres](https://node-postgres.com/api/pool) implementation, which in turn are all variables [Postgres](https://www.postgresql.org/) supports
 - Supplying any `RunnerOption`. This are related 1:1 with [node-pg-migrate](https://github.com/salsita/node-pg-migrate) implementation and will be used for [migrations](#migrations)
+- Supplying a Metrics component ([any `IMetricsComponent`](https://github.com/well-known-components/metrics)). This component will enable additional functionality for collecting metrics on querys.
 
 ```ts
 // src/components.ts
 
-await createPgComponent({ config, logs, metrics } /* optional config here */)
+await createPgComponent({ config, logs, metrics: metrics | undefined } /* optional config here */)
 
 // A possible optional'd look like:
 const { config } = createConfigComponent()
@@ -51,6 +52,7 @@ the API looks like this
 
 ```ts
   query<T>(sql: string): Promise<IDatabase.IQueryResult<T>>
+  // If it has been built with the metrics component this contract is also exposed:
   query<T>(sql: SQLStatement, durationQueryNameLabel?: string): Promise<IDatabase.IQueryResult<T>>
 ```
 
@@ -62,7 +64,7 @@ const id = getIdFromUnreliableSource()
 pg.query<TableType>(SQL`SELECT * FROM table WHERE id = ${id}`) // this results in ['SELECT * FROM table WHERE id = $1', id]
 ```
 
-suppliying a `durationQueryNameLabel` will trigger a metrics increment with that name.
+if `metrics` component has been provided, suppliying a `durationQueryNameLabel` will trigger a metrics increment with that name.
 
 **Streaming a query**
 

etc/pg-component.api.md

@@ -24,7 +24,7 @@ export namespace createPgComponent {
     export type NeededComponents = {
         logs: ILoggerComponent;
         config: IConfigComponent;
-        metrics: IMetricsComponent;
+        metrics?: IMetricsComponent;
     };
 }
 

src/index.ts

@@ -68,23 +68,17 @@ export async function createPgComponent(
     }
   }
 
-  async function query<T extends Record<string, any>>(sql: string): Promise<IDatabase.IQueryResult<T>>
-  async function query<T extends Record<string, any>>(
-    sql: SQLStatement,
-    durationQueryNameLabel?: string
-  ): Promise<IDatabase.IQueryResult<T>>
-  async function query<T extends Record<string, any>>(
-    sql: string | SQLStatement,
-    durationQueryNameLabel?: string
-  ): Promise<IDatabase.IQueryResult<T>> {
-    const rows = durationQueryNameLabel
-      ? await runReportingQueryDurationMetric(components, durationQueryNameLabel, () => pool.query<T>(sql))
-      : await pool.query<T>(sql)
-
-    return {
-      rows: rows.rows,
-      rowCount: rows.rowCount ?? 0
-    }
+  async function defaultQuery<T extends Record<string, any>>(sql: string | SQLStatement): Promise<IDatabase.IQueryResult<T>> {
+    const result = await pool.query<T>(sql)
+    return { ...result, rowCount: result.rowCount ?? 0 }
+  }
+
+  async function measuredQuery<T extends Record<string, any>>(sql: string | SQLStatement, durationQueryNameLabel?: string): Promise<IDatabase.IQueryResult<T>> {
+    const result = durationQueryNameLabel
+      ? await runReportingQueryDurationMetric({ metrics: components.metrics! }, durationQueryNameLabel, () => defaultQuery<T>(sql))
+      : await defaultQuery<T>(sql)
+
+    return result
   }
 
   async function* streamQuery<T>(sql: SQLStatement, config?: { batchSize?: number }): AsyncGenerator<T> {
@@ -169,7 +163,7 @@ export async function createPgComponent(
   }
 
   return {
-    query,
+    query: components.metrics ? measuredQuery : defaultQuery,
     streamQuery,
     getPool,
     start,
@@ -184,6 +178,6 @@ export namespace createPgComponent {
   export type NeededComponents = {
     logs: ILoggerComponent
     config: IConfigComponent
-    metrics: IMetricsComponent
+    metrics?: IMetricsComponent
   }
 }