chore: enhance libpq management (#3015)

* db_postgres: register pg socket fd to chronos better data available awareness
* waku_store protocol: better logs to track time and new store metrics

waku/common/databases/db_postgres/dbconn.nim

@@ -1,4 +1,4 @@
-import std/[times, strutils], results, chronos
+import std/[times, strutils, asyncnet, os, sequtils], results, chronos
 
 include db_connector/db_postgres
 
@@ -33,7 +33,17 @@ proc open*(connString: string): Result[DbConn, string] =
 
     return err("unknown reason")
 
-  ok(conn)
+  ## registering the socket fd in chronos for better wait for data
+  let asyncFd = cast[asyncengine.AsyncFD](pqsocket(conn))
+  asyncengine.register(asyncFd)
+
+  return ok(conn)
+
+proc closeDbConn*(db: DbConn) {.raises: [OSError].} =
+  let fd = db.pqsocket()
+  if fd != -1:
+    asyncengine.unregister(cast[asyncengine.AsyncFD](fd))
+  db.close()
 
 proc sendQuery(
     db: DbConn, query: SqlQuery, args: seq[string]
@@ -112,23 +122,17 @@ proc waitQueryToFinish(
   ## The 'rowCallback' param is != nil when the underlying query wants to retrieve results (SELECT.)
   ## For other queries, like "INSERT", 'rowCallback' should be nil.
 
-  while db.pqisBusy() == 1:
-    ## TODO: Enhance performance in concurrent queries.
-    ## The connection keeps busy for quite a long time when performing intense concurrect queries.
-    ## For example, a given query can last 11 milliseconds within from the database point of view
-    ## but, on the other hand, the connection remains in "db.pqisBusy() == 1" for 100ms more.
-    ## I think this is because `nwaku` is single-threaded and it has to handle many connections (20)
-    ## simultaneously. Therefore, there is an underlying resource sharing (cpu) that makes this
-    ## to happen. Notice that the _Postgres_ database spawns one process per each connection.
-    let success = db.pqconsumeInput()
-
-    if success != 1:
-      db.check().isOkOr:
-        return err("failed pqconsumeInput: " & $error)
+  var dataAvailable = false
+  proc onDataAvailable(udata: pointer) {.gcsafe, raises: [].} =
+    dataAvailable = true
+
+  let asyncFd = cast[asyncengine.AsyncFD](pqsocket(db))
 
-      return err("failed pqconsumeInput: unknown reason")
+  asyncengine.addReader2(asyncFd, onDataAvailable).isOkOr:
+    return err("failed to add event reader in waitQueryToFinish: " & $error)
 
-    await sleepAsync(timer.milliseconds(0)) # Do not block the async runtime
+  while not dataAvailable:
+    await sleepAsync(timer.milliseconds(1))
 
   ## Now retrieve the result
   while true:

waku/common/databases/db_postgres/pgasyncpool.nim

@@ -10,7 +10,7 @@ type PgAsyncPoolState {.pure.} = enum
   Live
   Closing
 
-type PgDbConn = object
+type PgDbConn = ref object
   dbConn: DbConn
   open: bool
   busy: bool
@@ -76,14 +76,11 @@ proc close*(pool: PgAsyncPool): Future[Result[void, string]] {.async.} =
       if pool.conns[i].busy:
         continue
 
-      if pool.conns[i].open:
-        pool.conns[i].dbConn.close()
-        pool.conns[i].busy = false
-        pool.conns[i].open = false
-
   for i in 0 ..< pool.conns.len:
     if pool.conns[i].open:
-      pool.conns[i].dbConn.close()
+      pool.conns[i].dbConn.closeDbConn()
+      pool.conns[i].busy = false
+      pool.conns[i].open = false
 
   pool.conns.setLen(0)
   pool.state = PgAsyncPoolState.Closed

waku/waku_store/protocol.nim

@@ -4,7 +4,7 @@
 {.push raises: [].}
 
 import
-  std/options,
+  std/[options, times],
   results,
   chronicles,
   chronos,
@@ -36,9 +36,11 @@ type WakuStore* = ref object of LPProtocol
 
 ## Protocol
 
+type StoreResp = tuple[resp: seq[byte], requestId: string]
+
 proc handleQueryRequest(
     self: WakuStore, requestor: PeerId, raw_request: seq[byte]
-): Future[seq[byte]] {.async.} =
+): Future[StoreResp] {.async.} =
   var res = StoreQueryResponse()
 
   let req = StoreQueryRequest.decode(raw_request).valueOr:
@@ -48,7 +50,7 @@ proc handleQueryRequest(
     res.statusCode = uint32(ErrorCode.BAD_REQUEST)
     res.statusDesc = "decoding rpc failed: " & $error
 
-    return res.encode().buffer
+    return (res.encode().buffer, "not_parsed_requestId")
 
   let requestId = req.requestId
 
@@ -65,7 +67,7 @@ proc handleQueryRequest(
     res.statusCode = uint32(error.kind)
     res.statusDesc = $error
 
-    return res.encode().buffer
+    return (res.encode().buffer, "not_parsed_requestId")
 
   res.requestId = requestId
   res.statusCode = 200
@@ -74,7 +76,7 @@ proc handleQueryRequest(
   info "sending store query response",
     peerId = requestor, requestId = requestId, messages = res.messages.len
 
-  return res.encode().buffer
+  return (res.encode().buffer, requestId)
 
 proc initProtocolHandler(self: WakuStore) =
   let rejectReposnseBuffer = StoreQueryResponse(
@@ -87,7 +89,8 @@ proc initProtocolHandler(self: WakuStore) =
   ).encode().buffer
 
   proc handler(conn: Connection, proto: string) {.async, gcsafe, closure.} =
-    var resBuf: seq[byte]
+    var successfulQuery = false ## only consider the correct queries in metrics
+    var resBuf: StoreResp
     self.requestRateLimiter.checkUsageLimit(WakuStoreCodec, conn):
       let readRes = catch:
         await conn.readLp(DefaultMaxRpcSize.int)
@@ -100,21 +103,34 @@ proc initProtocolHandler(self: WakuStore) =
         amount = reqBuf.len().int64, labelValues = [WakuStoreCodec, "in"]
       )
 
+      let queryStartTime = getTime().toUnixFloat()
+
       resBuf = await self.handleQueryRequest(conn.peerId, reqBuf)
+
+      let queryDuration = getTime().toUnixFloat() - queryStartTime
+      waku_store_time_seconds.inc(amount = queryDuration, labelValues = ["query-db"])
+      successfulQuery = true
     do:
       debug "store query request rejected due rate limit exceeded",
         peerId = conn.peerId, limit = $self.requestRateLimiter.setting
-      resBuf = rejectReposnseBuffer
+      resBuf = (rejectReposnseBuffer, "rejected")
+
+    let writeRespStartTime = getTime().toUnixFloat()
 
     let writeRes = catch:
-      await conn.writeLp(resBuf)
+      await conn.writeLp(resBuf.resp)
 
     if writeRes.isErr():
       error "Connection write error", error = writeRes.error.msg
       return
 
+    debug "after sending response", requestId = resBuf.requestId
+    if successfulQuery:
+      let writeDuration = getTime().toUnixFloat() - writeRespStartTime
+      waku_store_time_seconds.inc(amount = writeDuration, labelValues = ["send-resp"])
+
     waku_service_network_bytes.inc(
-      amount = resBuf.len().int64, labelValues = [WakuStoreCodec, "out"]
+      amount = resBuf.resp.len().int64, labelValues = [WakuStoreCodec, "out"]
     )
 
   self.handler = handler

waku/waku_store/protocol_metrics.nim

@@ -5,6 +5,11 @@ import metrics
 declarePublicGauge waku_store_errors, "number of store protocol errors", ["type"]
 declarePublicGauge waku_store_queries, "number of store queries received"
 
+## f.e., we have the "query" phase, where the node performs the query to the database,
+## and the "libp2p" phase, where the node writes the store response to the libp2p stream.
+declarePublicGauge waku_store_time_seconds,
+  "Time in seconds spent by each store phase", labels = ["phase"]
+
 # Error types (metric label values)
 const
   dialFailure* = "dial_failure"