nimbus-eth1/nimbus/db/aristo/aristo_debug.nim
Jacek Sieka f034af422a
Pre-allocate vids for branches (#2882)
Each branch node may have up to 16 sub-items - currently, these are
given VertexID based when they are first needed leading to a
mostly-random order of vertexid for each subitem.

Here, we pre-allocate all 16 vertex ids such that when a branch subitem
is filled, it already has a vertexid waiting for it. This brings several
important benefits:

* subitems are sorted and "close" in their id sequencing - this means
that when rocksdb stores them, they are likely to end up in the same
data block thus improving read efficiency
* because the ids are consequtive, we can store just the starting id and
a bitmap representing which subitems are in use - this reduces disk
space usage for branches allowing more of them fit into a single disk
read, further improving disk read and caching performance - disk usage
at block 18M is down from 84 to 78gb!
* the in-memory footprint of VertexRef reduced allowing more instances
to fit into caches and less memory to be used overall.

Because of the increased locality of reference, it turns out that we no
longer need to iterate over the entire database to efficiently generate
the hash key database because the normal computation is now faster -
this significantly benefits "live" chain processing as well where each
dirtied key must be accompanied by a read of all branch subitems next to
it - most of the performance benefit in this branch comes from this
locality-of-reference improvement.

On a sample resync, there's already ~20% improvement with later blocks
seeing increasing benefit (because the trie is deeper in later blocks
leading to more benefit from branch read perf improvements)

```
blocks: 18729664, baseline: 190h43m49s, contender: 153h59m0s
Time (total): -36h44m48s, -19.27%
```

Note: clients need to be resynced as the PR changes the on-disk format

R.I.P. little bloom filter - your life in the repo was short but
valuable
2024-12-04 11:42:04 +01:00

728 lines
20 KiB
Nim

# nimbus-eth1
# Copyright (c) 2023-2024 Status Research & Development GmbH
# Licensed under either of
# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
# http://www.apache.org/licenses/LICENSE-2.0)
# * MIT license ([LICENSE-MIT](LICENSE-MIT) or
# http://opensource.org/licenses/MIT)
# at your option. This file may not be copied, modified, or distributed
# except according to those terms.
{.push raises: [].}
import
std/[algorithm, sequtils, sets, strutils, tables],
eth/common,
results,
stew/[byteutils, interval_set],
./aristo_desc/desc_backend,
./aristo_init/[memory_db, memory_only, rocks_db],
"."/[aristo_desc, aristo_get, aristo_layers,
aristo_serialise, aristo_utils]
# ------------------------------------------------------------------------------
# Private functions
# ------------------------------------------------------------------------------
func orDefault(db: AristoDbRef): AristoDbRef =
if db.isNil: AristoDbRef(top: LayerRef.init()) else: db
# --------------------------
func toHex(w: VertexID): string =
w.uint64.toHex
func toHexLsb(w: int8): string =
$"0123456789abcdef"[w and 15]
func sortedKeys(tab: Table): seq =
tab.keys.toSeq.sorted
func sortedKeys(pPrf: HashSet): seq =
pPrf.toSeq.sorted
func toPfx(indent: int; offset = 0): string =
if 0 < indent+offset: "\n" & " ".repeat(indent+offset) else: ""
func squeeze(s: string; hex = false; ignLen = false): string =
## For long strings print `begin..end` only
if hex:
let n = (s.len + 1) div 2
result = if s.len < 20: s else: s[0 .. 5] & ".." & s[s.len-8 .. ^1]
if not ignLen:
result &= "[" & (if 0 < n: "#" & $n else: "") & "]"
elif s.len <= 30:
result = s
else:
result = if (s.len and 1) == 0: s[0 ..< 8] else: "0" & s[0 ..< 7]
if not ignLen:
result &= "..(" & $s.len & ")"
result &= ".." & s[s.len-16 .. ^1]
func stripZeros(a: string; toExp = false): string =
if 0 < a.len:
result = a.strip(leading=true, trailing=false, chars={'0'})
if result.len == 0:
result = "0"
elif result[^1] == '0' and toExp:
var n = 0
while result[^1] == '0':
let w = result.len
result.setLen(w-1)
n.inc
if n == 1:
result &= "0"
elif n == 2:
result &= "00"
elif 2 < n:
result &= "" & $n
# ---------------------
func ppKeyOk(
db: AristoDbRef;
key: HashKey;
rvid: RootedVertexID;
): string =
if key.isValid and rvid.isValid:
let rv = db.xMap.getOrVoid key
if rv.isValid:
if rvid != rv:
result = "(!)"
return
db.xMap[key] = rvid
func ppVid(vid: VertexID; pfx = true): string =
if pfx:
result = "$"
if vid.isValid:
result &= vid.toHex.stripZeros.toLowerAscii
else:
result &= "ø"
func ppVid(sid: StorageID; pfx = true): string =
if sid.isValid or not sid.vid.isValid:
sid.vid.ppVid(pfx)
else:
(if pfx: "$" else: "") & "®" & sid.vid.ppVid(false)
func ppVid(rvid: RootedVertexID; pfx = true): string =
if pfx:
result = "$"
result &= ppVid(rvid.root, pfx=false) & ":" & ppVid(rvid.vid, pfx=false)
func ppCodeHash(h: Hash32): string =
result = "¢"
if h == default(Hash32):
result &= "©"
elif h == EMPTY_CODE_HASH:
result &= "ø"
else:
result &= h.data.toHex.squeeze(hex=true,ignLen=true)
func ppVidList(vLst: openArray[VertexID]): string =
result = "["
if vLst.len <= 250:
result &= vLst.mapIt(it.ppVid).join(",")
else:
result &= vLst[0 .. 99].mapIt(it.ppVid).join(",")
result &= ",.."
result &= vLst[^100 .. ^1].mapIt(it.ppVid).join(",")
result &= "]"
proc ppKey(key: HashKey; db: AristoDbRef; pfx = true): string =
if pfx:
result = "£"
if key.to(Hash32) == default(Hash32):
result &= "©"
elif not key.isValid:
result &= "ø"
else:
# Reverse lookup
let rvid = db.xMap.getOrVoid key
if rvid.isValid:
result &= rvid.ppVid(pfx=false)
let vtx = db.getVtx rvid
if vtx.isValid:
let rc = vtx.toNode(rvid.root, db)
if rc.isErr or key != rc.value.digestTo(HashKey):
result &= ""
else:
result &= ""
else:
let tag = if key.len < 32: "[#" & $key.len & "]" else: ""
result &= @(key.data).toHex.squeeze(hex=true,ignLen=true) & tag
func ppLeafTie(lty: LeafTie, db: AristoDbRef): string =
let pfx = lty.path.to(NibblesBuf)
"@" & lty.root.ppVid(pfx=false) & ":" &
($pfx).squeeze(hex=true,ignLen=(pfx.len==64))
func ppPathPfx(pfx: NibblesBuf): string =
let s = $pfx
if s.len < 20: s else: s[0 .. 5] & ".." & s[s.len-8 .. ^1] & ":" & $s.len
func ppNibble(n: int8): string =
if n < 0: "ø" elif n < 10: $n else: n.toHexLsb
proc ppEthAccount(a: Account, db: AristoDbRef): string =
result = "("
result &= ($a.nonce).stripZeros(toExp=true) & ","
result &= ($a.balance).stripZeros(toExp=true) & ","
result &= a.codeHash.ppCodeHash & ","
result &= a.storageRoot.to(HashKey).ppKey(db) & ")"
func ppAriAccount(a: AristoAccount): string =
result = "("
result &= ($a.nonce).stripZeros(toExp=true) & ","
result &= ($a.balance).stripZeros(toExp=true) & ","
result &= a.codeHash.ppCodeHash & ")"
func ppPayload(p: LeafPayload, db: AristoDbRef): string =
case p.pType:
of AccountData:
result = "(" & p.account.ppAriAccount() & "," & p.stoID.ppVid & ")"
of StoData:
result = ($p.stoData).squeeze
func ppVtx(nd: VertexRef, db: AristoDbRef, rvid: RootedVertexID): string =
if not nd.isValid:
result = "ø"
else:
if not rvid.isValid:
result = ["L(", "B("][nd.vType.ord]
elif db.layersGetKey(rvid).isOk:
result = ["l(", "b("][nd.vType.ord]
else:
result = ["ł(", "þ("][nd.vType.ord]
case nd.vType:
of Leaf:
result &= nd.pfx.ppPathPfx & "," & nd.lData.ppPayload(db)
of Branch:
result &= nd.pfx.ppPathPfx & ":"
for n in 0'u8..15'u8:
if nd.bVid(n).isValid:
result &= nd.bVid(n).ppVid
if n < 15:
result &= ","
result &= ")"
proc ppNode(
nd: NodeRef;
db: AristoDbRef;
rvid = default(RootedVertexID);
): string =
if not nd.isValid:
result = "ø"
else:
if not rvid.isValid:
result = ["L(", "B("][nd.vtx.vType.ord]
elif db.layersGetKey(rvid).isOk:
result = ["l(", "b("][nd.vtx.vType.ord]
else:
result = ["ł(", "þ("][nd.vtx.vType.ord]
case nd.vtx.vType:
of Leaf:
result &= nd.vtx.pfx.ppPathPfx & ","
if nd.vtx.lData.pType == AccountData:
result &= "(" & nd.vtx.lData.account.ppAriAccount() & ","
if nd.vtx.lData.stoID.isValid:
let tag = db.ppKeyOk(nd.key[0],(rvid.root,nd.vtx.lData.stoID.vid))
result &= nd.vtx.lData.stoID.ppVid & tag
else:
result &= nd.vtx.lData.stoID.ppVid
if nd.key[0].isValid:
result &= nd.key[0].ppKey(db)
result &= ")"
else:
result &= nd.vtx.lData.ppPayload(db)
of Branch:
let keyOnly = nd.vtx.subVids.toSeq.filterIt(it.isValid).len == 0
result &= nd.vtx.pfx.ppPathPfx & ":"
for n in 0'u8..15'u8:
if nd.vtx.bVid(n).isValid:
let tag = db.ppKeyOk(nd.key[n],(rvid.root,nd.vtx.bVid(n)))
result &= nd.vtx.bVid(n).ppVid & tag
elif keyOnly and nd.key[n].isValid:
result &= nd.key[n].ppKey(db)
if n < 15:
result &= ","
result &= ")"
func ppXTab[T: VertexRef|NodeRef](
tab: Table[RootedVertexID,T];
db: AristoDbRef;
indent = 4;
): string =
proc ppT(v: T; r: RootedVertexID): string =
when T is VertexRef:
v.ppVtx(db, r)
elif T is NodeRef:
v.ppNode(db, r)
"{" & tab.sortedKeys
.mapIt((it, tab.getOrDefault it))
.mapIt("(" & it[0].ppVid & "," & it[1].ppT(it[0]) & ")")
.join(indent.toPfx(1)) & "}"
proc ppXMap*(
db: AristoDbRef;
kMap: Table[RootedVertexID,HashKey];
indent: int;
): string =
let pfx = indent.toPfx(1)
# Sort keys by root,
# entry int: 0=no-key 1=no-vertex 2=cant-compile 3=key-mistmatch 4=key-ok
var keyLst: seq[(VertexID,seq[(VertexID,HashKey,int)])]
block:
var root = VertexID(0)
for w in kMap.sortedKeys:
if w.root != root:
keyLst.add (w.root,newSeq[typeof keyLst[0][1][0]](0))
root = w.root
let
key = kMap.getOrVoid w
mode = block:
if key == VOID_HASH_KEY:
0
else:
db.xMap[key] = w
let vtx = db.getVtx(w)
if not vtx.isValid:
1
else:
let rc = vtx.toNode(w.root, db)
if rc.isErr:
2
elif key != rc.value.digestTo(HashKey):
3
else:
4
keyLst[^1][1].add (w.vid,key,mode)
# Join increasing sequences for pretty printing
var keySubLst: seq[(VertexID,seq[seq[(VertexID,HashKey,int)]])]
for (root,rootQ) in keyLst:
var
q: seq[(VertexID,HashKey,int)]
subQ: seq[typeof q]
for (vid,key,state) in rootQ:
if q.len == 0:
q.add (vid,key,state)
continue
if q[^1][0]+1 == vid and q[^1][2] == state:
q.add (vid,key,state)
continue
# Otherwise new sub queue
subQ.add q
q = @[(vid,key,state)]
if 0 < q.len:
subQ.add q
keySubLst.add (root,subQ)
proc pp(w: (VertexID,HashKey,int)): string =
proc pp(k: HashKey): string =
result = w[1].data.toHex.squeeze(hex=true,ignLen=true)
if k.len < 32:
result &= "[#" & $k.len & "]"
w[0].ppVid(pfx=false) & (
case w[2]:
of 0: ""
of 1: ""
of 2: "=" & w[1].pp()
of 3: "" & w[1].pp()
else: "")
result &= "{"
var qfx = ""
for (root,subQ) in keySubLst:
result &= qfx & "£" & root.ppVid(pfx=false) & ":"
qfx = pfx
var closeBracket = ""
if 1 < subQ.len or 1 < subQ[0].len:
result &= "["
closeBracket = "]"
for q in subQ:
if q.len < 3:
result &= q.mapIt(it.pp).join(",")
else:
result &= q[0].pp & ".." & q[^1].pp
result &= ","
result.setLen(result.len - 1)
result &= closeBracket
result &= "}"
proc ppBalancer(
fl: LayerRef;
db: AristoDbRef;
indent: int;
): string =
## Walk over filter tables
let
pfx = indent.toPfx
pfx1 = indent.toPfx(1)
pfx2 = indent.toPfx(2)
result = "<balancer>"
if fl.isNil:
result &= " n/a"
return
result &= pfx & "vTop=" & fl.vTop.ppVid
result &= pfx & "sTab" & pfx1 & "{"
for n,vid in fl.sTab.sortedKeys:
let vtx = fl.sTab.getOrVoid vid
if 0 < n: result &= pfx2
result &= $(1+n) & "(" & vid.ppVid & "," & vtx.ppVtx(db,vid) & ")"
result &= "}" & pfx & "kMap" & pfx1 & "{"
for n,vid in fl.kMap.sortedKeys:
let key = fl.kMap.getOrVoid vid
if 0 < n: result &= pfx2
result &= $(1+n) & "(" & vid.ppVid & "," & key.ppKey(db) & ")"
result &= "}"
proc ppBe[T](be: T; db: AristoDbRef; limit: int; indent: int): string =
## Walk over backend tables
let
pfx = indent.toPfx
pfx1 = indent.toPfx(1)
pfx2 = indent.toPfx(2)
result = "<" & $be.kind & ">"
var (dump,dataOk) = ("",false)
block:
let rc = be.getTuvFn()
if rc.isOk:
dump &= pfx & "vTop=" & rc.value.ppVid
dataOk = true
block:
dump &= pfx & "sTab"
var (n, data) = (0, "")
for (vid,vtx) in be.walkVtx:
n.inc
if n < limit:
if 1 < n: data &= pfx2
data &= $n & "(" & vid.ppVid & "," & vtx.ppVtx(db,vid) & ")"
elif n == limit:
data &= pfx2 & ".."
dump &= "(" & $n & ")"
if 0 < n:
dataOk = true
dump &= pfx1
dump &= "{" & data & "}"
block:
dump &= pfx & "kMap"
var (n, data) = (0, "")
for (vid,key) in be.walkKey:
n.inc
if n < limit:
if 1 < n: data &= pfx2
data &= $n & "(" & vid.ppVid & "," & key.ppKey(db) & ")"
elif n == limit:
data &= pfx2 & ".."
dump &= "(" & $n & ")"
if 0 < n:
dataOk = true
dump &= pfx1
dump &= "{" & data & "}"
if dataOk:
result &= dump
else:
result &= "[]"
proc ppLayer(
layer: LayerRef;
db: AristoDbRef;
vTopOk: bool;
sTabOk: bool;
kMapOk: bool;
indent = 4;
): string =
let
pfx1 = indent.toPfx(1)
pfx2 = indent.toPfx(2)
nOKs = vTopOk.ord + sTabOk.ord + kMapOk.ord
tagOk = 1 < nOKs
var
pfy = ""
proc doPrefix(s: string; dataOk: bool): string =
var rc: string
if tagOk:
rc = pfy
if 0 < s.len:
rc &= s & (if dataOk: pfx2 else: "")
pfy = pfx1
else:
rc = pfy
pfy = pfx2
rc
if not layer.isNil:
if 2 < nOKs:
result &= "<layer>".doPrefix(false)
if vTopOk:
result &= "".doPrefix(true) & "vTop=" & layer.vTop.ppVid
if sTabOk:
let
tLen = layer.sTab.len
info = "sTab(" & $tLen & ")"
result &= info.doPrefix(0 < tLen) & layer.sTab.ppXTab(db,indent+2)
if kMapOk:
let
tLen = layer.kMap.len
info = "kMap(" & $tLen & ")"
result &= info.doPrefix(0 < tLen)
result &= db.ppXMap(layer.kMap, indent+2)
# ------------------------------------------------------------------------------
# Public functions
# ------------------------------------------------------------------------------
func pp*(w: Hash32; codeHashOk: bool): string =
if codeHashOk:
w.ppCodeHash
elif w == EMPTY_ROOT_HASH:
"EMPTY_ROOT_HASH"
elif w == default(Hash32):
"default(Hash32)"
else:
w.data.toHex.squeeze(hex=true,ignLen=true)
func pp*(n: NibblesBuf): string =
n.ppPathPfx()
proc pp*(w: HashKey; db = AristoDbRef(nil)): string =
w.ppKey(db.orDefault)
proc pp*(w: Hash32; db = AristoDbRef(nil)): string =
w.to(HashKey).ppKey(db.orDefault)
proc pp*(w: openArray[HashKey]; db = AristoDbRef(nil)): string =
"[" & @w.mapIt(it.ppKey(db.orDefault)).join(",") & "]"
func pp*(lty: LeafTie, db = AristoDbRef(nil)): string =
lty.ppLeafTie(db.orDefault)
proc pp*(a: Account, db = AristoDbRef(nil)): string =
a.ppEthAccount(db.orDefault)
func pp*(vid: VertexID): string =
vid.ppVid
func pp*(rvid: RootedVertexID): string =
rvid.ppVid
func pp*(vLst: openArray[VertexID]): string =
vLst.ppVidList
func pp*(p: LeafPayload, db = AristoDbRef(nil)): string =
p.ppPayload(db.orDefault)
func pp*(nd: VertexRef, db = AristoDbRef(nil)): string =
nd.ppVtx(db.orDefault, default(RootedVertexID))
proc pp*(nd: NodeRef, db = AristoDbRef(nil)): string =
nd.ppNode(db.orDefault, default(RootedVertexID))
func pp*(e: (VertexID,AristoError)): string =
"(" & e[0].pp & "," & $e[1] & ")"
func pp*[T](rc: Result[T,(VertexID,AristoError)]): string =
if rc.isOk:
result = "ok("
when T isnot void:
result &= ".."
result &= ")"
else:
result = "err(" & rc.error.pp & ")"
func pp*(
sTab: Table[RootedVertexID,VertexRef];
db = AristoDbRef(nil);
indent = 4;
): string =
sTab.ppXTab(db.orDefault)
proc pp*(leg: Leg; root: VertexID; db = AristoDbRef(nil)): string =
let db = db.orDefault()
result = "(" & leg.wp.vid.ppVid & ","
block:
let key = db.layersGetKeyOrVoid (root, leg.wp.vid)
if not key.isValid:
result &= "ø"
elif (root, leg.wp.vid) != db.xMap.getOrVoid key:
result &= key.ppKey(db)
result &= ","
if 0 <= leg.nibble:
result &= $leg.nibble.ppNibble
result &= "," & leg.wp.vtx.pp(db) & ")"
proc pp*(hike: Hike; db = AristoDbRef(nil); indent = 4): string =
let
db = db.orDefault()
pfx = indent.toPfx(1)
result = "["
if hike.legs.len == 0:
result &= "(" & hike.root.ppVid & ")"
else:
if hike.legs[0].wp.vid != hike.root:
result &= "(" & hike.root.ppVid & ")" & pfx
result &= hike.legs.mapIt(it.pp(hike.root, db)).join(pfx)
result &= pfx & "(" & hike.tail.ppPathPfx & ")"
result &= "]"
func pp*[T: NodeRef|VertexRef|HashKey](
q: seq[(HashKey,T)];
db = AristoDbRef(nil);
indent = 4;
): string =
let db = db.orDefault
proc ppT(v: T): string =
when T is VertexID or T is RootedVertexID:
v.pp()
else:
v.pp(db)
"{" & q.mapIt("(" & it[0].ppKey(db) & "," & it[1].ppT & ")")
.join("," & indent.toPfx(1)) & "}"
func pp*[T: NodeRef|VertexRef|HashKey](
t: Table[HashKey,T];
db = AristoDbRef(nil);
indent = 4;
): string =
## Sort hash keys by associated vertex ID were possible
let db = db.orDefault
var
t0: Table[RootedVertexID,(HashKey,T)]
t1: Table[HashKey,T]
for (key,val) in t.pairs:
db.xMap.withValue(key,rv):
t0[rv[]] = (key,val)
do:
t1[key] = val
let
q0 = t0.sortedKeys.mapIt(t0.getOrDefault it)
q1 = t1.sortedKeys.mapIt((it, t1.getOrDefault it))
(q0 & q1).pp(db,indent)
proc pp*[T: HashKey](
t: Table[T,RootedVertexID];
db = AristoDbRef(nil);
indent = 4;
): string =
## Sort by second tab item vertex ID
let db = db.orDefault
proc ppT(v: T): string =
when T is VertexID or T is RootedVertexID:
v.pp()
else:
v.pp(db)
var rev: Table[RootedVertexID,seq[T]]
for (key,rvid) in t.pairs:
rev.withValue(rvid,val):
val[].add key
do:
rev[rvid] = @[key]
var flat: seq[(HashKey,RootedVertexID)]
for rvid in rev.keys.toSeq.sorted:
rev.withValue(rvid,keysPtr):
for key in keysPtr[]:
flat.add (key,rvid)
# Now sorted vy values
"{" & flat.mapIt("(" & it[0].ppT & "," & it[1].pp & ")")
.join("," & indent.toPfx(1)) & "}"
func pp*[T: HashKey](
t: TableRef[HashKey,T];
db = AristoDbRef(nil);
indent = 4;
): string =
pp(t[],db,indent)
proc pp*(
kMap: Table[RootedVertexID,HashKey];
db: AristoDbRef;
indent = 4;
): string =
db.ppXMap(kMap, indent)
# ---------------------
func pp*(tx: AristoTxRef): string =
result = "(uid=" & $tx.txUid & ",level=" & $tx.level
if not tx.parent.isNil:
result &= ", par=" & $tx.parent.txUid
result &= ")"
func pp*(wp: VidVtxPair; db: AristoDbRef): string =
"(" & wp.vid.pp & "," & wp.vtx.pp(db) & ")"
proc pp*(
layer: LayerRef;
db: AristoDbRef;
indent = 4;
sTabOk = true,
kMapOk = true,
vTopOk = true,
): string =
layer.ppLayer(
db.orDefault(), vTopOk=vTopOk, sTabOk=sTabOk, kMapOk=kMapOk, indent=indent)
proc pp*(
be: BackendRef;
db: AristoDbRef;
limit = 100;
indent = 4;
): string =
result = db.balancer.ppBalancer(db, indent+1) & indent.toPfx
case be.kind:
of BackendMemory:
result &= be.MemBackendRef.ppBe(db, limit, indent+1)
of BackendRocksDB, BackendRdbHosting:
result &= be.RdbBackendRef.ppBe(db, limit, indent+1)
of BackendVoid:
result &= "<NoBackend>"
proc pp*(
db: AristoDbRef;
indent = 4;
backendOk = false;
balancerOk = true;
topOk = true;
stackOk = true;
kMapOk = true;
sTabOk = true;
limit = 100;
): string =
if topOk:
result = db.layersCc.ppLayer(
db, sTabOk=sTabOk, kMapOk=kMapOk, vTopOk=true, indent=indent)
let stackOnlyOk = stackOk and not (topOk or balancerOk or backendOk)
if not stackOnlyOk:
result &= indent.toPfx(1) & "level=" & $db.stack.len
if (stackOk and 0 < db.stack.len) or stackOnlyOk:
let layers = @[db.top] & db.stack.reversed
var lStr = ""
for n,w in layers:
let
m = layers.len - n - 1
l = db.layersCc m
a = w.kMap.values.toSeq.filterIt(not it.isValid).len
c = l.kMap.values.toSeq.filterIt(not it.isValid).len
result &= "(" & $(w.kMap.len - a) & "," & $a & ")"
lStr &= " " & $m & "=(" & $(l.kMap.len - c) & "," & $c & ")"
result &= " =>" & lStr
if backendOk:
result &= indent.toPfx & db.backend.pp(db, limit=limit, indent)
elif balancerOk:
result &= indent.toPfx & db.balancer.ppBalancer(db, indent+1)
# ------------------------------------------------------------------------------
# End
# ------------------------------------------------------------------------------