Hi,
Thanks for the link I’ll take a lot more later.
Now a quick look seems funny :
Ideally, the hash function will assign each key to a unique bucket, but most hash table designs employ an imperfect hash function, which might cause hash collisions where the hash function generates the same index for more than one key. Such collisions must be accommodated in some way.
If I understand well, this is typically the case I have. Am I correct ?
Cordialement
Patrick GINHOUX
De : sr-users [mailto:sr-users-bounces@lists.sip-router.org] De la part de Daniel-Constantin Mierla
Envoyé : mardi 4 avril 2017 12:45
À : Kamailio (SER) - Users Mailing List <sr-users@lists.sip-router.org>
Objet : Re: [SR-Users] Why these 2 items in the same entry for a htable
Hello,
if you are not familiar with hash table structure, take a bit of time to read about it, a good article on wikipedia:
- https://en.wikipedia.org/wiki/Hash_table
The dump prints only details of the slots (buckets) that have data on it (size>0). The entry field in the dump content is practically the index of the slot.
I hope it helps!
Cheers,
Daniel
On 04.04.17 08:49, Ginhoux, Patrick wrote:
Hi,
While working on the project to migrate my kamailio.cfg script from kamailio 3.3.1 to 5.0.x, I discovered that in there are 2 items in the same htable.
Below the figure that illustrate this case :
1) Content of the MBXRANGE table :
mysql> select * from mbxrange;
+-----+-------------+-------------------------------------------------+------------+----------+
| id | key_name | key_value | value_type | key_type |
+-----+-------------+-------------------------------------------------+------------+----------+
| 0 | VERSION | 120104-173400 | 0 | 0 |
| 101 | 1 | min=0100000000;max=0199999999;node=OPMVTS1VSE02 | 0 | 0 |
| 102 | 2 | min=0200000000;max=0299999999;node=OPMVTS1VSE02 | 0 | 0 |
| 103 | 3 | min=0300000000;max=0399999999;node=OPMVTS1VSE02 | 0 | 0 |
| 104 | 4 | min=0400000000;max=0499999999;node=OPMVTS1VSE02 | 0 | 0 |
| 105 | 5 | min=0500000000;max=0599999999;node=OPMVTS1VSE02 | 0 | 0 |
| 106 | 6 | min=0600000000;max=0699999999;node=OPMVTS1VSE02 | 0 | 0 |
| 107 | 7 | min=0700000000;max=0799999999;node=OPMVTS1VSE02 | 0 | 0 |
| 108 | 8 | min=0800000000;max=0899999999;node=OPMVTS1VSE02 | 0 | 0 |
| 109 | 9 | min=0900000000;max=0999999999;node=OPMVTS1VSE02 | 0 | 0 |
| 199 | maxmbxrange | 9 | 0 | 0 |
+-----+-------------+-------------------------------------------------+------------+----------+
11 rows in set (0.00 sec)
2) modparam instruction used in my kamailio.cfg script:
modparam("htable", "htable", "mbxrangeHash=>size=4;dbtable=mbxrange;")
3) Result of « kamctl fifo sht_dump mbxrangeHash » command with kamailio version 3.3.x:
[root@op52is4router1 ~]# kamctl fifo sht_dump mbxrangeHash
Entry:: 0
6:: min=0600000000;max=0699999999;node=OPMVTS1VSE02
Entry:: 1
7:: min=0700000000;max=0799999999;node=OPMVTS1VSE02
Entry:: 2
4:: min=0400000000;max=0499999999;node=OPMVTS1VSE02
Entry:: 3
5:: min=0500000000;max=0599999999;node=OPMVTS1VSE02
Entry:: 4
2:: min=0200000000;max=0299999999;node=OPMVTS1VSE02
Entry:: 5
3:: min=0300000000;max=0399999999;node=OPMVTS1VSE02
VERSION:: 120104-173400
Entry:: 6
maxmbxrange:: 9
Entry:: 7
1:: min=0100000000;max=0199999999;node=OPMVTS1VSE02
Entry:: 14
9:: min=0900000000;max=0999999999;node=OPMVTS1VSE02
Entry:: 15
8:: min=0800000000;max=0899999999;node=OPMVTS1VSE02
Result of « kamcmd htable.dump mbxrangeHash » command with kamailio version 5.0.x :
[root@vm-vse02-siprouter1 ~]# kamcmd htable.dump mbxrangeHash
{
entry: 0
size: 1
slot: {
item: {
name: 6
value: min=0600000000;max=0699999999;node=OPMMMS1VSE02
type: str
}
}
}
{
entry: 1
size: 1
slot: {
item: {
name: 7
value: min=0700000000;max=0799999999;node=OPMMMS1VSE02
type: str
}
}
}
{
entry: 2
size: 1
slot: {
item: {
name: 4
value: min=0400000000;max=0499999999;node=OPMMMS1VSE02
type: str
}
}
}
{
entry: 3
size: 1
slot: {
item: {
name: 5
value: min=0500000000;max=0599999999;node=OPMMMS1VSE02
type: str
}
}
}
{
entry: 4
size: 1
slot: {
item: {
name: 2
value: min=0200000000;max=0299999999;node=OPMMMS1VSE02
type: str
}
}
}
{
entry: 5
size: 2
slot: {
item: {
name: 3
value: min=0300000000;max=0399999999;node=OPMMMS1VSE02
type: str
}
item: {
name: VERSION
value: 120104-173400
type: str
}
}
}
{
entry: 6
size: 1
slot: {
item: {
name: maxmbxrange
value: 9
type: str
}
}
}
{
entry: 7
size: 1
slot: {
item: {
name: 1
value: min=0100000000;max=0199999999;node=OPMMMS1VSE02
type: str
}
}
}
{
entry: 14
size: 1
slot: {
item: {
name: 9
value: min=0900000000;max=0999999999;node=OPMMMS1VSE02
type: str
}
}
}
{
entry: 15
size: 1
slot: {
item: {
name: 8
value: min=0800000000;max=0899999999;node=OPMMMS1VSE02
type: str
}
}
}
So, I can see :
- The entry number is not incremental 1 by 1 ; there are entry #1 to #7, then #14 and #15 (all have size=1)
- For the entry #5, its size is of 2 and it contains 2 items
I don’t say here that this is a problem, but the way the htable is loaded seems strange to me.
So if there people who can explain me if what I see is normal or not, and how the htable load process works, I would appreciate.
Thanks in advance.
Cordialement
Patrick GINHOUX
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