Tap chl Tin hgc va Dieu khien hgc, T.25, 3.3 (2009), 333-344
DANH GIA Dp SAN SANG CUA PHAN MEM CHjU LOI AP DUNG KY THUAT REJUVENATION VA NVP HAI PHIEN BAN
HUYNH QUYET THANG, VU HONG LINH Khoa Cong nghe thong tin, Dai hgc Bdch khoa Hd Npi
Abstract. Rejuvenation and NVP are two well-known software fault-tolerant techniques. They are based on two different concepts: design diversity and execution environment diversity. Previous researchs on these techniques mainly focus on evaluation and analysis of each approach separatelj'.
In this paper, we propose an approach for utilizing advantages of two techniques in order to improve fault-tolerant systems availability, especially continuously running system. Using continuous Markov chains, we evaluate the availability of two versions hot-standby system applying proposed model, taking into account correlation between two versions. Some experimental results to examine the reasonableness os the approach also are presented.
Tdm t a t . Ky thuat Rejuvenation va ky thuat NVP la hai ky thuat xay dung plian mem chiu loi tieu bieu, dai dien cho hai nhom phuong phap dua tren su da dang trong moi trudng thuc thi va su da dang trong moi trudng phat trien. Cac nghien cdu truoc kia ve hai ky thuat nay thudng chi ap dung va danh gia tung ky thuat mot each rieng le. Trong bai bao nay, chung ta thd nghiem mo hinh ket hgp hai ky thuat nay nham nang cao do san sang cho cac he thdng phan mem chiu ldi, dac biet la cac he thdng hoat dong lien tuc theo thdi gian. Su dung mo hinh Markov, chung toi danh gia do san sang cua he thdng du phdng nd'ng hai phien ban ap dung mo hinh ket hgp da de xuat, trong do CO xem xet den sir tuang quan gida hai phien ban. Mot sd ket qua thuc nghiem chdng minh tinh hpp Iy cda md hinh cung dugc trinh bay.
Keyword: software fault-tolerant, rejuvenation, NVP, availability, software aging
1. M ^ D A U
Tr-ong thdi gian gan day, nhieu nghien edu ve cac he thdng hoat dong va eung cap dieh vu lien tue theo thdi gian da chi ra hien t u g n g lao hda (Software Agging) trong eae he thdng phan mem [1,3, 4] khi phan mem hoat ddng lien tuc theo thdi gian, mot sd sai sdt se Iam cho he thdng bi lao hda, the hien qua viee tai nguyen bi rd ri, hieu nang he thdng giim [1, 3. 4, 5j.
Huang da nghien cdu ve hien t u g n g nay tr-ong he thdng thanh t o i n truyen thdng [1|, tr-ong dd dng dung theo thdi gian se gap phii hdng hde hay ngung hoat ddng. Huang de xuat phuang phap mdi, mang tfnh phdng ngda dugc gpi la b i o tri phdng ngda (Rejuvenation) de giii quyet van do lao hda phan mem [1|. Y t u d n g ca b i n cda p h u a n g p h i p nay la theo dinh k\- dung he thdng dang hoat dpng lien tuc, dpn dep tai nguyen he thdng sau dd khdi ddng lai he thdng nham d u a he thdng ve ti-ang thai hoat ddng tdt nhat ban dau [1, 2],
334 HU-V-NH QUYET THANG, VU HONG LINH
Co hai hudng nghien edu trong ITnh virc nghien cdu ve lao bda phan mem [1 — 7]. Hudng nghien cdu dira tren thurc nghiem t a p trung vao xac dinh va kiem t r a sir tdn tai cda lao hda phan mem va i n h hurdng cda nd len tai nguyen he thdng [1,2, 4|. Hirdng cdn lai la hudng dura tren md hinh, trong dd t a p trung vao viec danh g i i sir hieu q u i eda b i o tri phdng ngda va d u a la lieh b i o tri phdng ngda tdi uu [3, 5 — 7[.
Huang thurc hien md hinh lao hda trong he thdng bang mdt qua trinh gdm hai b u d c [1,4].
Ban dau he thdng hoat dgng trong trang thai hoan toan binh t h u d n g khdng ed loi, theo thdi gian, he thdng se rai vao trang t h i i ed k h i nang bi Idi va cudi cdng la rai vao trang thai bj Idi. Ap dung ehudi Markov lien tuc ve thdi gian, Huang da dira ra gidi ban de viec b i o tri phdng ngda dat duge hieu q u i [1,2,4].
Trivedi de xuat md hinh Rejuvenation sda doi, de phd hgp han vdi thirc te, sau dd de xuat md hinh ket hprp vdi ky thuat NVP [12] de tang eudng do san sang cho phan mem chiu Idi, tan dung sir da dang trong c i qua trinh phat trien va mdi trirdng thire thi. NVP dai dien cho nhdm cac ky t h u a t dura tren sir khac biet trong thiet ke va phat trien va Rejuvenation dai dien nhdm cac ky thuat d u a tren su khie biet trong mdi t r u d n g thire thi. Tiep tuc phat trien nghien edu theo dinh hudng nay, chung tdi di sau vao t h d nghiem md hinh cho he thdng du phdng ndng hai phien b i n , xay dung mdt sd danh gia ve do san sang, cdng nhu sir phu thude gida hai phien b i n , i n h hudng eda nd len do san sang eda he thdng.
Bai bao duge cau trdc nhu sau. Mue 1, gidi thieu m d dau. Muc 2 trinh bay md hinh ket hgp hai ky thuat Rejuvenation va NVP de nang eao dp san sang cho phan mem chiu ldi. Muc 3 trinh bay danh gia md hinh ap dung cho he thdng du phdng ndng hai phien b i n . Cac ket q u i t h d nghiem d u g c trinh bay trong Muc 4 cda bai bao. Va cudi cdng la ket luan va hirdng nghien edu tiep.
2. M O H I N H K E T H O P R E J U V E N A T I O N V A N V P 2 . 1 . Y tu-dtig
Cac ky thuat xay durng phan mem chiu Idi deu cd chung mdt muc dfeh la eii thien dugc dp tin dung eda he thdng tren cac nguyen ly khae nhau nhu sir k h i c biet ve thiet ke hay sir khac biet ve mdi t r u d n g thue thi.
Hai ky thuat nay la hai ky thuat tieu bieu cho hai nhdm ky t h u a t xay durng phan mem chiu ldi:
• NVP dai dien cho nhdm cac ky thuat d u a tren sir k h i c biet trong thiet ke va phat trien.
Diem manh cda ky thuat NVP la sir k h i c biet trong mdi trirdng thiet ke va phat trien, t d dd giim thieu mdi sur t u a n g quan ve ldi gida c i e phien b i n nhd viec cac phien b i n d u g c p h i t trien dge lap.
• Rejuvenation dai dien nhdm e i e ky thuat dura tren su- khae biet trong mdi t r u d n g thuc thi. Diem manh cda ky thuat Rejuvenation la nd tao ra sir khic biet trong mdi trirdng thurc thi cda phan mem, chdng lai hien t u g n g lao hda tien trinh nhd viec ehd ddng cho tien trinh ngdng hoat ddng, dgn dep tai nguyen sau do khdi ddng lai.
BANH GIA DO SAN SANG CUA PHAN MEM CHIU LOI 335 Ket hgp hai ky thuat, t i n dung dugc diem manh cda t d n g ky thuat xay dung phan mem chiu ldi, phan mem se cd dugc c i sir khae biet ve thiet ke, phat trien va va su khic biet trong mdi t r u d n g thue thi, t u dd dd san sang dugc nang cao,
2.2. M o h i n h k e t h o p
Xuat phat t d y t u d n g dugc trinh bay d tren, md hinh de x u a t de ket hgp hai ky thuat se gdm cd hai pha (Hinh 1).
• >
'•• 1 ^
1
1
\ Phien ban f
^ 1 h
Rej.
^ Phien ban
T
2
Rej.
.11
J Phien ban i 1 N J
Ry.
Hinh 1. Md hinh ket hgp Rejuvenation va NVP
• Pha phat trien: T d dac t i yeu cau ban dau, t u a n g t u nhu trong ky thuat lap trinh da phien bin NVP, N phien b i n se dugc phat trien ddc lap bdi cic ddi phat trien ddc lap vdi cic cdng cu khac nhau. Cac phien b i n duge eai dat rieng biet nham giim k h i nang gap phii nhdng Idi gidng nhau trong qua trinh hoat ddng, t u dd tang eudng tfnh san sang cda he thdng.
• Pha thirc thi: N phien b i n dugc d u a vao hoat ddng song song, tuy nhien khae vdi ky thuat NVP truyen thdng, chdng t a khdng sd dung bo quyet dinh de kiem t r a ket q u i eda eae phien bin, ma cac phien b i n dugc chay song song cung eung cap dieh vu cho ngirdi dung, Mdi phien b i n deu ap dung ky thuat Rejuvenation nham ngan ngda tinh trang ldi do lao hda tien trinh.
2.3. A p d u n g m o h i n h c h o h e t h o n g du" p h o n g n o n g
Tl-ong he thdng d u phdng ndng, vdi yeu eau hoat ddng va cung cap dich vu lien tuc, ngudi ta thudng dira tren nguyen t i c d u thda ve tai nguyen he thdng de d i m b i o tfnh san sang cda cda he thdng. Thdng thirdng, mdt phien b i n eda he thong d u g c nhan b i n va eho hoat ddng song song nham giim k h i nang gap sir cd cda he thdng va tang cudng tfnh san sang cda he thdng. Nhu the, k h i nang rat ldn cic phien b i n eda he thdng gap p h i i nhdng Idi gidng nhau va ddng thdi ngdng cung cap dich vu. Them vao dd, cac he thdng nay dugc yeu cau ehay lien tuc theo thdi gian, nen se x i y ra hien t u g n g lao hda tien trinh trong he thdng.
Nhir vay, chung t a cd the thay i-ang. he thdng du phdng ndng rat thfch hgp de ap dung md hinh de xuat d ti-en nham tang dp san sang eda he thdng,
Cac nghien cuu t r u d c day [8 - 12] ve eic he thdng chiu loi sd dung p h u a n g p h i p d u t h d a ve tai nguyen da chirng minh rang, he thdng chiu loi vdi hai phien b i n se cho hieu q u i cao
336 HUYNH QUYET THANG, VU HONG LINH
nhat. Ke t h d a ket q u i nghien cuu dd, chdng t a se sd dung sd phien b i n trong md hinh ket hgp b i o tri phdng ngda vdi lap trinh da phien b i n la N = 2. Ngoai ra, hai phien b i n nay dugc xay dung hoan toan ddc lap, theo ky thuat lap trinh da phien b i n NVP. D u a tren cdng mdt b i n yeu cau ve he thdng, hai phien b i n se dugc phan tfch, thiet ke va cai dat ddc lap hoan toan bdi hai nhdm p h i t trien khic nhau. Tuy nhien, k h i c vdi kj' thuat lap trinh nhieu phien b i n se khdng cd bd so sanh ket q u i gida hai phien b i n m a hai phien b i n nay se dirge eho hoat ddng song song. Them vao dd, mdi phien b i n se dugc ap dung ky thuat b i o tri phdng ngda. Tren cung quan diem vdi md hinh do Huang ve b i o tri phdng ngda chdng ta gii sd rang mdi phien b i n se bi thoai hda trong thdi gian hoat ddng va se tien tdi trang thai bi ldi neu khdng ed q u i trinh b i o tri phdng ngda duge kfch hoat khi he thdng chuyen sang trang thai cd k h i nang bi ldi.
3. P H U O N G P H A P D A N H G I A D O S I N S A N G C U A H E T H O N G X A Y D U N G T H E O M O H I N H K E T H O P R E J U V E N A T I O N
V A N V P H A I P H I E N B A N
Mdt he thdng d u phdng ndng hai phien b i n , vdi mdi phien b i n se cd hai mde thoai hda la cd k h i nang bi Idi va bi Idi. Thdi gian chuyen td trang t h i i cd k h i nang bi Idi sang trang thai bi ldi tuan theo phan phdi mu. Gpi X vk Y lan lugt la thdi gian thoai hda cda Phien b i n 1 va Phien b i n 2 vdi ham phan phdi xae suat la:
Fx{x) = 1 - e-'^i^, a; > 0, Al > 0,
FY{y) = l-e-^'y, y>0, X2>0. (1)
Neu qua trinh thoai hda dan den trang thai ldi cua hai phien b i n la ddc lap ve thdng ke, phan phdi ddng thdi se la:
F.x.Y{x,y) = P{X <x, Y<y}
= 1-{1-Fx{x)}{l-Fy{y)}
= 1 - e~^i-"-^22/_ (2)
Tr-ong thirc te, viec xay dung hai phien b i n hoan toan ddc lap vdi edng chdc nang, do vay chdng t a can xet den su t u a n g quan cua qua trinh t h o i i hda cda hai phien b i n . Trong nghien cdu nay chdng t a se sd dung phan phdi md hai chieu cua Marshall va Olkin [13] de bieu dien hien t u g n g hai phien b i n eung thoai hda song song. Viee ap dung phan phdi nay nham dan giin hda viee bieu dien q u i trinh thoai hda ddng thdi cua hai phien b i n va d i m b i o viee i p dung chudi Markov lien tue ve thdi gian de phan tfch he thdng. Vdi thdi gian X va Y eda hai phien b i n d tren, thdi gian thoii hda ddng thdi cda hai he thdng se tuan theo phan phdi mu hai chieu sau
F{x,y) = P{X <x, Y <y}
__ 2 _ g-Aix-A2!/-Ai2max(x,y)^ , „ ,
BANH GLA BO S.4N S.ANG CUA PHAN MEM CHIU LOI 337 G i i sd c i hai phien b i n eda he thdng dugc i p dung b i o tri phdng ngda, sd dung md hinh Rejuvenation do Trivedi de xuat [4[, chdng ta cd sa dd chuyen trang thai cda xfch .Markov lien tuc ve thdi gian bieu dien he thdng se la:
Hinh 2. Luac dd chuyen trang thai khi ap dung Rejuvenation ket hgp vdi NVP Cic trang thai t u a n g ung cua he thdng
Bang 1. Cac trang thai cda he thdng d u phdng ndng i p dung md hinh
Trang thai 0 1(3) 2(6) 5(7) 9(10) 11(12) 13(14) 4 8 15
Mo ta
Ca hai phien ban hoat dona binh thucma lihong loi
Phien ban 1 (2) hoat dons binh thucma. phien ban 2 (I) rai vao trang thai co the gay loi Phien ban 1 (2) hoat dpng binh thuong, phien ban 2 (1) bi l5i
Phien ban 1 (2) roi \ao irana tliai co the bi loi. phien ban 2 (1) bi loi Phien ban 1 (2) bao tri phona naiia. phien ban 2(1) hoat dong binh thuoTia Phien ban 1 (2) bao tri phona naua. phien ban 2 (i) rai vao trana thai co the bi loi Phien ban 1(2) bao tri phona natra. phien ban 2 (1) bi loi
Ca hai phien ban deu rai \ao trana thai co the bi loi Ca hai phien ban deu bi loi (he tliona ngung hoat dong) Ca hai phien ban trong qua trinh bao tri phong ngira
Dua ti-en dinh ughia cac ti-ang thai d tren. ta cd he thdng bi dung hoat ddng se t u a n g dirang vdi cic trang thai (8, 13. 14, 15).
Vdi cac tham sdAn. X12- t'i-ri.r3 {X-2i- X-2o. /.lo- ''2. r4) lan hrgt la tdc do chuyen trang thai tu hoat ddng binh t h u d n g sang cd the bi Idi. tdc do ldi td trang thai cd the bi Idi. tdc dd kfch hoat b i o tri phdng ngira ttr trang thai cd the bi Idi, tdc do phuc hdi t d khi b i o tri phdng ngda dugc kfch hoat, tdc dp hdi phuc sau ldi cua phien b i n 1(2). Va A.31, A32 (A3.3),A.34 lan lugt la tdc dp hai phien b i n ddng thdi thoai hda, tdc dp phien b i n 1 (2) ldi cdn phien b i n 2 (1) thoai hda ddng thdi, tdc do c i hai phien b i n ddng thdi bi Idi tir trang thai cd the bi ldi.
Gii sir {X{t) = i, i > 0}. / = 0, ,,15 la chudi Markov lien tuc ve thdi gian bieu dien trang thai thdng ke ciia he thdng.
Ggi Qo.j{l) -- Pr{X{t.) = j | A ' ( 0 ) = 0}. ^ > 0. j = 0, .,15 la xac suat he thdng a trang
338 HUYNH QUYET TH-ANG, VU HONG LTNH thai j tai thdi diem t biet trang thai ban dau la 0.
D u a tren e i c trang thai dinh nghTa d tren t a se cd dugc dp san sang eda he thdng la
A{t) =Qo,o{t) + Qo,i{t) + Qo,2{t) + Qo.3{t) + Qo,4{t) + Qo.o{t)
+ Qo,6{t) + Qo,7it) + Qo,s{t) + Qo.9{t) + Qo,io(i) + Qo.nit) + Qo.nit)- (4)
G i i sd rang tdn tai gidi han pj = lim Qo,j{t), j = 0,,., 15 dd chinh la x i e suat he thdng d trang t h i i j d trang t h i i on dinh.
Cho i —» OC t d p h u a n g trinh Chapman- Kolmogrov eda chudi Markov lien tuc ve thdi gian bieu dien he thdng t a se thu duge he p h u a n g trinh dai sd sau
- ( A n +A21 + A3i)po+^P9+^2PlO = 0 (5) -(A12 + A21 + A31 + fii)pi + AnPo + r2Pi2 = 0 (6)
-(A21 + r-3)p2 + A12P1 + r'2Pi4 = 0 (7) - ( A l l + >*22 + A33 + M2)p3 + A21P0 + ^-iPll = 0 (8)
-(A12 + A22 + A34 + Ml + p.2)P4 + A31P0 + A21P1 + Anps = 0 (9)
-(A22 + r3)p5 + -^32Pi + A21P2 + A12P4 = 0 (10)
- ( A l l + r 4 ) p 6 + A22P3+7'iPi3 = 0 (11) -(A12 + r4)p- + A33P3 + A22P4 + A11P6 = 0 (12)
-(r-3-|-r4)p8 +A34P4 + ^22P5 + -^12P7 = 0 • ' (13)
-(A21 + ri)pg + p.ipi + r3P2 + r-2Pi5 = 0 (14) - ( A l l + 7-2)pi0 + M2P3 + ^4P6 + ^1P15 = 0 (15) -(A22 + r i + A;2)PII + M1P4-1-A21P9 + r3P5 = 0 (16) - ( A i 2 + r2 + Pl)Pl2 + lJ-2Pi + Aiipio + 7-4P7 = 0 (17) - ( r i + r4)pi3 + A21P11 + M1P7 + '•3P8 = 0 (18) -(7-2 + ''3)Pl4 + A12P12 + A'2P5 + 7-4P8 = 0 (19) -{ri + r2)pi5 + M2P11 + 7-4P13 + M1P12 + 7"3Pl4 = 0 (20)
E]ioP7 = l- (21)
Giii p h u a n g trinh dai sd tren ta se thu dugc phan bd cda he thdng d trang t h i i dn dinh va do san sang cda he thdng khi dd la
A = pi + P2 + P3 + P4 + P5 + P6 + P7 + P8 + P9 + PlO + Pu + Pl2- 22
4. T H I > N G H I E M V A D A N H G I A 4.1. Thii- n g h i e m v o l S H A R P E
Bang edng cu SHARPE do GS. Trivedi (www.ee.duke.edu/kst) cung cap de md hinh hda he thdng t h u c nghiem [10] chdng t a se so sanh md hinh he thdng du phdng ndng ap dung b i o tri phdng ngda vdi md hinh Huang [1, 3] sda ddi va md hinh he thdng dir phdng ndng khdng ap dung b i o tri phdng ngda [4, 6|. T d dd nhSm xem xet i n h hudng ciia su khac biet trong thiet ke va sur k h i c biet trong mdi trudng thuc thi len dp tin ddng cua he thdng phdng ngua ndng.
DANH GIA BO SAN SANG CUA PHAN MEM CHIU LOI
De d a n giin hda trong thd nghiem chdng t a g i i sd rang A3 — A31 — A32 tham sd t h d nghiem dugc cho trong b i n g sau
Bdng 2. Cac tham sd t h d nghipm vdi S H A R P E
^^33
339 A34. Cac
Tham sd
All A1-2 A21 A22 r i 7'2
'•a
^4
Gii tri 240 gid 50 gid 240 gid
50 gid 6 /gid 6 /gid 1 /gid 1 /gid
Hinh 2 bieu dien do san sang d trang t h i i on dinh trong md hinh cda Trivedi. Cd the thay dg san sang d trang thai on djnh cda he thdng ed the dirge eii thien t d 0, 997 den 0, 998(0,1003%) khi thay doi tdc do b i o tri phdng ngua td- 0, 001 sang 0, 04.
Vdi he thdng d u phdng ndng khdng ap dung b i o tri phdng ngda, vdi cae tham sd d tren ta ed do san sang eda he thdng thu dugc la 0, 999909573.
Do san sang cda he thdng du phdng ndng khi i p dung b i o tri phdng ngd-a dugc bieu dien trong Hinh 2 va Hinh 3 tirang dng vdi hai t r u d n g hgp A3 = 1/500 vaAa = 0. Trudng hgp A3 = 0 t u a n g dng vdi t r u d n g hgp hai phien b i n la hoan toan ddc lap dudi gdc do Idi x i y ra trong phien b i n . Ta cd the thay dirge vdi tdc do b i o tri phdng ngda fii = fio = 0, 05 he thdng dat duge do san sang la 0, 99996 (so vdi 0, 99985.). So sanh hai dd thi ta thay rang tham sd t u a n g quan A3 i n h hudng manh len do san sang eda he thdng, cu the la khi A3 tang len thi su t u a n g quan gida hai phien b i n trong viee x i y ra ldi cang ldn lam cho do san sang cda he thdng giim xudng.
Legend:
• HuangMotiifiEd
Hinh 3. Do san sang trong md hinh cda Ti-ivedi
340 HUYNH QUYET THANG, VU HONG LINH
Legend:
mu2=001
* m u 2 = 0 . 0 2 mu2=0,03
•*-mu2=0.04 mu2=mul
D.02 0.03 rej. rate
Hinh 4- Dp san sang cda he thdng d u phdng ndng vdi A3 = 1/500
Hinh 5 the hien i n h hirdng eua he sd t u a n g quan gida hai phien b i n den do san sang cua he thdng. Chdng t a cd the thay dugc do san sang cda he thdng thay ddi k h i nha.nh theo A3, dat cue dai khi A3, hai he thdng hoan toan doc lap.
Dinh gia chung: Nhu vay, cd the ket Iuan do san sang eda phan mem cd the d u g r dieu khien bdi md hinh hai tham sd str da dang trong p h i t trien va sir da dang trong mdi trudng thuc thi. Hai phien b i n dugc phat trien ddc lap theo nguyen tac eda p h u a n g phap NVP, he sd t u a n g quan cua hai phien b i n i n h hudng manh len do san sang cda he thdng. Ti-ong khi dd, tdc do Rejuvenation cd the dugc xac dinh de ngan ngda tinh trang lao hda tien trinh trong hai phien b i n , td dd nang eao do san sang.
Legend:
• mu2=0 mu2=0.01 i m u 2 = 0 , D 2 mu2=0,D3
* T n u 2 = 0 , 0 4 mu2::mu1
0 0 2 0 03 rej. rate
Hinh 5. Do san sang cda he dtr phdng ndng vdi A3 = 0
DANH GIA DO SAN SANG CUA PHAN MEM CHIU LOI 341
Legend:
• lam3=0 Iam3=1_300
• i l a m 3 = l _ 5 D 0
0.02 0 03 rej. rate
Hinh 6. Dd san sang cda he d u phdng ndng vdi cic gia tri khic nhau eda A3
4.2. Thii" n g h i e m t r e n t h u ' c t e
Qua trinh thd nghiem md hinh tren thirc te duge thire hien tai t h u vien Ta Quang Bdu Dai hoc Bach khoa Ha Ndi, trong giai doan 1 vao t h i n g 5/2009 (3 tuan) va giai doan 2 t d t h i n g 8/2009 den 11/2009. He thdng duge t h d nghiem la He thdng phuc vu tra euu tai t h u vien Ta Quang Bi'ru, dugc xay dung gdm hai phien b i n hoat ddng theo ca che dtr phdng ndng, xuat phat td mot dac t i yeu cau ban dau cda he thdng hai phien b i n tren dugc phat trien ddc lap theo quy trinh cda ky t h u i t lap trinh da phien b i n :
Phien b i n 1 dirge phat trien dira tren nen cdng nghe .Net cua Microsoft, tliirc thi tren mdi trirdng IIS web server.
Phien b i n 2 dirge phat trien dira tren edng nghe Java Servlet eda Sun Micro System, thuc thi tren mdi trudng Tomcat web sei-ver.
Hai phien b i n tren duge cho hoat ddng song song, eung cung cap dich vu cho ngudi diing thdng qua ea che can bang t i i (load-balancing). Hai phien b i n dirge ap dung ky thuat Rejuvenation nham ngan ngda hien t u g n g lao hda tien trinh.
Ti-ong giai doan (5/2009), thiV nghiem ddng thdi c i hai he thdng. Trong giai doan t u t h i n g 8/2009 chi ap dung he thdng hoat ddng theo ca che b i o tri phdng ngda. Ky thuat b i o tri phdng ngda d hai phien b i n tren ehi ddng lai d viee ddng hoat ddng cda dng dung, thu dpn tai nguyen cda web server. Chdng ta se thdng ke thdi gian hoat ddng cda he thdng. thdi gian he thdng bi Idi, thdi gian bao tri phdng ngda, t u dd tfnh toan dp san sang cua he thdng va so sanh vdi he thong d u phdng ndng cd hai phien b i n gidng nhau, khdng ap dung b i o tri phdng ngda.
C a c k e t q u a t h u du'g'c iihif s a u
\'di he thdng chi gdm hai phie'n b i n gidng nhau, khdng ap dung b i o tri phdng ngira:
342 HUYNH QU'/ET THANG, VU HONG LINH Bdng 3. Dp san sang cda he thdng du phdng ndng Thong so
Tong thai gian hoat dong Tong so yeu cau nhan duoc
Tong thai gian ca hai phien ban khong hoat dpng Do san sang cua he thong
Gia tri
(Giai doan 1: thang 5/2009) 72 gia = 72 X 60 X 60 = 259200 (s) 32 348 (yeu cau)
87(s)
(259200 - 87)/259200 = 0,999664
Vdi he thdng ap dung md hinh ket hgp b i o tri phdng ngua va lap trinh da phien b i n ap dung b i o tri phdng ngda vdi cdng toe dp 2740 yeu c a u / 1 lan b i o tt-i phdng ngda.
Bdng 4- Do san sang cda he thdng d u phdng ndng ap dung md hinh
Thong sd
rang th&i gian tioat (Jong Tdng s6 yeu ciu ntiSn dwcrc long tt)oi gian ptii^n ban. Net bi ldi Tdng tii&i gian phidn bin Java bi lii Tdng tiidi gian phien bin .Net bao tri phdng ngi/a
Tdng th&i gian phidn ban Java bao tri phdng ngCra
Ting th&i gian ca hai phidn bin khdng hdat ddng
Dd sin sing cua hi thing
Gii tri
(Giai doan 1: thing 5/2009) 72 qi& = 72*60*60 = 259200 (s) 28 472 (ydu ciu)
243 (s) 389 (s) 847 (s) 679 (s) 27 (s)
= f259200-27j/259200 = 0.999895833
Gii tri
(Giai doan 2: thing 8-11/2009) 960 qi& = 960*60*60 = 345600 48 1394 (ydu ciu)
4108 (s) 6521 (s) 14319 (s) 11323 (s) 359 (s)
=(3456000-359)73456000=
0.999896123
N h a n x e t ket qud
- Khi ap dung md hinh vao he thdng, do san sang eda he thdng dirge cii thien.
- Mae dd thdi gian khdng hoat ddng cda mdi phien b i n tang len (tdng thdi gian bi loi va b i o tri phdng ngda) tuy nhien thdi gian e i hai phien b i n khdng hoat dgng lai giim xudng, dieu nay ed the giii thich do ap dung b i o tri phdng ngua, xac suat he thdng bi loi giim xudng, dac biet cac Idi do t u a n g quan gida, hai phien bin.
- Do thdi gian t h u e nghiem ehua dd dai, nen dp san sang cua he thdng chira hgi tu ve gia tri gidi han.
Tdm lai, qua sd lieu thu dugc d tren, ta cd the thay d u g c viec ap dung md hinh ket hap giua b i o tri phdng ngda va lap trinh da phien b i n vao he thdng cd cii thien dd s i n sang cda he thdng. Trong thdi gian tdi, cic t i c gii se tiep tuc thurc hien viec t h d nghiem vdi thdi gian Idn han de ed duge nhdng ket q u i chinh x i c han nda.
5. K E T L U A N V A H l T ^ N G P H A T T R I E N
Tl-ong bai bao nay chdng t a da nghien cdu ve md hinh ket hgp hai ky thuat Rejuvenation va NVP trong dd i p dung A^ = 2, de tang cudng dp s i n sang cda phan mem chiu loi, cu the la eie phan mem hoat ddng lien tuc theo thdi gian, trong dd x i y ra hien tirgng lao hda tien trinh. Dua tren p h u a n g phap dung chuoi Markov lien tue ve thdi gian, chdng t a da d i n h
DANH GIA DO S.\N SANG CUA PHAN MEM CHIU LOI 3 4 3 gii dugc dp s i n sang eda he thdng d u phdng ndng hai phien b i n i p dung md hinh nay, i n h
hudng eda hai tham sd ca bin: t u a n g quan gida hai phien b i n va toe dp b i o tri phdng ngda len dp s i n sang eda he thdng. Bai b i o da chdng minh duge sir ket hgp gida sir da dang trong p h i t trien va sir da dang trong mdi trudng thuc thi lam tang do san sang eda he thdng vdi tdc do b i o tri phdng ngda hgp Iy.
Trong thdi gian tdi, de hoan thien md hinh chdng t a se xet den t r u d n g hgp trong do thdi gian b i o tri phdng ngda la x i c dinh va md rdng chudi Markov lien tue ve thdi gian thanh chuoi semi-Markov de md hinh hda ehi'nh x i c han c i c budc chuyen trang thai trong he thdng [13|. Them vao dd, cd t h e phat trien md hinh theo hirdng xem xet den trang thai cda he thdng thay doi theo t i i , phat trien thuat toan de xac dinh toe dp b i o tri phdng ngda tdi uu.
T A I L I E U T H A M K H A O
[1[ Huang.Y,Kintala C.,Nick K., N. Dudley Fulton, Software rejuvenation: analysis, module and applications, Proceedings of the Twenty-Fifth International Symposium on Fault-Tolerant Computing Psisudena, CA, USA, 1995 (.381-391).
[2] Artur Andrzejak, Luis Silva, Deterministic Models of Software Aging and Optimal Rejuvena- tion Schedules. CoreGRlD Technical Report, Number TR-0047, November 2, 2006. Institute on System Architecture. URL: http://w\v\v.coregrid.net.
[3] K. Vaidyanathan and K. S. Trivedi, A comprehensive model for software rejuvenation, IEEE Transactions on Dependable and Secure Computing 2 (2) (April-June 2005).
[4| Y. Bao, X. Sun, and K. S. Trivedi, A workload-based analysis of software aging and rejuvenation, IEEE Transactions on Reliability 54 (3) (2005) (541-548).
[5| M. Grottke, L. Li, K. Vaidyanathan, and K. S. Trivedi, Analysis of software aging in a Web server, IEEE Transactions on Reliability bb (3) (2006) 411-420.
[6[ K. S. Trivedi, K. Vaidynathan and K. Goseva-Popstojanova, Analysis of Software Aging and Rejuvenation, in Recent Developments in Quality Reliability and Information Technology-Trends and Future Directions, P. K. Kapur, A. Kumar, Y. Singh, P. C, Jha, and A, K. Bardhanm (editors), IMH, New Delhi, INDIA, 2004 (25-42).
[7| T.Dohi, K. Goseva-Popstojanova, K. Vaidyanathan, K. S. Trivedi and S. Osaki, Software Rejuvenation- Modeling and Applications, in Springer Handbook of Reliability, H.Pham (ed- itor). Springer Verlag, Feb. 2003 (245-263).
[8| Pham Thanh Trung, Huj-nh Quyet Thang, Building the reliability prediction model of component-based software architectures, International Journal of Information Technology 5 (1) (2009) 17-25,
|9| Huynh Quyet Thang, Pham Ba Quang, Nguyen Tien Dat, Investigate the relation between the correctness and the number of versions of fault tolerant software systems. International Journal of Computer Science and Engineering 1 (1) (2007) ISSN 1307-3699. 18-23.
344 HUYNH QUYET THANG, VU HONG LINH
[10| Kisho S. Trivedi, Robin Sahner, SHARPE at the age of twenty two, ACM SIGMETRICS Performance Evaluation Review 36 (4) (March 2009) SPECIAL ISSUE: Special issue on tools for computer performance modeling and reliability analysis, pages 52-57.
[11| Pham Ba Quang, Dao Ngoc Kien, Huynh Quyet Thing, Md hinh phan niem chiu ldi BK-FTS:
thu nghiem, so sanh va danh gia, Tap chi Tin hgc vd Dieu khiin hoc 21 (4) (2005) 323-336.
[12( Igirdas Avizienis, The Methodology of N-Version Programming, in R. Lieu, editor, Software Fault Tolerance, John Wiley & Sons, 1995.
|13| W. K. Ching, K. Ng. Michael, Markov Chains - Models, Algorithms and .Applications, Springer Science-tBusiness Media, Inc., 2006.
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