Thread: Postgresql Database Lock Problem
Problem: Database Lock ---------------------------------- Dear all I am working as a database administrator in a company. Our Database system is Postgresql-8.3.5 and Application server is Jboss used for our Adempiere ERP system. This is a web based ERP system. All servers are running on RHEL. Now our system is going to on-line and users are entering old data. So transactions are occurring very frequently. Now I am facing the problem is the application server just hangs at busy hour and it does not accept any new connection. When I restart the server (Adempiere, Jboss) it works fine for a few hours and problem occurs again. When this problem occurs the database server shows the following log LOG: process 19181 still waiting for ShareLock on transaction 18025221 after 1002.251 ms STATEMENT: SELECT CurrentNext, CurrentNextSys, IncrementNo, Prefix, Suffix, DecimalPattern, AD_Sequence_ID FROM AD_Sequence WHERE Name = $1 AND AD_Client_ID = $2 AND IsActive='Y' AND IsTableID='N' AND IsAutoSequence='Y' ORDER BY AD_Client_ID DESC FOR UPDATE OF AD_Sequence LOG: process 19181 acquired ShareLock on transaction 18025221 after 1298870.572 ms STATEMENT: SELECT CurrentNext, CurrentNextSys, IncrementNo, Prefix, Suffix, DecimalPattern, AD_Sequence_ID FROM AD_Sequence WHERE Name = $1 AND AD_Client_ID = $2 AND IsActive='Y' AND IsTableID='N' AND IsAutoSequence='Y' ORDER BY AD_Client_ID DESC FOR UPDATE OF AD_Sequence and the lock table informations are as following: adempiere=# select * from pg_locks where granted = 'y' and mode = 'ExclusiveLock'; locktype | database | relation | page | tuple | virtualxid | transactionid | classid | objid | objsubid | virtualtransaction | pid | mode | granted ---------------+----------+----------+------+-------+------------+---------------+---------+-------+----------+--------------------+-------+---------------+--------- transactionid | | | | | | 18386552 | | | | 39/1733 | 19196 | ExclusiveLock | t virtualxid | | | | | 24/1586 | | | | | 24/1586 | 19181 | ExclusiveLock | t transactionid | | | | | | 18386856 | | | | 24/1586 | 19181 | ExclusiveLock | t virtualxid | | | | | 39/1733 | | | | | 39/1733 | 19196 | ExclusiveLock | t transactionid | | | | | | 18386574 | | | | 39/1733 | 19196 | ExclusiveLock | t transactionid | | | | | | 18386563 | | | | 39/1733 | 19196 | ExclusiveLock | t transactionid | | | | | | 18386869 | | | | 24/1586 | 19181 | ExclusiveLock | t virtualxid | | | | | 50/20 | | | | | 50/20 | 19217 | ExclusiveLock | t transactionid | | | | | | 18386846 | | | | 24/1586 | 19181 | ExclusiveLock | t tuple | 250427 | 251989 | 209 | 7 | | | | | | 24/1586 | 19181 | ExclusiveLock| t (10 rows) adempiere=# select * from pg_locks where granted = 'f'; locktype | database | relation | page | tuple | virtualxid | transactionid | classid | objid | objsubid | virtualtransaction | pid | mode | granted ---------------+----------+----------+------+-------+------------+---------------+---------+-------+----------+--------------------+-------+-----------+--------- transactionid | | | | | | 18386574 | | | | 24/1586 | 19181 | ShareLock | f (1 row) *** Here you can see that process 19196 have ExclusiveLock on transaction 18386574 and process 19181 is waiting for ShareLock to the same transaction. When I monitor the Application server sessions from Jboss console normally I can see one of three stats R-Ready, K-Keep Alive and S-Service. When the application server hangs all sessions goes to Service mode. Please give me your appropriate and valuable solution in this regard. I am eagerly looking forward for your quick reply. Thanks in advance: --------------------------- Shohorab Hossain Send instant messages to your online friends http://uk.messenger.yahoo.com
Can you provide the layout of your table and all indexes that are present on said table? Sounds like a incorrectly indexed table possibly. -----Original Message----- From: pgsql-admin-owner@postgresql.org [mailto:pgsql-admin-owner@postgresql.org] On Behalf Of shohorab hossain Sent: Tuesday, November 17, 2009 1:26 PM To: pgsql-admin@postgresql.org; pgsql-docs@postgresql.org; pgsql-general@postgresql.org Subject: [ADMIN] Postgresql Database Lock Problem Problem: Database Lock ---------------------------------- Dear all I am working as a database administrator in a company. Our Database system is Postgresql-8.3.5 and Application server is Jboss used for our Adempiere ERP system. This is a web based ERP system. All servers are running on RHEL. Now our system is going to on-line and users are entering old data. So transactions are occurring very frequently. Now I am facing the problem is the application server just hangs at busy hour and it does not accept any new connection. When I restart the server (Adempiere, Jboss) it works fine for a few hours and problem occurs again. When this problem occurs the database server shows the following log LOG: process 19181 still waiting for ShareLock on transaction 18025221 after 1002.251 ms STATEMENT: SELECT CurrentNext, CurrentNextSys, IncrementNo, Prefix, Suffix, DecimalPattern, AD_Sequence_ID FROM AD_Sequence WHERE Name = $1 AND AD_Client_ID = $2 AND IsActive='Y' AND IsTableID='N' AND IsAutoSequence='Y' ORDER BY AD_Client_ID DESC FOR UPDATE OF AD_Sequence LOG: process 19181 acquired ShareLock on transaction 18025221 after 1298870.572 ms STATEMENT: SELECT CurrentNext, CurrentNextSys, IncrementNo, Prefix, Suffix, DecimalPattern, AD_Sequence_ID FROM AD_Sequence WHERE Name = $1 AND AD_Client_ID = $2 AND IsActive='Y' AND IsTableID='N' AND IsAutoSequence='Y' ORDER BY AD_Client_ID DESC FOR UPDATE OF AD_Sequence and the lock table informations are as following: adempiere=# select * from pg_locks where granted = 'y' and mode = 'ExclusiveLock'; locktype | database | relation | page | tuple | virtualxid | transactionid | classid | objid | objsubid | virtualtransaction | pid | mode | granted ---------------+----------+----------+------+-------+------------+---------------+---------+-------+----------+--------------------+-------+---------------+--------- transactionid | | | | | | 18386552 | | | | 39/1733 | 19196 | ExclusiveLock | t virtualxid | | | | | 24/1586 | | | | | 24/1586 | 19181 | ExclusiveLock | t transactionid | | | | | | 18386856 | | | | 24/1586 | 19181 | ExclusiveLock | t virtualxid | | | | | 39/1733 | | | | | 39/1733 | 19196 | ExclusiveLock | t transactionid | | | | | | 18386574 | | | | 39/1733 | 19196 | ExclusiveLock | t transactionid | | | | | | 18386563 | | | | 39/1733 | 19196 | ExclusiveLock | t transactionid | | | | | | 18386869 | | | | 24/1586 | 19181 | ExclusiveLock | t virtualxid | | | | | 50/20 | | | | | 50/20 | 19217 | ExclusiveLock | t transactionid | | | | | | 18386846 | | | | 24/1586 | 19181 | ExclusiveLock | t tuple | 250427 | 251989 | 209 | 7 | | | | | | 24/1586 | 19181 | ExclusiveLock| t (10 rows) adempiere=# select * from pg_locks where granted = 'f'; locktype | database | relation | page | tuple | virtualxid | transactionid | classid | objid | objsubid | virtualtransaction | pid | mode | granted ---------------+----------+----------+------+-------+------------+---------------+---------+-------+----------+--------------------+-------+-----------+--------- transactionid | | | | | | 18386574 | | | | 24/1586 | 19181 | ShareLock | f (1 row) *** Here you can see that process 19196 have ExclusiveLock on transaction 18386574 and process 19181 is waiting for ShareLock to the same transaction. When I monitor the Application server sessions from Jboss console normally I can see one of three stats R-Ready, K-Keep Alive and S-Service. When the application server hangs all sessions goes to Service mode. Please give me your appropriate and valuable solution in this regard. I am eagerly looking forward for your quick reply. Thanks in advance: --------------------------- Shohorab Hossain Send instant messages to your online friends http://uk.messenger.yahoo.com -- Sent via pgsql-admin mailing list (pgsql-admin@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-admin
[ cc's trimmed a bit ] shohorab hossain <shohorab23@yahoo.com> writes: > LOG: process 19181 still waiting for ShareLock on transaction 18025221 > after 1002.251 ms > STATEMENT: SELECT CurrentNext, CurrentNextSys, IncrementNo, Prefix, Suffix, > DecimalPattern, AD_Sequence_ID FROM AD_Sequence WHERE Name = $1 AND > AD_Client_ID = $2 AND IsActive='Y' AND IsTableID='N' AND > IsAutoSequence='Y' ORDER BY AD_Client_ID DESC FOR UPDATE OF > AD_Sequence > LOG: process 19181 acquired ShareLock on transaction 18025221 after > 1298870.572 ms > STATEMENT: SELECT CurrentNext, CurrentNextSys, IncrementNo, Prefix, Suffix, > DecimalPattern, AD_Sequence_ID FROM AD_Sequence WHERE Name = $1 AND > AD_Client_ID = $2 AND IsActive='Y' AND IsTableID='N' AND > IsAutoSequence='Y' ORDER BY AD_Client_ID DESC FOR UPDATE OF > AD_Sequence It looks to me like the database is doing exactly what you are telling it to, ie, waiting until it can get an update lock on the selected row(s) of AD_Sequence. What you need to look into is what the other transaction was doing that caused it to sit on uncommitted changes to those rows for 1300 seconds. Most likely this is an application bug or bad application design (like failing to commit changes reasonably promptly, or maybe not understanding the semantics of FOR UPDATE in the first place). regards, tom lane
Next time this is happening join the pg_lock table to the pg_stat_activity table to see which query is holding the lock for a bazillion milliseconds, while it's happening. That query / statement may give you some clue what's wrong.
The statement that creates lock and waiting is in following. This is from pg_stats and pg_stat_activity view. Here AD_Sequence is a table that maintains sequence number for all database objects. It automatically generates primary keyvalue for all table insert. I think it also generates transaction related ID. For that reason it needs to update nextsequence value for transaction ID. Statment: ====================== SELECT CurrentNext, CurrentNextSys, IncrementNo, Prefix, Suffix, DecimalPattern, AD_Sequence_ID FROM AD_Sequence WHERE Name= $1 AND AD_Client_ID = $2 AND IsActive='Y' AND IsTableID='N' AND IsAutoSequence='Y' ORDER BY AD_Client_ID DESC FOR UPDATEOF AD_Sequence AD_Sequence Table Definition ===================== adempiere=# \d ad_sequence Table "adempiere.ad_sequence" Column | Type | Modifiers ----------------+-----------------------------+------------------------------ ad_sequence_id | numeric(10,0) | not null ad_client_id | numeric(10,0) | not null ad_org_id | numeric(10,0) | not null isactive | character(1) | default 'Y'::bpchar created | timestamp without time zone | not null default now() createdby | numeric(10,0) | not null updated | timestamp without time zone | not null default now() updatedby | numeric(10,0) | not null name | character varying(60) | not null description | character varying(255) | vformat | character varying(40) | isautosequence | character(1) | not null default 'Y'::bpchar incrementno | numeric(10,0) | not null startno | numeric(10,0) | not null currentnext | numeric(10,0) | not null currentnextsys | numeric(10,0) | not null isaudited | character(1) | default 'N'::bpchar istableid | character(1) | default 'N'::bpchar prefix | character varying(255) | suffix | character varying(255) | startnewyear | character(1) | default 'N'::bpchar datecolumn | character varying(60) | decimalpattern | character varying(40) | Indexes: "ad_sequence_pkey" PRIMARY KEY, btree (ad_sequence_id) "ad_sequence_name" UNIQUE, btree (ad_client_id, name) Check constraints: "ad_sequence_isactive_check" CHECK (isactive = ANY (ARRAY['Y'::bpchar, 'N'::bpchar])) "ad_sequence_isaudited_check" CHECK (isaudited = ANY (ARRAY['Y'::bpchar, 'N'::bpchar])) "ad_sequence_isautosequence_check" CHECK (isautosequence = ANY (ARRAY['Y'::bpchar, 'N'::bpchar])) "ad_sequence_istableid_check" CHECK (istableid = ANY (ARRAY['Y'::bpchar, 'N'::bpchar])) "ad_sequence_startnewyear_check" CHECK (startnewyear = ANY (ARRAY['Y'::bpchar, 'N'::bpchar])) Foreign-key constraints: "sequenceclient" FOREIGN KEY (ad_client_id) REFERENCES ad_client(ad_client_id) DEFERRABLE INITIALLY DEFERRED "sequenceorg" FOREIGN KEY (ad_org_id) REFERENCES ad_org(ad_org_id) DEFERRABLE INITIALLY DEFERRED With Thanks & Regards: --------------------- Shohorab Hossain ----- Original Message ---- From: Scott Marlowe <scott.marlowe@gmail.com> To: shohorab hossain <shohorab23@yahoo.com> Cc: pgsql-admin@postgresql.org; pgsql-docs@postgresql.org; pgsql-general@postgresql.org Sent: Wednesday, November 18, 2009 2:55:25 Subject: Re: [GENERAL] Postgresql Database Lock Problem Next time this is happening join the pg_lock table to the pg_stat_activity table to see which query is holding the lock for a bazillion milliseconds, while it's happening. That query / statement may give you some clue what's wrong. Get your preferred Email name! Now you can @ymail.com and @rocketmail.com. http://mail.promotions.yahoo.com/newdomains/aa/
At first I would like to thank you all for your quick response. Now my question is why two processes ID 19181 and 19196 are trying to access the same transaction 18386574 at the same time. Here I have got Process ID, Transaction ID and SQL statement from pg_locks and pg_stat_activity view. Is it possible to find from which Application form/window the query is being running. With Thanks & Regards: --------------------- Shohorab Hossain ----- Original Message ---- From: Tom Lane <tgl@sss.pgh.pa.us> To: shohorab hossain <shohorab23@yahoo.com> Cc: pgsql-general@postgresql.org Sent: Wednesday, November 18, 2009 1:47:53 Subject: Re: [GENERAL] Postgresql Database Lock Problem [ cc's trimmed a bit ] shohorab hossain <shohorab23@yahoo.com> writes: > LOG: process 19181 still waiting for ShareLock on transaction 18025221 > after 1002.251 ms > STATEMENT: SELECT CurrentNext, CurrentNextSys, IncrementNo, Prefix, Suffix, > DecimalPattern, AD_Sequence_ID FROM AD_Sequence WHERE Name = $1 AND > AD_Client_ID = $2 AND IsActive='Y' AND IsTableID='N' AND > IsAutoSequence='Y' ORDER BY AD_Client_ID DESC FOR UPDATE OF > AD_Sequence > LOG: process 19181 acquired ShareLock on transaction 18025221 after > 1298870.572 ms > STATEMENT: SELECT CurrentNext, CurrentNextSys, IncrementNo, Prefix, Suffix, > DecimalPattern, AD_Sequence_ID FROM AD_Sequence WHERE Name = $1 AND > AD_Client_ID = $2 AND IsActive='Y' AND IsTableID='N' AND > IsAutoSequence='Y' ORDER BY AD_Client_ID DESC FOR UPDATE OF > AD_Sequence It looks to me like the database is doing exactly what you are telling it to, ie, waiting until it can get an update lock on the selected row(s) of AD_Sequence. What you need to look into is what the other transaction was doing that caused it to sit on uncommitted changes to those rows for 1300 seconds. Most likely this is an application bug or bad application design (like failing to commit changes reasonably promptly, or maybe not understanding the semantics of FOR UPDATE in the first place). regards, tom lane Get your preferred Email name! Now you can @ymail.com and @rocketmail.com. http://mail.promotions.yahoo.com/newdomains/aa/
Now I am using the following parameter to temporary resolve the locking problem statment_timeout = 20s With Thanks & Regards: --------------------- Shohorab Hossain ----- Original Message ---- From: shohorab hossain <shohorab23@yahoo.com> To: Tom Lane <tgl@sss.pgh.pa.us> Cc: pgsql-general@postgresql.org Sent: Wednesday, November 18, 2009 14:41:09 Subject: Re: [GENERAL] Postgresql Database Lock Problem At first I would like to thank you all for your quick response. Now my question is why two processes ID 19181 and 19196 are trying to access the same transaction 18386574 at the same time. Here I have got Process ID, Transaction ID and SQL statement from pg_locks and pg_stat_activity view. Is it possible to find from which Application form/window the query is being running. With Thanks & Regards: --------------------- Shohorab Hossain ----- Original Message ---- From: Tom Lane <tgl@sss.pgh.pa.us> To: shohorab hossain <shohorab23@yahoo.com> Cc: pgsql-general@postgresql.org Sent: Wednesday, November 18, 2009 1:47:53 Subject: Re: [GENERAL] Postgresql Database Lock Problem [ cc's trimmed a bit ] shohorab hossain <shohorab23@yahoo.com> writes: > LOG: process 19181 still waiting for ShareLock on transaction 18025221 > after 1002.251 ms > STATEMENT: SELECT CurrentNext, CurrentNextSys, IncrementNo, Prefix, Suffix, > DecimalPattern, AD_Sequence_ID FROM AD_Sequence WHERE Name = $1 AND > AD_Client_ID = $2 AND IsActive='Y' AND IsTableID='N' AND > IsAutoSequence='Y' ORDER BY AD_Client_ID DESC FOR UPDATE OF > AD_Sequence > LOG: process 19181 acquired ShareLock on transaction 18025221 after > 1298870.572 ms > STATEMENT: SELECT CurrentNext, CurrentNextSys, IncrementNo, Prefix, Suffix, > DecimalPattern, AD_Sequence_ID FROM AD_Sequence WHERE Name = $1 AND > AD_Client_ID = $2 AND IsActive='Y' AND IsTableID='N' AND > IsAutoSequence='Y' ORDER BY AD_Client_ID DESC FOR UPDATE OF > AD_Sequence It looks to me like the database is doing exactly what you are telling it to, ie, waiting until it can get an update lock on the selected row(s) of AD_Sequence. What you need to look into is what the other transaction was doing that caused it to sit on uncommitted changes to those rows for 1300 seconds. Most likely this is an application bug or bad application design (like failing to commit changes reasonably promptly, or maybe not understanding the semantics of FOR UPDATE in the first place). regards, tom lane Get your preferred Email name! Now you can @ymail.com and @rocketmail.com. http://mail.promotions.yahoo.com/newdomains/aa/ New Email addresses available on Yahoo! Get the Email name you've always wanted on the new @ymail and @rocketmail. Hurry before someone else does! http://mail.promotions.yahoo.com/newdomains/aa/