Hi, there is the question about synchronized on
"org.h2.engine.Engine#openSession" method. For example we have two
simultaneous threads. Each of them opens a connection to separate DB file.
If one of these threads will run some heavy operation inside connection
creation (like restoring DB files after JVM crash) another one will wait on
"openSession". It is clear why connections to the same DB should do that,
but why a separate one should?
*Info:*
- H2 Version: checked in 182 (found in 176)
- Used connection URL:
jdbc:h2:D:/tmp/8.6/h2/DB_NAME;LOG=1;MVCC=TRUE;PAGE_SIZE=16384;CACHE_TYPE=TQ;ALIAS_COLUMN_NAME=TRUE;IGNORECASE=TRUE;MAX_MEMORY_ROWS=100000;DB_CLOSE_DELAY=0;CIPHER=AES;TRACE_LEVEL_FILE=3;TRACE_LEVEL_SYSTEM_OUT=3
There is next threads dump in that moment:
*Thread #1 opens connection to DB #1*
-------------------------------------------------------------------
"Thread #1"@599 in group "main": RUNNING
getEntry():-1, ZipFile {java.util.zip}
getEntry():306, ZipFile {java.util.zip}
getEntry():227, JarFile {java.util.jar}
getJarEntry():210, JarFile {java.util.jar}
getResource():840, URLClassPath$JarLoader {sun.misc}
getResource():199, URLClassPath {sun.misc}
run():358, URLClassLoader$1 {java.net}
run():355, URLClassLoader$1 {java.net}
doPrivileged():-1, AccessController {java.security}
findClass():354, URLClassLoader {java.net}
loadClass():425, ClassLoader {java.lang}
loadClass():308, Launcher$AppClassLoader {sun.misc}
loadClass():358, ClassLoader {java.lang}
getPageStore():2381, Database {org.h2.engine}
open():666, Database {org.h2.engine}
openDatabase():266, Database {org.h2.engine}
<init>():260, Database {org.h2.engine}
openSession():60, Engine {org.h2.engine}
openSession():167, Engine {org.h2.engine}
createSessionAndValidate():145, Engine {org.h2.engine}
createSession():128, Engine {org.h2.engine}
createSession():26, Engine {org.h2.engine}
connectEmbeddedOrServer():347, SessionRemote {org.h2.engine}
<init>():108, JdbcConnection {org.h2.jdbc}
<init>():92, JdbcConnection {org.h2.jdbc}
connect():72, Driver {org.h2}
getConnection():571, DriverManager {java.sql}
getConnection():215, DriverManager {java.sql}
createConnection():160, H2CompactingTest {com.keysurvey.contact}
access$000():23, H2CompactingTest {com.keysurvey.contact}
run():46, H2CompactingTest$1 {com.keysurvey.contact}
run():745, Thread {java.lang}
*Thread #2 opens connection to the same DB #1*
-------------------------------------------------------------------
"Thread #2"@602 in group "main": MONITOR
openSession():160, Engine {org.h2.engine}
createSessionAndValidate():145, Engine {org.h2.engine}
createSession():128, Engine {org.h2.engine}
createSession():26, Engine {org.h2.engine}
connectEmbeddedOrServer():347, SessionRemote {org.h2.engine}
<init>():108, JdbcConnection {org.h2.jdbc}
<init>():92, JdbcConnection {org.h2.jdbc}
connect():72, Driver {org.h2}
getConnection():571, DriverManager {java.sql}
getConnection():215, DriverManager {java.sql}
createConnection():160, H2CompactingTest {com.keysurvey.contact}
access$000():23, H2CompactingTest {com.keysurvey.contact}
run():76, H2CompactingTest$2 {com.keysurvey.contact}
run():745, Thread {java.lang}
*Thread #3 opens connection to the different DB #2*
-------------------------------------------------------------------
"Thread #3"@604 in group "main": MONITOR *<--- Why?*
openSession():160, Engine {org.h2.engine}
createSessionAndValidate():145, Engine {org.h2.engine}
createSession():128, Engine {org.h2.engine}
createSession():26, Engine {org.h2.engine}
connectEmbeddedOrServer():347, SessionRemote {org.h2.engine}
<init>():108, JdbcConnection {org.h2.jdbc}
<init>():92, JdbcConnection {org.h2.jdbc}
connect():72, Driver {org.h2}
getConnection():571, DriverManager {java.sql}
getConnection():215, DriverManager {java.sql}
createConnection():160, H2CompactingTest {com.keysurvey.contact}
access$000():23, H2CompactingTest {com.keysurvey.contact}
run():106, H2CompactingTest$3 {com.keysurvey.contact}
run():745, Thread {java.lang}
-------------------------------------------------------------------
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