02、Solr4.8.0源码分析(2)之Solr的启动(一)
上文写到Solr的启动过程是在SolrDispatchFilter的init()里实现，当Tomcat启动时候会自动调用init();
Solr的启动主要在 this.cores = createCoreContainer();语句中实现。
/**
*初始化，当tomcat启动时候开始初始化，其中主要调用createCoreContainer来实现Solr的初始化
*/
public void init(FilterConfig config) throws ServletException
{
log.info("SolrDispatchFilter.init()");
try {
// web.xml configuration
this.pathPrefix = config.getInitParameter( "path-prefix" );
this.cores = createCoreContainer();
log.info("user.dir=" + System.getProperty("user.dir"));
}
catch( Throwable t ) {
// catch this so our filter still works
log.error( "Could not start Solr. Check solr/home property and the logs");
SolrCore.log( t );
if (t instanceof Error) {
throw (Error) t;
}
}
log.info("SolrDispatchFilter.init() done");
}
Solr的启动过程主要包括：
1、 获取SolrHome：分别先后通过JNDI，Systemproperty，defaultdirectory三种方式尝试获取；
2、 实例化启动过程中使用的类加载器SolrResourceLoader；
3、 加载solrhome下的solr.xml文件，封装为ConfigSolr；
4、 实例化一个CoreContainer,通过CoreContainer来加载cores；
5、 遍历SolrHome，当寻找到含有core.properties的文件夹，则作为一个core；
6、 多线程加载cores；
7、 加载每个core时先加载solrconfig.xml封装为SolrConfig；
8、 再加载schema.xml封装为IndexSchema；
9、 最后实例化SolrCore；
以下是createCoreContainer()实现代码，该函数就包含了以上的启动过程。
/**
* Override this to change CoreContainer initialization
* @return a CoreContainer to hold this server's cores
*/
protected CoreContainer createCoreContainer() {
SolrResourceLoader loader = new SolrResourceLoader(SolrResourceLoader.locateSolrHome());
ConfigSolr config = loadConfigSolr(loader);
CoreContainer cores = new CoreContainer(loader, config);
cores.load();
return cores;
}
1、 获取SolrHome信息；
Solr通过三种方式来获取SolrHome,分别是JNDI,System property,以及当前路径。
JNDI的java:comp/env/solr/home的获取，主要通过在tomcat/conf/Catalina/localhost目录下新建solr.xml。Tomcat启动的时候就会该目录下自动获取 SolrHome的信息.
System property的SolrHome获取是直接在tomcat启动脚本catalina.sh中加入set JAVA_OPTS -Dsolr.solr.home=/Users/rcf/workspace/java/solr 。
最后的获取SolrHome的方式就是在当前目录下查找。
/**
* Determines the solrhome from the environment.
* Tries JNDI (java:comp/env/solr/home) then system property (solr.solr.home);
* if both fail, defaults to solr/
* @return the instance directory name
*/
/**
* Finds the solrhome based on looking up the value in one of three places:
* <ol>
* <li>JNDI: via java:comp/env/solr/home</li>
* <li>The system property solr.solr.home</li>
* <li>Look in the current working directory for a solr/ directory</li>
* </ol>
*
* The return value is normalized. Normalization essentially means it ends in a trailing slash.
* @return A normalized solrhome
* @seenormalizeDir(String)
*/
public static String locateSolrHome() {
String home = null;
// Try JNDI
try {
Context c = new InitialContext();
home = (String)c.lookup("java:comp/env/"+project+"/home");
log.info("Using JNDI solr.home: "+home );
} catch (NoInitialContextException e) {
log.info("JNDI not configured for "+project+" (NoInitialContextEx)");
} catch (NamingException e) {
log.info("No /"+project+"/home in JNDI");
} catch( RuntimeException ex ) {
log.warn("Odd RuntimeException while testing for JNDI: " + ex.getMessage());
}
// Now try system property
if( home == null ) {
String prop = project + ".solr.home";
home = System.getProperty(prop);
if( home != null ) {
log.info("using system property "+prop+": " + home );
}
}
// if all else fails, try
if( home == null ) {
home = project + '/';
log.info(project + " home defaulted to '" + home + "' (could not find system property or JNDI)");
}
return normalizeDir( home );
}
<Context docBase="/Users/rcf/workspace/java/tomcat/apache-tomcat-8.0.9/webapps/solr.war" debug="0" crossContext="true" >
<Environment name="solr/home" type="java.lang.String" value="/Users/rcf/workspace/java/solr" override="true" />
</Context>
获取完SolrHome后,就会实例化SolrResourceLoader。因为传进去的parent是null，所以parents是ContextClassLoader，并且加载了SolrHome/lib/下的文件.
/**
* <p>
* This loader will delegate to the context classloader when possible,
* otherwise it will attempt to resolve resources using any jar files
* found in the "lib/" directory in the specified instance directory.
* </p>
*
* @param instanceDir - base directory for this resource loader, if null locateSolrHome() will be used.
* @seelocateSolrHome
*/
public SolrResourceLoader( String instanceDir, ClassLoader parent, Properties coreProperties )
{
if( instanceDir == null ) {
this.instanceDir = SolrResourceLoader.locateSolrHome();
log.info("new SolrResourceLoader for deduced Solr Home: '{}'",
this.instanceDir);
} else{
this.instanceDir = normalizeDir(instanceDir);
log.info("new SolrResourceLoader for directory: '{}'",
this.instanceDir);
}
this.classLoader = createClassLoader(null, parent);
addToClassLoader("./lib/", null, true);
reloadLuceneSPI();
this.coreProperties = coreProperties;
}
/**
* Convenience method for getting a new ClassLoader using all files found
* in the specified lib directory.
*/
static URLClassLoader createClassLoader(final File libDir, ClassLoader parent) {
if ( null == parent ) {
parent = Thread.currentThread().getContextClassLoader();
}
return replaceClassLoader(URLClassLoader.newInstance(new URL[0], parent),
1 libDir, null);
1}
/**
* Adds every file/dir found in the baseDir which passes the specified Filter
* to the ClassLoader used by this ResourceLoader. This method <b>MUST</b>
* only be called prior to using this ResourceLoader to get any resources, otherwise
* it's behavior will be non-deterministic. You also have to {link @reloadLuceneSPI}
* before using this ResourceLoader.
*
* <p>This method will quietly ignore missing or non-directory <code>baseDir</code>
* folder.
*
* @param baseDir base directory whose children (either jars or directories of
* classes) will be in the classpath, will be resolved relative
* the instance dir.
* @param filter The filter files must satisfy, if null all files will be accepted.
* @param quiet Be quiet if baseDir does not point to a directory or if no file is
* left after applying the filter.
*/
void addToClassLoader(final String baseDir, final FileFilter filter, boolean quiet) {
File base = FileUtils.resolvePath(new File(getInstanceDir()), baseDir);
if (base != null && base.exists() && base.isDirectory()) {
File[] files = base.listFiles(filter);
if (files == null || files.length == 0) {
if (!quiet) {
log.warn("No files added to classloader from lib: "
+ baseDir + " (resolved as: " + base.getAbsolutePath() + ").");
}
} else {
this.classLoader = replaceClassLoader(classLoader, base, filter);
}
} else {
if (!quiet) {
log.warn("Can't find (or read) directory to add to classloader: "
+ baseDir + " (resolved as: " + base.getAbsolutePath() + ").");
}
}
}