AEM instance not starting

After working half day my AEM instance goes down all the times. See below error. Not able to restart. startup log doesn't display anything but error log has below stack trace. please help.

31.01.2017 13:24:06.322 *ERROR* [0:0:0:0:0:0:0:1 [1485890646313] GET /libs/granite/core/content/login.html HTTP/1.1] org.apache.sling.engine.impl.SlingMainServlet service: Uncaught Problem handling the request
org.apache.sling.api.SlingException: Unable to setup processor: Unable to get component of class 'interface org.apache.sling.rewriter.Generator' with type 'htmlparser'.
    at org.apache.sling.rewriter.impl.ProcessorManagerImpl.getProcessor(ProcessorManagerImpl.java:451)
    at org.apache.sling.rewriter.impl.RewriterResponse.getProcessor(RewriterResponse.java:172)
    at org.apache.sling.rewriter.impl.RewriterResponse.getWriter(RewriterResponse.java:110)
    at org.apache.sling.engine.impl.DefaultErrorHandler.sendError(DefaultErrorHandler.java:173)
    at org.apache.sling.engine.impl.DefaultErrorHandler.delegateFailed(DefaultErrorHandler.java:71)
    at org.apache.sling.engine.impl.DefaultErrorHandler.handleError(DefaultErrorHandler.java:135)
    at org.apache.sling.engine.impl.SlingRequestProcessorImpl$2.render(SlingRequestProcessorImpl.java:377)
    at org.apache.sling.engine.impl.filter.AbstractSlingFilterChain.doFilter(AbstractSlingFilterChain.java:77)
    at org.apache.sling.rewriter.impl.RewriterFilter.doFilter(RewriterFilter.java:83)
    at org.apache.sling.engine.impl.filter.AbstractSlingFilterChain.doFilter(AbstractSlingFilterChain.java:68)
    at org.apache.sling.i18n.impl.I18NFilter.doFilter(I18NFilter.java:129)
    at org.apache.sling.engine.impl.filter.AbstractSlingFilterChain.doFilter(AbstractSlingFilterChain.java:68)
    at org.apache.sling.engine.impl.SlingRequestProcessorImpl.handleError(SlingRequestProcessorImpl.java:384)
    at org.apache.sling.engine.impl.SlingRequestProcessorImpl.doProcessRequest(SlingRequestProcessorImpl.java:186)
    at org.apache.sling.engine.impl.SlingMainServlet.service(SlingMainServlet.java:216)
    at org.apache.felix.http.base.internal.handler.ServletHandler.handle(ServletHandler.java:85)
    at org.apache.felix.http.base.internal.dispatch.InvocationChain.doFilter(InvocationChain.java:79)
    at com.adobe.granite.license.impl.LicenseCheckFilter.doFilter(LicenseCheckFilter.java:308)
    at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:135)
    at org.apache.felix.http.base.internal.dispatch.InvocationChain.doFilter(InvocationChain.java:74)
    at org.apache.felix.http.sslfilter.internal.SslFilter.doFilter(SslFilter.java:89)
    at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:135)
    at org.apache.felix.http.base.internal.dispatch.InvocationChain.doFilter(InvocationChain.java:74)
    at org.apache.sling.security.impl.ReferrerFilter.doFilter(ReferrerFilter.java:290)
    at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:135)
    at org.apache.felix.http.base.internal.dispatch.InvocationChain.doFilter(InvocationChain.java:74)
    at org.apache.sling.i18n.impl.I18NFilter.doFilter(I18NFilter.java:129)
    at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:135)
    at org.apache.felix.http.base.internal.dispatch.InvocationChain.doFilter(InvocationChain.java:74)
    at org.apache.sling.featureflags.impl.FeatureManager.doFilter(FeatureManager.java:116)
    at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:135)
    at org.apache.felix.http.base.internal.dispatch.InvocationChain.doFilter(InvocationChain.java:74)
    at org.apache.sling.engine.impl.log.RequestLoggerFilter.doFilter(RequestLoggerFilter.java:75)
    at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:135)
    at org.apache.felix.http.base.internal.dispatch.InvocationChain.doFilter(InvocationChain.java:74)
    at org.apache.felix.http.base.internal.dispatch.Dispatcher.dispatch(Dispatcher.java:124)
    at org.apache.felix.http.base.internal.DispatcherServlet.service(DispatcherServlet.java:61)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:812)
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:587)
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:221)
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127)
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
    at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:215)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
    at org.eclipse.jetty.server.Server.handle(Server.java:499)
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:311)
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257)
    at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:544)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:635)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:555)
    at java.lang.Thread.run(Unknown Source)
Caused by: java.io.IOException: Unable to get component of class 'interface org.apache.sling.rewriter.Generator' with type 'htmlparser'.
    at org.apache.sling.rewriter.impl.PipelineImpl.getPipelineComponent(PipelineImpl.java:160)
    at org.apache.sling.rewriter.impl.PipelineImpl.init(PipelineImpl.java:85)
    at org.apache.sling.rewriter.impl.ProcessorManagerImpl.getProcessor(ProcessorManagerImpl.java:444)
    ... 54 common frames omitted