ACCUMULO-1217 Includes notes on monitor and tracer in component list. Also expanded on the ability to run hot-spares with the GC and monitor (master already had a note about this) that perform automatic failover when the active instance dies.
Project: http://git-wip-us.apache.org/repos/asf/accumulo/repo Commit: http://git-wip-us.apache.org/repos/asf/accumulo/commit/97a309dd Tree: http://git-wip-us.apache.org/repos/asf/accumulo/tree/97a309dd Diff: http://git-wip-us.apache.org/repos/asf/accumulo/diff/97a309dd Branch: refs/heads/master Commit: 97a309dd224e8478b881cd4e0cb0d47da3ebdb59 Parents: 3e749fb Author: Josh Elser <els...@apache.org> Authored: Mon Mar 24 17:26:32 2014 -0700 Committer: Josh Elser <els...@apache.org> Committed: Mon Mar 24 17:26:32 2014 -0700 ---------------------------------------------------------------------- .../accumulo_user_manual/chapters/design.tex | 24 +++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/accumulo/blob/97a309dd/docs/src/main/latex/accumulo_user_manual/chapters/design.tex ---------------------------------------------------------------------- diff --git a/docs/src/main/latex/accumulo_user_manual/chapters/design.tex b/docs/src/main/latex/accumulo_user_manual/chapters/design.tex index 72e1ddf..8507f24 100644 --- a/docs/src/main/latex/accumulo_user_manual/chapters/design.tex +++ b/docs/src/main/latex/accumulo_user_manual/chapters/design.tex @@ -66,7 +66,8 @@ found in the write-ahead log to the tablet. Accumulo processes will share files stored in HDFS. Periodically, the Garbage Collector will identify files that are no longer needed by any process, and -delete them. +delete them. Multiple garbage collectors can be run to provide hot-standby support. +They will perform leader election among themselves to choose a single active instance. \subsection{Master} @@ -80,6 +81,27 @@ shutdown and recovery of changes in write-ahead logs when Tablet servers fail. Multiple masters may be run. The masters will choose among themselves a single master, and the others will become backups if the master should fail. +\subsection{Tracer} + +The Accumulo Tracer process supports the distributed timing API provided by Accumulo. +One to many of these processes can be run on a cluster which will write the timing +information to a given Accumulo table for future reference. Seeing the section on +Tracing for more information on this support. + +\subsection{Monitor} + +The Accumulo Monitor is a web application that provides a wealth of information about +the state of an instance. The Monitor shows graphs and tables which contain information +about read/write rates, cache hit/miss rates, and Accumulo table information such as scan +rate and active/queued compactions. Additionally, the Monitor should always be the first +point of entry when attempting to debug an Accumulo problem as it will show high-level problems +in addition to aggregated errors from all nodes in the cluster. See the section on Monitoring +for more information. + +Multiple Monitors can be run to provide hot-standby support in the face of failure. Due to the +forwarding of logs from remote hosts to the Monitor, only one Monitor process should be active +at one time. Leader election will be performed internally to choose the active Monitor. + \subsection{Client} Accumulo includes a client library that is linked to every application. The client
