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Subject [4/7] git commit: ACCUMULO-1217 Includes notes on monitor and tracer in component list.
Date Tue, 25 Mar 2014 00:37:30 GMT
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.


Branch: refs/heads/1.6.0-SNAPSHOT
Commit: 97a309dd224e8478b881cd4e0cb0d47da3ebdb59
Parents: 3e749fb
Author: Josh Elser <>
Authored: Mon Mar 24 17:26:32 2014 -0700
Committer: Josh Elser <>
Committed: Mon Mar 24 17:26:32 2014 -0700

 .../accumulo_user_manual/chapters/design.tex    | 24 +++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)
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.
@@ -80,6 +81,27 @@ shutdown and recovery of changes in write-ahead logs when Tablet servers
 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.
+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.
+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
+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.
 Accumulo includes a client library that is linked to every application. The client

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