Github user dyozie commented on a diff in the pull request:
https://github.com/apache/incubator-hawq-docs/pull/88#discussion_r96980622
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+---
+title: HAWQ Administrative Log Files
+---
+
+Log files are files that include messages and other information about your
HAWQ deployment, including the database and utilities.
+
+Every database instance in HAWQ \(master, standby, and segments\) runs a
PostgreSQL database server with its own server log file. You generate log files
when you invoke HAWQ management utilities directly, or indirectly via Ambari
management operations. Additionally, other components in your HAWQ cluster
(PXF, HDFS) generate log files of their own.
+
+These log files are distinctly located, formatted, configured, and managed.
+
+**Locating Log Files**
+
+HAWQ administrative log files reside in pre-defined or configured
locations on the local file system of the HAWQ node.
+
+**Configuring Logging Parameters**
+
+Configurable logging parameters may affect what, when, and where messages
are logged. You configure HAWQ administrative logging options via HAWQ server
configuration parameters or command line options.
+
+**Managing Log Files**
+
+Log files are created and/or rotated at pre-defined or configured
intervals. Note that administrative log files are not automatically truncated
or deleted. The administrator must implement and periodically run scripts to
clean up these log files.
+
+## <a id="topic28"></a>HAWQ Database Server Log Files
+
+
+### <a id="logfile_locate_db"></a>Locating HAWQ Log Files
+
+Each HAWQ master, standby, and segment database instance has its own
server log file. Daily log files are created in the `pg_log` subdirectory of
the master and segment data directory on the respective HAWQ node. You can
obtain the master data directory location from the `hawq_master_directory`
property value set in the
`$GPHOME/etc/`[`hawq-site.xml`](../reference/HAWQSampleSiteConfig.html)
configuration file. Similarly, you can obtain the segment data directory
location from the `hawq_segment_directory` property value from `hawq-site.xml`.
+
+The naming convention for HAWQ database server log files is
`hawq-<date>_<time>.[csv|log]`. For example, `hawq-2017-01-02_061611.csv` or
`hawq-2017-01-03_001704.log`. The number and size of log files present for a
given \<date\> is dependent upon the values of certain HAWQ server
configuration parameters (discussed later in this document).
+
+### <a id="logfile_format_db"></a>HAWQ Log Format
+
+The HAWQ server log files are written in text or comma-separated values
\(CSV\) format.
+
+HAWQ log entries may include the following fields:
+
+<table>
+ <tr><th>#</th><th>Field Name</th><th>Data
Type</th><th>Description</th></tr>
+ <tr><td>1</td><td>event_time</td><td>timestamp with time zone</td><td>Th
time that the log entry was written to the log</td></tr>
+ <tr><td>2</td><td>user_name</td><td>varchar(100)</td><td>The database
user name</td></tr>
+ <tr><td>3</td><td>database_name</td><td>varchar(100)</td><td>The
database name</td></tr>
+ <tr><td>4</td><td>process_id</td><td>varchar(10)</td><td>The system
process ID (prefixed with "p")</td></tr>
+ <tr><td>5</td><td>thread_id</td><td>varchar(50)</td><td>The thread count
(prefixed with "th-")</td></tr>
+ <tr><td>6</td><td>remote_host</td><td>varchar(100)</td><td>The
hostname/address of the client machine (if on master node). The
hostname/address of the master (if on segment node).</td></tr>
+ <tr><td>7</td><td>remote_port</td><td>varchar(10)</td><td>The segment or
master port number</td></tr>
+ <tr><td>8</td><td>session_start_time</td><td>timestamp with time
zone</td><td>The time the session connection was opened</td></tr>
+ <tr><td>9</td><td>transaction_id</td><td>int</td><td>The top-level
transaction ID on the master; this ID is the parent of any
subtransactions.</td></tr>
+ <tr><td>10</td><td>gp_session_id</td><td>text</td><td>The session
identifier number (prefixed with "con")</td></tr>
+ <tr><td>11</td><td>gp_command_count</td><td>text</td><td>The command
number within a session (prefixed with "cmd")</td></tr>
+ <tr><td>12</td><td>gp_segment</td><td>text</td><td>The segment content
identifier. The master always has a content ID of -1.</td></tr>
+ <tr><td>13</td><td>slice_id</td><td>text</td><td>The slice ID (portion
of the query plan being executed)</td></tr>
+ <tr><td>14</td><td>distr_tranx_id</td><td>text</td><td>The distributed
transaction identifier</td></tr>
+ <tr><td>15</td><td>local_tranx_id</td><td>text</td><td>The local
transaction identifier</td></tr>
+ <tr><td>16</td><td>sub_tranx_id</td><td>text</td><td>The subtransaction
identifier</td></tr>
+ <tr><td>17</td><td>event_severity</td><td>varchar(10)</td><td>The event
severity; values include: LOG, ERROR, FATAL, PANIC, DEBUG1, DEBUG2</td></tr>
+ <tr><td>18</td><td>sql_state_code</td><td>varchar(10)</td><td>The SQL
state code associated with the log message</td></tr>
+ <tr><td>19</td><td>event_message</td><td>text</td><td>The log or error
message text</td></tr>
+ <tr><td>20</td><td>event_detail</td><td>text</td><td>The detail message
text associated with an error or warning message</td></tr>
+ <tr><td>21</td><td>event_hint</td><td>text</td><td>The hint message text
associated with an error or warning message</td></tr>
+ <tr><td>22</td><td>internal_query</td><td>text</td><td>The
internally-generated query text</td></tr>
+ <tr><td>23</td><td>internal_query_pos</td><td>int</td><td>The cursor
index into the internally-generated query text</td></tr>
+ <tr><td>24</td><td>event_context</td><td>text</td><td>The context in
which this message is generated</td></tr>
+ <tr><td>25</td><td>debug_query_string</td><td>text</td><td>User-supplied
query string with full detail for debugging. This string can be modified for
internal use.</td></tr>
+ <tr><td>26</td><td>error_cursor_pos</td><td>int</td><td>The cursor index
into the query string</td></tr>
+ <tr><td>27</td><td>func_name</td><td>text</td><td>The function in which
this message is generated</td></tr>
+ <tr><td>28</td><td>file_name</td><td>text</td><td>The name of the source
file in which the message originated</td></tr>
+ <tr><td>29</td><td>file_line</td><td>int</td><td>The line number of the
source file in which the message originated</td></tr>
+ <tr><td>30</td><td>stack_trace</td><td>text</td><td>The stack trace text
associated with this message</td></tr>
+</table>
+
+**Note**: Log entries may not include values for all log fields. For
example, the `slice_id` field is populated only for log entries associated with
a query worker process.
+
+Example HAWQ server log file entries in a `.csv` file:
+
+``` pre
+2017-01-02 01:19:55.293050
PST,"gpadmin","testdb",p381034,th-1259067104,"[local]",,2017-01-02 01:19:21
PST,28083,con3595,cmd7,seg-1,,,x28083,sx1,"LOG","00000","ConnID 207. Acquired
resource from resource manager, (256 MB, 0.062500 CORE) x 1.",,,,,,"INSERT INTO
extblwstrings VALUES ('my string');",0,,"rmcomm_QD2RM.c",868,
+2017-01-02 06:16:06.383827
PST,,,p360256,th-1259067104,,,,0,,,seg-10000,,,,,"LOG","00000","database system
is shut down",,,,,,,0,,"xlog.c",7882,
+```
+
+Example HAWQ server log file entries in a `.log` file:
+
+``` pre
+2017-01-03 00:17:04.848268 PST|||706424|startup||:-LOG: database system
was shut down at 2017-01-03 00:16:58 PST
+2017-01-03 00:17:04.988778 PST|gpadmin|template1|706437|cmd1|x31410|:-LOG:
statement: SELECT oid,rolname,rolsuper,rolresqueue FROM pg_authid
+2017-01-03 00:17:04.990520 PST|||706432|master resource manager||:-LOG:
Resource manager successfully loaded role specifications.
+```
+
+### <a id="logfile_examine_db"></a>Examining HAWQ Log Files
+
+You will examine the HAWQ log files to obtain information about your HAWQ
deployment, as well as diagnose problems.
+
+Identify log entries of related transactions using the `transaction_id`.
You can identify related log entries of a particular query by the query's
session identifier \(`gp_session_id`\) and command identifier
\(`gp_command_count`\).
+
+Alternatively, you can use the
[*hawq_toolkit*](../reference/toolkit/hawq_toolkit.html#topic16) administrative
schema to query HAWQ log files when the
[`gp_log_format`](../reference/guc/parameter_definitions.html#gp_log_format)
server configuration parameter value specifies `csv` format log files.
+
--- End diff --
This is great info, but are there any example SQL commands we could include
or link to from here?
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