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https://issues.apache.org/jira/browse/HDFS-4712?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13716650#comment-13716650
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Colin Patrick McCabe commented on HDFS-4712:
--------------------------------------------
{code}
+ if (jVal.l == NULL)
+ strcpy(dataNodeInfos->hostName,"");
+ else
+ jExc = newCStr(env, jVal.l, &dataNodeInfos->hostName);
{code}
You want {{dataNodeInfos->hostName = strdup("")}} here
{code}
+ typedef struct hdfsDataNodeInfo_s {
+ long capacity; /* The raw capacity */
+ long dfsUsed; /* The used space by the data node*/
+ char *hostName; /* HostName as supplied by the datanode during
registration as its name*/
+ tTime lastUpdate; /* The time when this information was accurate */
+ char *location; /* The rack name */
+ long remaining; /* The raw free space */
+ short xceiverCount; /* The number of active connections */
+ } hdfsDataNodeInfo;
{code}
Please use {{int64_t}} instead of {{long}} here. {{long}} has different sizes
on different architectures, but these quantities should always be 64-bit. I
think it makes more sense to use {{uint32_t}} for xceiverCount, since I don't
know if "32767 will be enough for anyone."
{code}
+ if (hdfsDataNodeInfos[i]->hostName) {
+ free(hdfsDataNodeInfos[i]->hostName);
+ }
+ if (hdfsDataNodeInfos[i]->location) {
+ free(hdfsDataNodeInfos[i]->location);
+ }
{code}
You don't need to test if something is NULL before calling {{free}} on it.
{{free}} ignores NULL pointers.
{{hdfsGetDataNodeInfo}}: the error handling is wrong here. You should return
NULL when there is an error. You must also free the memory you've allocated on
this line:
{code}
+ dataNodeInfoList = calloc(jNumDataNodeInfos, sizeof(hdfsDataNodeInfo*));
{code}
It is preferrable to use a pattern like this:
{code}
if (bad thing) {
ret = EIO;
goto done;
}
done:
if (ret) {
free(resources);
resources = NULL;
errno = ret;
}
return resources;
{code}
This way:
* You always free the resources on error.
* setting errno is the last thing you do, and won't be overwritten by another
function call.
* You return NULL on error rather than a bogus pointer.
thanks
> New libhdfs method hdfsGetDataNodes
> -----------------------------------
>
> Key: HDFS-4712
> URL: https://issues.apache.org/jira/browse/HDFS-4712
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: libhdfs
> Reporter: andrea manzi
> Attachments: HDFS-4712.patch, hdfs.c.diff, hdfs.h.diff
>
>
> we have implemented a possible extension to libhdfs to retrieve information
> about the available datanodes ( there was a mail on the hadoop-hdsf-dev
> mailing list initially abut this :
> http://mail-archives.apache.org/mod_mbox/hadoop-hdfs-dev/201204.mbox/%3CCANhO-
> [email protected]%3E)
> i would like to know how to proceed to create a patch, cause on the wiki
> http://wiki.apache.org/hadoop/HowToContribute i can see info about JAVA
> patches but nothing related to extensions in C.
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