pmlogrewrite man page

pmlogrewrite — rewrite Performance Co-Pilot archives

Synopsis

$PCP_BINADM_DIR/pmlogrewrite [-Cdiqsvw ] [-c config] inlog [outlog]

Description

pmlogrewrite reads a set of Performance Co-Pilot (PCP) archive logs identified by inlog and creates a PCP archive log in outlog. Under normal usage, the -c option will be used to nominate a configuration file or files that contains specifications (see the Rewriting Rules Syntax section below) that describe how the data and metadata from inlog should be transformed to produce outlog.

The typical uses for pmlogrewrite would be to accommodate the evolution of Performance Metric Domain Agents (PMDAs) where the names, metadata and semantics of metrics and their associated instance domains may change over time, e.g. promoting the type of a metric from a 32-bit to a 64-bit integer, or renaming a group of metrics. Refer to the Examples section for some additional use cases.

pmlogrewrite is most useful where PMDA changes, or errors in the production environment, result in archives that cannot be combined with pmlogextract(1). By pre-processing the archives with pmlogrewrite the resulting archives may be able to be merged with pmlogextract(1).

The input inlog must be a set of PCP archive logs created by pmlogger(1), or possibly one of the tools that read and create PCP archives, e.g. pmlogextract(1) and pmlogreduce(1). inlog is a comma-separated list of names, each of which may be the base name of an archive or the name of a directory containing one or more archives.

If no -c option is specified, then the default behavior simply creates outlog as a copy of inlog. This is a little more complicated than cat(1), as each PCP archive is made up of several physical files.

While pmlogrewrite may be used to repair some data consistency issues in PCP archives, there is also a class of repair tasks that cannot be handled by pmlogrewrite and pmloglabel(1) may be a useful tool in these cases.

Command Line Options

The command line options for pmlogrewrite are as follows:

-C
Parse the rewriting rules and quit. outlog is not created. When -C is specified, this also sets -v and -w so that all warnings and verbose messages are displayed as config is parsed.
-c config
If config is a file or symbolic link, read and parse rewriting rules from there. If config is a directory, then all of the files or symbolic links in that directory (excluding those beginning with a period “.”) will be used to provide the rewriting rules. Multiple -c options are allowed.
-d
Desperate mode. Normally if a fatal error occurs, all trace of the partially written PCP archive outlog is removed. With the -d option, the partially created outlog archive log is not removed.
-i
Rather than creating outlog, inlog is rewritten in place when the -i option is used. A new archive is created using temporary file names and then renamed to inlog in such a way that if any errors (not warnings) are encountered, inlog remains unaltered.
-q
Quick mode, where if there are no rewriting actions to be performed (none of the global data, instance domains or metrics from inlog will be changed), then pmlogrewrite will exit (with status 0, so success) immediately after parsing the configuration file(s) and outlog is not created.
-s
When the “units” of a metric are changed, if the dimension in terms of space, time and count is unaltered, then the scaling factor is being changed, e.g. BYTE to KBYTE, or MSEC-1 to USEC-1, or the composite MBYTE.SEC-1 to KBYTE.USEC-1. The motivation may be (a) that the original metadata was wrong but the values in inlog are correct, or (b) the metadata is changing so the values need to change as well. The default pmlogrewrite behaviour matches case (a). If case (b) applies, then use the -s option and the values of all the metrics with a scale factor change in each result will be rescaled. For finer control over value rescaling refer to the RESCALE option for the UNITS clause of the metric rewriting rule described below.
-v
Increase verbosity of diagnostic output.
-w
Emit warnings. Normally pmlogrewrite remains silent for any warning that is not fatal and it is expected that for a particular archive, some (or indeed, all) of the rewriting specifications may not apply. For example, changes to a PMDA may be captured in a set of rewriting rules, but a single archive may not contain all of the modified metrics nor all of the modified instance domains and/or instances. Because these cases are expected, they do not prevent pmlogrewrite executing, and rules that do not apply to inlog are silently ignored by default. Similarly, some rewriting rules may involve no change because the metadata in inlog already matches the intent of the rewriting rule to correct data from a previous version of a PMDA. The -w flag forces warnings to be emitted for all of these cases.

The argument outlog is required in all cases, except when -i is specified.

Rewriting Rules Syntax

A configuration file contains zero or more rewriting rules as defined below.

Keywords and special punctuation characters are shown below in bolditalic font and are case-insensitive, so METRIC, metric and Metric are all equivalent in rewriting rules.

The character “#” introduces a comment and the remainder of the line is ignored. Otherwise the input is relatively free format with optional white space (spaces, tabs or newlines) between lexical items in the rules.

A global rewriting rule has the form:

GLOBAL { globalspec ... }

where globalspec is zero or more of the following clauses:

HOSTNAME -> hostname

Modifies the label records in the outlog PCP archive, so that the metrics will appear to have been collected from the host hostname.

TIME -> delta

Both metric values and the instance domain metadata in a PCP archive carry timestamps. This clause forces all the timestamps to be adjusted by delta, where delta is an optional sign “+” (the default) or “-”, an optional number of hours followed by a colon “:”, an optional number of minutes followed by a colon “:”, a number of seconds, an optional fraction of seconds following a period “.”. The simplest example would be “30” to increase the timestamps by 30 seconds. A more complex example would be “-23:59:59.999” to move the timestamps backwards by one millisecond less than one day.

TZ -> "timezone"

Modifies the label records in the outlog PCP archive, so that the metrics will appear to have been collected from a host with a local timezone of timezone. timezone must be enclosed in quotes, and should conform to the valid timezone syntax rules for the local platform.

An indom rewriting rule modifies an instance domain and has the form:

INDOM domain.serial { indomspec ... }

where domain and serial identify one or more existing instance domains from inlog - typically domain would be an integer in the range 1 to 510 and serial would be an integer in the range 0 to 4194304.

As a special case serial could be an asterisk “*” which means the rule applies to every instance domain with a domain number of domain.

If a designated instance domain is not in inlog the rule has no effect.

The indomspec is zero or more of the following clauses:

INAME "oldname" -> "newname"

The instance identified by the external instance name oldname is renamed to newname. Both oldname and newname must be enclosed in quotes.

As a special case, the new name may be the keyword DELETE (with no quotes), and then the instance oldname will be expunged from outlog which removes it from the instance domain metadata and removes all values of this instance for all the associated metrics.

If the instance names contain any embedded spaces then special care needs to be taken in respect of the PCP instance naming rule that treats the leading non-space part of the instance name as the unique portion of the name for the purposes of matching and ensuring uniqueness within an instance domain, refer to pmdaInstance(3) for a discussion of this issue.

As an illustration, consider the hypothetical instance domain for a metric which contains 2 instances with the following names:

red
eek urk

Then some possible INAME clauses might be:

"eek" -> "yellow like a flower"
Acceptable, oldname "eek" matches the "eek urk" instance.
"red" -> "eek"
Error, newname "eek" matches the existing "eek urk" instance.
"eek urk" -> "red of another hue"
Error, newname "red of another hue" matches the existing "red" instance.

INDOM -> newdomain.newserial

Modifies the metadata for the instance domain and every metric associated with the instance domain. As a special case, newserial could be an asterisk “*” which means use serial from the indom rewriting rule, although this is most useful when serial is also an asterisk. So for example:
indom 29.* { indom -> 109.* } will move all instance domains from domain 29 to domain 109.

INDOM -> DUPLICATE newdomain.newserial

A special case of the previous INDOM clause where the instance domain is a duplicate copy of the domain.serial instance domain from the indom rewriting rule, and then any mapping rules are applied to the copied newdomain.newserial instance domain. This is useful when a PMDA is split and the same instance domain needs to be replicated for domain domain and domain newdomain. So for example if the metrics foo.one and foo.two are both defined over instance domain 12.34, and foo.two is moved to another PMDA using domain 27, then the following rewriting rules could be used:
indom 12.34 { indom -> duplicate 27.34 }
metric foo.two { indom -> 27.34 pmid -> 27.*.* }

INST oldid -> newid

The instance identified by the internal instance identifier oldid is renumbered to newid. Both oldid and newid are integers in the range 0 to 231-1.

As a special case, newid may be the keyword DELETE and then the instance oldid will be expunged from outlog which removes it from the instance domain metadata and removes all values of this instance for all the associated metrics.

A metric rewriting rule has the form:

METRIC metricid { metricspec ... }

where metricid identifies one or more existing metrics from inlog using either a metric name, or the internal encoding for a metric's PMID as domain.cluster.item. In the latter case, typically domain would be an integer in the range 1 to 510, cluster would be an integer in the range 0 to 4095, and item would be an integer in the range 0 to 1023.

As special cases item could be an asterisk “*” which means the rule applies to every metric with a domain number of domain and a cluster number of cluster, or cluster could be an asterisk which means the rule applies to every metric with a domain number of domain and an item number of item, or both cluster and item could be asterisks, and rule applies to every metric with a domain number of domain.

If a designated metric is not in inlog the rule has no effect.

The metricspec is zero or more of the following clauses:

DELETE

The metric is completely removed from outlog, both the metadata and all values in results are expunged.

INDOM -> newdomain.newserial [ pick ]

Modifies the metadata to change the instance domain for this metric. The new instance domain must exist in outlog.

The optional pick clause may be used to select one input value, or compute an aggregate value from the instances in an input result, or assign an internal instance identifier to a single output value. If no pick clause is specified, the default behaviour is to copy all input values from each input result to an output result, however if the input instance domain is singular (indom PM_INDOM_NULL) then the one output value must be assigned an internal instance identifier, which is 0 by default, unless over-ridden by a INST or INAME clause as defined below.

The choices for pick are as follows:

OUTPUT FIRST
choose the value of the first instance from each input result
OUTPUT LAST
choose the value of the last instance from each input result
OUTPUT INST instid
choose the value of the instance with internal instance identifier instid from each result; the sequence of rewriting rules ensures the OUTPUT processing happens before instance identifier renumbering from any associated indom rule, so instid should be one of the internal instance identifiers that appears in inlog
OUTPUT INAME "name"
choose the value of the instance with name for its external instance name from each result; the sequence of rewriting rules ensures the OUTPUT processing happens before instance renaming from any associated indom rule, so name should be one of the external instance names that appears in inlog
OUTPUT MIN
choose the smallest value in each result (metric type must be numeric and output instance will be 0 for a non-singular instance domain)
OUTPUT MAX
choose the largest value in each result (metric type must be numeric and output instance will be 0 for a non-singular instance domain)
OUTPUT SUM
choose the sum of all values in each result (metric type must be numeric and output instance will be 0 for a non-singular instance domain)
OUTPUT AVG
choose the average of all values in each result (metric type must be numeric and output instance will be 0 for a non-singular instance domain)

If the input instance domain is singular (indom PM_INDOM_NULL) then independent of any pick specifications, there is at most one value in each input result and so FIRST, LAST, MIN, MAX, SUM and AVG are all equivalent and the output instance identifier will be 0.

In general it is an error to specify a rewriting action for the same metadata or result values more than once, e.g. more than one INDOM clause for the same instance domain. The one exception is the possible interaction between the INDOM clauses in the indom and metric rules. For example the metric sample.bin is defined over the instance domain 29.2 in inlog and the following is acceptable (albeit redundant):

indom 29.* { indom -> 109.* }
metric sample.bin { indom -> 109.2 }

However the following is an error, because the instance domain for sample.bin has two conflicting definitions:

indom 29.* { indom -> 109.* }
metric sample.bin { indom -> 123.2 }

INDOM -> NULL[ pick ]

The metric (which must have been previously defined over an instance domain) is being modified to be a singular metric. This involves a metadata change and collapsing all results for this metric so that multiple values become one value.

The optional pick part of the clause defines how the one value for each result should be calculated and follows the same rules as described for the non-NULL INDOM case above.

In the absence of pick, the default is OUTPUT FIRST.

NAME -> newname

Renames the metric in the PCP archive's metadata that supports the Performance Metrics Name Space (PMNS). newname should not match any existing name in the archive's PMNS and must follow the syntactic rules for valid metric names as outlined in pmns(5).

PMID -> newdomain.newcluster.newitem

Modifies the metadata and results to renumber the metric's PMID. As special cases, newcluster could be an asterisk “*” which means use cluster from the metric rewriting rule and/or item could be an asterisk which means use item from the metric rewriting rule. This is most useful when cluster and/or item is also an asterisk. So for example:
metric 30.*.* { pmid -> 123.*.* } will move all metrics from domain 30 to domain 123.

SEM -> newsem

Change the semantics of the metric. newsem should be the XXX part of the name of one of the PM_SEM_XXX macros defined in <pcp/pmapi.h> or pmLookupDesc(3), e.g. COUNTER for PM_TYPE_COUNTER.

No data value rewriting is performed as a result of the SEM clause, so the usefulness is limited to cases where a version of the associated PMDA was exporting incorrect semantics for the metric. pmlogreduce(1) may provide an alternative in cases where re-computation of result values is desired.

TYPE -> newtype

Change the type of the metric which alters the metadata and may change the encoding of values in results. newtype should be the XXX part of the name of one of the PM_TYPE_XXX macros defined in <pcp/pmapi.h> or pmLookupDesc(3), e.g. FLOAT for PM_TYPE_FLOAT.

Type conversion is only supported for cases where the old and new metric type is numeric, so PM_TYPE_STRING, PM_TYPE_AGGREGATE and PM_TYPE_EVENT are not allowed. Even for the numeric cases, some conversions may produce run-time errors, e.g. integer overflow, or attempting to rewrite a negative value into an unsigned type.

UNITS -> newunits [ RESCALE ]

newunits is six values separated by commas. The first 3 values describe the dimension of the metric along the dimensions of space, time and count; these are integer values, usually 0, 1 or -1. The remaining 3 values describe the scale of the metric's values in the dimensions of space, time and count. Space scale values should be 0 (if the space dimension is 0), else the XXX part of the name of one of the PM_SPACE_XXX macros, e.g. KBYTE for PM_TYPE_KBYTE. Time scale values should be 0 (if the time dimension is 0), else the XXX part of the name of one of the PM_TIME_XXX macros, e.g. SEC for PM_TIME_SEC. Count scale values should be 0 (if the time dimension is 0), else ONE for PM_COUNT_ONE.

The PM_SPACE_XXX, PM_TIME_XXX and PM_COUNT_XXX macros are defined in <pcp/pmapi.h> or pmLookupDesc(3).

When the scale is changed (but the dimension is unaltered) the optional keyword RESCALE may be used to chose value rescaling as per the -s command line option, but applied to just this metric.

When changing the domain number for a metric or instance domain, the new domain number will usually match an existing PMDA's domain number. If this is not the case, then the new domain number should not be randomly chosen; consult $PCP_VAR_DIR/pmns/stdpmid for domain numbers that are already assigned to PMDAs.

Examples

To promote the values of the per-disk IOPS metrics to 64-bit to allow aggregation over a long time period for capacity planning, or because the PMDA has changed to export 64-bit counters and we want to convert old archives so they can be processed alongside new archives.

metric disk.dev.read { type -> U64 }
metric disk.dev.write { type -> U64 }
metric disk.dev.total { type -> U64 }

The instances associated with the load average metric kernel.all.load could be renamed and renumbered by the rules below.

# for the Linux PMDA, the kernel.all.load metric is defined
# over instance domain 60.2
indom 60.2 {
    inst 1 -> 60 iname "1 minute" -> "60 second"
    inst 5 -> 300 iname "5 minute" -> "300 second"
    inst 15 -> 900 iname "15 minute" -> "900 second"
}

If we decide to split the “proc” metrics out of the Linux PMDA, this will involve changing the domain number for the PMID of these metrics and the associated instance domains. The rules below would rewrite an old archive to match the changes after the PMDA split.

# all Linux proc metrics are in 7 clusters
metric 60.8.* { pmid -> 123.*.* }
metric 60.9.* { pmid -> 123.*.* }
metric 60.13.* { pmid -> 123.*.* }
metric 60.24.* { pmid -> 123.*.* }
metric 60.31.* { pmid -> 123.*.* }
metric 60.32.* { pmid -> 123.*.* }
metric 60.51.* { pmid -> 123.*.* }
# only one instance domain for Linux proc metrics
indom 60.9 { indom -> 123.0 }

Files

For each of the inlog and outlog archive logs, several physical files are used.

archive.meta
metadata (metric descriptions, instance domains, etc.) for the archive log
archive.0
initial volume of metrics values (subsequent volumes have suffixes 1, 2, ...).
archive.index
temporal index to support rapid random access to the other files in the archive log.

PCP Environment

Environment variables with the prefix PCP_ are used to parameterize the file and directory names used by PCP. On each installation, the file /etc/pcp.conf contains the local values for these variables. The $PCP_CONF variable may be used to specify an alternative configuration file, as described in pcp.conf(5).

See Also

PCPIntro(1), pmdaInstance(3), pmdumplog(1), pmlogger(1), pmlogextract(1), pmloglabel(1), pmlogreduce(1), pmLookupDesc(3), pmns(5), pcp.conf(5) and pcp.env(5).

Diagnostics

All error conditions detected by pmlogrewrite are reported on stderr with textual (if sometimes terse) explanation.

Should the input archive log be corrupted (this can happen if the pmlogger instance writing the log suddenly dies), then pmlogrewrite will detect and report the position of the corruption in the file, and any subsequent information from that archive log will not be processed.

If any error is detected, pmlogrewrite will exit with a non-zero status.

Referenced By

pcp-archive(5), pmdaperfevent(1), pmlogcheck(1), pmlogextract(1), pmlogger_check(1), pmloglabel(1).

Performance Co-Pilot